Showing papers in "Journal of Molluscan Studies in 2014"
TL;DR: It is suggested that P. canaliculata snails might have a better ability to colonize Asian paddy ecosystems than P. maculata, which had been suggested to be the pure line, and was less tolerant to cold.
Abstract: We collected the invasive apple snails, Pomacea canaliculata and P. maculata (formerly, P. insularum), in their native endemic regions of Argentina and investigated tolerances to cold and desiccation, in order to ascertain any difference between the species and to compare these traits with those reported for apple snails in invaded areas of Asia. All of the four studied populations of P. canaliculata and P. maculata showed enhanced cold tolerance after cold acclimation, as reported for P. canaliculata in invaded areas. Two populations of P. canaliculata and one population of P. maculata that had been suggested to be hybrid based on nuclear gene structures were found to have a tolerance to cold temperature approximately similar to that reported for P. canaliculata in Japan. However, the remaining population of P. maculata, which had been suggested to be the pure line, was less tolerant to cold. The same population of P. maculata, collected in a permanent lake, was much less tolerant to desiccation than the other three Pomacea populations, which were collected from ephemeral ponds. Two probable hybrid populations of P. canaliculata and P. maculata showed desiccation tolerance that was intermediate between the pure lines of both species. On the basis of these results, in addition to probable hybridization between the two species, we suggest that P. canaliculata snails might have a better ability to colonize Asian paddy ecosystems than P. maculata.
43 citations
TL;DR: This study investigated the pattern of outcrossing over time after a single mating in a freshwater snail, Lymnaea stagnalis, using a microsatellite marker and reveals that overall body size is positively correlated with paternity longevity.
Abstract: Reproductive success is a crucial variable to understand the action of sexual selection, but its quantification is not straightforward because several factors cause nonrandom fertilization success. One of these factors is female sperm storage, which leads to prolonged paternity gain ( paternity longevity). In particular, knowledge about paternity longevity is crucial in simultaneous hermaphrodites, since their ability to self-fertilize adds a further layer of complexity to the quantification of male reproductive success. Here, we investigated the pattern of outcrossing over time after a single mating in a freshwater snail, Lymnaea stagnalis, using a microsatellite marker. We found that offspring are produced from stored sperm for a little over 2 months on average. Furthermore, the pattern of paternity indicates an active role for the female reproductive system in the transport of received sperm to the sperm storage organ. To quantify paternity longevity in a sperm-storing mating system, we propose to use the time when half the offspring are sired by a focal donor (Paternity Longevity 50; PL50), in addition to total storage duration. Intriguingly, we reveal that overall body size is positively correlated with paternity longevity. Although the exact mechanism of sperm storage and its contribution to male reproductive success remain to be revealed, this study provides useful information and new perspectives on sperm storage and sexual selection in this simultaneous hermaphrodite.
35 citations
TL;DR: In this article, confocal Raman microscopy was used to map the spatial distribution of polyenes within the shell of the bivalve Arctica islandica and to determine their chemical characteristics (chain length).
Abstract: Many of the pigments that are widely found in coloured parts of mollusc shells are polyenes, i.e. molecules with a central polyenic chain (carbon-carbon single and double bonds). Due to a resonant coupling of these molecules at wavelengths typically used in Raman spectroscopy, this method is well suited to investigate their occurrence in biogenic materials. Here we use confocal Raman microscopy to map the spatial distribution of polyenes within the shell of the bivalve Arctica islandica and to determine their chemical characteristics (chain length). Polyene chain length does not differ between shells from different localities (off Iceland, Baltic Sea and North Sea). We also show that the pigment polyenes are not only located at the outside of the shell, but also within the shell, developing the same layered pattern typical for growth bands. This finding raises the question as to whether polyenes may play a role in the biomineralization process itself.
32 citations
TL;DR: The embryonic and larval development of Ruditapes decussatus, from fertilization to metamorphosis, is described and Shell formation during embryonic development is investigated using SEM and transmission electron microscopy.
Abstract: The embryonic and larval development of Ruditapes decussatus, from fertilization to metamorphosis, is described using scanning electron microscopy (SEM). Shell formation during embryonic development is investigated using SEM and transmission electron microscopy (TEM). Released oocytes are about 67 mm in diameter. Gastrulation takes place by epiboly and starts 7 h after fertilization (T0 þ 7 h). The early gastrula is characterized by the appearance of a large, open cavity posteriorly and a small, round blastopore anteriorly, which represent the shell field and the blastopore, respectively. In TEM views, the open cavity expands under and posterior to the developing prototrochal pad. The shell field comprises a few cells in which microvilli progressively regress; these cells will secrete the periostracum. After 13 h (T0 þ 13 h) the late gastrula has differentiated into a typically pyriform and motile trochophore. The periostracum emerges from periostracum-secreting cells (T1) and spreads over shell-secretory cells (T3). Thus, the trochophore is laterally compressed and the periostracum inserts to the mantle edge. Typical straight-hinged D-shaped larvae develop from a trochophore by 26 h postfertilization (T0 þ 26 h) and by then the valves completely enclose the soft body of the larva. At T0 þ 39 h, the newly hatched veliger larva is already enclosed in the fully calcified prodissoconch I (PI) and the prototroch has transformed into the velum. Late D-larvae already have a developed digestive system and start exogenous feeding. At the same time, the prodissoconch II is newly secreted at the margin of the PI. Settlement occurs at 27 d postfertilization (T0 þ 27 d), when the larvae are about 207 mm long. Once metamorphosis is completed, the mantle folds begin the secretion of the dissoconch shell and the postlarval stage is reached.
29 citations
TL;DR: This case study discusses currently available methods of species delimitation and their integrative application to heterobranch sea slugs and concludes that the morphological and body colour differences observed between Mediterranean and Brazilian specimens are not due to intraspecific variation in C. peregrina.
Abstract: One of the main difficulties in the taxonomy of heterobranch sea slugs is the interpretation of small morphological and body colour differences in a group of specimens, sympatric or allopatric, as variation of a single species or indicative of similar, but different, species. The aeolid Cratena peregrina is one of the most common and typical nudibranchs from the Mediterranean Sea and was recently informally recorded from Senegal, South Africa, India and in the western Atlantic. In the present work, we investigate the potential presence of C. peregrina on the coast of Brazil. Brazilian and Mediterranean specimens are compared through multiple approaches, including (1) a molecular phylogenetic analysis based on a mitochondrial and a nuclear marker (cytochrome c oxidase subunit I and H3, respectively); (2) performing population analyses such as haplotype networks via TCS and Birky’s coalescence-based K/u ratio; (3) automatic barcode gap discovery and (4) comparative morphological study. As a result of our integrative species delimitation approach, we conclude that the morphological and body colour differences observed between Mediterranean and Brazilian specimens are not due to intraspecific variation in C. peregrina and that C. peregrina is not present in Brazil. Instead, Brazilian specimens belong to a new species, C. minor n. sp., which is described herein. We use this case study to discuss currently available methods of species delimitation and their integrative application to heterobranch sea slugs.
29 citations
TL;DR: An historical perspective on the development and composition of comparable land snail assemblages from various interglacials from the Middle and Late Pleistocene, and from the Holocene is provided.
Abstract: The land snail assemblages in NW Europe exhibit marked gradients in diversity related to both latitude and longitude. These gradients, in turn, are linked to regional differences in temperature and moisture, although other non-climatic factors may be involved. Such diversity patterns have been described for the modern land snail faunas of NW Europe, especially those that inhabit forest. Here we provide an historical perspective on the development and composition of comparable land snail assemblages from various interglacials from the Middle and Late Pleistocene, and from the Holocene. We review the land snail assemblages from tufa sequences, which provide the best faunal records for each of the temperate periods. Data from 32 Quaternary sites in 7 NW European countries are considered. Assemblages from ‘forest optima’ of Pleistocene interglacial periods are richer in species compared with those from the Holocene. Correspondence analysis (CA) of data from 25 Quaternary sites in the regions where both Pleistocene and Holocene sites occur (i.e. southern England, northern France and Germany) resulted in a geographical separation of the assemblages into a western and eastern group. CA on each geographical group resulted in chronological divisions separating Pleistocene sites from the Holocene sequences. This separation results from the occurrence of numerous Central and Eastern European species in the Pleistocene faunas, whereas Holocene assemblages are characterized by species with mostly Western and Northern European modern ranges. This difference appears to reflect climatic influences, rather than resulting from anthropogenic effects. CA of 19 Holocene tufas produced geographical clusters clearly related to their position on a west-east gradient, presumably linked to some effect of ‘continentality’. During the mid Holocene, the diversity of forest snails from tufas in southern England exceeded the totals from the richest calcareous woodland sites in the region today. Further work is needed to establish whether this pattern holds for other regions of NW Europe.
27 citations
TL;DR: Phylogenetic trees show that the 13 protein-encoding mt gene sequences (equivalent codons) of P. acuta are phylogenetically informative despite a considerable intraspecific divergence and the atypical gene order in its mt genome.
Abstract: Mitochondrial (mt) sequences are frequently used for phylogenetic reconstruction and for identification of species of molluscs. This study expands the phylogenetic range of Hygrophila (Panpulmonata) for which such sequence data are available by characterizing the full mt genome of the invasive freshwater snail Physella acuta (Physidae). The mt genome sequences of two P. acuta isolates from Stubblefield Lake, New Mexico, USA, differed in length (14,490 vs 14,314 bp) and showed 11.49% sequence divergence, whereas ITS1 and ITS2 sequences from the nuclear genome differed by 1.75%. The mt gene order of P. acuta (cox1, P, nad6, nad5, nad1, D, F, cox2, Y, W, nad4L, C, Q, atp6, R, E, rrnS, M, T, cox3, I, nad2, K, V, rrnL, L1, A, cytb, G, H, L2, atp8, N, nad2, S1, S2, nad4) differs considerably from the relatively conserved gene order within Panpulmonata. Phylogenetic trees show that the 13 protein-encoding mt gene sequences (equivalent codons) of P. acuta group according to gastropod phylogeny, yet branch lengths and dN/dS ratios for P. acuta indicate elevated amino acid substitutions relative to other gastropods. This study indicates that mt sequences of P. acuta are phylogenetically informative despite a considerable intraspecific divergence and the atypical gene order in its mt genome.
26 citations
TL;DR: It is demonstrated that Costasiella is a basal member of the Limapontioidea, however a final conclusion on the origin of functional kleptoplasty within Sacoglossa is still not possible, and this findings support the previous suggestion that during starvation klePToplasts primarily represent a sort of larder, whose function might benefit from ongoing photosynthesis.
Abstract: The evolution and origin of functional kleptoplasty (sequestration and retention of functional plastids) within the Sacoglossa is still controversial. While some authors have suggested that it is a synapomorphy of the parapodia-bearing Plakobranchoidea, others have suggested an earlier origin at the base of the more inclusive clade Plakobranchacea. The latter is supported by the presence of kleptoplasts in Costasiella ocellifera, a ceras-bearing member of Limapontioidea, in which they remain functional for several weeks and fix CO2. However, the phylogenetic relationships of Costasiella, especially with regard to the Plakobranchoidea, have not been satisfactorily demonstrated, and the photosynthetic ability and the importance of photosynthesis within the genus remain poorly studied. In this study we analyse the phylogenetic position, photosynthetic activity and importance of photosynthesis for survival during starvation of five Costasiella species, but focusing on C. ocellifera. We demonstrate that Costasiella is a basal member of the Limapontioidea, however a final conclusion on the origin of functional kleptoplasty within Sacoglossa is still not possible. Three Costasiella species maintain functional chloroplasts (of which C. ocellifera shows long-term retention, and both C. kuroshimae and C. sp. 1 short-term retention) and together form a monophyletic group, feeding mainly on Avrainvillea. The two nonphotosynthetic species, C. nonatoi and C. sp. 2, represent the sister clade and feed on algae other than Avrainvillea. Intriguingly, C. ocellifera survived under nonphotosynthetic conditions for a minimum of 38 d, demonstrating that photosynthates may not be essential in order to survive starvation. These findings support our previous suggestion that during starvation kleptoplasts primarily represent a sort of larder, whose function might benefit from ongoing photosynthesis.
26 citations
TL;DR: Comparative analyses showed egg size to be evolutionarily labile, but also revealed a highly significant negative relationship between egg size and the nurse-egg-to-embryo ratio, indicating that evolutionary changes in egg size among species are balanced by changes in the number of nurse eggs allocated to each offspring.
Abstract: Despite the importance of Nucella as a model system in numerous fields of biology, no phylogenetic analysis of the genus, including every widely recognized species, has been conducted. We have analysed about 4,500 bp of DNA from six different genes (three mitochondrial, three nuclear) from each taxon in the genus. Our results showed western Pacific N. heyseana and N. freycinetii as distinct and distantly related, but found no evidence that N. elongata is distinct from N. heyseana .W e also resolved N. heyseana as the closest living relative of the North Atlantic N. lapillus and, using the fossil record for calibration, inferred a minimum separation time between Atlantic and Pacific lineages of at least 6.2 Ma, slightly pre-dating the opening of the Bering Strait. Comparative analyses showed egg size to be evolutionarily labile, but also revealed a highly significant negative relationship between egg size and the nurse-egg-to-embryo ratio. The negative correlation indicates that evolutionary changes in egg size among species are balanced by changes in the number of nurse eggs allocated to each offspring, indicating that interspecific variation in the nurse-egg-to-embryo ratio has not been driven by divergent selection on hatching size, but may instead be a response to variation in other factors, such as parent-offspring conflict.
23 citations
TL;DR: This work states that P.M. and M.R. are supported by Fundacao para a Ciencia e a Tecnologia through a postdoctoral scholarship (SFRH/BPD/40832/2007) and 'Ciencia 2008' contract, respectively.
Abstract: We acknowledge the valuable comments and suggestions made by Daniel L. Graf, Simon Schneider and an anonymous reviewer on an earlier version of the manuscript. We are also grateful to John Babaluk for his comments and for improving the grammar and style of the manuscript. P.M. and M.M.R. are supported by Fundacao para a Ciencia e a Tecnologia through a postdoctoral scholarship (SFRH/BPD/40832/2007) and 'Ciencia 2008' contract, respectively.
22 citations
TL;DR: Berghia was found to be monophyletic, although its relationship with other aeolidiids was not resolved, and the morphological studies corroborate the molecular findings and differences in external coloration can distinguish closely related species.
Abstract: The aeolid genus Berghia was described by Trinchese in 1877, with Berghia coerulescens (Laurillard, 1832) as type species. The validity of Berghia has been questioned by some authors, who have considered it a junior synonym of Spurilla Bergh, 1864. The lack of consensus has caused confusion, blurring the differences between these two genera. A recent molecular phylogeny of Aeolidiidae supported the monophyly of Berghia and helped to resolve the controversy about its relationship with Spurilla. Here, specimens of Berghia from the eastern and western Atlantic were examined from molecular and morphological points of view. Berghia was found to be monophyletic, although its relationship with other aeolidiids was not resolved. The morphological studies corroborate our molecular findings and differences in external coloration can distinguish closely related species. So far, Berghia comprises 10 species: B. coerulescens, B. verrucicornis, B. norvegica, B. benteva, B. creutzbergi, B. columbina, B. rissodominguezi, B. stephanieae, B. marcusi and a new species from Senegal, B. marinae.
TL;DR: The two Koreamya species with remarkably differently shaped shells were monophyletic, suggesting that their symbiotic associations with Lingula have the same evolutionary origin and the possibility of host switching between sea anemones and Lingula.
Abstract: Many members of the bivalve superfamily Galeommatoidea have symbiotic associations with other marine benthic invertebrates. Among them, Koreamya arcuata (A. Adams, 1856) is distinctive because it is the only known bivalve symbiotic with brachiopods. Here we describe Koreamya setouchiensis n. sp. as the second example in this genus, based on specimens collected in and around the Seto Inland Sea, Japan. Similar to K. arcuata, this bivalve species attaches to the anterior end of the shell valve of living Lingula anatina Lamarck, 1801 by means of byssal threads. However, shell morphologies of the two bivalve species are clearly different; K. setouchiensis has an ovate shell, while K. arcuata has an elongatedtriangular shell. These morphological differences are probably due to the difference in posture on the hosts. To understand how symbiotic association with Lingula evolved in Galeommatoidea, we performed molecular phylogenetic analyses using three nuclear (18S, 28S and H3) and one mitochondrial (COI) genes. The two Koreamya species with remarkably differently shaped shells were monophyletic, suggesting that their symbiotic associations with Lingula have the same evolutionary origin. Furthermore, the Koreamya clade formed a monophyletic group with anemone-associated galeommatoideans (Nipponomontacuta actinariophila and Montacutona sp.). This result and their morphological similarities suggest the possibility of host switching between sea anemones and Lingula.
TL;DR: The results support the idea that continuously-disturbed habitats are associated with altered passive dispersal and colonization dynamics, distorted biogeographic boundaries and faunal homogenization.
Abstract: Habitat disturbance alters environmental conditions and can affect biotic exchange. While the process of biotic exchange is difficult to quantify in the field, it affects community assembly and thus species abundance distributions, diversity, faunal homogeneity and biogeographic patterns. Here, we provide the first comprehensive assessment of habitat-specific assemblage structure and turnover in slow, active dispersers, namely slugs (Mollusca: Gastropoda). We compare species richness, densities, assemblage homogeneity and spatial turnover from nine differently disturbed habitat types (total: 729 sites) within an area spanning the border between two major European biogeographic regions, the Atlantic and the Continental Regions. Gardens, mesic open habitats and successions tended to harbour many introduced species. The nonmetric multidimensional scaling plot revealed a gap, rather than a transition, between disturbed habitats (including woody successions) and mature forest stands. This gap indicates a tipping point for slug assemblages related to food sources and microclimate. Anthropogenic disturbance blurred the effect expected from the border between the biogeographic regions. When compared with broadleaved forests as the natural vegetation cover, human disturbance doubled the range before spatial faunal dissimilarity occurred in physically highly fragmented gardens, and more than tripled it in continuously-disturbed habitat types such as mesic open habitats. Our results support the idea that continuously-disturbed habitats are associated with altered passive dispersal and colonization dynamics, distorted biogeographic boundaries and faunal homogenization.
TL;DR: A novel method based on high-resolution melting (HRM) analysis was used to visualize the coexistence of species-specific single nucleotide polymorphisms or insertion-deletion variations from both oyster species, suggesting the existence of bidirectional gametic compatibility between C. angulata and C. sikamea.
Abstract: To the best of our knowledge, the hybridization potential between the two closely related oyster species, Crassostrea sikamea and C. angulata, has yet to be reported. Moreover, hybrids obtained in most early experiments on oyster hybridization have been inadequately validated by genetic methods. In this study, a novel method based on high-resolution melting (HRM) analysis was used to visualize the coexistence of species-specific single nucleotide polymorphisms or insertion-deletion variations from both oyster species. Mitochondrial cytochrome c oxidase subunit I sequences were used to track the genetic material from a female to its descendants, while the nuclear genomic sequences of the first ribosomal internal transcribed spacer regions were used to track the genetic material from both parents and confirm hybrids of C. sikamea and C. angulata. Based on HRM analysis, bidirectional gametic compatibility between C. angulata and C. sikamea was successfully detected, although only several hundreds of larvae successfully hatched from tens of millions of C. angulata eggs inseminated by C. sikamea sperm, and the larvae were inviable. These results suggest the existence of bidirectional gametic compatibility between C. angulata and C. sikamea. Hybrids from C. sikamea eggs and C. angulata sperm showed higher growth rates and survival success during the swimming-larva stage, and may be potentially used for the genetic improvement of oyster aquaculture. This study provides a useful and reliable method for confirming hybrids in samples from either laboratory research or ecological field studies.
TL;DR: A lack of clustering of the occurrences of different snail species along the altitudinal gradient indicated a Gleasonian meta-community structure with individualistic responses of the various species to environmental parameters, including temperature, which are strongly correlated with altitude.
Abstract: We investigated the land-snail fauna of rain forests on the eastern slopes of Pico Biao on Bioko Island in the Gulf of Guinea. Thirty-seven plots were studied along an altitudinal transect reaching from sea level (lowland rain forest) to an altitude of 1,830 m (mossy forest). A total of 1,755 specimens were collected and were assigned to 68 land-snail species. Eleven species were new records for Bioko. At least 15 of the recorded species are endemic to Bioko. The degree of endemism was high in mossy forest (23%) and in lowland rain forest (20%), but lower in montane forest (8%). Species richness showed a humpshaped distribution along the altitudinal gradient with a maximum at 500 m a.s.l. Species richness peaked in forests in which there had been selective logging more than 50 years ago, indicating that some disturbance may have beneficial effects on biodiversity. Species richness was correlated with the thickness of leaf litter. The availability and quality of suitable microhabitats is more important for the occurrence of snail species than gradients of otherwise often decisive environmental parameters like temperature, which are strongly correlated with altitude. A lack of clustering of the occurrences of different snail species along the altitudinal gradient indicated a Gleasonian meta-community structure with individualistic responses of the various species to environmental parameters. No negative co-occurrence patterns that might provide evidence for interspecific competition could be detected. The frequent coexistence of morphologically similar, and presumably ecologically equivalent, congeneric species may indicate that such equivalents do not exclude each other as predicted by the neutral theory of biodiversity. However, current knowledge about individual snail species is too scanty to exclude the possibility that niches of congeneric species differ in some details.
TL;DR: It is suggested that a further taxonomic revision of Japanese Bradybaenidae is needed and, to address this issue, genital anatomy is useful in addition to molecular phylogenetic analyses.
Abstract: The Japanese Archipelago harbours high diversity of endemic bradybaenid land snails. However, there have been few systematic studies of these snails. The resolution of the taxonomy and phylogenetic relationships of these bradybaenid land snail taxa is important both for describing species diversity and for promoting the conservation of these land snails. We investigated the molecular phylogeny of Bradybaena and Phaeohelix using the CO1 and internal transcribed spacer genes, to clarify whether morphological traits and the current species taxonomy of these genera reflect their phylogenetic relationships. Our results show that the Japanese species in these genera are genetically divided into three clades, and the geographical distribution pattern of the lineages tends to reflect phylogenetic relationships. Although the nominal species taxonomy of these genera was not consistent with their molecular phylogenetic relationships, their shell and genital morphology reflected phylogenetic relationships to some extent. Inferred phylogeny and observed genital morphology showed that Phaeohelix submandarina, P. miyakejimana and Bradybaena circulus oceanica from Hachijo-kojima Island belong to P. phaeogramma. In addition, the distinction between Bradybaena and Phaeohelix was not supported by molecular phylogeny, showing instead that Phaeohelix should be synonymized with Bradybaena. This study suggests that a further taxonomic revision of Japanese Bradybaenidae is needed and, to address this issue, genital anatomy is useful in addition to molecular phylogenetic analyses.
TL;DR: This study recapitulates the background to the taxonomic problem, presents a summary of previously published morphological characters to identify species, provides diagnoses of these species and analyses new and previously published sequences from the cytochrome oxidase I barcoding gene, thus showing the utility of this gene to identifyspecies.
Abstract: Distinguishing the various Recent taxa of the pteropod genus Creseis, especially the nominal species Creseis acicula (Rang, 1828), C. clava (Rang, 1828), C. virgula (Rang, 1828 )a ndC. conica Eschscholtz, 1829, has long been problematic. Based on misinterpretations of the shell morphology, some of these were deemed to represent subspecies or forms, or were synonymized with other species in this group. Shell-morphological and nomenclatural evidence has recently been provided demonstrating that C. clava and C. acicula in fact represent a single species, for which the name C. clava is valid. Both C. conica and C. virgula represent independent species, and the same is true for C. chierchiae (Boas, 1886). This study recapitulates the background to the taxonomic problem, presents a summary of previously published morphological characters to identify species, provides diagnoses of these species and analyses new and previously published sequences from the cytochrome oxidase I barcoding gene, thus showing the utility of this gene to identify species. The data demonstrate that four Recent species should be recognized: C. clava, C. conica, C. virgula and C. chierchiae, but the last of these and its f. constricta, although clearly differing by shell-morphological characteristics, should be studied further by molecular techniques. Hyalocylis striata (Rang, 1828) and Styliola subula (Quoy & Gaimard, 1827), traditionally included in the Creseidae, are easily recognized on shell characteristics. A key to the identification of members of this family is provided.
TL;DR: Results indicate that the three Nipponacmea species can be efficiently identified by DNA barcoding and are possibly due to the local and regional hydrographic conditions in the Yangtze River estuary, the large salt marsh in the river delta and difference of temperature between northern and southern China.
Abstract: To identify the Nipponacmea limpets along the coast of China, their taxonomy was investigated with three molecular markers (one mitochondrial gene, COI; two nuclear markers, 28S rDNA and H3). Three species (N. radula, N. fuscoviridis and N. nigrans) were found among 274 individuals collected from 14 sites. Intraspecific variation was far less than interspecific variation and obvious barcoding gaps existed. These results indicate that the three Nipponacmea species can be efficiently identified by DNA barcoding. The phylogeographic patterns of the three species were also analysed using COI sequences. There was clear biogeographic separation between the northern N. radula and the southern two species (N. fuscoviridis and N. nigrans), with the Yangtze River estuary as a barrier. In the southern N. fuscoviridis, there was a star-shaped haplotype network and the dominant haplotype was detected in all populations. In the northern N. radula, there were five main haplotypes; some adjacent populations showed no significant difference according to the pairwise Fst values. The southern N. nigrans showed two main haplotypes. The phylogeographic break between the Nipponacmea species is possibly due to the local and regional hydrographic conditions in the Yangtze River estuary, the large salt marsh in the river delta and difference of temperature between northern and southern China.
TL;DR: Results suggest that E. viridis retained chloroplasts exclusively from C. tomentosum, and further analysis using starved individuals suggests carotenoid retention over Chls during the digestion of kleptoplasts.
Abstract: Some sacoglossan sea slugs are capable of retaining functional chloroplasts ‘stolen’ from macroalgae (kleptoplasts). The present study surveyed the pigment composition of the sea slug Elysia viridis (Montagu, 1804) and its food source Codium tomentosum from three different locations along the Portuguese coast. The pigments siphonaxanthin, trans and cis-neoxanthin, violaxanthin, siphonaxanthin dodecenoate, chlorophyll (Chl) a and Chl b, 1,1- and b,1-carotenes and an unidentified carotenoid were observed in all E. viridis analysed. With the exception of the unidentified carotenoid, the same pigment profile was recorded for the macroalga C. tomentosum. Pigments characteristic of other macroalgae present in the sampling locations (Ulva sp. or the epiphyte Ceramium sp. present on C. tomentosum) were not detected in the slugs (Chl c, fucoxanthin, lutein, b,b-carotene). These results suggest that E. viridis retained chloroplasts exclusively from C. tomentosum. The differentiation between sea slugs and respective food source from different locations indicated that the site of collection was less relevant to the separation of groups than differences between the macroalgae and the sea slugs. In general, the carotenoids to Chl a ratios were significantly higher in E. viridis than in C. tomentosum. Further analysis using starved individuals suggests carotenoid retention over Chls during the digestion of kleptoplasts. Finally, despite a loss of 80% of Chl a in E. viridis starved for 2 weeks, measurements of maximum quantum yield of photosystem II (Fv/Fm) using variable Chl a fluorescence indicated a decrease of only 5% of the photosynthetic capacity of kleptoplasts.
TL;DR: Histological analyses revealed specialized morphological structures of the digestive gland (‘cisternae’ and ‘fine tubuli’) that house Symbiodinium that suggest an advanced state of mutualistic symbiosis that enables M. engeli to survive times of food shortage.
Abstract: For the first time, specimens of the nudibranch Melibe engeli hosting zooxanthellae (Symbiodinium spp.) were cultured for more than 9 months in aquaria in order to study this symbiotic system. Melibe engeli, in contrast to other previously studied ‘solar-powered’ nudibranchs, does not obtain its symbionts by feeding on prey that house Symbiodinium, but as by-catch from the water column. Specimens were exposed to different experimental conditions (nonfeeding vs feeding, light vs darkness) to estimate the efficiency of this putative mutualistic symbiosis. Photosynthetic efficiency of Symbiodinium measured by means of PAM fluorometry remained high, independent of experimental treatment. Specimens kept under nonfeeding conditions survived the whole experimental period, grew to modest size and laid fertile egg clutches continuously. Specimens fed additionally with crustaceans and turbellarians grew faster and larger and laid more egg clutches, implying higher fecundity. Symbiodinium density was higher in fed specimens, but is potentially regulated actively by M. engeli through various mechanisms. Fed specimens kept in continuous darkness died relatively soon, suggesting that light is crucial for survival. Histological analyses revealed specialized morphological structures of the digestive gland (‘cisternae’ and ‘fine tubuli’) that house Symbiodinium. These data suggest an advanced state of mutualistic symbiosis that enables M. engeli to survive times of food shortage.
TL;DR: It is found that females respond to chemical cues significantly more strongly than males, suggesting that males may reduce their antipredator behaviour in order to increase the chance of mating, suggesting a trade-off between predation avoidance and reproduction.
Abstract: Many animals show alarm responses (ARs) to chemical cues released from predators or injured conspecifics. However, the prey often makes a trade-off between predation avoidance and reproduction, resulting in pronounced sex differences in AR and in sex-biased predation. This phenomenon has rarely been investigated in snails. The freshwater snail Pomacea canaliculata is reported to exhibit an AR to chemical cues released from predators or injured conspecifics. Here, we investigate the sex differences in AR in the snail to chemical cues released from its predator turtle Chinemys reevesii and injured conspecifics. By exposing adult females and males of equivalent size to turtles, we also evaluate the sex-biased predation in the snail. We find that females respond to chemical cues significantly more strongly than males. The predation experiment shows that more females survived than males after a week of predation. These results suggest that males may reduce their antipredator behaviour in order to increase the chance of mating, suggesting a trade-off between predation avoidance and reproduction.
TL;DR: It is found that S. souverbiana consumed and damaged all available species, but showed a strong preference for the most abundant and moderately digestible Z. capricorni and H. ovalis, and the former was preferred when both were available.
Abstract: By amalgamating all seagrass-associated grazing invertebrates into an epiphyte-feeding guild, the currently accepted model of seagrass trophic dynamics ignores the diverse range of invertebrates that feed directly on, and do considerable damage to, seagrasses. Of the wide range of invertebrates documented to damage seagrass directly, the gastropod genus Smaragdia has adaptations and ecology that suggests it could be a specialized seagrass-feeding group, of which at least two species are known preferentially to consume seagrass. This paper investigated the dietary associations of Smaragdia souverbiana, one of the most widely distributed but least studied species of the genus, in the subtropical eastern Australian part of its range. Using field-based assessments of grazing damage and targeted laboratory feeding trials, we assessed the dietary associations, digestive ability and feeding preferences of S. souverbiana with local seagrasses (Halophila ovalis, Zostera capricorni and Cymodocea serrulata). We found that this species consumed and damaged all available species, but showed a strong preference for the most abundant and moderately digestible Z. capricorni. Although it avoided seagrass bearing a high epiphyte load in a laboratory context, considerable amounts of epiphytic material were found in the faeces of field-caught individuals. Grazing and digestibility of seagrass cells was higher in Z. capricorni and H. ovalis, and the former was preferred when both were available. This study adds to the growing body of literature demonstrating that S. souverbiana - and potentially many other grazing invertebrates - cause considerable damage to seagrasses directly, rather than targeting epiphytes.
TL;DR: The morphology and ecology of representatives of the taxonomically ambiguous genus Trochulus, which comprises several genetically highly divergent mitochondrial clades, is investigated and it is suggested that its subspecies spent at least the last glaciation in or close to the presently inhabited areas.
Abstract: In this study we investigated the morphology and ecology of representatives of the taxonomically ambiguous genus Trochulus. The main focus was on the T. hispidus complex, which comprises several genetically highly divergent mitochondrial clades, as determined in a parallel molecular genetic study. We analysed shell morphology and anatomical traits and asked whether the clades are differentiated in these characters. In addition, the related species T. oreinos and T. striolatus were investigated and compared with the T. hispidus complex. Finally, we compared the ecological requirements of the taxa. Among the genetic clades of the T. hispidus complex there was no clear morphological differentiation and geographic populations could not be distinguished based on their morphology. The investigated characters of the genital anatomy did not allow discrimination of any of the T. hispidus clades and were not even diagnostic for the group as a whole. The morphotype of T. sericeus is present in all clades and thus cannot be assigned to a genetic group or any specific population. Thus, our morphological data do not provide evidence that any of the mitochondrial T. hispidus clades represent separate species. Concerning interspecific delimitation, the T. hispidus complex was clearly differentiated from T. striolatus and T. oreinos by shell morphological and anatomical characters, e.g. sculpture of shell surface and details of the penis. Finally, the habitat of T. oreinos is different from those of the other two species. In contrast to the lack of correspondence between genetic and morphological differentiation within the T. hispidus complex, related species display intraspecific morphological differentiation corresponding with mitochondrial clades: within T. striolatus there was a slight morphological differentiation between the subspecies T. s. striolatus, T. s. juvavensis and T. s. danubialis. The two subspecies of T. oreinos could be discriminated by a small but consistent difference in the cross-section of the penis. The unequal levels of intraspecific differentiation are caused by different evolutionary histories as a consequence of disparities in ecological demands, dispersal ability and use of glacial refugia: both the T. hispidus complex and T. striolatus are fast-spreading, euryoecious organisms which are able to (re-)colonize habitats and survive under different climate conditions. While the T. hispidus complex probably survived the Pleistocene in several glacial refugia, for T. striolatus one glacial refugium is suggested. Trochulus oreinos differs from the other taxa, as it is a slow disperser with a narrow ecological niche. We suggest that its subspecies spent at least the last glaciation in or close to the presently inhabited areas.
TL;DR: This research aims to demonstrate the efforts towards in-situ applicability of EMMARM, which aims to provide real-time information about the response of the immune system to EMTs.
Abstract: Wallace M. Meyer, III1, Deena T. A. Gary2, Norine W. Yeung2,3, Clarissa Dirks4, Kelley Leung2, Julian A. Leon2, Dylan T. B. Ressler2, Patrick A. Curry2 and Kenneth A. Hayes3,5 Department of Biology, Pomona College, 175 W 6th Street, Claremont, CA 91711, USA; Pacific Biosciences Research Center, University of Hawaii, Manoa, Honolulu, HI 96822, USA; National Museum of Natural History, Smithsonian Institution, Washington, DC, USA; The Evergreen State College, 2700 Evergreen Parkway NW, Olympia, WA 98505, USA; and Department of Biology, Howard University, 415 College St. NW, Washington, DC 20059, USA
TL;DR: This paper aims to demonstrate the efforts towards in-situ applicability of EMMARM, as to provide real-time information about concrete mechanical properties such as E-modulus and compressive strength.
Abstract: Ph.D. Grant SFRH/
BD/77872/2011 of the Portuguese Foundation for Science and
Technology (FCT)
TL;DR: Comparison of the adult mode of life with those of modern cephalopods suggested that ammonites of the suborder Ancyloceratina had developed a stationary brooding phase that could have several ecological advantages over free-swimming monomorph ammonites.
Abstract: Cretaceous heteromorph ammonites of the suborder Ancyloceratina had a striking ontogenetic change in their shell shape. Juveniles had virtually all possible types of coiling of their shells, ranging from regular planispiral and orthoconic to torticonic, hamitoconic and gyroconic. The adults uncoiled the last whorl of their shell forming a U-shaped recurved body chamber with the aperture facing upward. Examination of ribbing pattern and its resolution in various parts of the living chamber in 11 species revealed that the ribs were less developed and had some traces of wear on the inner surface of the hooked chamber, being well developed both on the lateral and outer lower parts. This could indicate that the adult animals were semi-loosely hooked (Ancyloceras, Macroscaphites) or permanently clipped (Scaphites, Hoploscaphites) onto either horizontal or upwardly angled stipes of non-calcified algal macrophytes or branched animals. Comparison of the adult mode of life with those of modern cephalopods suggested that ammonites of the suborder Ancyloceratina had developed a stationary brooding phase that could have several ecological advantages over free-swimming monomorph ammonites.
TL;DR: Soft-body characters do not contradict, and may even support, the counterintuitive sister-group relationship with shell-less, wormshaped Rhodopemorpha, and structural diversity among minute lower Heterobranchia is highlighted.
Abstract: The Murchisonellidae are a small taxon of minute snails with a high-spired shell that occur in shallow marine habitats. Molecular phylogenetics recently revealed that they are not members of the externally similar yet phylogenetically derived Pyramidellidae, but instead potentially one of the oldest clades among the heterobranch Gastropoda. Furthermore, current data surprisingly indicate a sister-group relationship with Rhodopemorpha, highly aberrant marine slugs with previously unclear affinities. Murchisonellidae are characterized by a specialized pincer-like radula, but very little further data exist on soft-body anatomy for most species, and there are only a few observations of living animals. Investigation of the anatomy of Murchisonellidae may thus yield new data providing insights into early heterobranch evolution and that of enigmatic Rhodopemorpha. We collected live specimens of the murchisonellid Koloonella cf. minutissima (Laseron, 1951), a member of a genus known mainly from eastern Australia. We provide detailed live photographs and interactive 3D data on all major organ systems, based on serial histological sections. The mantle cavity is shown to contain several distinct glands, a pair of which is conspicuously similar to glands found in Rhodopemorpha. The anterior digestive system contains a unique four-toothed radula, a feeble pharynx and a special, vacuolated oesophageal bulb. The reproductive system is complex and diaulic, and contains unusual structures. These results highlight structural diversity among minute lower Heterobranchia. Soft-body characters do not contradict, and may even support, the counterintuitive sister-group relationship with shell-less, wormshaped Rhodopemorpha. The classification of Murchisonellidae is discussed and a revised scheme is proposed.
TL;DR: Comparison of family representation, species richness and body-size patterns across site to continental scales for the North American terrestrial gastropod fauna shows assumptions of self-similarity between observational scales in terrestrial Gastropods are inappropriate.
Abstract: Some suggest that because of scale independence major biodiversity metrics can be estimated at large scales from analysis of a well chosen suite of individual sites. Others have attempted to estimate individual site patterns from analysis of the continental pool. But does such cross-scale extrapolation work? This issue is addressed for the North American terrestrial gastropod fauna by comparison of family representation, species richness and body-size patterns across site to continental scales. These data demonstrate profound differences: while the continental fauna is dominated by large body-size families such as the Polygyridae, Helminthoglyptidae, Oreohelicidae, Succineidae and Urocoptidae, average site faunas are most frequently represented by small body-sized families like the Vertiginidae, Gastrodontidae, Oxychilidae, Euconulidae, Punctidae, Valloniidae, Strobilopsidae and Ellobiidae. Species richness within sites tends to be 2–7 times smaller than random draws of individuals of the same number from regional or continental pools, indicating the potential for strong bias in the construction of site faunas. And, while the body-size spectrum for average site faunas is strongly right-skewed, the continental pool is strongly left-skewed. Thus, although taxa with biovolumes .16 mm 3 dominate the continental fauna (79.4% of total), they make up only a small average fraction (4.1%) of individual site species lists. Within most regions, site faunas are overrepresented in species with biovolumes , 4m m 3 and underrepresented in species with biovolumes .128 mm 3 as compared with the regional pool. As a result, assumptions of self-similarity between observational scales in terrestrial gastropods are inappropriate.