Showing papers in "The Biological Bulletin in 2019"
TL;DR: It is hypothesized that similar mechanisms at the organism level will lead to similar adaptive consequences at the population level across taxa, among which the formation of egg banks, the coexistence of species, and the possibility of differentiation among populations and local adaptation stand out.
Abstract: An in-depth look at the basic aspects of dormancy in cyclic parthenogenetic organisms is now possible thanks to research efforts conducted over the past two decades with rotifer dormant embryos. In this review, we assemble and compose the current knowledge on four central themes: (1) distribution of dormancy in animals, with an overview on the phylogenetic distribution of embryo dormancy in metazoans, and (2) physiological and cellular processes involved in dormancy, with a strong emphasis on the dormant embryos of cyclically parthenogenetic monogonont rotifers; and discussions of (3) the selective pressures and (4) the evolutionary and population implications of dormancy in these animals. Dormancy in metazoans is a widespread phenomenon with taxon-specific features, and rotifers are among the animals in which dormancy is an intrinsic feature of their life cycle. Our review shows that embryo dormancy in rotifers shares common functional pathways with other taxa at the molecular and cellular level, despite the independent evolution of dormancy across phyla. These pathways include the arrest of similar metabolic routes and the usage of common metabolites for the stabilization of cellular structures and to confer stress resistance. We conclude that specific features of recurrent harsh environmental conditions are a powerful selective pressure for the fine-tuning of dormancy patterns in rotifers. We hypothesize that similar mechanisms at the organism level will lead to similar adaptive consequences at the population level across taxa, among which the formation of egg banks, the coexistence of species, and the possibility of differentiation among populations and local adaptation stand out. Our review shows how studies of rotifers have contributed to improved knowledge of all of these aspects.
35 citations
TL;DR: This review examines how the understanding of programmed developmental and metabolic arrest during diapause intersects with the increasing body of knowledge about animal co-development and co-evolution with microorganisms to find research questions that bridge the historically distinct fields of seasonal ecology and host-microbe interactions.
Abstract: Dormancy and diapause are key adaptations in many organisms, enabling survival of temporarily or seasonally unsuitable environmental conditions. In this review, we examine how our understanding of programmed developmental and metabolic arrest during diapause intersects with the increasing body of knowledge about animal co-development and co-evolution with microorganisms. Host-microbe interactions are increasingly understood to affect a number of metabolic, physiological, developmental, and behavioral traits and to mediate adaptations to various environments. Therefore, it is timely to consider how microbial factors might affect the expression and evolution of diapause in a changing world. We examine how a range of host-microbe interactions, from pathogenic to mutualistic, may have an impact on diapause phenotypes. Conversely, we examine how the discontinuities that diapause introduces into animal host generations can affect the ecology of microbial communities and the evolution of host-microbe interactions. We discuss these issues as they relate to physiology, evolution of development, local adaptation, disease ecology, and environmental change. Finally, we outline research questions that bridge the historically distinct fields of seasonal ecology and host-microbe interactions.
30 citations
TL;DR: Evidence supporting the neurotransmitter role of GABA in gastropod molluscs is reviewed, with an emphasis on its presence in identified neurons and well-characterized neural circuits, to indicate that GABAergic signaling participates in the selection and specification of motor programs, as well as the bilateral coordination of motor circuits.
Abstract: The neurotransmitter gamma-aminobutyric acid (GABA) is widely distributed in the mammalian central nervous system, where it acts as a major mediator of synaptic inhibition. GABA also serves as a neurotransmitter in a range of invertebrate phyla, including arthropods, echinoderms, annelids, nematodes, and platyhelminthes. This article reviews evidence supporting the neurotransmitter role of GABA in gastropod molluscs, with an emphasis on its presence in identified neurons and well-characterized neural circuits. The collective findings indicate that GABAergic signaling participates in the selection and specification of motor programs, as well as the bilateral coordination of motor circuits. While relatively few in number, GABAergic neurons can influence neural circuits via inhibitory, excitatory, and modulatory synaptic actions. GABA's colocalization with peptidergic and classical neurotransmitters can broaden its integrative capacity. The functional properties of GABAergic neurons in simpler gastropod systems may provide insight into the role of this neurotransmitter phenotype in more complex brains.
27 citations
TL;DR: This review provides a summary of the current understanding of noncoding RNAs and their involvement in regulating dormancy.
Abstract: Dormancy is evolutionarily widespread and can take many forms, including diapause, dauer formation, estivation, and hibernation. Each type of dormancy is characterized by distinct features; but accumulating evidence suggests that each is regulated by some common processes, often referred to as a common "toolkit" of regulatory mechanisms, that likely include noncoding RNAs that regulate gene expression. Noncoding RNAs, especially microRNAs, are well-known regulators of biological processes associated with numerous dormancy-related processes, including cell cycle progression, cell growth and proliferation, developmental timing, metabolism, and environmental stress tolerance. This review provides a summary of our current understanding of noncoding RNAs and their involvement in regulating dormancy.
24 citations
TL;DR: This work investigates whether a colored patch, the meral spot, signals weapon performance in the stomatopod Neogonodactylus oerstedii and finds that darker meral spots correlate with higher strike impulse, which reflects the total force integrated over time.
Abstract: During animal contests over resources, opponents often signal their fighting ability in an attempt to avoid escalating to physical attack. A reliable signal is beneficial to receivers because it allows them to avoid injuries from engaging in contests they are unlikely to win. However, a signaler could benefit from deceiving an opponent by signaling greater fighting ability or greater aggressive intent than the signaler possesses. Therefore, the reliability of agonistic signals has long intrigued researchers. We investigated whether a colored patch, the meral spot, signals weapon performance in the stomatopod Neogonodactylus oerstedii. During fights over possession of refuges, stomatopods can injure or even kill opponents with their ultrafast strike. We found that darker meral spots correlate with higher strike impulse, which reflects the total force integrated over time. Furthermore, we demonstrate that stomatopods that strike more often with both appendages have darker meral spots and that the first hit in a two-appendage strike has a greater mean strike impulse than that of a single-appendage strike. This indicates that stomatopods with darker meral spots tend to invest more energy in each strike. Our results provide evidence that stomatopods use total reflectance as an honest signal of weapon performance or aggressive intent. This improves our understanding of the evolution of agonistic signals.
15 citations
TL;DR: Long-lasting embryonic dormancy in invertebrates defies the authors' understanding of what constitutes life because, for example, eggs of some copepods can delay hatching for decades or even centuri...
Abstract: Long-lasting embryonic dormancy in invertebrates defies our understanding of what constitutes life because, for example, eggs of some copepods can delay hatching for decades or even centuri...
15 citations
TL;DR: It appears as if the most obvious impacts of the bleeding process take place during the first one to two weeks after crabs are bled, with the greatest differences between bled and control females.
Abstract: Horseshoe crabs are harvested by the biomedical industry in order to create Limulus amebocyte lysate to test medical devices and pharmaceutical drugs for endotoxins. Most previous studies o...
14 citations
TL;DR: Low larval pH magnified the impact of larval nutritional stress on competence for metamorphosis and increased carryover effects of larVAL nutrition on juvenile growth, and Trans-life-cycle effects of Larval nutrition were thus modulated by larval exposure to ocean acidification.
Abstract: Ocean acidification poses a significant threat to calcifying invertebrates by negatively influencing shell deposition and growth. An organism's performance under ocean acidification is not determined by the susceptibility of one single life-history stage, nor is it solely controlled by the direct physical consequences of ocean acidification. Shell development by one life-history stage is sometimes a function of the pH or pCO2 levels experienced during earlier developmental stages. Furthermore, environmental factors such as access to nutrition can buffer organismal responses of calcifying invertebrates to ocean acidification, or they can function as a co-occurring stressor when access is low. We reared larvae and juveniles of the planktotrophic marine gastropod Crepidula fornicata through combined treatments of nutritional stress and low pH, and we monitored how multiple stressors endured during the larval stage affected juvenile performance. Shell growth responded non-linearly to decreasing pH, significantly declining between pH 7.6 and pH 7.5 in larvae and juveniles. Larval rearing at pH 7.5 reduced juvenile growth as a carryover effect. Larval rearing at pH 7.6 reduced subsequent juvenile growth despite the absence of a negative impact on larval growth, demonstrating a latent effect. Low larval pH magnified the impact of larval nutritional stress on competence for metamorphosis and increased carryover effects of larval nutrition on juvenile growth. Trans-life-cycle effects of larval nutrition were thus modulated by larval exposure to ocean acidification.
11 citations
TL;DR: It is shown that Arctic Calanus has a broad depth distribution in winter, indicating that diapause at depth is a facultative strategy and implications for the species’ roles in Arctic ecosystems are suggested.
Abstract: Diapause at depth is considered an integral part of the life cycle of Calanus copepods, but few studies have focused on the Arctic species Calanus glacialis and Calanus hyperboreus. By anal...
11 citations
TL;DR: Gene expression profiling studies on the life cycle and diapause program of Neocalanus flemingeri Miller that were conducted as part of a long-term observation program in the northern Gulf of Alaska are reviewed and related to the ecology of this species and to that of other calanids.
Abstract: Post-embryonic diapause in copepods is an adaptation that allows species in the copepod family Calanidae to thrive in high-latitude environments by transforming a short spring phytoplankton bloom into large numbers of lipid-rich individuals capable of surviving a long period of starvation. The copepods, with their high-energy lipid reservoirs, are a critical food source for higher trophic levels, making the Calanidae a key component of high-latitude marine ecosystems. The physiological ecology of the developmental program remains poorly understood. However, new studies using high-throughput RNA sequencing approaches are giving detailed access to physiological status by generating gene expression profiles for both field-collected and laboratory-incubated individuals. These are beginning to characterize the diapause phenotype, elucidate the transcriptional and physiological progression through the diapause program, and illustrate the effects of organism-environment interactions. This paper reviews gene expression profiling studies on the life cycle and diapause program of Neocalanus flemingeri Miller (1988) that were conducted as part of a long-term observation program in the northern Gulf of Alaska. It summarizes recent findings and relates them to the ecology of this species and to that of other calanids.
11 citations
TL;DR: The results suggest two possible scenarios by which the morphology of the phoronid lophophore has transformed over evolutionary time, consistent with the view that theLophophorates are monophyletic.
Abstract: Confocal laser scanning microscopy was used to study the myoanatomy of the lophophore of three phoronids with different types of lophophore: Phoronis ijimai, Phoronis australis, and Phoronopsis harmeri. A four-part ground plan of the lophophoral musculature was detected in all three species and was previously reported for Phoronis ovalis. The ground plan includes (i) a circular muscle, (ii) longitudinal muscles of the tentacular lamina, (iii) groups of paired distal muscles of the tentacular lamina, and (iv) frontal and abfrontal muscles of the tentacles. In P. australis, the tentacular lamina contains strong abfrontal and numerous frontal muscles. Phoronis harmeri has an inner circular muscle and arch-like muscles. Among all studied phoronids, the four-part ground plan of the lophophoral musculature is least complex in P. ijimai, which has a horseshoe-shaped lophophore. The results suggest two possible scenarios by which the morphology of the phoronid lophophore has transformed over evolutionary time. According to the first scenario, the morphology of the ancestral horseshoe-shaped lophophore became more complicated in the case of most phoronids but became simplified in the case of P. ovalis and bryozoans. According to the second scenario, the lophophore gradually transformed from a simple oval shape to a horseshoe shape and then to a spiral shape. The four-part ground plan of the lophophoral musculature is also present in bryozoans, which is consistent with the view that the lophophorates are monophyletic.
TL;DR: The results imply that the timing of diapause termination and subsequent migration to the surface may be delayed if copepods are exposed to oil pollution during diAPause or diappause termination, which could have detrimental effects on ecosystem dynamics.
Abstract: Calanus finmarchicus and Calanus glacialis are keystone zooplankton species in North Atlantic and Arctic marine ecosystems because they form a link in the trophic transfer of nutritious lip...
TL;DR: This was the first study to monitor individuals in the same population of oyster toadfish in situ continuously throughout the mating season, and the pulse repetition rate of the tonal part of the call was significantly related to ambient water temperature during both short-term and long-term monitoring.
Abstract: Acoustic communication is vital across many taxa for mating behavior, defense, and social interactions. Male oyster toadfish, Opsanus tau, produce courtship calls, or “boatwhistles,” charac...
TL;DR: It is suggested that larger clones experience a greater number of somatic cell divisions and consequently have an elevated potential to accumulate mutations, and corals at shallower depths may be exposed to abiotic conditions such as elevated thermal regimes, which promote increased mutation rates.
Abstract: In modular organisms, the propagation of genetic variability within a clonal unit can alter the scale at which ecological and evolutionary processes operate. Genetic variation within an ind...
TL;DR: In this paper, the effects of salinity stress on behavior (movement distance) and patterns of gene expression (using RNA sequencing) of the intertidal gastropod Batillaria attramentaria were investigated.
Abstract: Salinity is one of the most crucial environmental factors that structures biogeographic boundaries of aquatic organisms, affecting distribution, abundance, and behavior. However, the association between behavior and gene regulation underlying acclimation to changes in salinity remains poorly understood. In this study, we investigated the effects of salinity stress on behavior (movement distance) and patterns of gene expression (using RNA sequencing) of the intertidal gastropod Batillaria attramentaria. We examined responses to short-term (1-hour) and long-term (30-day) acclimation to a range of salinities (43, 33 [control], 23, 13, and 3 psu). We found that the intertidal B. attramentaria is able to tolerate a broad range of salinity from 13 to 43 psu but not the acute low salinity of 3 psu. Behavioral experiments showed that salt stress significantly influenced snails' movement, with lower salinity resulting in shorter movement distance. Transcriptomic analyses revealed critical metabolic pathways and genes potentially involved in acclimation to salinity stress, including ionic and osmotic regulation, signal and hormonal transduction pathways, water exchange, cell protection, and gene regulation or epigenetic modification. In general, our study presents a robust, integrative laboratory-based approach to investigate the effects of salt stress on a nonmodel gastropod facing detrimental consequences of environmental change. The current genetic results provide a wealth of reference data for further research on mechanisms of ionic and osmotic regulation and adaptive evolution of this coastal gastropod.
TL;DR: It is shown that although the distribution of the genetic cline has not appreciably changed, there is a notable association of decreased reproductive output at lower latitudes of the distribution in the “northern” lineage of B. glandula.
Abstract: The barnacle Balanus glandula is a broadly distributed species in the temperate northeastern Pacific that is notable for a robust genetic cline between about 36° and 40° N latitude. Prior work established the evolutionary origins of this pattern and proposed that it is maintained by environmental selection. In recent years, "climate velocity" studies in marine habitats have shown dramatic distributional shifts for many species as they track their preferred temperature range in a warming ocean. We re-sampled B. glandula across its entire geographic range to determine whether there has been any shift in this genetic distribution, a development signaling that temperature or other climate factors are maintaining this genetic cline. Additionally, we asked whether the spatially distributed mitochondrial lineages also vary in reproductive output with latitude, using location as a proxy for temperature and other coastal environmental factors. Here we show that although the distribution of the genetic cline has not appreciably changed, there is a notable association of decreased reproductive output at lower latitudes of the distribution in the "northern" lineage of B. glandula.
TL;DR: The authors found a significant reduction in auditory-evoked fast-starts that lasted for at least 24 hours after fish were returned to normoxic conditions, and whether hypoxia has a prolonged impact on behavior once the fish are returned tonormoxic conditions.
Abstract: Anthropogenic activities and climate change have resulted in an increase of hypoxic conditions in nearshore ecosystems worldwide. Depending on the persistence of a hypoxic event, the survival of aquatic animals can be compromised. Temperate fish exposed to hypoxia display a reduction in the probability of eliciting startle responses thought to be important for escape from predation. Here we examine the effect of hypoxia on the probability of eliciting fast-startle responses (fast-starts) of a tropical fish, the white grunt (Haemulon plumieri), and whether hypoxia has a prolonged impact on behavior once the fish are returned to normoxic conditions. White grunts collected from the San Juan Bay Estuary in Puerto Rico were exposed to an oxygen concentration of 2.5 mg L-1 (40% dissolved oxygen). We found a significant reduction in auditory-evoked fast-starts that lasted for at least 24 hours after fish were returned to normoxic conditions. Accessibility to the neuronal networks that underlie startle responses was an important motivator for this study. Mauthner cells are identifiable neurons found in most fish and amphibians, and these cells are known to initiate fast-starts in teleost fishes. The assumption that most of the short-latency responses in this study are Mauthner cell initiated provided the impetus to characterize the white grunt Mauthner cell. The identification of the cell provides a first step in understanding how low oxygen levels may impact a single cell and its circuit and the behavior it initiates.
TL;DR: Retaining an array of different nematocyst types to deliver a single venom, rather than sustaining the high metabolic cost necessary to maintain a dynamically evolving venom, may be more advantageous, given the vastly different interspecific interactions that adult medusa encounter in coastal zones.
Abstract: In this quantitative proteomics study we determined the variety and relative abundance of toxins present in enriched preparations of two nematocyst types isolated from the primary tentacles...
TL;DR: It is hypothesized that Hydra evolved in an unstable freshwater habitat in which survival required that its life cycle include the use of a bet-hedging reproductive strategy and the formation of an embryo that is desiccation resistant and that can remain dormant for long periods of time.
Abstract: Despite the fact that Hydra has been studied for more than 200 years, we know surprisingly little about its life history. We show that Hydra vulgaris embryos hatch sporadically over a perio...
TL;DR: Molluscan veliger larvae and some annelid larvae capture particulate food between a preoral prototrochal band of long cilia that create a current for both swimming and feeding and a postora as discussed by the authors.
Abstract: Molluscan veliger larvae and some annelid larvae capture particulate food between a preoral prototrochal band of long cilia that create a current for both swimming and feeding and a postora...
TL;DR: The characterization of the structure, development, and composition of pens from Doryteuthis pealeii is reported, concluding that the pen is one of the least complex, load-bearing, chitin-rich structures currently known and is amenable to further studies to elucidate natural construction mechanisms using chit in and protein.
Abstract: The pen, or gladius, of the squid is an internalized shell It serves as a site of attachment for important muscle groups and as a protective barrier for the visceral organs The pen's durability and flexibility are derived from its unique composition of chitin and protein We report the characterization of the structure, development, and composition of pens from Doryteuthis pealeii The nanofibrils of the polysaccharide β-chitin are arranged in an aligned configuration in only specific regions of the pen Chitin is secreted early in development, enabling us to characterize the changes in pen morphology prior to hatching The chitin and proteins are assembled in the shell sac surrounded by fluid that has a significantly different ionic composition from squid plasma Two groups of proteins are associated with the pen: those on its surface and those embedded within the pen Only 20 proteins are identified as embedded within the pen Embedded proteins are classified into six groups, including chitin associated, protease, protease inhibitors, intracellular, extracellular matrix, and those that are unknown The pen proteins share many conserved domains with proteins from other chitinous structures We conclude that the pen is one of the least complex, load-bearing, chitin-rich structures currently known and is amenable to further studies to elucidate natural construction mechanisms using chitin and protein
TL;DR: Evidence is presented that proteins in the colloblasts of the ctenophore Pleurobrachia bachei incorporate catecholic compounds similar to the amino acids l-3,4-dihydroxyphenylalanine and its derivatives in cnidarian nerves, suggesting that they may play a role in prey capture and in association with the subepithelial nerve net.
Abstract: Ctenophores, or comb jellies, are among the earliest-diverging extant animal lineages. Several recent phylogenomic studies suggest that they may even be the sister group to all other animal...
TL;DR: Variation in diet between locations suggests that the slugs may be exhibiting local adaptation in their dietary choices, and it highlights ecological differences between the Caribbean-wide reef-dwelling ecotypes and the mangrove lagoon ecotypes found in the Florida Keys.
Abstract: Sacoglossan sea slugs feed by suctorially consuming siphonaceous green algae. Most sacoglossan species are feeding specialists, but the Caribbean coral reef-dwelling Elysia crispata is poly...
TL;DR: This work regards this orthonectid found from the marine worm Xenoturbella bocki as a new species, Rhopalura xenoturbellae sp.
Abstract: Orthonectida is a phylum of marine invertebrates known to parasitize many invertebrate animals. Because of its simple body plan, it was suggested that it belong to Mesozoa, together with Di...
TL;DR: The optimal and lethal temperatures of larval sea urchins are document and used to calculate the warming tolerance and the thermal safety margin of early larval stages of seven tropical species, showing that the optimal temperature is very close to the lethal temperature.
Abstract: In species with complex life cycles, early developmental stages are often less thermally tolerant than adults, suggesting that they are key to predicting organismal response to environmental warming. Here we document the optimal and lethal temperatures of larval sea urchins, and we use those to calculate the warming tolerance and the thermal safety margin of early larval stages of seven tropical species. Larvae of Echinometra viridis, Echinometra lucunter, Lytechinus williamsi, Eucidaris tribuloides, Tripneustes ventricosus, Clypeaster rosaceus, and Clypeaster subdepressus were reared at 26, 28, 30, 32, and 34 °C for 6 days. The temperatures at which statistically significant reductions in larval performance are evident are generally the same temperatures at which statistically significant reductions in larval survival were detected, showing that the optimal temperature is very close to the lethal temperature. The two Echinometra species had significantly higher thermal tolerance than the other species, with some surviving culture temperatures of 34 °C and showing minimal impacts on growth and survival at 32 °C. In the other species, larval growth and survival were depressed at and above 30 or 32 °C. Overall, these larvae have lower warming tolerances (1 to 5 °C) and smaller thermal safety margins (-3 to 3 °C) than adults. Survival differences among treatments were evident by the first sampling on day 2, and survival at the highest temperatures increased when embryos were exposed to warming after spending the first 24 hours at ambient temperature. This suggests that the first days of development are more sensitive to thermal stress than are later larval stages.
TL;DR: A mismatch between the species’ thermal tolerance and winter water temperature is the most likely mechanism for this failed invasion of the non-native sea anemone Sagartia elegans.
Abstract: Failed invasions can be a key component for understanding and controlling introduced populations because understanding mechanisms behind failures can improve effective controls. In 2000, the non-native sea anemone Sagartia elegans was first found in Salem, Massachusetts, and it recolonized each summer. No individuals of S. elegans have been found after 2010, despite intensive search efforts. A mismatch between the species' thermal tolerance and winter water temperature is the most likely mechanism for this failed invasion. In both laboratory- and field-based temperature growth studies, S. elegans began regressing at 11 °C, stopped asexually reproducing at 9 °C, and died by 4 °C. These temperatures are above the average winter sea surface temperature in the Gulf of Maine, therefore suggesting that S. elegans requires a warm-water refuge. Another potential contributor to the disappearance of S. elegans is low genetic diversity as a result of establishment of only females (likely clones) and no males.
TL;DR: Two juvenile specimens of a new species of Oreaster were collected at Parque Nacional Arrecife Alacranes and Triángulos Oeste in the southern Gulf of Mexico and DNA of mitochondrial loci identifies them as members of the same clade as cloning larvae ofOreaster found abundantly in waters of the Florida Current-Gulf Stream system.
Abstract: Two juvenile specimens of a new species of Oreaster were collected at Parque Nacional Arrecife Alacranes and Triangulos Oeste in the southern Gulf of Mexico. DNA of mitochondrial loci identifies them as members of the same clade as cloning larvae of Oreaster found abundantly in waters of the Florida Current-Gulf Stream system, and distinct from Oreaster clavatus and Oreaster reticulatus, the two known Oreasteridae species in the North Atlantic. Larvae from the new species of Oreaster persist as clones but also metamorphose and settle to the benthos with typical asteroid morphology.
TL;DR: Two colonial cnidarians were examined in this context, and the data suggest that scaling was negatively allometric in Sympodium sp.
Abstract: Metabolic activation can have a profound impact, for instance, by more than compensating for the lower resting metabolic rates of large organisms compared to smaller ones. In some animals, activity can easily be judged by the rate of muscle-driven movement. In sessile organisms, however, judging activity is less straightforward, although feeding often results in metabolic activation. Two colonial cnidarians were examined in this context, using entirely lab-grown material to remove any artifactual effects of experimental manipulations. Hydractinia symbiolongicarpus is a carnivorous hydroid that uses active muscular contractions to drive its gastrovascular fluid. Sympodium sp., on the other hand, is an octocoral that hosts photosynthetic Symbiodinium and uses cilia to propel its gastrovascular fluid. Measures of oxygen uptake indicated that feeding activated metabolism in H. symbiolongicarpus. While light treatment had no effect on subsequent dark metabolism in Sympodium sp., stress activated metabolism to an extent comparable to H. symbiolongicarpus. In both taxa, different individual size measures or synthetic size measures derived from principal component analysis produced different scaling relationships between metabolism and size. On balance, the data suggest that scaling was negatively allometric in Sympodium sp. and nearly isometric in H. symbiolongicarpus; yet metabolic activation was comparable in the two species. Regardless of the size measure used, active and resting colonies of H. symbiolongicarpus exhibited similar scaling relationships. Colonial animals may lack the large difference between resting and active metabolic rates found in highly active animals, and this may be related to how their metabolism scales with size.
TL;DR: The external anatomy, ciliary bands, neurons, and muscles were examined in the development of the brooded vitellaria larva of Ophioplocus esmarki, a brooding brittle star that is unable to swim in the water column.
Abstract: The bilaterally symmetrical, feeding larval stage is an ancestral condition in echinoderms. However, many echinoderms have evolved abbreviated development and form a pentamerous juvenile without a feeding larva. Abbreviated development with a non-feeding vitellaria larva is found in five families of brittle stars, but very little is known about this type of development. In this study, the external anatomy, ciliary bands, neurons, and muscles were examined in the development of the brooded vitellaria larva of Ophioplocus esmarki. The external morphology throughout development shows typical vitellaria features, including morphogenetic movements to set up the vitellaria body plan, an anterior preoral lobe, a posterior lobe, transverse ciliary bands, and development of juvenile structures on the mid-ventral side. An early population of neurons forms at the base of the preoral lobe at the pre-vitellaria stage after the initial formation of the coelomic cavities. These early neurons may be homologous to the apical neurons that develop in echinoderms with feeding larval forms. Neurons form close to the ciliary bands, but the vitellaria larva lacks the tracts of neurons associated with the ciliary bands found in echinoderms with feeding larvae. Additional neurons form in association with the axial complex and persist into the juvenile stage. Juvenile nerves and muscles form with pentamerous symmetry in the late vitellaria stage in a manner similar to their development within the late ophiopluteus larva. Even though O. esmarki is a brooding brittle star, its developmental sequence retains the general vitellaria shape and structure; however, the vitellaria larvae are unable to swim in the water column.
TL;DR: Gonadal maturity was delayed and gamete production was reduced in nearshore conchs compared to offshore animals, and it is apparent that some yet unidentified factor(s) is interfering with hormone production in the cerebral ganglia, to the detriment of gonad development and shell formation.
Abstract: In the Florida Keys, queen conchs (Lobatus gigas) occur in two spatially distinct regions: nearshore in habitats immediately adjacent to the shoreline and offshore in habitats along the ree...