Showing papers in "The Biological Bulletin in 2018"
TL;DR: This study enhances the understanding of the link between symbiont identity and the performance of the overall symbiosis, which is important for understanding the potential establishment and persistence of novel host-symbiont pairings.
Abstract: The genus Symbiodinium is physiologically diverse and so may differentially influence symbiosis establishment and function. To explore this, we inoculated aposymbiotic individuals of the sea anemone Exaiptasia pallida (commonly referred to as "Aiptasia"), a model for coral symbiosis, with one of five Symbiodinium species or types (S. microadriaticum, S. minutum, phylotype C3, S. trenchii, or S. voratum). The spatial pattern of colonization was monitored over time via confocal microscopy, and various physiological parameters were measured to assess symbiosis functionality. Anemones rapidly formed a symbiosis with the homologous symbiont, S. minutum, but struggled or failed to form a long-lasting symbiosis with Symbiodinium C3 or S. voratum, respectively. Symbiodinium microadriaticum and S. trenchii were successful but reached their peak density two weeks after S. minutum. The spatial pattern of colonization was identical for all Symbiodinium taxa that were ultimately successful, starting in the oral disk and progressing to the tentacles, before invading the column and, finally, the pedal disk. In all cases, proliferation through the anemone's tentacles was patchy, suggesting that symbionts were being expelled into the gastrovascular cavity and re-phagocytosed by the host. However, the timing of these various spatial events differed between the different Symbiodinium taxa. Furthermore, S. microadriaticum and S. trenchii were less beneficial to the host, as indicated by lower rates of photosynthesis, anemone growth, and pedal laceration. This study enhances our understanding of the link between symbiont identity and the performance of the overall symbiosis, which is important for understanding the potential establishment and persistence of novel host-symbiont pairings. Importantly, we also provide a baseline for further studies on this topic with the globally adopted "Aiptasia" model system.
43 citations
TL;DR: Study of biochemical bases for differential growth and energy utilization during larval growth of the bivalve Crassostrea gigas exposed to increasing levels of experimental ocean acidification reveals the mechanisms of resilience thresholds to environmental change.
Abstract: Exogenous environmental factors alter growth rates, yet information remains scant on the biochemical mechanisms and energy trade-offs that underlie variability in the growth of marine invertebrates. Here we study the biochemical bases for differential growth and energy utilization (as adenosine triphosphate [ATP] equivalents) during larval growth of the bivalve Crassostrea gigas exposed to increasing levels of experimental ocean acidification (control, middle, and high pCO2, corresponding to ∼400, ∼800, and ∼1100 µatm, respectively). Elevated pCO2 hindered larval ability to accrete both shell and whole-body protein content. This negative impact was not due to an inability to synthesize protein per se, because size-specific rates of protein synthesis were upregulated at both middle and high pCO2 treatments by as much as 45% relative to control pCO2. Rather, protein degradation rates increased with increasing pCO2. At control pCO2, 89% of cellular energy (ATP equivalents) utilization was accounted for by just 2 processes in larvae, with protein synthesis accounting for 66% and sodium-potassium transport accounting for 23%. The energetic demand necessitated by elevated protein synthesis rates could be accommodated either by reallocating available energy from within the existing ATP pool or by increasing the production of total ATP. The former strategy was observed at middle pCO2, while the latter strategy was observed at high pCO2. Increased pCO2 also altered sodium-potassium transport, but with minimal impact on rates of ATP utilization relative to the impact observed for protein synthesis. Quantifying the actual energy costs and trade-offs for maintaining physiological homeostasis in response to stress will help to reveal the mechanisms of resilience thresholds to environmental change.
19 citations
TL;DR: Work presented here contradicts the canonical view that hemocyanins are restricted to molluscs and arthropods, suggesting that the occurrence of copper-based blood pigments in metazoans has been underestimated and support the idea of the presence of oxygen carrier hemocianins being widespread across metazans with an evolutionary history characterized by frequent losses.
Abstract: Among animals, two major groups of oxygen-binding proteins are found: proteins that use iron to bind oxygen (hemoglobins and hemerythrins) and two non-homologous hemocyanins that use copper...
18 citations
TL;DR: Investigation in the sea anemone Aiptasia pallida suggests a regulatory role of sphingolipid signaling in cnidarian-Symbiodinium symbiosis and symbiont uptake and upregulation of both rheostat enzymes on the first day of host recolonization by symbionts suggests a role for the rheastat in host-symbiont recognition during symbiosis onset.
Abstract: In host-microbe interactions, signaling lipids function in interpartner communication during both the establishment and maintenance of associations Previous evidence suggests that sphingolipids play a role in the mutualistic cnidarian-Symbiodinium symbiosis Exogenously applied sphingolipids have been shown to alter this partnership, though endogenous host regulation of sphingolipids by the sphingosine rheostat under different symbiotic conditions has not been characterized The rheostat regulates levels of pro-survival sphingosine-1-phosphate (S1P) and pro-apoptotic sphingosine (Sph) through catalytic activities of sphingosine kinase (SPHK) and S1P phosphatase (SGPP) The role of the rheostat in recognition and establishment of cnidarian-Symbiodinium symbiosis was investigated in the sea anemone Aiptasia pallida by measuring gene expression, protein levels, and sphingolipid metabolites in symbiotic, aposymbiotic, and newly recolonized anemones Comparison of two host populations showed that symb
14 citations
TL;DR: The pharmacological results are consistent with the involvement of TRP-like channels in mechanosensing by L. polyedra and the presence and function ofTRP channels in a dinoflagellate emphasize the evolutionary conservation of both the channel structures and their functions.
Abstract: Transient receptor potential (TRP) ion channels are common components of mechanosensing pathways, mainly described in mammals and other multicellular organisms. To gain insight into the evo...
14 citations
TL;DR: Variation in the quality and quantity of ROS generation and its implications for subsequent antioxidant production suggest that different stress mechanisms are at play in Symbiodinium cells during stress events.
Abstract: Oxidative stress inside cells occurs when the production of reactive oxygen species (ROS) is no longer efficiently counterbalanced by the generation of antioxidants. In this study, we measu...
14 citations
TL;DR: The collection and description of the smallest living specimens of K. polythalamius yet discovered are reported and the species identity of these individuals are confirmed by using sequences of three genetic markers.
Abstract: Kuphus polythalamius (Teredinidae) is one of the world’s largest, most rarely observed, and least understood bivalves. Kuphus polythalamius is also among the few shallow-water marine specie...
13 citations
TL;DR: It is concluded that obligate symbiosis with large sea anemones and cleaner mutualism with reef fishes both contribute to explaining aspects of the life history of Pederson shrimps, especially their apparent mating system of pure-search polygynandry.
Abstract: Cleaner organisms perform key functional roles in reducing rates of parasitism in marine communities. Pederson cleaner shrimps Ancylomenes pedersoni are major cleaners of reef fishes in the tropical western Atlantic and form obligate symbioses with host sea anemones. Information about their life-history traits would contribute to understanding how symbiosis impacts life-history evolution in crustaceans, but little is known about patterns of growth and reproduction in this anemone shrimp. We quantified growth, sexual reproduction, senescence, and mortality in individuals of A. pedersoni under laboratory conditions and their abundance and population size structure on coral reefs in St. Thomas, U.S. Virgin Islands. Von Bertalanffy growth curves were fitted to the data to determine age-size relationships, and the Beverton-Holt model was used to estimate mortality rates and size at maximum yield. Individuals grew rapidly when young, then slowed their growth after reaching sexual maturity at ~6 months. Individuals were gonochoric, with males attaining significantly smaller body sizes and shorter life spans than did females. Prior to death at <2 years, members of both genders exhibited senescence during which they ceased reproducing, shrank (females only), and decreased their activity levels over ~1-4 weeks. Field populations were abundant and composed mostly of juveniles during both years examined. Populations appeared to be stable but highly dynamic in terms of individuals, reaching maximum yield at 4 months of age. We conclude that obligate symbiosis with large sea anemones and cleaner mutualism with reef fishes both contribute to explaining aspects of the life history of Pederson shrimps, especially their apparent mating system of pure-search polygynandry. This life-history information also provides a scientific basis for sustainable fishery management and aquaculture of this key coral reef organism.
12 citations
TL;DR: It is proposed that the populations analyzed are divergent enough to constitute two different species from within this common Antarctic genus known for its phenotypic plasticity.
Abstract: Within the Southern Ocean, the Antarctic Circumpolar Current is hypothesized to facilitate a circumpolar distribution for many taxa, even though some, such as pycnogonids, are assumed to ha...
11 citations
TL;DR: The goal of this project was to identify the RNA and protein products of putative clock genes in the central nervous system of three nudibranchs, Hermissenda crassicornis, Melibe leonina, and Tritonia diomedea, and share greater sequence similarity with Mus musculus orthologs than Drosophila melanogaster Orthologs, which is consistent with the closer phylogenetic relationships recovered between lophotrochozoan and vertebrate ortholog
Abstract: While much is known about the genes and proteins that make up the circadian clocks in vertebrates and several arthropod species, much less is known about the clock genes in many other invertebrates, including nudibranchs. The goal of this project was to identify the RNA and protein products of putative clock genes in the central nervous system of three nudibranchs, Hermissenda crassicornis, Melibe leonina, and Tritonia diomedea. Using previously published transcriptomes (Hermissenda and Tritonia) and a new transcriptome (Melibe), we identified nudibranch orthologs for the products of five canonical clock genes: brain and muscle aryl hydrocarbon receptor nuclear translocator like protein 1, circadian locomotor output cycles kaput, non-photoreceptive cryptochrome, period, and timeless. Additionally, orthologous sequences for the products of five related genes-aryl hydrocarbon receptor nuclear translocator like, photoreceptive cryptochrome, cryptochrome DASH, 6-4 photolyase, and timeout-were determined. Phylogenetic analyses confirmed that the nudibranch proteins were most closely related to known orthologs in related invertebrates, such as oysters and annelids. In general, the nudibranch clock proteins shared greater sequence similarity with Mus musculus orthologs than Drosophila melanogaster orthologs, which is consistent with the closer phylogenetic relationships recovered between lophotrochozoan and vertebrate orthologs. The suite of clock-related genes in nudibranchs includes both photoreceptive and non-photoreceptive cryptochromes, as well as timeout and possibly timeless. Therefore, the nudibranch clock may resemble the one exhibited in mammals, or possibly even in non-drosopholid insects and oysters. The latter would be evidence supporting this as the ancestral clock for bilaterians.
11 citations
TL;DR: Female biochemical composition was not influenced by temperature, but ovarian maturation and spawning were inhibited at 33 °C, which indicates a negative effect of this temperature on nutrient transfer to the oocytes.
Abstract: Maternal provisioning is particularly important in invertebrates with abbreviated development because large energy reserves must be provided for the developing embryo. In this context, the objective of the present study was to analyze in an aquatic invertebrate with direct development the effect of temperature on female biochemical composition and reserve allocation to maturing ovaries, which determine egg quality. A decapod crustacean, the freshwater shrimp Neocaridina davidi, was used as experimental model. Newly hatched juveniles were exposed to 28 °C or 33 °C. Females showed mature ovaries and spawned at 28 °C (control ovigerous females), but no ovigerous female was found at 33 °C. After a 200-day period, half of the females at 33 °C were transferred to 28 °C, where they rapidly showed mature ovaries and spawned (transferred ovigerous females). Ovigerous females and females that did not spawn at 28 °C (control non-ovigerous females) and at 33 °C (high-temperature non-ovigerous females) were sacrificed to determine their biochemical composition. The number, volume, weight, and biochemical composition of the eggs from transferred and control ovigerous females were also analyzed as indicators of their quality. Female biochemical composition was not influenced by temperature, because control and high-temperature non-ovigerous females had similar lipid, protein, and glycogen contents. However, ovarian maturation and spawning were inhibited at 33 °C, which indicates a negative effect of this temperature on nutrient transfer to the oocytes. This effect was rapidly reversed after females were moved to 28 °C; the eggs from control and transferred ovigerous females were of similar quality, except for a lower protein content in the latter. The present results provide valuable information on reserve allocation to reproduction under thermal stress.
TL;DR: The dynamics of social interactions in the Tüpfel long-fin nacre mutant line is compared to wild-type zebrafish; and evidence is presented suggesting that differences could be a consequence of a disruption of proper visual social signals.
Abstract: Use of zebrafish as a model organism in biomedical research has led to the generation of many genetically modified mutant lines to investigate various aspects of developmental and cellular processes. However, the broader effects of the underlying mutations on social and motor behavior remain poorly examined. Here, we compared the dynamics of social interactions in the Tupfel long-fin nacre mutant line, which lacks skin pigmentation, to wild-type zebrafish; and we determined whether status-dependent differences in escape and swimming behavior existed within each strain. We show that despite similarities in aggressive activity, Tupfel long-fin nacre pairs exhibit unstable social relationships characterized by frequent reversals in social dominance compared to wild-type pairs. The lack of strong dominance relationships in Tupfel long-fin nacre pairs correlates with weak territoriality and overlapping spatial distribution of dominants and subordinates. Conversely, wild-type dominants displayed strong territoriality that severely limited the movement of subordinates. Additionally, the sensitivity of the startle escape response was significantly higher in wild-type subordinates compared to dominants. However, status-related differences in sensitivity of escape response in Tupfel long-fin nacre pairs were absent. Finally, we present evidence suggesting that these differences could be a consequence of a disruption of proper visual social signals. We show that in wild-type pairs dominants are more conspicuous, and that in wild-type and Tupfel long-fin nacre pairings wild-type fish are more likely to dominate Tupfel long-fin nacres. Our results serve as a cautionary note in research design when morphologically engineered zebrafish for color differences are utilized in the study of social behavior and central nervous system function.
TL;DR: Results indicate that albumen gland-capsule gland complex biosynthesis limits a constantly high reproductive output, and lowering fecundity by targeting biosynthesis could effectively reduce the rate of this species’ spread.
Abstract: High fecundity often contributes to successful invasives. In molluscs, this may be facilitated by the albumen gland-capsule gland complex, which in gastropods secretes the egg perivitelline fluid that nourishes and protects embryos. The biochemistry of the albumen gland-capsule gland complex and its relationship with fecundity remain largely unknown. We addressed these issues in Pomacea canaliculata (Lamarck, 1822), a highly invasive gastropod whose fecundity and reproductive effort exceed those of ecologically similar gastropods. We evaluated the dynamics of its major secretion compounds (calcium, polysaccharides, and total proteins) as well as the gene expression and stored levels of perivitellins during key moments of the reproductive cycle, that is, before and after first copulation and at low, medium, and high reproductive output. Copulation and first oviposition do not trigger the onset of albumen gland-capsule gland complex biosynthesis. On the contrary, soon after an intermediate reproductive effort, genes encoding perivitellins overexpressed. A high reproductive effort caused a decrease in all albumen gland-capsule gland complex secretion components. Right after a high reproductive output, the albumen gland-capsule gland complex restored the main secretion components, and calcium recovered baseline reserves; but proteins and polysaccharides did not. These metabolic changes in the albumen gland-capsule gland complex after multiple ovipositions were reflected in a reduction in egg mass but did not compromise egg quality. At the end of the cycle, egg dry weight almost doubled the initial albumen gland-capsule gland complex weight. Results indicate that albumen gland-capsule gland complex biosynthesis limits a constantly high reproductive output. Therefore, lowering fecundity by targeting biosynthesis could effectively reduce the rate of this species' spread.
TL;DR: It is concluded that these two early sensory systems may play an important role in the development of settlement competency of this biofouling invasive bivalve, Dreissena.
Abstract: Although understanding of the neuronal development of Trochozoa has progressed recently, little attention has been paid to freshwater bivalves, including species with a strong ecological im...
TL;DR: Evidence is observed to support the hypothesis that the switch in male mating tactics depends on female choice in oval squids and that this is transmitted via visual communication, and that female squids signal their mating receptivity visually and that male squids alter their mating tactics accordingly.
Abstract: Oval squids are polyandrous, with one female mating with multiple males during the spawning season There are two alternative male mating tactics used by Sepioteuthis lessoniana Larger males place spermatophores at the opening of the oviduct using a male-parallel mating posture, whereas smaller males attach spermatophores around the female buccal membrane using a male-upturned mating posture If the route of egg transportation is taken into consideration, male-parallel mating would be expected to result in higher fertilization success than male-upturned mating Although these male mating tactics are largely dependent on the body size of the male relative to that of the female, it is unclear how female choice affects the male's mating tactics and his mating success Squids are highly visual animals, and they communicate through dynamic body patterning In the present study, we observed that smaller male squids in captivity would attempt to mate with a larger female using the male-parallel tactic repeatedly, but they failed to be successful most of the time because of a rejection signal by the female In contrast, when the males switched to the male-upturned tactic, the mating success rate was increased significantly, with much less female rejection signal This finding suggests that female squids signal their mating receptivity visually and that male squids alter their mating tactics accordingly This is the evidence to support the hypothesis that the switch in male mating tactics depends on female choice in oval squids and that this is transmitted via visual communication
TL;DR: Stolonial movement in the psychrophilic demosponge Amphilectus lobatus combines traits of crawling along the substrate and asexual reproduction and relies on massive cell dedifferentiation followed by coordinated cell migration to the point of new sponge body formation and their subsequent differentiation into specialized cell types.
Abstract: Sponges (phylum Porifera) traditionally are represented as inactive, sessile filter-feeding animals devoid of any behavior except filtering activity. However, different time-lapse technique...
TL;DR: These studies suggest that P. xiphias is a tractable model for continuing investigations of circadian and diel vertical migration influences on plankton physiology, and are supported by the respiration experiments, which show an underlying cycle in metabolic rate, with a peak at dawn.
Abstract: The diel vertical migration of zooplankton is a process during which individuals spend the night in surface waters and retreat to depth during the daytime, with substantial implications for...
TL;DR: The results of this study show that P. maculata is well adapted for survival in the absence of water, and the ability to sustain travel over land and to endure long periods of aerial exposure suggests that the dry-down of infested bodies of water would not significantly impact populations of P. Maculata.
Abstract: Apple snails, in the genus Pomacea, have gained considerable notoriety for their impact on invaded habitats. Louisiana is currently under invasion by Pomacea maculata, which represents a po...
TL;DR: Findings indicate that the “trophosome” does not fundamentally increase oxygen requirement compared to other gastropod holobionts, and cold temperatures induce a stress response in Alviniconcha, resulting in aberrantly high uptake.
Abstract: Physiological traits are the foundation of an organism's success in a dynamic environment, yet basic measurements are unavailable for many taxa and even ecosystems. We measured routine metabolism in two hydrothermal vent gastropods, Alviniconcha marisindica (n = 40) and the scaly-foot gastropod Chrysomallon squamiferum (n = 18), from Kairei and Edmond vent fields on the Central Indian Ridge (23-25°S, about 3000 meter depth). No previous studies have measured metabolism in any Indian Ocean vent animals. After recovering healthy animals to the surface, we performed shipboard closed-chamber respirometry experiments to compare oxygen uptake at different temperatures (10, 16, and 25 °C) at surface pressure (1 atm). The physiology of these species is driven by the demands of their chemoautotrophic symbionts. Chrysomallon has very enlarged respiratory and circulatory systems, and endosymbionts are housed in its trophosome-like internal esophageal gland. By contrast, Alviniconcha has chemoautotrophic bacteria within the gill and less extensive associated anatomical adaptations. Thus, we predicted that routine oxygen consumption of Chrysomallon might be higher than that of Alviniconcha. However, oxygen consumption of Chrysomallon was not higher than that of Alviniconcha, and, further, Chrysomallon maintained a steady metabolic demand in two widely separated experimental temperatures, while Alviniconcha did not. We interpret that these findings indicate that (1) the "trophosome" does not fundamentally increase oxygen requirement compared to other gastropod holobionts, and (2) cold temperatures (10 °C) induce a stress response in Alviniconcha, resulting in aberrantly high uptake. While these two large gastropod species co-occur, differences in oxygen consumption may reflect the separate niches they occupy in the vent ecosystem.
TL;DR: The early embryonic development of the caridean shrimp Lysmata boggessi is described, from immediately after fertilization to the hatching of the zoea larva, using fluorescence microscopy and whole-mount nuclear staining with 4′,6-diamidino-2-phenylindole.
Abstract: There are a limited number of model species for decapod experimental embryology. To improve our understanding of developmental pattern evolution in the Decapoda, here we describe the early embryonic development of the caridean shrimp Lysmata boggessi, from immediately after fertilization to the hatching of the zoea larva, using fluorescence microscopy and whole-mount nuclear staining with 4',6-diamidino-2-phenylindole. Lysmata boggessi follows the standard caridean pattern of early development, with early holoblastic cleavage that will later become superficial, to form a blastoderm. We found no evidence of stereotypical cleavage and the formation of blastomere interlocking bands, which suggests there is diversity in developmental patterns within the Caridea. Gastrulation starts 37 hours after fertilization, and the embryonized nauplius is formed 2 days later. Enlarged headlobes, early retinal differentiation, and delayed pereopod development are characteristics of the post-naupliar stages in this species. To facilitate comparative studies with other crustacean species, we propose a staging method based on our findings. Lysmata boggessi is a protandric simultaneous hermaphrodite that is relatively easy to breed in captivity and amenable to laboratory experimentation in studies of embryonic development.
TL;DR: The results show that the rhopalia are readily regrown after amputation and have developed most, if not all, neural elements within two weeks, substantiate the amazing regenerative ability in Cnidaria.
Abstract: Cubozoans have the most intricate visual apparatus within Cnidaria. It comprises four identical sensory structures, the rhopalia, each of which holds six eyes of four morphological types. Two of these eyes are camera-type eyes that are, in many ways, similar to the vertebrate eye. The visual input is used to control complex behaviors, such as navigation and obstacle avoidance, and is processed by an elaborate rhopalial nervous system. Several studies have examined the rhopalial nervous system, which, despite a radial symmetric body plan, is bilaterally symmetrical, connecting the two sides of the rhopalium through commissures in an extensive neuropil. The four rhopalia are interconnected by a nerve ring situated in the oral margin of the bell, and together these structures constitute the cubozoan central nervous system. Cnidarians have excellent regenerative capabilities, enabling most species to regenerate large body areas or body parts, and some species can regenerate completely from just a few hundred cells. Here we test whether cubozoans are capable of regenerating the rhopalia, despite the complexity of the visual system and the rhopalial nervous system. The results show that the rhopalia are readily regrown after amputation and have developed most, if not all, neural elements within two weeks. Using electrophysiology, we investigated the functionality of the regrown rhopalia and found that they generated pacemaker signals and that the lens eyes showed a normal response to light. Our findings substantiate the amazing regenerative ability in Cnidaria by showing here the complex sensory system of Cubozoa, a model system proving to be highly applicable in studies of neurogenesis.
TL;DR: The results suggest that brood effects are present across a wide range of morphological characteristics and that future experiments involving Callinectes sapidus morphology or its functionality should explicitly account for inter-brood variation.
Abstract: External morphology has been shown to influence predation and locomotion of decapod larvae and is, therefore, directly related to their ability to survive and disperse. The first goal of this study was to characterize first-stage blue crab zoeal morphology and its variability across larval broods to test whether inter-brood differences in morphology exist. The second was to identify possible correlations between maternal characteristics and zoeal morphology. The offspring of 21 individuals were hatched in the laboratory, photographed, and measured. Zoeae exhibited substantial variability, with all metrics showing significant inter-brood differences. The greatest variability was seen in the zoeal abdomen, rostrum, and dorsal spine length. A principal component analysis showed no distinct clustering of broods, with variation generally driven by larger zoeae. Using observed morphology, models of drag induced by swimming and sinking also showed significant inter-brood differences, with a maximum twofold difference across broods. In contrast to trends in other decapod taxa, maternal characteristics (female carapace width and mass and egg sponge volume and mass) are not significant predictors of zoeal morphology. These results suggest that brood effects are present across a wide range of morphological characteristics and that future experiments involving Callinectes sapidus morphology or its functionality should explicitly account for inter-brood variation. Additionally, inter-brood morphological differences may result in differential predation mortality and locomotory abilities among broods.
TL;DR: This study is the first to use scanning electron microscopy to quantify overall structural diversity in cypris antennules by measuring 26 morphological parameters, including the structure of sensory organs, and shows that species from a coastal hard-bottom habitat may share a nearly identical antennular structure that is distinct from barnacles from other habitats.
Abstract: Barnacle cypris antennules are important for substratum attachment during settlement and on through metamorphosis from the larval stage to sessile adult. Studies on the morphology of cirrip...
TL;DR: The morphology and function of plumose setae on cyprids of Balanus glandula and other species across the clade Cirripedia are described, suggesting that this cuticular arrangement is effective in swimming, may eliminate the need for muscles to close the setal array, and may represent a unique swimming structure within the Crustacea.
Abstract: Many crustacean swimming appendages carry arrays of plumose setae-exoskeletal, feather-like structures of long bristles (setae) with short branches (setules) distributed along two sides. Although closely spaced, setae are not physically interconnected. Setal arrays function during swimming as drag-based leaky paddles that push the organism through water. Barnacle cyprids, the final, non-feeding larval stage, swim with six pairs of legs (thoracopods) that open and close setal arrays in alternating high-drag power strokes and low-drag recovery strokes. While studying cyprid swimming, we found that their thoracopods contained setae permanently cross-linked by fused setules. These cuticular connections would seem highly unlikely because setae are individually produced exoskeletal secretions, and the connections imply unknown processes for the production or modification of crustacean setae. We describe the morphology and function of plumose setae on cyprids of Balanus glandula and other species across the clade Cirripedia. Setules from adjacent plumose setae are seamlessly joined at their tips and occur in three distinct linkage patterns. Thoracopods lack muscles to open and close the array; interconnected setae are instead pulled apart, producing a paddle-like fan with high drag when appendages spread laterally during power strokes. Setules are spring-like, passively closing setae into tight bundles with low drag during recovery strokes. The linked setules occur in the three main clades of the Cirripedia. This cuticular arrangement is effective in swimming, may eliminate the need for muscles to close the setal array, and may represent a unique swimming structure within the Crustacea.
TL;DR: It is reported that the applied combination of epicatechin + thermal stress has a synergistic memory-enhancing effect; that is, when the two are applied in combination, memory persists longer than when either is applied alone.
Abstract: When applied individually, thermal stress (1 hour at 30 °C) and (-)epicatechin (a flavonol found in green tea, e.g.) each enhance long-term memory formation following operant conditioning o...
TL;DR: It is found that the appearance of prey and their movement at a vertical angle of 45° are specific factors that can initiate hunting behavior of pharaoh cuttlefish, and this is the first report of a stimulus that elicits stereotyped hunting behavior by coleoid cephalopods.
Abstract: Cuttlefish exhibit typical hunting behavior, including elongating tentacles against specific prey such as prawn and mysid shrimp. Cuttlefish hunting behavior involves three different actions: attention, positioning, and seizure. Hunting behavior is innate and stereotypic behavior, and it is present in newly hatched juveniles. Factors associated with prey are known to induce this behavior, similar to the sign stimulus, whereby young herring chicks imitate pecking behavior against a red dot on their parent's bill. Although the hunting behavior of cuttlefish has been described and used as an indicator to test learning and memory, details of a stimulus that can elicit this behavior remain unknown. Here, we used a variety of visual stimuli presented on a computer screen to investigate the factors that induce hunting behavior of pharaoh cuttlefish, Sepia pharaonis. We found that the appearance of prey (western king prawn, Melicertus latisulcatus) and their movement at a vertical angle of 45° are specific factors that can initiate hunting behavior. We also showed that the height of prey can attract cuttlefish and initiate hunting. To the best of our knowledge, this is the first report of a stimulus that elicits stereotyped hunting behavior by coleoid cephalopods.
TL;DR: These findings support earlier indirect observations showing that sea stars recognize M. trossulus as a more preferable prey than M. edulis, and show that A. rubens preferred smaller mussels to larger ones, irrespective of their species affinity.
Abstract: Sea stars Asterias rubens are important natural enemies of the blue mussel Mytilus in the North Atlantic. We asked whether these predators distinguish between the cryptic species M. edulis ...
TL;DR: Although the symbionts responded differently to heat stress, the lack of differences in symbiont densities between treated and control late nymphs suggests the existence of an adaptive genetic process to restore phenological synchrony during the development of immatures in preparation for adult life.
Abstract: Global warming may impact biodiversity by disrupting biological interactions, including long-term insect-microbe mutualistic associations. Symbiont-mediated insect tolerance to high tempera...
TL;DR: It is suggested that temperature stress influences H2O2 production, which in turn impacts coral settlement, and internal concentrations (produced under heat stress) have the capacity to impact recruitment under a changing climate.
Abstract: Hydrogen peroxide (H2O2) is involved in the regulation of numerous reproductive and morphogenic processes across an array of taxa. Extracellular H2O2 can be widespread in oceanic waters, an...
TL;DR: It is found that self and non-self stimuli differentially influenced two effector systems: cnida discharge and tentacle contraction and several receptor systems are involved that integrate chemical and mechanical cues in order to initiate appropriate and graded effector responses during competition for space.
Abstract: Certain species of sea anemone live in tightly packed communities, among clonemates and non-clonemates. Competition for space leads to intraspecific and interspecific aggressive interactions among anemones. The initial aggressive interactions appear to involve reciprocal discharge of cnidae triggered by contact with non-self feeding tentacles. We asked whether molecules contained in anemone-derived mucus constituted an important cue alone or in combination with cell surface molecules in stimulating aggressive or avoidance behaviors. In this study, we found that self and non-self stimuli differentially influenced two effector systems: cnida discharge and tentacle contraction. Interspecific mucus enhanced nematocyst discharge by 44% and spirocyst discharge by 90%, as compared to baseline discharge obtained in seawater alone. Conspecific stimuli accompanying touch inhibited specific tentacle contractions occurring on the far side of anemones relative to the site of contact. The greatest tentacle contractions occurred with exposure to interspecific mucus and tissue. Thus, several receptor systems are involved that integrate chemical and mechanical cues in order to initiate appropriate and graded effector responses during competition for space.