Biological Bulletin最新文献

AbstractHatschek published the first comprehensive description of amphioxus development in the late nineteenth century. For him, a key event in early embryology was the evagination of the anterior end of the pharynx to form a right diverticulum and a left diverticulum-precursors, respectively, of the rostral coelom and preoral organ. Here we reexamine Hatschek's proposed diverticula with serial block-face scanning electron microscopy, a technique for generating fine-structural models of tissues in three dimensions. We find that no such diverticula ever form in the embryo. Instead, the anterior tip of the gut transforms into a mass of irregularly organized cells, the source of the peritoneal lining of the rostral coelom. Moreover, a cluster of cells associated with the first left segment is the likely source of the preoral organ. The discussion considers how the absence of Hatschek's gut diverticula impacts previously suggested homologies relating deuterostome head cavities.

AbstractDecapod crustaceans with wide distributions have shown different patterns of population structure in certain species, which clarified processes related to population dynamics and intraspecific variation. The aim of the current study is to assess phylogeographic patterns of the intertidal crab Cyclograpsus integer H. Milne Edwards, 1837, as well as its wide distribution in the western Atlantic Ocean, from the US to Brazil. We hypothesize that the genetic structure of C. integer is influenced by the interaction of different geographic barriers. We analyzed partial sequences of the mitochondrial gene cytochrome c oxidase subunit I deriving from specimens collected along the western Atlantic distribution of C. integer. The phylogenetic reconstruction, haplotype networks, demographic history, divergence time, and discrete phylogeography of C. integer do not confirm our hypothesis. The wide distribution can be explained by the potential of C. integer larvae to disperse through northern Brazilian and Brazilian currents, which helps maintain gene flow across natural barriers. In addition, C. integer population size has increased in the Atlantic Ocean over the past 0.01-0.10 million years, with emphasis on two large separate groups and on the north-to-south spatiotemporal diffusion of its populations. While there is some evidence of genetic differentiation between the tropical northwestern Atlantic and the tropical/warm-temperate southwestern Atlantic regions, the overall genetic structure is low. The Amazon-Orinoco Plume appears to have limited influence as a barrier, further emphasizing the species' capacity for larval dispersal and genetic homogenization across its range. These findings highlight the importance of oceanographic features in shaping genetic patterns of widely distributed marine organisms and underscore the value of C. integer as a model for studying genetic connectivity in marine ecosystems.

Introduction: in 2016, a switch from trivalent oral poliovirus vaccine (OPV) (containing serotypes 1,2,3) to bivalent OPV (types 1,3) was implemented globally. We assessed the seroprevalence of poliovirus antibody levels in selected Nigerian states, before and after the switch, documented poliovirus type2 outbreak responses conducted and ascertained factors associated with immunity gaps based on seroprevalence rates.

Methods: we conducted a secondary analysis of stored serum samples from the 2018 Nigeria National HIV/AIDS Indicator and Impact Survey. Serum from 1,185 children aged 0-119 months residing in one southern and four northern states were tested for serotype-specific PV neutralizing antibodies; seropositivity was a reciprocal titer ≥8. We conducted regression analysis to determine sociodemographic risk factors associated with low seroprevalence using SAS 9.4.

Results: children aged 24-119 months (pre-switch cohort) had seroprevalence against PV1, PV2, and PV3, of 97.3% (95% CI:96.4-98.2), 93.8% (95% CI:92.2-95.5), and 91.3% (95% CI:89.2-93.4), while children aged <24 months (post-switch) had seroprevalence of 86.0% (95% CI:81.2-90.8), 55.6% (95% CI: 47.7-63.4), and 77.2% (95% CI:71.0-83.4) respectively. Regression analysis showed age <24 months was associated with lower seroprevalence against all PV serotypes, (p<0.0001); females had lower seroprevalence against PV1 (p=0.0184) and PV2 (p=0.0354); northern states lower seroprevalence against PV1 (p=0.0039), while well-water source lower seroprevalence against PV3 (p=0.0288).

Conclusion: this study showed high seroprevalence rates against PV 1, 2, and 3 in pre-switch children (aged 24-119 months). However, post-switch children (<24 months) had low immunity against PV2 despite outbreak responses. Strategies to increase routine immunization coverage and high-quality polio campaigns can increase immunity against polio virus.

AbstractEastern oysters (Crassostrea virginica) are sessile, relying on a larval phase to disperse in estuaries. Oyster larval swimming behavior can alter dispersal trajectories and patterns of population connectivity. Experiments were conducted to test how both (1) acclimation time to new environmental conditions and (2) larval swimming behavior change with salinity and larval age. Acclimation time to changes in salinity was longest in lower salinity (6 ppt) and decreased with age. To test changes in behavior with salinity, larvae were placed into four salinities (6, 10, 16, and 22 ppt) where swimming was recorded. To test changes in behavior with age, larvae aged 6, 12, and 15 days were recorded. In both experiments, swimming paths were mapped in two dimensions, behavior of each path was categorized, and speed, direction, and acceleration were calculated. The frequency of upward, neutral, and downward swimming behaviors did not differ across salinity treatments but did vary with age, whereas the frequency of behavior types varied with both salinity and ontogeny. As an example, diving was observed more frequently in low salinity, and more downward helices were observed in moderate salinity, while younger larvae swam upward with more frequency than older larvae. Surprisingly, diving was observed in 10%-15% of all larvae across all ages. Given the consequence of larval behavior to marine invertebrate dispersal, changes in swimming over larval age and in response to environmental changes have important implications to marine population stability and structure.

AbstractWithin phylum Chordata, the subphylum Cephalochordata (amphioxus and lancelets) has figured large in considerations of the evolutionary origin of the vertebrates. To date, these discussions have been predominantly based on knowledge of a single cephalochordate genus (Branchiostoma), almost to the exclusion of the other two genera (Asymmetron and Epigonichthys). This uneven pattern is illustrated by cephalochordate hematology, until now known entirely from work done on Branchiostoma. The main part of the present study is to describe hemocytes in the dorsal aorta of a species of Asymmetron by serial block-face scanning electron microscopy. This technique, which demonstrates three-dimensional fine structure, showed that the hemocytes have a relatively uniform morphology characterized by an oval shape and scanty cytoplasm. Ancillary information is also included for Branchiostoma hemocytes, known from previous studies to have relatively abundant cytoplasm; our serial block-face scanning electron microscopy provides more comprehensive views of the highly variable shapes of these cells, which typically extend one or several pseudopodium-like protrusions. The marked difference in hemocyte morphology found between Asymmetron and Branchiostoma was unexpected and directs attention to investigating comparable cells in the genus Epigonichthys. A broader knowledge of the hemocytes in all three cephalochordate genera would provide more balanced insights into the evolution of vertebrate hematopoiesis.

AbstractSensory feedback plays an essential role in shaping rhythmic animal movements. In the crustacean stomatogastric nervous system, which is responsible for grinding and filtering food particles in the animal's foregut, a number of mechanoreceptors whose activity affects motor output have been characterized. The hepatopancreas duct receptor neurons, which are located in the pyloric region of the foregut that is responsible for filtering, are among the less well understood groups of stomatogastric mechanoreceptors. Although they were first described decades ago in a number of decapod species, many questions remain about their role in shaping the movements produced by the stomatogastric nervous system. Here we provide the first anatomical and physiological evidence that there are also hepatopancreas duct receptors in the crab Cancer borealis, and we demonstrate that hepatopancreas duct receptor spiking produced by mechanical stimulation modifies the properties of an ongoing pyloric motor program.

AbstractMorphologies of animal appendages are highly diversified depending on animal lifestyles. In cephalopods (Mollusca, Cephalopoda), an individual possesses multiple arms that contribute to elaborate behaviors, and suckers on them enable various arm functions. In octopus hatchlings, arm and sucker morphologies can be divided into two different types due to alternative posthatching lifestyles, that is, pelagic or benthic lifestyles, although the underlying developmental differences have yet to be elucidated. In this study, therefore, detailed developmental processes of arms and suckers were observed during embryogenesis in two different octopus species, Octopus parvus and Amphioctopus fangsiao, showing pelagic and benthic posthatching lifestyles, respectively. In O. parvus, sucker formation stopped at a relatively early stage in which three suckers on an arm were produced. In addition, at late embryonic stages, cell proliferation was hardly detected in whole arms, while in A. fangsiao, sucker production continued throughout embryogenesis and cell proliferation also remained active in whole arms even in the late stages. Therefore, although further investigations in other octopus species are required, it is suggested that in octopus evolution, the developmental program of suckers has been modified in accordance with the acquisition of a novel lifestyle.

AbstractMarine invertebrates with biphasic life cycles feature life history transitions that coincide with habitat changes from benthic adults to planktonic embryos and larvae, then a return to the benthos as a juvenile at metamorphosis. The metamorphic transition exposes animals to a new suite of benthic predators, and high mortality often occurs in the hours and days following settlement. Juvenile invertebrates may produce phenotypically plastic morphological defenses when predator cues are detected. However, time lags inherent to phenotypic plasticity may delay the production of defenses until after the period of highest vulnerability. It should, therefore, be beneficial for planktonic larvae approaching settlement to detect waterborne cues from benthic predators and produce juvenile phenotypes appropriate for postmetamorphic survival. Echinoderms are useful models for testing transhabitat and trans-life history stage phenotypic plasticity because many species have larvae that construct their juvenile phenotype while still in the water column. In this study, we tested whether planktonic echinoderm larvae exposed to cues from benthic predators modified their juvenile phenotypes at settlement. Green urchin (Strongylocentrotus droebachiensis) and Pacific sand dollar (Dendraster excentricus) larvae were exposed to predatory green crab (Carcinus maenus) or red rock crab (Cancer productus) cues, respectively, from their early-stage juvenile rudiment formation through settlement. Green urchin larvae exposed to predator cues settled with significantly more juvenile spines compared to unexposed controls. Sand dollars exhibited earlier settlement, larger disk area, fewer spines, and shorter spines when exposed to benthic predator cues. Sand dollar larvae were also exposed to cues from planktonic crab larvae and in response settled sooner and larger, with even fewer and shorter spines than those exposed to benthic predator cues. These results suggest that echinoderm larvae alter their juvenile phenotype in response to predator cues, but the response varies between species, and responses to planktonic threats may be prioritized over benthic ones.

AbstractThe pond snail Lymnaea stagnalis employs aerial respiration under hypoxia and can be operantly conditioned to reduce this behavior. When applied individually, a heat shock (30 °C for 1 h) and the flavonoid quercetin enhance long-term memory formation for the operant conditioning of aerial respiration. However, when snails are exposed to quercetin before the heat shock, long-term memory is no longer enhanced. This is because quercetin prevents the heat-induced upregulation of heat-shock proteins 70 and 40. When we tested the memory outcome of operant conditioning due to the simultaneous exposure to quercetin and 30 °C, we found that Lymnaea entered a quiescent survival state. The same behavioral response occurred when snails were simultaneously exposed to quercetin and pond water made hypoxic by bubbling nitrogen through it. Thus, in this study, we performed six experiments to propose a physiological explanation for that curious behavioral response. Our results suggest that bubbling nitrogen in pond water, heating pond water to 30 °C, and bubbling nitrogen in 30 °C pond water create a hypoxic environment, to which organisms may respond by upregulating the heat-shock protein system. On the other hand, when snails experience quercetin together with these hypoxic conditions, they can no longer express the physiological stress response evoked by heat or hypoxia. Thus, the quiescent survival state could be an emergency response to survive the hypoxic condition when the heat-shock proteins cannot be activated.