Biological Bulletin最新文献

AbstractThe chiton Chaetopleura isabellei is a common species in the intertidal shores of the southwestern Atlantic Ocean. This study investigates the age, individual growth, and mortality of C. isabellei on an intertidal boulder shore in San Antonio Bay (40°45' S, 064°56' W), Patagonia, Argentina. Growth rings on the valves were validated as annual, forming during the warm season, a pattern unusual among chitons. The age structure showed a stable population, with most individuals between 2 and 7 years and a maximum observed longevity of 11 years. The growth pattern, analyzed through both polynomial models and the von Bertalanffy growth model, indicated rapid growth during early years, followed by slower growth in later stages. Mortality was best described by the Siler mortality model, indicating variable mortality rates across the lifespan, with higher risks during early and late life stages. These findings provide insights into the life history of C. isabellei, emphasizing the influence of environmental factors on growth and mortality in this species.

AbstractIn ponds of the northeastern United States, benthic macroinvertebrates can dominate the local biomass. Isopods, predatory leeches, and fingernail clams can attain dense populations and suffer heavy predation pressure by fish. We predicted that pond benthic macroinvertebrates would recognize the proximity of predatory fish and avoid or vacate that area as an inducible behavioral defense. We deployed cages with and without predatory fish (sunfish and golden shiners) in a naturally fishless pond in October and November of 2020 and 2021. After at least 2 days, we collected leaf packs from directly under the cages and compared the number of invertebrates residing within. Surprisingly, the population densities of the dominant taxa (isopods, leeches, and clams) suggested that they did not avoid fish. Leeches and isopods may even reside in higher numbers near live sunfish, perhaps because feces from the fish augment the locally available food and nutrient levels. Our present field results support earlier laboratory findings: benthic macroinvertebrates in ponds may not respond to fish cues. Bottom-up control may dominate in ponds, providing important implications for conservation of these threatened ecosystems.

AbstractThe Atlantic white shrimp, Penaeus setiferus, is a commercially important species that is abundant along the United States' east coast and Gulf of Mexico. Like other similar organisms, this species is vulnerable to black gill disease, where gills become heavily melanized as part of an immune response associated with gill irritants or parasitic infection. The melanization blackens the gills, making the disease obvious. Black gill is thought to be stimulated by high temperature, high salinity, and low oxygen. In this study, we investigated whether the presence of black gill influences the ability of shrimp to take up oxygen across the gills. Shrimp were made to exercise on an underwater treadmill while measurements of oxygen uptake were made. Measurements were made in well-oxygenated water (100% air saturation) and moderate (50% air saturation) and severe (30% air saturation) hypoxia. In quiescent animals, there was no difference in oxygen uptake between control shrimp with no black gill and those with obvious black gill infections. Oxygen uptake increased by as much as twofold when shrimp were active on the treadmill. In both control and black gill groups, oxygen uptake declined in hypoxia, but the decline was greater in black gill shrimp, suggesting an impairment to taking up oxygen. Thus, black gill significantly impairs the ability of shrimp to take up oxygen under hypoxic conditions when shrimp are active. These results provide a mechanistic basis for potential negative impacts of shrimp populations suffering with outbreaks of black gill.

AbstractRibbed mussels are typically found in Spartina alterniflora salt marshes and can form dense aggregations along low marsh shorelines and tidal creeks. The presence of ribbed mussels within marshes is well documented, and many studies have examined their importance in these ecosystems. However, it is not known whether mussels settle preferentially in S. alterniflora habitat and what factors influence observed aggregations of mussels. Knowing this is important for current efforts in salt marsh restoration. Therefore, we conducted experiments with competent larvae to test whether chemical or physical cues of S. alterniflora or adult conspecifics stimulate settlement and metamorphosis. More larvae settled and metamorphosed in the presence of a S. alterniflora leaf, although not on the leaf, and in water conditioned with S. alterniflora than in seawater controls. The presence of chemical or physical cues from conspecifics had no effect on settlement and metamorphosis relative to controls. Larvae settle and metamorphose in response to chemical cues from S. alterniflora, resulting in ribbed mussels being found predominantly in S. alterniflora habitat. However, because there was no response to conspecifics, other factors are likely responsible for their aggregated distribution. Further work is required to determine the factors resulting in mussel aggregation, including movement of juvenile mussels and environmental filtering.

AbstractMany marine invertebrates possess biphasic life histories, during which larvae develop in the plankton and adults inhabit the benthos. The transition between phases entails the settlement of larvae onto substrata, completion of metamorphosis, and survival as vulnerable early juveniles. The perimetamorphic period, encompassing settlement and the interval immediately following settlement, is a key determinant of adult abundance and distribution. However, because settling larvae and early juveniles are difficult to observe in the field, the ecology of this period remains poorly understood. We performed experiments to elucidate the settlement preferences of Asterias forbesi and Asterias rubens, keystone predators on the east coast of North America, on substrata common to their intertidal habitats. Larval Asterias exhibit clear selectivity in settlement, with shells of the blue mussel, Mytilus edulis, most preferred. The algae Chondrus crispus and crustose coralline algae also induced high rates of settlement, while little settlement was observed on rocks with biofilm and no settlement occurred in controls. When inductive cues were subsequently added to controls, high frequencies of settlement occurred immediately, confirming the competency of larvae to settle and their ability to delay metamorphosis in the absence of appropriate cues. Our results demonstrate that Asterias larvae have specific settlement preferences and that settlement can be postponed in this species if no suitable substrate is available.

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.