Distribution Of Larvae Research Articles

Yucatan shelf’s larval density and distribution of Auxis spp. and Caranx crysos are primarily driven by regional upwelling and seasonality

The extensive Yucatan Shelf (YS) in the southern Gulf of Mexico provides habitat for many marine species and supports important fisheries. A striking feature is the regional upwelling along its eastern margin due to the interaction of the Yucatan Current with the western slope of the Yucatan Channel. Coupled with easterly winds, the upwelled water fertilizes the shelf and contributes to high productivity in an otherwise oligotrophic region. However, an understanding of the role that regional upwelling plays on fish spawning and larval fish distributions is limited. We describe the distribution, frequency of occurrence, and densities of two commercially important neritic species (Auxis spp. and Caranx crysos) with contrasting life histories (different adult habitat, neritic vs. neritic and oceanic, and with spawning peak vs. year around spawner). The relationship between larval density and environmental variables, including upwelling indicators, was examined for three oceanographic cruises that covered the entire YS and which were held during summer through fall (2015, 2016 and 2018). None (Auxis spp.) or very few (C. crysos) larvae were caught during the late fall cruise in November. The highest densities of both taxa were found during the summer cruise in July, consistent with their spawning periods. Both species were mostly distributed beyond the 40 m isobath, and the highest densities were found over the central and eastern shelf. Generalized additive models indicated that Auxis spp. and C. crysos densities were correlated with low chlorophyll a concentration (located in the outer shelf) and a shallower 22.5 °C isotherm (a proxy for upwelling), indicating that regional upwelling was associated with higher larval fish densities.

Распределение очагов инвазии литоральных моллюсков партенитами и личинками трематод в губах и заливах Мурманского побережья в мае–июне 2021 года

Species composition and geographical variation in the distribution of digenean parthenite and larvae in intertidal snails in the littoral zones along the Murmansk coast were examined. Four species of littoral gastropods (Littorina saxatilis, L. obtusata, L. littorea and Nucella lapillus) were investigated. We found 10 species of digeneans, of which 9 have marine birds as a final host. The exception was Podocotyle atomon which uses fish as a definitive host. Larvae of trematode Microphallus pygmaeus, M. piriformes and Podocotyle atomon are found everywhere on the Murmansk coast. The richest helminth fauna were recorded in the Kola Bay and in Ivanovskaya Bay, the poorest helminth fauna were recorded in Dvorovaya Bay. No pronounced trends in distribution of infection foci were noted. Trematode prevalence appears to be predominantly determined by local site condition favoring or hindering final host (birds and fishes) abundance.

Advances in understanding physical and biological controls on eggs and larval distribution in Pacific fisheries: A review

The early stages of fish, comprising eggs and larvae, are exceptionally fragile and sensitive to environmental dynamics and climate change. Pacific Ocean (PO) currents play an important role in shaping the distribution of marine organisms, influencing global climate patterns, heat distribution, coastal temperatures, and nutrient redistribution. These currents reveal significant changes within the climate system. Their variability across different timescales can be attributed to the complex interplay of physical forces. These currents are subjected to diverse anthropogenic factors, exerting detrimental effects on the dispersal of fish larvae. Furthermore, climate change variables, including alterations in tropical PO temperature associated with the ENSO cycle, Atlantic Nino modes influencing equatorial Atlantic temperature, changes in ocean salinity, polar ice cap melting, increasing greenhouse gases, marine heatwaves, and fluctuations in subsurface flows, directly impact the distribution, abundance, and species composition of early life stages. Major Pacific fisheries, such as those targeting Pacific sardines, saury, and anchovies, undergo population booms and declines due to significant alterations in the current dynamics of currents and fronts within the PO. The anticipated intensification of the ENSO cycle, characterized by more frequent and severe El Niño (warm) and La Niña (cold) events as a result of climate change, is expected to significantly impact the early developmental stages of important commercial fish stocks regularly. This review synthesizes the current understanding of the physical and biological parameters driving changes in ocean currents and their implications for early fish dispersion, emphasizing the critical need for research in this area to inform global conservation efforts, fisheries management, and food security.

Low potential of fish as a source of infection with Angiostrongylus cantonensis

Abstract Objectives Fish are hypothesized to act as paratenic hosts for the zoonotic nematode Angiostrongylus cantonensis, cause of human eosinophilic meningitis. There is a lack of data confirming the relevance of fish in A. cantonensis life cycle and their contribution to human infection. Materials and methods We conducted a series of experiments to investigate survival and infectivity of A. cantonensis larvae in Clarias gariepinus (catfish; n=30) and Oreochromis niloticus (tilapia; n=24). Each fish was inoculated with 10,000 third-stage larvae (L3). Larval survival was assessed through artificial digestion of fish tissues one, two, and three weeks post-infection. To investigate early stages of infection, four catfish were inoculated with 10,000 L3 each and sacrificed 3 days post-infection. qPCR and histopathological examinations were performed to evaluate larval distribution and tissue reactions. Two infected catfish, sacrificed one week post-infection, were used to feed Wistar rats. Results After 45 days, the rats were not shedding L1, indicating the absence of infection. One week post-infection, dead larvae were present in digested tissues of both fish species, and the same was observed two and three weeks after exposure. qPCR analysis revealed that intestine was the most heavily infected organ. Histopathology identified dead larvae within granulomas in intestines and liver. Early-stage infection experiment showed that fish sacrificed three days post-inoculation contained viable L3 which were infective to Wistar rats. Conclusions While A. cantonensis L3 can survive and remain infective in fish for a short period, they typically die within first few days post-infection. This suggests that fish may not be significant long-term paratenic hosts for A. cantonensis but may play a temporary role in its transmission to mammals (including humans) and birds. These results are consistent with previous studies on freshwater shrimps and highlight the importance of understanding aquatic host interactions in the epidemiology of this zoonotic food-borne pathogen.

Influence of the parasitoid Cotesia vestalis on the distribution of diamondback moth larvae on cabbage plants

Influence of the parasitoid Cotesia vestalis on the distribution of diamondback moth larvae on cabbage plants

Distributions of larvae and juveniles of Pacific saury Cololabis saira during winter in relation to oceanographic structures in the central and western North Pacific Ocean

AbstractFor small pelagic fish, the physical and feeding environments during the larval and juvenile periods significantly affect recruitment to standing stock. To understand the variation in environmental conditions experienced by larvae and juveniles, this study determined the distribution of larval and juvenile Pacific saury Cololabis saira over a distance of more than 6900 km in an east–west direction in relation to the ocean environment in winter. Specimens were collected from the western and central parts of the North Pacific Ocean, mainly in January and February 2018 and 2020. Larvae (≤39.9 mm) were broadly distributed around the Kuroshio Current and the Kuroshio Extension Current. Larval densities in the water masses around the Kuroshio Extension Current were as high as, or even significantly higher than, those around the Kuroshio Current, which is considered the main spawning ground. Most juveniles (≥40.0 mm) were captured north of the Kuroshio Extension Current, where sea surface temperatures were lower and chlorophyll a concentrations were higher. The generalized additive model analysis also suggested that, compared to larvae, juveniles tended to be distributed in areas with lower sea surface temperatures and in more eastern areas. The extensive distribution of Pacific saury larvae and juveniles indicates that it is necessary to focus not only on the marine environment around the Kuroshio region but also on the Kuroshio Extension region to understand the recruitment variability of this species.

Vertical distribution of Pacific oyster Crassostrea gigas larvae and modeling larval transport in Hiroshima Bay, Japan

Understanding vertical distribution of planktonic larvae is essential for elucidating larval dispersal and recruitment processes. We investigated the vertical distribution and horizontal transport of Pacific oyster Crassostrea gigas larvae by field observations and numerical simulations during their main spawning season in Hiroshima Bay, Japan. In field observations, despite horizontal differences and slight diurnal/semi-diurnal changes depending on larval sizes, most larvae were distributed in the upper 3 m layer. The relationship between C. gigas larvae and environmental conditions revealed that larval density increased with increasing temperature and chlorophyll a concentration, and the density peaked at salinity of approximately 20 for all larval sizes. The observed results suggest that the distribution characteristics of C. gigas larvae are suitable for survival in an estuarine area, where environmental conditions are potentially favorable but hydrodynamic conditions can drastically change over the short term due to variations in river discharge. To examine the effect of high river discharge on larval transport, numerical simulations were conducted using a particle-tracking model incorporating the vertical motion of C. gigas larvae. The simulation results reproduced the spatio-temporal dynamics of planktonic and settled larvae after the high river discharge. Although most particles simulating larvae outflowed from the main spawning area, an area of high particle density at the end of simulation corresponded with the offshore area for seedling collection. The present study suggests the role of vertical distribution of C. gigas larvae for recruitment, and the prospect of sustainability in oyster aquaculture with respect to seedling collection despite the frequent heavy rainfall associated with climate change.

Distribution of lobster larvae, Homarus americanus, and zooplankton prey in the gulf of maine and georges bank stock area

The American lobster, Homarus americanus H. Milne-Edwards, 1837 supports a valuable fishery subject to rapid warming of the Gulf of Maine (GOM) and Georges Bank (GBK). Comprehensive information related to large-scale larval distribution is lacking due to the logistical challenge of sampling their hyper-dispersed larvae. In 2021, we established seasonal abundance patterns of larvae and their prey in the GOM on an unprecedented spatial scale with a season-long survey at transects spanning approximately 300 km of coastline. We compared the current distribution of larvae with historical surveys with respect to differences between inshore and offshore (5 versus 40 km), and between eastern and western hydrographic regions. We also examined spatial and temporal patterns in the abundance of zooplankton prey. The distribution of recently hatched stage I larvae extended offshore at the transect off Rye, NH and was consistent with the reported movement of ovigerous lobsters offshore to hatch their eggs. By contrast, stage I larvae were most abundant nearshore and rare offshore at other transects along the coast. Our results confirmed historical patterns of high abundance of competent stage IV larvae in the western Gulf of Maine and low abundance in the east. We also identified the potential for a temporal mismatch between the abundance of larvae and the biovolume of copepods at transects in Milbridge, ME and Rye, NH with peak copepod abundance occurring either well before or after the peak abundance of lobster larvae. The data collected fill a gap in our understanding of larval distributions and seasonal progression in the Gulf of Maine, establish a baseline for future studies, and provide an opportunity to validate established biophysical models of larval transport. Yet a longer time series of broad-scale surveys is needed to better understand intricacies of factors influencing larval abundance and distribution. The project was an industry-led collaboration with government and academic scientists providing proof of concept for future collaborative research.

First evidences in the Gulf of Cádiz (northeastern Atlantic Ocean) as a spawning area of bullet tuna species (Auxis rochei)

The bullet tuna, Auxis rochei, is a commercially significant scombrid in small-scale inshore fisheries in the northeastern Atlantic and western Mediterranean. We hypothesized that the Gulf of Cádiz could serve as a spawning area of bullet tuna. We analysed the gonads and GSI of 428 individuals (23.9–48.7 cm SFL) caught by Portuguese and Spanish traps along the south Atlantic Iberian Peninsula, as well as by Spanish recreational fishery between 2004 and 2021. Larvae of bullet tuna were collected during surveys conducted on the northern shelf of the Gulf of Cádiz in June and August. Bullet tuna landings exhibited high seasonality in the Gulf of Cádiz, peaking during the warmest months, notably from August to October. Analysis of maturity data, monthly GSI variations, larvae distribution, and landings indicate that bullet tuna is reproductively active in the Gulf of Cádiz, particularly in July and August. A more comprehensive understanding of the reproductive behaviour of bullet tuna in this region is essential to confirm its reproductive success and to study recruitment mechanisms further.

Characterization of Anopheles Mosquitoes Larvae Breeding habitats in Selected Six Local Government Areas in Ekiti State, South-West Nigeria

This study explored the spatial distribution and attributes of Anopheles mosquito larvae breeding sites in six local government areas of Ekiti State, Nigeria. It employed a cross-sectional design, randomly sampling larvae habitats across three distinct locations, resulting in the assessment of a total of 18 breeding sites. The assessment of habitat characteristics and physico-chemical parameters of larvae breeding water-bodies was conducted through visual inspection and laboratory procedures, adhering to the standard protocol outlined by the World Health Organization (WHO). The objective of this study is to characteriseAnopheles mosquito larvae breeding habitats in six selected local government areas in Ekiti State using WHO protocol.. Two local governments were selected each from the three senatorial districts in the state and a survey was conducted to identify dams, rivers, swamps, marshlands, and temporary water ponds within each zone for Anopheles mosquito larvae using WHO protocols. Measurements of water temperature and pH were conducted twice in a week using a multi-parameter meter (PHB500- ww portable ph meter).Anopheles mosquito larvae were collected across the eighteen breeding sites in the selected six LGA in Ekiti using standard dipper, pasteur pipettes and scooping techniques and reared to adult in the laboratory. Most of the larvae habitats encountered were stagnant water bodies 10(56%) with the mean of 122.2 ± 41.20 followed by Tyre track 4(22%) with the mean of 129.8 ± 41.20, slowly flowing 2(11%) with the mean of 186.0 ± 16.97 and gutter 2(11%) with the mean of 170.0 ± 98.9. Types of breeding site across the six study area were all temporary sites 18(100%), more than half 13 (72%) of the habitats origin of water were natural, 11(61%) of the breeding habitats’ specific water body were stagnant water bodies. Furthermore, majority 14(78%) of the water bodies were polluted, 16(89%) were exposed to sunlight and it was also discovered that the all the breeding habitats across the six study area were around settlements (houses). Therefore physicochemical characteristics such as Temperature (r=0.896, p=0.016), pH (r=0.865, p=0.026) and Electrical conductivity (r=0.865, p=0.045) were significantly associated with larvae abundant with a strong positive correlation while the physicochemical characteristics such as DO and TDS were not significantly associated with larvae abundance .

THE EFFECT OF THE EXPERIMENTAL INVASION OF T. PSEUDOSPIRALIS ON THE MORPHOLOGY OF THE SPLEEN OF LAYING HENS (GALLUS DOMESTICUS)

Background. Еhe study of the reaction of the organs of the immune system of birds with nematodes is relevant for the development of treatment regimens. Numerous models have been developed for laboratory animals (mice and rats), carnivores (hori, etc.) and birds (quails, chickens). In the latter, a capsule-free type of trichinella parasitizes, which has a number of reproduction features. In this study, a model of experimental invasion of T. pseudospiralis was used. The role of the spleen in the formation of anti-nematodosis immunity and its reaction to the introduction of the parasite in chicken (Gallus domesticus) has been studied. The purpose of this study was to investigate morphological changes in the structure of the spleen in trichinellosis caused by T. pseudospiralis in chickens in the muscular stage of the invasive process. Materials and methods. By the method of analogues, 2 groups of 6 heads were formed. The birds of the experimental group were weighed and T. pseudospiralis larvae isolate was injected into the goiter at a dose of 2 lich. / g of body weight (3200-3600 thousand larvae per bird). T. pseudospiralis larvae used for experimental infection of poultry were previously isolated from the muscles of birds, and were maintained on laboratory animals. All chickens were kept and fed under identical conditions. In order to determine the distribution of larvae in the muscles of T. pseudospiralis poultry, 6 chickens of the experimental group were euthanized 3.5 months after experimental infection. The birds were removed from the experiment in accordance with the "Rules for carrying out work using experimental animals" and in accordance with the principles of the Declaration of Helsinki, and approved by the Institutional Review Board. The intensity of invasion (AI, lich./g) for each chicken and the average for the group and AI by the distribution of larvae in the slice were determined. Histological preparations of the spleen were prepared according to the classical method and stained with hematoxylin – eosin. Results. After digestion of muscle mass in artificial gastric juice, the number of larvae was 2570+640 l./g of muscles (average AI from muscle samples of the studied groups), no trichinella larvae were found in the control group. By CT, the largest AI was found in the muscles of the head (5.5+1.5 larvae in the section). The parenchyma of the organ of the spleen is represented by red and white pulp, in healthy birds the area of the red pulp was 10 + 5% of the area of the organ, and the white pulp 76.5 + 5% of the mass of the organ. In chickens infected with trichinella larvae, the area of the white pulp increased dramatically to 90% of the organ area and more. Conclusion. The chicken spleen is actively involved in the pathogenesis of helminthiasis of birds. The follicles of the white pulp, as in the trichinosis of white mice, grow, merging into large conglomerates. In birds, as well as in mammals, the number of large lymphocytes and plasmocytes increases, which indicates the similarity of intercellular interactions and the reaction of immunocompetent cells to the introduction of the parasite.

Anoxic waters constrain the vertical distribution of fish developmental stages in an oxygen minimum zone

AbstractIn the Eastern Tropical North Pacific Oxygen Minimum Zone (ETNP‐OMZ), fish larvae undergo development amidst highly variable dissolved oxygen environments. As OMZs expand, understanding the implications of low‐oxygen environments on fish development becomes increasingly relevant for fisheries management and ecosystem modeling. Using horizontal zooplankton tows to track five oxygen levels (oxic [200 μmol/kg], hypoxic [100 μmol/kg] suboxic [10 μmol/kg], anoxic [<1 μmol/kg], and deep [10 μmol/kg at ~ 1000 m depth]), this study analyzed the three‐dimensional distribution of fish larvae and adults across the ETNP‐OMZ. Results revealed a wide midwater anoxic core, extending from Costa Rica to Baja California, that was almost devoid of fish larvae (< 1 larvae/1000 m3). Early larval stages primarily inhabited the oxic and hypoxic levels above the core, while postflexion and transformation stages occurred across a wider oxygen gradient, including the deep level below the anoxic core. Epipelagic species (e.g., Auxis sp.) were predominantly found in the surface oxic level, whereas coastal‐demersal species (e.g., Bregmaceros bathymaster, Ophidion spp.) were prevalent in the hypoxic level above the core. Meso‐bathypelagic species (e.g., Diogenichthys laternatus, Cyclothone spp.) were present throughout the study area, including below the anoxic core as transformation larvae and juveniles. These findings indicate that a vertical expansion of anoxic waters in OMZs could further constrain the habitat of epipelagic species, while also affecting the ontogenic vertical movements of meso‐bathypelagic species.

Parasitic system Ixodes persulcatus (Ixodinae) – Borrelia garinii – small mammals in the northwest of Russia

Relationships between members of the parasitic system formed by the taiga tick Ixodes persulcatus (Schulze, 1930) at the preimaginal developmental stages, Borrelia garinii and small mammals were studied. Transovarial transmission of B. garinii in the taiga tick was not found. In natural biotopes of northwestern Russia, small mammals that were hosts of the preimaginal stages of Ixodes persulcatus included Myodes glareolus (Schreber, 1780) (52–53%), Sorex araneus Linnaeus, 1758 (33–34%), and Apodemus uralensis (Pallas, 1811) (14%). Larvae and nymphs were most numerous on hosts at the beginning of the season, in May and June. Subsequently, their number decreased by 5–10 times and slightly increased in September. In populations, up to 31.9% of M. glareolus individuals and 20.5% of A. uralensis individuals were infected with B. garinii. The aggregated type of distribution of taiga tick larvae and nymphs on hosts has been revealed. Infection of the main part of hungry larvae and nymphs occurred at the beginning of the activity season after wintering when feeding on overwintered infected hosts. This period is the key in circulation (exchange between vectors and reservoir hosts) and the preservation of B. garinii in the natural focus of borreliosis in northwestern Russia. Vertical transmission of B. garinii is possible from larvae and nymphs fed at the beginning of the season to nymphs and adult ticks that had molted in August-September, respectively. Horizontal transmission of the pathogen from small mammals, especially the bank vole, to larvae and nymphs, and vice versa, ensures the circulation and persistence of B. garinii in natural foci. The question of the preservation of the pathogen in overwintering preimaginal stages of ticks requires further research.

Distribution of fish larvae and juveniles on salinity in an estuary predicted from remote sensing and fuzzy logic approach

Distribution of fish larvae and juveniles on salinity in an estuary predicted from remote sensing and fuzzy logic approach

A decade-long study demonstrates that a population of invasive sea lamprey (Petromyzon marinus) can be controlled by introducing sterilized males

The release of sterilized insects to control pest populations has been used successfully during the past 6 decades, but application of the method in vertebrates has largely been overlooked or met with failure. Here, we demonstrate for the first time in fish, that a small population of sea lamprey (Petromyzon marinus; Class Agnatha), arguably one of the most impactful invasive fish in the world, can be controlled by the release of sterilized males. Specifically, the release of high numbers of sterile males (~ 1000's) into a geographically isolated population of adult sea lamprey resulted in the first multiyear delay in pesticide treatment since treatments began during 1966. Estimates of percent reduction in recruitment of age-1 sea lamprey due to sterile male release ranged from 7 to 99.9% with the precision of the estimate being low because of substantial year-to-year variability in larval density and distribution. Additional monitoring that accounts for recruitment variability in time and space would reduce uncertainty in the degree to which sterile male release reduces recruitment rates. The results are relevant to vertebrate pest control programs worldwide, especially as technical opportunities to sterilize vertebrates and manipulate sex ratios expand.

Seasonal fish larvae abundance and composition in seagrass habitats of coastal East Africa.

Seagrass habitats play a major role in fisheries productivity through nursery functions and feeding grounds for diverse fish species. However, little is known about the seasonal distribution of fish larvae at large spatial scales in coastal East Africa. We investigated drivers of the seasonal fish larvae abundance and composition in seagrass habitats in Kenya and Tanzania. We found a high diversity of fish larvae (54 families) inhabiting seagrass habitats that differed between sites and seasons. Fish larvae abundance were highest in Kenya, particularly during the northeast monsoon season. Overall, total larval abundances per site were low, reaching less than 190 individuals/100m3 in Kenya and less than 40 individuals/100m3 in Tanzania, likely related to the low productivity and strong hydrodynamic processes in this region. Our data suggests that most of the fish spawn year-round in these tropical waters as we did not find strong seasonal patterns. All sites had a high relative abundance of larvae from demersal spawning fishes, indicating that many fish species move to coastal sites for spawning. Primary productivity and dissolved oxygen, driven by hydrodynamics conditions are positively related to fish larvae productivity both in Kenya and Tanzania. These findings indicate that the occurrence of both resident and transient fish larvae in seagrass meadows is driven by strong hydrodynamic and tidal processes that transport fish larvae across adjacent habitats.

Assessing the Conservation Value of Artificial and Natural Reefs via Ichthyoplankton Spatio-Temporal Dynamics

The distribution of fish eggs and larvae (ichthyoplankton) reflects spawning and nursery areas as well as dispersal routes. This study’s goal is to demonstrate how the identification of ichthyoplankton species and stages and their spatial distribution among natural reefs (NRs) and artificial reefs (ARs) may serve as decision-making tools in conservation and fishery management. Natural reefs exhibited an eight-times higher abundance of eggs, as well as the highest abundance of larvae in the yolk-sac and preflexion phases. In contrast, ARs had the highest abundance of larvae in the flexion and postflexion phases. Natural reefs may serve as breeding grounds for Scaridae, Labridae, and Mugilidae; whereas, ARs may serve as breeding sites for Lutjanidae, Synodontidae, Carangidae, Fistularidae, and Haemulidae. Our study revealed differences between ARs and NRs, which demonstrate the potential of artificial reefs to expand the supply and settlement options of reef fishes and consequently can lead to increased fish production with potential benefits to adjacent fishing areas through connectivity. Thus, ARs as no-take sites can be effective tools for both fishery management and biodiversity conservation. The findings highlight the potential use of ichthyoplankton tools and the importance of considering both types of reefs in marine conservation and management efforts.

DNA metabarcoding as a tool for characterising the spatio-temporal distribution of planktonic larvae in the phylum Echinodermata

AbstractMetabarcoding is revolutionising the analysis of biodiversity in marine ecosystems, especially as it provides a means of detecting and identifying cryptic life stages in field samples. The planktonic larval stage of many species underpins the abundance and distribution of adult populations but is challenging to characterise given the small size of larvae and diffuse distributions in pelagic waters. Yet, planktonic larval dynamics are key to understanding phenomena observed in adult populations, such as the boom-and-bust dynamics exhibited by some echinoderms. Rapid changes in echinoderm population density can have significant effects on local benthic ecosystems. For example, outbreaks of the crown-of-thorns sea star (CoTS) on the Great Barrier Reef (GBR) have led to considerable declines in coral cover. Here, we used a DNA metabarcoding approach to investigate the spatio-temporal distribution and diversity of echinoderm larvae on the GBR, including CoTS. Generalised linear mixed models revealed that echinoderm larval richness, was significantly correlated with temporal variables (i.e. season and year) which is consistent with expected fluctuations in larval output based on adult spawning periodicity. However, neither site-specific differences in echinoderm larval richness, nor correlations between larval composition and environmental, temporal, or spatial variables were found. This study validates the utility of metabarcoding approaches for detecting and characterising echinoderm larvae, including CoTS, which could prove useful to future monitoring efforts. Our findings suggest that metabarcoding can be used to better understand the life history of planktonic larvae, and analyses combining environmental (e.g., temperature, nutrients) and oceanographic (e.g., currents) data could deliver valuable information on the factors influencing their spatio-temporal distributions.

Potential impacts of offshore wind energy development on physical processes and scallop larval dispersal over the US Northeast shelf

This study examines the potential impact of offshore wind energy facilities on the local and regional circulation, stratification, and scallop larval dispersal and settlement over the U.S. Northeast continental shelf. A coupled high-resolution (up to ∼ 1.0 m), wind turbine-resolving hydrodynamical (NS-FVCOM) and scallop individual-based (Scallop-IBM) model was employed. Comparisons were made for scenarios with and without wind turbine generators (WTGs), encompassing three-dimensional flow fields, water temperature, bottom stress/vertical mixing, scallop larval dispersal, settlement, and distributions. The interaction of M2 tidal currents with monopiles generates significant horizontal flow shear on the downflow lee side. The fluid–structure interaction-induced mesoscale currents deviate substantially from the idealized flow fields examined typically in the device-scale laboratory or coarse-grid hydrodynamical models with subgrid-scale explicit parametrizations. Stratification induces noteworthy changes in the flow around individual monopiles throughout the water column, with the maximum bottom stress primarily oriented in the onshore-offshore direction and vertical eddy viscosity occurring around all directions of individual monopiles. The deployment of a WTG array amplifies offshore low-frequency subtidal flow around 40 to 50-m isobaths, forming mesoscale eddies over the shelf. This enhanced flow contributes to offshore water transport, redirecting scallop larvae toward the Nantucket Lightship Closed Area (NLCA). The accumulation of larvae in the NLCA is attributed to eddy-induced retention.

Spontaneous intersibling polymorphism in the development of dopaminergic neuroendocrine cells in sea urchin larvae: impacts on the expansion of marine benthic species.

The plasticity of the nervous system plays a crucial role in shaping adaptive neural circuits and corresponding animal behaviors. Understanding the mechanisms underlying neural plasticity during development and its implications for animal adaptation constitutes an intriguing area of research. Sea urchin larvae offer a fascinating subject for investigation due to their remarkable evolutionary and ecological diversity, as well as their diverse developmental forms and behavioral patterns. We conducted immunochemical and histochemical analyses of serotonin-containing (5-HT-neurons) and dopamine-containing (DA-positive) neurons to study their developmental dynamics in two sea urchin species: Mesocentrotus nudus and Paracentrotus lividus. Our approach involved detailed visualization of 5-HT- and DA-positive neurons at gastrula-pluteus stages, coupled with behavioral assays to assess larval upward and downward swimming in the water column, with a focus on correlating cell numbers with larval swimming ability. The study reveals a heterochronic polymorphism in the appearance of post-oral DA-positive neuroendocrine cells and confirms the stable differentiation pattern of apical 5-HT neurons in larvae of both species. Notably, larvae of the same age exhibit a two- to four-fold difference in DA neurons. An increased number of DA neurons and application of dopamine positively correlate with larval downward swimming, whereas 5-HT-neurons and serotonin application induce upward swimming. The ratio of 5-HT/DA neurons determines the stage-dependent vertical distribution of larvae within the water column. Consequently, larvae from the same generation with a higher number of DA-positive neurons tend to remain at the bottom compared to those with fewer DA-positive neurons. The proportion of 5-HT and DA neurons within larvae of the same age underlies the different potentials of individuals for upward and downward swimming. A proposed model illustrates how coordination in humoral regulation, based on heterochrony in DA-positive neuroendocrine cell differentiation, influences larval behavior, mitigates competition between siblings, and ensures optimal population expansion. The study explores the evolutionary and ecological implications of these neuroendocrine adaptations in marine species.