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This study examined whether the potential early survival of sand lance in the Bisan Strait, central Seto Inland Sea, can be explained by variations in the growth rate and duration in the early life stages. Otolith microstructure analysis was conducted to examine the growth trajectories of specimens collected in six sampling years: 2011–2014, 2019, and 2020. There were significant differences in the growth rates of larvae and juveniles among sampling years, but such differences were likely attributable to variations in temperature in given seasons. Relative growth rates standardized by temperature were negatively correlated with the duration of the larval stage, suggesting that faster-growing individuals at given temperatures had a shorter larval stage. In each sampling year, there was a significant relationship between standardized hatch date and relative growth rate during the larval stage but not the juvenile stage. Within a given season, later-born larvae seemed to grow faster relative to the temperature experienced, and the higher percentages of the faster-growing larvae were likely associated with higher recruitment and recruitment per egg production. These findings suggest that the proportion of faster-growing sand lance larvae in a cohort at given temperatures explains the variation in potential early survival, but the higher temperatures in recent years may not necessarily contribute to improved early survival.

The aim of the study was to compare the relative gene expression of Haemonchus contortus P-glycoprotein genes (Hco-pgp) between fourth (L4), infective (L3), and transitory infective (xL3) larval stages as laboratory models to study ivermectin (IVM) resistance. The H. contortus resistant to IVM (IVMr) and susceptible to IVM (IVMs) strains were used to develop xL3 in vitro culture and to infect Meriones unguiculatus (gerbils) to collect L4 stages. Morphometric differences were evaluated from 25 individuals of H. contortus from each strain. Relative gene expression from xL3 and L4 was determined between comparison of IVMr stages and from IVMr vs IVMs stages. Seven Hco-pgp genes (1, 2, 3, 4, 9, 10, and 16) were analysed by RT-qPCR using L3 stage as control group, per strain, and GAPDH and β-tubulin as constitutive genes. Morphological changes were confirmed between xL3 and L4 developing oral shape, oesophagus, and intestinal tube. In addition, the body length and width showed statistical differences (p < 0.05). The Hco-pgp1, 2, 3, and 4 genes (p < 0.05) were upregulated from 7.1- to 463.82-fold changes between IVMr stages, and Hco-pgp9 (13.12-fold) and Hco-pgp10 (13.56-fold) genes showed differences between L4 and xL3, respectively. The comparative study between IVMr vs IVMs strains associated to xL3 and L4 displayed significant upregulation for most of the Hco-pgp genes among 4.89–188.71 fold-change. In conclusion, these results suggest the use of H. contortus xL3 and L4 as suitable laboratory models to study IVMr associated with Hco-pgp genes to contribute to the understanding of anthelmintic resistance.

The early life stages of marine organisms are pivotal in shaping community dynamics and resource availability. In this study, we focused on Portunus trituberculatus , a crustacean integral to China’s fisheries economy, and examined the effect of sea surface temperature (SST) in its critical early life stages on subsequent yields. To analyze the correlation between SST in different larval stages and the corresponding yield of P. trituberculatus , we simulated the transport and distribution of larvae from 2014 to 2022 by employing circulation models and Lagrangian particle tracking experiments (LPTE). In the five years (2014, 2015, 2016, 2019, and 2020), particles were transported in a northwestern direction and moved in the direction of low SST. The distribution of particles in the megalopa stage (M stage) were located in the region of the lower temperature. In 2017, 2018, and 2021, the particles were transported in a northeastern direction but they did not move with the gradient of low SST in these years, and the particles in the last M stage were located in the region where the SST was at the peak of the time period. In 2022, the distribution was observed for most of the particles in the southwestern part of Zhejiang coast, a small part of them were transported in the northwestern direction and a small amount of particles was distributed offshore along the northern area of the Zhejiang coast. The correlations between the SST at each stage of larvae with the corresponding year’s yield showed that the yield of P. trituberculatus decreased significantly ( R =−0.772, P =0.015) with increasing SST at the M stage. This study preliminarily explains the correlation between SST at the larval stage and the yield of P. trituberculatus and provides essential information for scientific stock enhancement in the future.

Following the recovery of the metacercariae of a brachylaimid trematode from the rectum of the frog from Ase in Delta State, Nigeria, we investigated the land snails in the locality to establish their roles in the life cycle of the parasite. Of the four land snails investigated from Ase ( , , , and ), and a sp. from Tombia (Bayelsa State), four harboured larval stages of the bracylaimid. Only and the sp. harboured cercariogenous sporocysts and are therefore presumed to serve as the first intermediate hosts of the parasite. Metacercariae were recovered from the spp. and the spp. and so serve as the second intermediate hosts. No larval brachylaimids were recovered from . Metacercariae from and were cultured in 14 days old chicks of . Parasites recovered from the experimental hosts 7, 14, 21 and 28 days post-infection, showed progressive development of the parasite with the full maturity attained by the 28 day post-infection. Adult parasites recovered from the experimental birds and from free range chicken purchased from Ase and Tombia showed that the brachylaimid infecting these birds was , a parasite previously reported in domestic chicken in Ghana. There is need to investigate the host range of the parasite in Nigeria as this trematode is also known to infect the Guinea fowl in Ghana.

The external morphology of the larval steps in the development of the Anomuran crab Allopetrolisthes punctatus is described using material obtained under laboratory conditions and from field samples. All stages are presented with photos taken with a scanning electron microscope. For the first time in this species, and in a similar way as described for the whole family Porcellanidae, it was possible to identify one prezoea, two zoeal and one megalopa stages. The main difference between the zoeal stages is the translucid spine in the center of the telson of the zoea II, surrounded by five gross setae at each side. Also, we also studied first juvenile stages to know the size at which sexual pleopods appear, which in our samples it occurred at 1.97 mm of carapace length.

Deiratonotus japonicus (D. japonicus) inhabits isolated locations and upstream brackish waters from Kanagawa Prefecture to Okinawa Prefecture in Japan. This species faces the threat of extinction because of changing habitat conditions. Our previous studies have shown that its complete larval development from hatching to metamorphosis consists of five zoeal stages and one megalopal stage. In this study, the effect of temperature on the survival and growth of larval development in D. japonicus under controlled laboratory conditions of 13, 18, 23, 24, 25, and 26 °C was investigated by rearing larvae (30 PSU; 12:12 h light/dark cycle; fed a diet of Brachionus plicatilis rotundiformis and Artemia sp. nauplii). The survival rates and developmental periods were measured for each larval stage. The highest survival rates were obtained at 18–24 °C. Metamorphosis to megalopa occurred at 23–25 °C. There were rapid and synchronous developments at 25–26 °C but delayed and extended developments at 13 °C. The molting period decreased with increasing temperature. With decreasing temperature, the beginning of the development and duration of molting was prolonged. In addition, there were very low survival rates at 13 °C and 26 °C in all zoeal stages. Our results indicate that the early larval stages of D. japonicus are well adapted to 18–24 °C, the range observed in the estuarine marine environment of the Kita River during the breeding season. Optimum larval survival and growth were obtained at 23 °C. Temperature significantly affected the survival rate, developmental period, and molting of the larvae. The relationship between the cumulative periods of development from hatching through individual larval stages (y) and temperatures (T) was described as a power function (y = a × Tb).

Induced homologous tetraploid oysters are typically derived from a limited number of effective parents, with subsequent breeding steps likely to cause inbreeding, which may cause their own production performance to decline. To explore the performance of inbreeding, we established outbred (F0) and inbred lines (F1 and F2) in tetraploid Pacific oyster. Cleavage rate, shell height, survival rate, and total weight were compared. Inbreeding coefficients in F0, F1, and F2 were 0, 0.25, and 0.375, respectively. The results showed that there was no significant difference in cleavage rate between outbred line and inbred lines. The F1 showed distinct growth and survival depression only at larval stage, but no depression at grow-out stage. F1 growth and survival IDC values at larval stage were − 1.29% to 0.03% and − 0.31% to 0.01%, respectively. However, depressed growth and survival rate appeared in almost all F2 growth cycle; F2 growth and survival IDC values were − 1.10% to − 0.78% and − 3.14% to − 4.51% in larval stage and − 0.48% to − 0.25% and − 0.79% to − 0.64% in grow-out stage, respectively. Growth and survival rate at Longkou and Qingdao sites showed no depression in the F1 line during grow-out stage. The results indicate that inbreeding depressed growth and in particular survival in tetraploid oysters. With increased inbreeding levels, depressed growth and survival became more distinct. We provided important insights on the inbred lines construction and further breeding of tetraploid oysters.

To discover new molecules or review the biological activity and toxicity of therapeutic substances, drug development, and research relies on robust biological systems to obtain reliable results. Phenotype-based screenings can transpose the organism’s compensatory pathways by adopting multi-target strategies for treating complex diseases, and zebrafish emerged as an important model for biomedical research and drug screenings. Zebrafish’s clear correlation between neuro-anatomical and physiological features and behavior is very similar to that verified in mammals, enabling the construction of reliable and relevant experimental models for neurological disorders research. Zebrafish presents highly conserved physiological pathways that are found in higher vertebrates, including mammals, along with a robust behavioral repertoire. Moreover, it is very sensitive to pharmacological/environmental manipulations, and these behavioral phenotypes are detected in both larvae and adults. These advantages align with the 3Rs concept and qualify the zebrafish as a powerful tool for drug screenings and pre-clinical trials. This review highlights important behavioral domains studied in zebrafish larvae and their neurotransmitter systems and summarizes currently used techniques to evaluate and quantify zebrafish larvae behavior in laboratory studies.

Larval development in marine fish is a critical phase for aquaculture, as morphological and physiological changes during early ontogeny largely determine survival and subsequent performance. Paralabrax humeralis , a serranid species from the southeastern Pacific, has potential for aquaculture diversification in northern Chile; however, information on its early developmental biology and allometric growth under culture conditions remains limited. Larvae were obtained from spontaneous spawning of broodstock and reared under semi-intensive production system conditions. From hatching to 35 days post-hatching (DPH), 10–18 larvae were sampled daily and measured for total length and multiple morphometric variables related to feeding and locomotion. Developmental stages were identified following standard larval classifications, and allometric growth patterns were analyzed using power regression models. Growth trajectories were explored using LOESS smoothing, and inflection points were estimated through slope comparison analyses. Five developmental stages were identified: yolk sac, preflexion, flexion, postflexion, and early juvenile. Early development showed pronounced positive allometric growth in head and tail-related structures, reflecting functional prioritization of feeding and swimming. During flexion, growth coefficients shifted, indicating changes in developmental priorities. In postflexion and juvenile stages, most body proportions exhibited a trend toward isometric growth. Inflection points in body proportion growth were detected between 7.99 and 8.73 mm total length. The overall specific growth rate was 7.2% day -1 . The observed allometric patterns indicate distinct ontogenetic growth priorities associated with key functional transitions during early development. These findings establish a morphological baseline for P. humeralis and provide essential information for optimizing larviculture protocols, supporting its incorporation into aquaculture systems in northern Chile.

Most marine organisms present an indirect lifecycle where a planktonic larval stage reaches competency before settling to the substrate and metamorphosing. Despite the critical importance of these early life history stages, little is known about how global change-related stressors, in particular ocean acidification (OA), affect marine larval settlement and metamorphosis. To date, 48 studies have investigated the effects of OA on larval settlement, focussing mostly on tropical corals (16), echinoderms (11) and fish (8). Most studies show negative effects of OA during settlement and post-settlement processes. For instance, reduced settlement is typically seen along natural pH gradients and in experimentally lowered pH treatments. This generally results in reduced settlement selectivity and metamorphosis and poorer post-settlement fitness. Carryover effects of OA exposure can also occur, with larval environmental history influencing early post-settlement performance. We conclude that OA may (1) alter larval supply for settlement by altering horizontal swimming behaviour or vertical migration; (2) directly influence settlement success through changes in the nature and distribution of suitable settlement substrates (e.g. biofilm, crustose coralline algae); and (3) mediate carryover effects at settlement by altering larval development or larval energy budgets. In contrast to fish larvae, there is little evidence for most invertebrate larvae that their perception of settlement cues is directly influenced by reduced pH. A summation of how OA affects the settlement and metamorphosis of marine invertebrates is timely, since altered settlement rates will influence the future distributions, abundances and ecology of marine benthic communities.