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In the past 100 years since the birth of fisheries oceanography, research on the early life history of fishes, particularly the larval stage, has been extensive, and much progress has been made in identifying the mechanisms by which factors such as feeding success, predation, or dispersal can influence larval survival. However, in recent years, the study of fish early life history has undergone a major and, arguably, necessary shift, resulting in a growing body of research aimed at understanding the consequences of climate change and other anthropogenically induced stressors. Here, we review these efforts, focusing on the ways in which fish early life stages are directly and indirectly affected by increasing temperature; increasing CO₂ concentrations, and ocean acidification; spatial, temporal, and magnitude changes in secondary production and spawning; and the synergistic effects of fishing and climate change. We highlight how these and other factors affect not only larval survivorship, but also the dispersal of planktonic eggs and larvae, and thus the connectivity and replenishment of fish subpopulations. While much of this work is in its infancy and many consequences are speculative or entirely unknown, new modeling approaches are proving to be insightful by predicting how early life stage survival may change in the future and how such changes will impact economically and ecologically important fish populations.

Coral reef fish have considerable larval behavioral capabilities that can lead to successful completion of the early pelagic life phase. In particular, vertical migration during ontogeny increases retention near natal reefs and decreases losses due to transport by currents. For those larvae that are not returning home, the relative influence of behavior (biology) and currents (physics) on their arrival pattern among adjacent and distant reefs is not known. Moreover, interactions of the naturally small-scale larval movements with those of larger-scale currents need to be evaluated with regard to the spatial patterns of recruitment. We used an offline Lagrangian stochastic modeling approach to explore the relative influence of physical (i.e. eddy perturbation, diffusion) and biological processes (i.e. vertical movement, mortality) on the connectivity of the coral reef fish population in the western Caribbean, a region with complex geomorphology and circulation. This study revealed that the impact of larval behavior extends beyond enhancing the process of self-recruitment by changing population connectivity patterns. Connectivity was significantly influenced by larval vertical movement, survival, and by the eddy field, all controlling arrival patterns near reefs. A sensitivity analysis was done to gauge the robustness of the results by varying the model parameters. We found that particle-tracking models with homogeneous parameterization of the sub-grid motion tended to bias dispersal from and along the reef track, which can be mitigated by using spatially explicit parameters calculated from the Eulerian velocity fields. Finally, larval survival emerged as a key component for connectivity estimates, the study of which poses a great challenge in tropical ecosystems.

Investigating the main factors regulating the growth and survival of fish in early stages of development is essential for the understanding of their trophic relationships. Most fish larvae are active planktonic predators which feed on motile prey and their success in foraging is influenced by several factors, such as the availability of suitable prey. We aimed to investigate the role of ciliate protists as a food resource in the different stages of development of fish larvae of Astyanax lacustris, when presented to a natural prey assembly. Our results show, through an experimental approach, that ciliate protists are an important item in A. lacustris larvae diet, especially in the early stages of their development, becoming an additional resource in more advanced stages, when A. lacustris larvae change their food preference, selecting larger food items such as adult copepods.

The effects of stress during early vertebrate development can be especially harmful. Avoiding stressors in fish larvae is essential to ensure the health of adult fish and their reproductive performance and overall production. We examined the consequences of direct exposure to successive acute stressors during early development, including their effects on miR-29a and its targets, survival, hatching and malformation rates, larval behaviour and cartilage and eye development. Our aim was to shed light on the pleiotropic effects of early-induced stress in this vertebrate model species. Our results showed that direct exposure to successive acute stressors during early development significantly upregulated miR-29a and downregulated essential collagen transcripts col2a1a, col6a2 and col11a1a, decreased survival and increased malformation rates (swim bladder, otoliths, cardiac oedema and ocular malformations), promoting higher rates of immobility in larvae. Our results revealed that stress in early stages can induce different eye tissular architecture and cranioencephalic cartilage development alterations. Our research contributes to the understanding of the impact of stressful conditions during the early stages of zebrafish development, serving as a valuable model for vertebrate research. This holds paramount significance in the fields of developmental biology and aquaculture and also highlights miR-29a as a potential molecular marker for assessing novel larval rearing programmes in teleost species.

The life cycles of fishes are complex and varied, and knowledge of the early life stages is important for understanding the biology, ecology, and evolution of fishes. InEarly Life History of Marine Fishes,Bruce S. Miller and Arthur W. Kendall Jr., bring together in a single reference much of the research available and its application to fishery science-knowledge increasingly important because for most fishes, adult populations are determined at the earliest stages of life. Clear and well written, this book offers expert guidance on how to collect and analyze larval fish data and on how this information is interpreted by applied fish biologists and fisheries managers.

To describe the species composition of fish larvae and juveniles in the Nanji Islands, monthly collection was conducted at 12 stations around the Nanji Islands from March 2023 to February 2024 by using horizontal tow at the surface layer. The fish larvae and juveniles were collected by a larva net (1.3 m mouth diameter, 0.5 mm mesh aperture). A total of 6446 fish larvae and juveniles were collected, belonging to 59 species and 54 genera in 11 families. Most of them were preflexion larvae (93.31%). Gobiidae, with eight species, was the most diverse family. Based on the index of relative importance (IRI) result, the dominant species was Sebastiscus marmoratus (Cuvier, 1829), accounting for 84.52% of the total number of samples collected. The common species were Stolephorus commersonii Lacepède, 1803; Omobranchus elegans (Steindachner, 1876); Nibea albiflora (Richardson, 1846); Parablennius yatabei (Jordan & Snyder, 1900); Lateolabrax maculatus (McClelland, 1844); and Odontamblyopus lacepediiand (Temminck & Schlegel, 1845). Other species were all rare species. The highest species number was in September (18 species), and the highest density was in December. Only one fish larva was collected in April. Pielou’s evenness index was highest in November, while Margalef’s richness index and Shannon–Wiener diversity were highest in September. The result of cluster analysis showed that the 11 months (except April) could be divided into four groups. The species number, density, and three diversity indexes showed no significant correlation with temperature and salinity.

We investigated the influence of host species on intestinal microbiota by comparing the gut bacterial community structure of four cohabitating freshwater fish larvae, silver carp, grass carp, bighead carp, and blunt snout bream, using denaturing gradient gel electrophoresis (DGGE) of the amplified 16S and 18S rRNA genes. Similarity clustering indicated that the intestinal microbiota derived from these four fish species could be divided into four groups based on 16S rRNA gene similarity, whereas the eukaryotic 18S rRNA genes showed no distinct groups. The water sample from the shared environment contained microbiota of an independent group as indicated by both 16S and 18S rRNA genes segments. The bacterial community structures were visualized using rank-abundance plots fitted with linear regression models. Results showed that the intestinal bacterial evenness was significantly different between species (P less than 0.05) and between species and the water sample (P less than 0.01). Thirty-five relatively dominant bands in DGGE patterns were sequenced and grouped into five major taxa: Proteobacteria (26), Actinobacteria (5), Bacteroidetes (1), Firmicutes (2), and Cyanobacterial (1). Six eukaryotes were detected by sequencing 18S rRNA genes segments. The present study suggests that the intestines of the four fish larvae, although reared in the same environment, contained distinct bacterial populations, while intestinal eukaryotic microorganisms were almost identical.

Background Cystinosis is a rare, incurable lysosomal storage disease caused by mutations in the CTNS gene encoding the cystine transporter cystinosin, which leads to lysosomal cystine accumulation in all cells of the body. Patients with cystinosis display signs of podocyte damage characterized by extensive loss of podocytes into the urine at early disease stages, glomerular proteinuria, and the development of focal segmental glomerulosclerosis (FSGS) lesions. Although standard treatment with cysteamine decreases cellular cystine levels, it neither reverses glomerular injury nor prevents the loss of podocytes. Thus, pathogenic mechanisms other than cystine accumulation are involved in podocyte dysfunction in cystinosis. Methods We used immortalized patient-derived cystinosis, healthy, and CTNS knockdown podocytes to investigate podocyte dysfunction in cystinosis. The results were validated in our newly in-house developed fluorescent ctns −/− [Tg(fabp10a:gc-EGFP)] zebrafish larvae model. To understand impaired podocyte functionality, static and dynamic permeability assays, tracer-metabolomic analysis, flow cytometry, western blot, and chemical and dynamic redox-sensing fluorescent probes were used. Results In the current study, we discovered that cystinosis podocytes demonstrate increased ferroptotic cell death caused by mitochondrial reactive oxygen species (ROS)-driven membrane lipid peroxidation. Moreover, cystinosis cells present a fragmented mitochondrial network with impaired tricarboxylic acid cycle (TCA) cycle and energy metabolism. Targeting mitochondrial ROS and lipid peroxidation improved podocyte function in vitro and rescued proteinuria in vivo in cystinosis zebrafish larvae. Conclusions Mitochondrial ROS contribute to podocyte injury in cystinosis by driving lipid peroxidation and ferroptosis, which in turn lead to podocyte detachment. This finding adds cystinosis to the list of podocytopathies associated with mitochondrial dysfunction. The identified mechanisms reveal new therapeutic targets and highlight lipid peroxidation as an exploitable vulnerability of cystinosis podocytes.

The transport of larval coral reef fishes to juvenile habitat inherently requires that they survive the planktonic journey; however, the processes governing survival—particularly those related to feeding—are not well known. Monthly sampling across the Straits of Florida allowed for analyses of the diets and diet variability of several co-occurring taxa of coral reef fish larvae from the families Serranidae, Lutjanidae, Mullidae, Pomacentridae, Labridae, Scaridae and Acanthuridae. The proportions of larvae with food present in the gut were high (0.94 to 1.0) for all taxa except scarids (0.04), and diets were generally narrow and predator-specific.Serranusspp. (Serranidae) diets changed little with growth and were composed almost entirely of calanoid copepods, while the labridsThalassoma bifasciatumandXyrichtysspp. consumed harpacticoid and cyclopoid (FarranulaandOncaea) copepods almost exclusively throughout ontogeny. Lutjanine and acanthurid larvae relied increasingly upon appendicularians with growth, and mullids exhibited an ontogenetic shift from nauplii to calanoid copepodites and appendicularians. Cluster analysis examining diet similarity among taxa yielded clear groupings: small acanthurids, labrids, appendicularian-feeders, and a fourth group consisting of subgroups of larvae with calanoid and mixed diets. Within larval taxa, canonical correspondence analysis indicated how diet varied with several environmental and larva-specific variables. The trophic niche breadth of 4 taxa decreased significantly with growth, while other taxa exhibited no significant change. These results highlight distinct differences between high- and low-latitude regions, most notably the taxon-specific trophic roles and the apparent niche partitioning of larval fishes within the diverse planktonic food webs of lower latitudes.

Fluoxetine (FLX) is one of the main antidepressants used worldwide. After human use, FLX enters the aquatic ecosystems, where it has commonly detected in the high ng/L concentration range. Several investigations have shown that exposure to different concentrations of FLX caused different adverse effects towards a number of aquatic species. However, the information on the onset and the relationship between molecular and behavioral FLX-induced effects remains scant. The aim of this study was to assess the effects induced by two FLX concentrations, namely 50 ng/L and 500 ng/L, on swimming activity of zebrafish ( Danio rerio ) larvae at 96-h post-fertilization (hpf) and to investigate if such behavioral effects were related to modulation of the expression of oxidative stress-related ( sod1 , sod2 , cat , gpxa , and gst ), stress- and anxiety-related ( oxtl , prl2 , npy , and ucn3l ) genes, and genes encoding for the transporters of the main neurotransmitters ( slc6a3 , slc6a4a , slc6a4b , slc6a11 ). Fluoxetine exposure altered the swimming behavior of larvae, as shown by the reduction of the distance traveled by treated larvae in response to an external stimulus. Such behavioral change was related, at molecular level, to an enhanced expression of sod1 , cat , and gpxa , suggesting an overproduction of pro-oxidant molecules. In addition, FLX modulated the expression of oxtl , slc6a4a , slc6a4b , and slc6a11 , suggesting its capability to affect anxiety- and neurotransmitter-related genes.