Journal of fish biology最新文献

Atlantic salmon is an important aquaculture species that has fascinated naturalists for centuries, resulting in its biology being widely characterized. Certain details about the early development and the inheritance of meristic variation in the post-cranial axial skeleton are, however, largely unexplored. The present study gives a detailed description of the sequence of formation of the post-cranial axial skeleton based on whole-mount staining and used radiology to investigate the inheritance of meristic variation in isogenic hybrid all-male families of Atlantic salmon (~4 kg). Eight different families were created by crossing two homozygous double haploid XX females (dam A, B) with four different double haploid homozygous YY super males (sires a to d). In the caudal fin complex, the first bone to form is hypural 1 and its associated lepidotrichia followed by a bidirectional formation of new bones. In the dorsal and anal fins, development starts in the cranial part, and new bones form bidirectionally towards the head and tail fin. The neural and haemal arches start to form at segment 43, and further development is bidirectional. The first parapophysis form in the caudal part of the abdomen followed by a unidirectional completion cranially. The first ribs form at segment 3 and new ribs develop unidirectional caudally. Chordacentra formation starts at segment 24 followed by formation of chordacentrum number 58 (caudal-most vertebra). New chordacentrae form bidirectionally from segment 24 in parallel with the formation of chordacentrum number 57. The first epineuralia form at segment 1 followed by a unidirectional completion caudally until segment 30. The first supraneuralia to develop is number 10 closely followed by number 1, then new supraneurals form bidirectionally from number 10. Analysis of the inheritance on the post-cranial axial skeletal bones showed a strong maternal effect on total vertebrae centra and tail fin lepidotrichia counts. For these skeletal counts, dam A produced offspring with modes of 58 and 45 respectively, while dam B produced offspring with modes of 59 and 42. The higher number of total vertebrae centra produced by dam B was associated with additional abdominal and/or transitional vertebrae. The completion of formation in different post-cranial axial skeletal parts are either bi- or unidirectional, and the initiation of formation is site specific for each skeletal part with some inter-part similarities. Further, the present results may suggest that there has been a maternally driven selection for more abdominal vertebrae associated with a higher number of total vertebrae, and more tail fin lepidotrichia associated with a lower number of total vertebrae. These changing meristic counts may impact on important fitness-related traits, such as fecundity and swimming ability, making the present findings relevant for both ecological and aquaculture sciences.

Chromis tweddlei, a new species of damselfish, is described from seven specimens, 88.8-111.1 mm standard length (SL), collected during a 2008 expedition by the R.V. Dr. Fridtjof Nansen at 214-219 m depth (an unusually deep occurrence for the genus) on the Cargados Carajos Bank, Mascarene Plateau, southwestern Indian Ocean. Chromis tweddlei sp. nov. closely resembles Chromis axillaris, Chromis pelloura, and Chromis woodsi, the only congeners occurring in the western Indian Ocean (WIO) that share the character of having 14 dorsal-fin spines and a dark caudal band. Chromis tweddlei sp. nov. can be distinguished from its regional congeners by having II,13-14 anal-fin rays, 19-20 pectoral-fin rays, 18-19 tubed lateral-line scales, 4 scales above lateral line to the origin of dorsal fin, 29-32 total gill rakers, and colouration, including a caudal band that tapers anteriorly the full length of the caudal peduncle. A key to the 14 dorsal-fin spine species of Chromis from the WIO is provided.

To clarify the differences between migratory and non-migratory salmonids during the parr-smolt transformation, we conducted experiments on steelhead (SH) and rainbow trout (RT) Oncorhynchus mykiss. We examined relationships among different parameters of osmoregulatory, endocrine, immune, and stress-related regulation in these fish following free selection of salinities. For this, we used an experimental halocline aquarium in which the upper layer was filled with fresh water and the lower with seawater. There was no significant difference between the two trout strains in terms of the number of fish in the final positions after the overnight trial. However, the time spent by each fish in the lower tank during the overnight trial was significantly longer in SH than in RT. Additionally, the time spent by each fish in the lower tank and plasma cortisol concentration were significantly correlated in RT, but not in SH. Similarly, plasma osmolality after the trial had a significant positive correlation with plasma cortisol concentration in RT, but not in SH. The plasma cortisol and mRNA levels of sodium-potassium ATPase-α3 in the gill were negatively correlated, as were several types of cortisol receptors in the gill and brain, in RT. Meanwhile, the genes expressed in SH were positively correlated with plasma cortisol. In SH, plasma cortisol was also significantly correlated with immune and stress-related factors, which was not seen in RT. Our results suggest that the studied factors are important to behavioral and physiological differences in anadromy among salmonid species.

This study investigated the impact of an oxygen-rich spray on rainbow trout subjected to short-term air exposure episodes. These episodes can be due to sampling procedures or catch-and-release (C&R) practices, focusing on behavioral, haematological, and physiological responses. For this, 12 rainbow trout were divided into two groups: control and oxygen-rich sprayed fish. The fish were chased for 3 min and exposed to air for 6 s, and blood and behavior parameters were assessed. Simulated C&R resulted in partial physiological reflex impairment across groups. However, sprayed fish exhibited significant differences during recovery in head complex reflex and faster tendencies to regain orientation compared to control. Haematological analyses revealed that the treated group displayed reduced erythrocyte swelling and maintenance of red blood cell (RBC) counts, indicating reduced need for compensatory responses to hypoxia. Meanwhile, stress-related indicators, including cortisol, glucose, and lactate, remained unaffected by the treatment, suggesting no interference of spraying with the fish ability to launch a healthy stress response. No adverse effects were observed on skin surfaces or gills after an exploratory analysis. Overall, the oxygen-rich spray exhibited favorable effects, indicating potential benefits in protecting rainbow trout during C&R practices or sampling episodes. Moreover, there is a possible wider application of this methodology to benefit other species of fish subjected to stressors such as aquaculture, research, and fisheries management.

Pinfish (Lagodon rhomboides) are highly abundant in coastal ecosystems of the Gulf of Mexico and western Atlantic Ocean and serve as a crucial link in marine food webs. Despite their ecological relevance, little is known about this species' susceptibility to anthropogenic climate change. Here, we characterized patterns of mitochondrial genetic divergence and examined the upper thermal tolerance of pinfish across a large portion of the species' range. We found little evidence of population genetic differentiation among distant localities with divergent temperature regimes (e.g., Mexico and North Carolina), using two mitochondrial markers (cytochrome b [CytB] and cytochrome c oxidase I [COI]). This suggests high genetic connectivity, which implies low potential for local adaptation of populations to different thermal conditions along a latitudinal gradient. To further examine population-scale differences in thermal tolerance, we assessed the critical thermal maxima (CT_max) of pinfish from four localities: North Carolina, Florida Keys, Alabama, and Texas. We found that CT_max was similar across sites, with all localities showing an average CT_max within a 1°C temperature range (34.5-35.5°C). This suggests that southern populations of pinfish may be more susceptible to the detrimental effects of ocean warming, as individuals in lower latitudes regularly experience temperatures within a few degrees of their CT_max. Finally, we examined the influence of varying salinity on the upper thermal limit of the pinfish and found that pinfish show no variation in CT_max under salinity conditions ranging from hypo- to hypersaline (15-35 ppt). These results show that pinfish can tolerate a wide range of environmental parameters but may rely on phenotypic plasticity, rather than local adaptation, to distinct conditions to cope with different environmental regimes.

The roughskin dogfish Centroscymnus owstonii, a deep-sea shark, has a patchy global distribution, with most knowledge stemming from incidentally captured specimens. Using a deep-sea remote lander video system, we observed multiple C. owstonii individuals alive on the footage at 1054 m off Little Cayman, Cayman Islands, Western Atlantic Ocean, marking, to our knowledge, the first record of the species in the Greater Antilles, central Caribbean Sea, while also adding a new species locality record for the Cayman Islands. This study expands our knowledge of the distribution of the roughskin dogfish in the region, and highlights the utility of video lander systems for enhancing and expanding our understanding of the biology and diversity of deep-sea sharks.

Underwater fish object detection serves as a pivotal research direction in marine biology, aquaculture management, and computer vision, yet it poses substantial challenges due to the complexity of underwater environments, occultations, and the small-sized and frequently moving fish in aquaculture. Addressing these challenges, we propose a novel underwater fish object detection algorithm named Fish-Finder. First, we engendered a structure titled "C2fBF," utilizing the dual-path routing attention protocol of BiFormer. The primary objective of this structure is to alleviate the perturbations induced by underwater intricacies during the phase of downsampling in the backbone network, thereby discerning and conserving finer contextual features. Subsequently, we co-opted the RepGFPN method within our neck network-a distinctive approach that adeptly merges high-level semantic constructs with low-level spatial specifics, thus fortifying its multi-scale detection prowess. Then, in an endeavor to diminish the sensitivity toward positional aberrations during the detection of diminutive aquatic creatures, we incorporated a novel bounding box regression loss function, the Wasserstein loss, to the existing CIoU. This innovative function gauges the congruity between the predicted bounding box Gaussian distribution and the reference bounding box Gaussian distribution. Finally, in regard to the dataset, we independently assembled a specific dataset termed "SmallFish." This unique dataset, meticulously designed for the detection of small-scale fish within intricate underwater settings, includes 5000 annotated images of small fish. Experimental results demonstrate that, compared to the state-of-the-art detection methods, our proposed method improves the accuracy by $2.58\%$ and $2.32\%$ , and mean average precision (mAP) increases $2.6\%$ and $2.53\%$ in public dataset Kaggle-Fish and our SmallFish dataset, respectively.

Temperature is a leading environmental factor determining the sex ratio of some animal populations, such as fish, amphibians, and reptiles. However, the underlying mechanism by which temperature affects gender is still poorly understood. Transient receptor potential a1b (Trpa1b) belongs to the ion channel family of transient receptor potentials and exhibits dual thermosensitivity to heat and cold. In this study, we have unveiled a novel function of the trpa1b gene. Zebrafish generated through clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 with Trpa1b-null manifest a male-biased sex ratio. The quantity of primordial germ cells (PGCs) in zebrafish is closely linked to gender determination and gonadal development. Yet the role of the trpa1b gene in zebrafish reproductive development remains unexplored in the literature. Our investigation revealed a significant reduction in PGCs in Trpa1b mutant zebrafish compared to their wild-type counterparts 24-h postfertilization (hpf). Transcriptome sequencing of tissues near the reproductive crest of embryos at 1.25 days postfertilization (dpf) revealed differential changes in PGC-related marker genes and genes related to sperm cell development and differentiation. The relative expression of ddx4 and sycp3 genes was significantly downregulated, whereas amh was significantly upregulated at 20 dpf in trpa1b^-/- zebrafish. The results of this study provide valuable insights and references for studying the molecular mechanism of sex determination in zebrafish. Undoubtedly, these results will further enhance our understanding of gender differentiation and gonadal development in fish and other vertebrates.

Warmer and more variable temperatures have been implicated in the recent decline of Atlantic salmon (Salmo salar) in Eastern Canada. To date, we know little on how ecologically relevant thermal fluctuations affect swimming performance in fishes. The goal of this study is to determine the effects of warm versus cool diel thermal variability on swimming efficiency and the speed limit for sustainable aerobically fueled swimming. We acclimated wild S. salar juveniles to a cool and a warm ecologically realistic diel thermal profile (16-21 and 19-24°C), and then tested individuals over a common acute change in temperature (16-24°C). We measured metabolic rate and swimming kinematics at a range of swimming speeds, at five temperatures (16, 18, 20, 22, and 24°C) and calculated swimming efficiency. Our temperature acclimation did not appear to significantly affect energetic and kinematic swimming efficiency, but acute exposure to high temperature did increase overall metabolic rate. It appears that wild S. salar can swim efficiently and sustainably during both acute cool and warm exposures, and after acclimation to diel thermal variation of 16-21 or 19-24°C.