International Journal of Aquatic Biology
Volume:11 Issue: 5, Oct 2023

The reproductive cycle of the Spondylus varius in Lianga Bay, Surigao del Sur, Philippines, was studied from September 2018 to October 2019. Histological examination showed that this species is gonochoric. The spawning occurred at the size of 80-100 mm shell length. Spondylus varius showed a continuous breeding season from December to April. The highest peak was recorded in April 2019. From August to October, the early and late gametogenesis stage predominates. Annual gonad development and spawning period coincided with the increase in sea surface temperature. In terms of management, it is important to leave a proportion of reproductively mature individuals in the population to allow breeding and recruitment. Thus, it is recommended that the collection of individuals smaller than 65 mm should be restricted and a ban on fishing imposed from February to May.

The Loa River is the longest Chilean river with 440 km, located in the Atacama Desert. It has three tributaries’ rivers, and its fauna has been poorly studied, due to mainly access difficulties. The aim of the present study was the first characterization of benthic invertebrate community structure in a confluence of Loa and Salado rivers considering the derive invertebrates and benthic communities. The results revealed that species composition in benthic samples has no significant differences between Salado and Loa rivers before the confluence with Salado River, but both sites had significantly high species numbers in comparison to Loa River in Calama after Salado confluence whereas in derive species composition did not have species differences. Finally, the results of null models revealed that species number for three sites had no structured pattern for benthic and derive samples. Ecological and biogeographical topics were discussed here.

Gonadotropin-releasing hormone (GnRH) is the foremost neuroendocrine peptide required in the reproduction system. Characterization and the involvement of GnRH in fish reproduction, especially in fish species has been complicated by the discovery of multiple GnRH forms. In this paper, we determined the molecular characterization and phylogenetic analysis of GnRH1 and GnRH2 genes in a commercially cultured catfish, Hemibagrus nemurus. This species is a high-demand freshwater fish worldwide especially in the Asia Pacific regions due to its thick flesh and high nutritional value. Problems in their breeding restrict the production of this species in captivity. Therefore, a thorough study of the GnRH genes is important due to their critical role in stimulating the secretion of gonadotropins hormone, which leads to the release of steroid hormones and activates the reproduction system. A complete open reading frame (ORF) of GnRH1 and GnRH2 genes was obtained through PCR amplification and cloned into TOPO® TA Cloning® kit, following sequence assembly and phylogenetic analysis. Phylogenetic analysis revealed the GnRH1 and GnRH2 of H. nemurus were clustered with Siluriformes, consisting of mostly catfish species including Pangasius nasutus and Pangasianodon hypopthalmus. The cDNA of GnRH1 was 371 bp with an ORF of 262 bp encoding a highly variable 81 amino acids, while the cDNA of GnRH2 was 376 bp with an ORF of 260 bp encoding a highly conserved 87 amino acids. This study could offer an advanced idea to develop a new GnRH agonist for artificial breeding of H. nemurus and other catfish sp.

The presence of mucopolysaccharides, glycogen, protein, and lipid component in the cellular constituents of saccus vasculosus of Pygocentrus nattereri Kner, 1858 were demonstrated histochemically using light microscopy. The saccus vasculosus was richly vascularized and comprised of a number of loculi enclosed by blood sinusoids. The loculi contained predominant coronet cells and supporting cells. Plenty of secretory materials were observed in the lumen. Periodic acid Schiff's reaction in combination with Alcian blue for mucopolysaccharides was positive for the apical protuberances of coronet cells and secretory matters in the lumen. Significant amounts of glycogen and protein were localized in coronet cells and blood cells. The coronet cells along with luminar protrusion contained an appreciable amount of DNA and RNA. Lipid is notably detected through Sudan black reaction in globular protrusion of coronet cells. The silver reaction was employed to investigate the presence and distribution of neurons within the epithelial lining as well as other regions of the saccus vasculosus. These histochemical tests revealed that the saccus vasculosus served dually as both a secretory and sensory organ.

Microplastic (MP) content in the gastropod, Telescopium telescopium, collected from the mangrove forest of Versova Creek, Mumbai was investigated. In total, 60 specimens were collected and pooled into six groups of 10 animals, each according to their weight and size. The concentration of extracted MP was expressed as the number of MP particles g-1 soft tissue (wet weight) and Ind.-1 (individual). MP was detected in all six groups and ranged from ~1 to 4 MP/g soft tissue and ~4 to 23 MP/individual. The minimum number of MP both in soft tissue and in each individual were 1.12 MP/g and 3.6 MP/Ind, respectively, and were found to be present in the lowest wet weight group (3.21±0.33 g). The size of the longest dimension of MP varied from 21-435 μm, most of which were smaller than 100 μm. The majority of the MP found in each weight group were colorless and transparent fragments were the most prevalent shape (55.20%). FTIR analysis showed polyethylene, polypropylene, and polyurethane were the major polymer types. The study reports the microplastic content in a gastropod, Telescopium inhabiting the mangroves of Mumbai, India. As an algal feeder/detritivore, the presence of MP in its soft tissue suggests molluscans are prone to consuming MP, relative to the environmental availability. They had a higher proportion of MP than body weight, indicating the potential transfer of MP into higher trophic levels of the mangrove ecosystem. Irregular fragment MP dominance indicates Telescopium graze on weathered plastic items covered by fouling algae and contributes to MP formation.

Ichthyophthirius multifiliis, a protozoan parasite, is a significant problem for fish farmers and Aquarium fish worldwide. This study aimed to evaluate the immunization of rainbow trout with gamma-irradiated, formalin inactive, and live theronts of I. multifiliis. In this study, fish were exposed to gamma-irradiated, formalin-inactivated, and live I. multifiliis theronts. Then, the histopathological changes in the mucous layers of the skin and intestines were studied after 7 and 14 days of exposure. Although no significant morphological changes were observed in the skin and intestines of the treated fish, the number of skin goblet cells increased significantly in fish treated with formalin-inactivated, gamma-inactivated, and live trophonts on 7 and 14 days. Compared to the negative control group, an increase in epidermal thickness on the skin was observed in fish challenged with formalininactivated, gamma-inactivated, and live trophonts. The numbers of mucous cells/total enterocytes in the intestinal epithelium of fish exposed to gamma-irradiated, formalin-inactivated, and trophonts live were higher than in non-infected fish. Moreover, a significant increase was found in the mucous cell numbers of the pyloric fold in treated fish with gamma-irradiated and formalin inactive trophonts at the first and second weeks. The results showed that the gamma-irradiated trophonts and formalin inactive trophonts could be safe for use in rainbow trout against I. multifiliis

One of the primary challenges in larval fish production lies in ensuring the nutritional quality of live feed. Most marine fish hatcheries commonly rely on rotifers and Artemia as live prey for the larvae. However, these live food sources often lack essential fatty acids crucial for normal growth. An encouraging solution to this nutritional deficiency is the utilization of thraustochytrids. This group of microorganisms exhibits a remarkable capacity to accumulate substantial amounts of omega-3 fatty acids, particularly DHA (docosahexaenoic acid). Thus, the present study explores the potential of utilizing Schizochytrium sp. as an enrichment source for Artemia and its effect on the development of Pompano (Trachinotus blochii) larvae. This study compares the larval performance of pompano-fed three different diets: Schizochytrium-enriched Artemia, Artemia enriched with commercial enrichment, and unenriched Artemia as a control group. Several key parameters were evaluated, including growth, survival rates, fatty acid levels, digestive enzyme activities, and the larvae's response to stress. The results revealed significantly higher survival rates and increased stress resistance in larvae that were fed Artemia enriched with Schizochytrium sp. and commercial enrichment compared to those fed unenriched live feed. The larvae fed with Schizochytrium-enriched Artemia exhibited the highest levels of DHA, body weight, and body length in comparison to the other treatments. Additionally, the enrichment with Schizochytrium demonstrated the capacity to enhance the digestive enzyme activities of the larvae, potentially leading to improved larval digestion and, consequently, enhanced growth, survival, and stress resilience. This study highlights the promising potential of Schizochytrium sp. as an effective enrichment source for Artemia, leading to remarkable improvements in the performance and nutritional quality of pompano larvae.

The effect of salinity (<1, 7, and 15 ppt) on some physiological and nutritional parameters of common carp (Cyprinus carpio) juveniles was examined in two trials. In the first trial, the activity of the common liver enzymes (alkaline phosphatase ALP, Aspartate transaminase AST, and Alanine transaminase ALT) in the blood serum, and total plasma protein level on the 1st, 7th, and 14th day of exposure, using 90 fish (14.05±2.01 g) were studied. In the second trial, the growth and feed efficiency performance (weight gain WG, relative growth rate RGR, specific growth rate SGR, and feed conversion ratio FCR), and apparent digestibility coefficients ADCs of dry matter, nutrients, and energy were investigated during ten ten-week rearing period using another 90 fish (15.71±1.59 g). The results showed that the activity of the ALP was increased significantly (P≤0.05) with increasing salinity on the 1st day, and continued to the following 7th and 14th day periods. AST in 7 and 15 ppt showed significantly (P≤0.05) higher activity levels compared with 1 ppt on the 1st day, similar differences were found on the 7th and 14th day for 15 ppt, but not for 7 ppt during the same periods. ALT exhibited significantly (P≤0.05) higher activity in 7 and 15 ppt relative to <1 ppt during all periods. Total plasma protein fluctuated slightly (P>0.05) on the 1st and 7th day and decreased significantly (P≤0.05) in 15 ppt only on the 14th day. Significantly (P≤0.05) better specific growth rate SGR and feed conversion ratio FCR were observed in the lowest salinity (<1 ppt) while the worst in the highest (15 ppt). The ADCs of dry matter, nutrients, and digestible energy were decreased significantly (P≤0.05) with increasing water salinity.

This study aimed to examine the feasibility of two algal species of Coelastrella saipanensis (Chlorophyceae) and Oscillatoria duplisecta (Cyanophyceae) to produce bioethanol production at different light intensities. In the present study, light-intensity treatments at 27, 36, and 67 μmol m-2 s-1 were used to stimulate bioethanol production from microalga. The effects of these treatments on C. saipanensis and O. duplisecta were investigated on their growth, carbohydrate and lipids contents. The results showed that the stationary phase of C. saipanensis started on the sixth day under light intensities of 27 and 36 μmol m-2 s-1 and on the eighth day under light intensity of 67 μmol m-2 s-1. The stationary stage of blue-green algae O. duplisecta started on day eight, sixth, and seventh under light intensities of 27, 36, and 67 μmol m-2 s-1, respectively. The highest amount of carbohydrate content was 0.182, and 0.310 mg/l for C. saipanensis and O. duplisecta under light intensity of 36 μmol m-2 s-1. The highest amount of lipid was 0.95 g/l for C. saipanensis under a light intensity of 36 μmol m-2 s-1, while 0.74 g/L was the highest amount of lipid for O. duplisecta under 67 μmol m-2 s-1 at a light intensity of 36 μmol m-2 s-1. The highest percentage of bioethanol in C. saipanensis and O. duplisecta were 11.35 and 10.23%, respectively. The 18S rRNA and 16S rRNA genes were used for the identification, and the sequences of algae matched those registered in the GenBank (MT375484.1 for C. saipanensis and MW405018.1 for O. duplisecta). The phylogenetic tree of the ITS area was analyzed inside the 18S rRNA and 16S rRNA and the sequences showed a strong resemblance to those species registered in the Genebank.

The five fish species viz. Periophthalmus waltoni, Silurus triostegus, Heteropneustes fossilis, Mastacembelus mastacembelus, and Coptodon zilli were collected in the Shatt Al-Arab River from February to June 2019. The samples were transferred to the laboratory to measure their total lengths and weights. To examine the skin histology and structure in these fishes, a skin sample was taken from the dorsal part close to the lateral line. The results showed that the skin of fish contains two layers: the first is the epidermis, which includes the epithelium. The thickness of the tissue in fish varied from 3 to 20 layers. In this layer, there are mucous cells that were spared and varied in their abundance from one species to another. The dermis includes two layers of stratum spongiosum and stratum compactum. These two layers consist of pigment cells that spread directly under the epidermis in a dark brown color. In C. zilli and H. fossilis, a third layer was found under stratum compactum as hypodermis; the highest thickness of the dermis was recorded in C. zilli.

A study was designed to (1) establish the taxonomy of diatom species in the Euphrates River, and (2) determine the effect of the main environmental factors on diatom community distribution in the Euphrates River. From 14 sites along part of the Euphrates River, samples of diatoms and water were taken during 2016. Diatom samples were collected from the water by phytoplankton nets at a randomly selected site. A total of 96 diatom species were recorded during the study period. Using correlation factor analysis, patterns of diatom species distributions in connection to environmental variables were discovered. Temperature, total suspended solids, total alkalinity, and phosphate (PO4) were all significantly and strongly linked with diatom species in both habitats (r = 0.85, 0.88, 0.92, and 0.83, respectively). Fragilaria crotonensis Kitton 1869 had a higher total number recorded (881.64 cells/l×103) during the study period, and site 2 had a higher total number compared with other sites (4845 cells/l×103). November had a higher total number recorded compared with other months (13722.64 cells/l×103). As a result, we concluded that in lotic systems, environmental conditions can affect the existence and distribution of diatoms.