Histological Comparison of the Edible Water Frog (Pelophylax ridibundus Pallas, 1771) Gonads Before and After Reproduction

In this study, testicular and ovarian structures of economically important edible Pelophylax ridibundus (Pallas, 1771) were histologically examined before and after reproduction in male and female individuals. Fourty eight (24 ♀, 24 ♂) adult frogs were collected from Gölbaşı Lake in Hatay. The average weight and length values of female frogs collected from nature were found to be 56.61±19.59 g and 79.54±7.07 mm; while, the average weight and length values of male frogs were 36.63±12.84 g and 69.29±9.15 mm, respectively. Frogs were brought to the frog farm established in Aydıncık and placed in breeding ponds with a width of 1m2. Frogs in the ponds were brought to the laboratory of Iskenderun Technical University in different periods, before breeding (March) and after breeding (June). Then, histological samples were taken from ovary and testis. The female frogs were determined ready for reproduction. Moreover, a large number of mature oocytes in the before breeding ovaries in vitellogenic stage, while after reproduction oocytes in primary structure and oocytes which have atresia status observed. Also, increase in the thickness of the theca layer was determined. In the male frog seminiferous tubules containing a large number of spermatogonia, spermatocyte, spermatid and a small number of spermatozoons including sperm bundles and leydig cells were found before reproduction. After the reproduciton, the density of spermatogonia, spermatocyte and spermatids were decreased; while, the density of spermatozoon and sperm bundle were increased in the seminiferous tubules. This study will contribute to the determination of mating and spawning in frog breeding by revealing the histological status of the gonad structure of P. ridibundus in the breeding process.

The FTZ-F1 gene encodes two functionally distinct nuclear receptor isoforms in the ectoparasitic copepod salmon louse (Lepeophtheirus salmonis)

The salmon louse, Lepeophtheirus salmonis, is an ectoparasitic crustacean that annually inflicts substantial losses to the aquaculture industry in the northern hemisphere and poses a threat to the wild populations of salmonids. The salmon louse life cycle consists of eight developmental stages each separated by a molt. Fushi Tarazu Factor-1 (FTZ-F1) is an ecdysteroid-regulated gene that encodes a member of the NR5A family of nuclear receptors that is shown to play a crucial regulatory role in molting in insects and nematodes. Characterization of an FTZ-F1 orthologue in the salmon louse gave two isoforms named αFTZ-F1 and βFTZ-F1, which are identical except for the presence of a unique N-terminal domain (A/B domain). A comparison suggest conservation of the FTZ-F1 gene structure among ecdysozoans, with the exception of nematodes, to produce isoforms with unique N-terminal domains through alternative transcription start and splicing. The two isoforms of the salmon louse FTZ-F1 were expressed in different amounts in the same tissues and showed a distinct cyclical expression pattern through the molting cycle with βFTZ-F1 being the highest expressed isoform. While RNA interference knockdown of βFTZ-F1 in nauplius larvae and in pre-adult males lead to molting arrest, knockdown of βFTZ-F1 in pre-adult II female lice caused disruption of oocyte maturation at the vitellogenic stage. No apparent phenotype could be observed in αFTZ-F1 knockdown larvae, or in their development to adults, and no genes were found to be differentially expressed in the nauplii larvae following αFTZ-F1 knockdown. βFTZ-F1 knockdown in nauplii larvae caused both down and upregulation of genes associated with proteolysis and chitin binding and affected a large number of genes which are in normal salmon louse development expressed in a cyclical pattern. This is the first description of FTZ-F1 gene function in copepod crustaceans and provides a foundation to expand the understanding of the molecular mechanisms of molting in the salmon louse and other copepods.

Comparative transcriptomic analysis of the different developmental stages of ovary in red swamp crayfish Procambarus clarkii

Background The red swamp crayfish Procambarus clarkii is a freshwater species that possesses high adaptability, environmental tolerance, and fecundity. P. clarkii is artificially farmed on a large scale in China. However, the molecular mechanisms of ovarian development in P. clarkii remain largely unknown. In this study, we identified four stages of P. clarkii ovary development, the previtellogenic stage (stage I), early vitellogenic stage (stage II), middle vitellogenic stage (stage III), and mature stage (stage IV) and compared the transcriptomics among these four stages through next-generation sequencing (NGS). Results The total numbers of clean reads of the four stages ranged from 42,013,648 to 62,220,956. A total of 216,444 unigenes were obtained, and the GC content of most unigenes was slightly less than the AT content. Principal Component Analysis (PCA) and Anosim analysis demonstrated that the grouping of these four stages was feasible, and each stage could be distinguished from the others. In the expression pattern analysis, 2301 genes were continuously increase from stage I to stage IV, and 2660 genes were sharply decrease at stage IV compared to stages I-III. By comparing each of the stages at the same time, four clusters of differentially expressed genes (DEGs) were found to be uniquely highly expressed in stage I (136 genes), stage II (43 genes), stage III-IV (49 genes), and stage IV (22 genes), thus exhibiting developmental stage specificity. Moreover, in comparisons between adjacent stages, the number of DEGs between stage III and IV was the highest. GO enrichment analysis demonstrated that nutrient reservoir activity was highest at stage II and that this played a foreshadowing role in ovarian development, and the GO terms of cell, intracellular and organelle participated in the ovary maturation during later stages. In addition, KEGG pathway analysis revealed that the early development of the ovary was mainly associated with the PI3K-Akt signaling pathway and focal adhesion; the middle developmental period was related to apoptosis, lysine biosynthesis, and the NF-kappa B signaling pathway; the late developmental period was involved with the cell cycle and the p53 signaling pathway. Conclusion These transcriptomic data provide insights into the molecular mechanisms of ovarian development in P. clarkii. The results will be helpful for improving the reproduction and development of this aquatic species.

Development of the silver eel (Anguilla marmorata) gonad during downstream migration in the Lake Poso system, Central Sulawesi

The Lake Poso system is located in Central Sulawesi and is connected to the Tomini Bay by the Poso River. It is known that five out of nine Indonesian eel species were found at the Poso River. Anguilla marmorata is the most caught species. However, uncontrolled catching during downstream migration and the construction of a hydropower plant threaten the silver eel in the Lake Poso system. Research on silver eel (A. marmorata) in Lake Poso was conducted to determine and compare the condition of gonad development as part of the reproductive process. This represents essential information in eel fisheries management in Lake Poso. The eels were collected through bamboo traps (waya masapi). The present study calculates the GSI and HSI values, and histological analyses characterize the gonad. The GSI of eel ranges from 1.95 to 5.69%, and the HSI value ranges from 0.83 to 1.16%. Histological observation showed that eels from Tentena (Lake Poso outlet) and from the estuary of Poso River have ovaries in the early vitellogenic stage (III) and the vitellogenic stage (IV).

Effect of silkworm (Bombyx mori) pupae on the growth and maturation of Rainbow shark Epalzeorhynchos frenatum (Fowler, 1934) under captive rearing

The aim of this study was to determine the impact of replacing fishmeal with silkworm pupae (Bombyx mori) meal in the diet of rainbow shark Epalzeorhynchos frenatum (Fowler, 1934), on growth and maturation. Four isonitrogenous and isocalorific experimental diets (35% CP) were prepared using silkworm pupae (SWP) replacing fish meal at three different levels viz., 30% (T1), 40% (T2) and 50% (T3) and diet with only fish meal served as control (C). The experimental trail was conducted in hapas, in duplicates, installed in an earthen pond. The fish (average weight - 1.4 g and total length - 5.24 cm) were stocked @10 nos. per hapa. During the experimental period, water quality parameters were monitored routinely. The experimental diets T1, T2 and T3 performed significantly better than diet C (control) in terms of growth performance. Among the four diets, T1 showed significantly higher weight gain (5.18±0.28 g), specific growth rate, SGR (2.54±0.07% day-1), protein efficienvy ratio, PER (1.50±0.04) and food conversion ratio, FCR (1.91±0.06) compared to other treatment groups. Among all the diets, highest gonadosomatic index, GSI (14.90%) was obtained in fish fed diet T1. At the end of the experiment, all the experimental diets fed fishes showed similar stages of maturity, late vitellogenic stage. Overall, the results of the present study conclude that SWP can be used as a low-cost animal protein to replace fish meal upto 30% in the diet.

Reproductive Biology of Geodia Species (Porifera, Tetractinellida) From Boreo-Arctic North-Atlantic Deep-Sea Sponge Grounds

Boreo-arctic sponge grounds are essential deep-sea structural habitats that provide important services for the ecosystem. These large sponge aggregations are dominated by demosponges of the genus Geodia (order Tetractinellida, family Geodiidae). However, little is known about the basic biological features of these species, such as their life cycle and dispersal capabilities. Here, we surveyed five deep-sea species of Geodia from the North-Atlantic Ocean and studied their reproductive cycle and strategy using light and electron microscopy. The five species were oviparous and gonochoristic. Synchronous development was observed at individual and population level in most of the species. Oocytes had diameters ranging from 8 μm in previtellogenic stage to 103 μm in vitellogenic stage. At vitellogenic stages, oocytes had high content of lipid yolk entirely acquired by autosynthesis, with no participation of nurse cells. Intense vertical transmission of bacterial symbionts to the oocytes by phagocytosis through pseudopodia was observed, especially in late stages of oogenesis. The density of oocytes within the sponge tissue was on average 10 oocytes/mm2 across all species, higher than that of most temperate and tropical oviparous species studied elsewhere. Spermatic cysts were widespread over the tissue during early stages, or fused in larger cysts, around the canals in later stages, and occupying between 1.5 and 12% of the tissue in males. The reproductive season spanned similar periods for all Geodia spp.: from late spring to early autumn. During the reproductive peak of each species, between 60 and 90% of the population was engaged in reproduction for most species. Given the present hazards that threaten the boreo-arctic tetractinellid sponge grounds, it becomes crucial to understand the processes behind the maintenance and regeneration of populations of keystone deep-sea species in order to predict the magnitude of human impacts and estimate their ability to recover. The information provided in this study will be useful for developing adequate conservation strategies for these vulnerable deep-sea habitats.

Characterization and expression analysis of E75 during ovarian development and juvenile growth of the mud crab, Scylla paramamosain Estampador, 1950 (Brachyura, Portunidae)

In arthropods, E75 is an important nuclear receptor to regulate various physiological processes, such as development and reproduction. In this study, a 3551 bp cDNA of E75 (SpE75) with a typical domain organization of the nuclear hormone receptor was cloned from Scylla paramamosain. A qRT-PCR analysis revealed that, during ovarian development, the expression of SpE75 significantly increased after the onset of vitellogenesis and reached its peak value at the early vitellogenic stage. In vitro and in vivo experiments showed that 20-hydroxyecdysone significantly induced the transcriptions of the genes of both SpE75 and vitellogenin in the ovary. During juvenile crab (C1) development, the expression of SpE75 increased from 0 h (postmoult stage) to 96 h (premoult stage) and kept a low level in the fasting crabs. Together, these results indicate that SpE75 may be playing an important role in the regulation of ovarian development and somatic growth, as a component of ecdysone signalling in crustaceans.

The Involvement of Hormones in Fish: Basic and Applied Aspects of Russian Sturgeon (Acipenser Gueldenstaedtii)

Fish are a very large group, containing a huge variety of over 33,000 species.Scientific knowledge about the interaction between hormones of the somatic axis (SA) and the gonadotropic axis (GA), both of which function in the brain, and the pituitary gonad axis (BPG) that controls growth and reproduction, is vital for the domestication of fish in aquaculture.The Acipenserida family comprises 27 species, some of which have a very high economic value, among them Russian sturgeon (Acipenser gueldenstaedtii) that adapted to growth in aquaculture conditions. Many aspects aimed at improving the adaptation and production of Russian sturgeon (Acipenser gueldenstaedtii) have been studied for quite a long time. Models based on the results of our and others’ studies describing the interaction between GA and SA during oogenesis in Russian sturgeon have been suggested. The mRNA relative level of FSH during vitellogenesis (VTL) was higher in females than in males, affecting VTL secretion of vitellogenin (Vg); however, it was lower in the pre-vitellogenic stage than in VTL. No difference was found in mRNA levels of the luteinizing hormone (LH) in Russian sturgeon during the first four years of growth. During its first five years of growth, the level of GH mRNA was higher in females than in males, but due to the high standard deviation of the mean, the difference was not significant. IGF-I mRNA expression differed between the various tissues.

Nr5a1b promotes and Nr5a2 inhibits transcription of lhb in the orange-spotted grouper, Epinephelus coioides†

Nr5a1 (Sf-1) up-regulates lhb expression across vertebrates; however, its regulatory roles on fshb remain to be defined. Moreover, the involvement of Nr5a2 in the regulation of gonadotropin expression is not clear either. In the present study, the involvement of Nr5a1b (a homologue of Nr5a1) and Nr5a2 in the regulation of lhb and fshb expression in the orange-spotted grouper was examined. Dual fluorescent immunohistochemistry using homologous antisera showed that in the pituitary of orange-spotted groupers, Lh cells contain both immunoreactive Nr5a1b and Nr5a2 signals, whereas Fsh cells contain neither of them. In LβT2 cells, Nr5a1b up-regulated basal activities of lhb and fshb promoters possibly via Nr5a sites, and synergistically (on lhb promoter) or additively (on fshb promoter) with forskolin. Surprisingly, Nr5a2 inhibited basal activities of lhb promoter possibly via Nr5a sites and attenuated the stimulatory effects of both forskolin and Nr5a1b. In contrast, Nr5a2 had no effects on fshb promoter. Chromatin immunoprecipitation analysis showed that both Nr5a1b and Nr5a2 bound to lhb promoter, but not fshb promoter in the pituitary of the orange-spotted grouper. The abundance of Nr5a1b bound to lhb promoter was significantly higher at the vitellogenic stage than the pre-vitellogenic stage, whereas that of Nr5a2 exhibited an opposite trend. Taken together, data of the present study demonstrated antagonistic effects of Nr5a1b and Nr5a2 on lhb transcription in the orange-spotted grouper and revealed novel regulatory mechanisms of differential expression of lhb and fshb genes through Nr5a homologues in vertebrates.