Changes of major carotenoids in gonads of sea urchins (Strongylocentrotus intermedius and S. nudus) at maturation

Changes in the carotenoid content in gonads of two sea urchins species were investigated during maturation. The content of echinenones and carotenes, the two major carotenoid fractions in gonads, is highest for Strongylocentrotus intermedius at the spawning gametogenic stage of gonad maturation for both sexes. For S. nudus, the content of these pigments is highest at stages of active gametogenesis and spawning for males and at the growth stage for females. A comparison of the carotenoid content dynamics during maturation of gonads for males, females and animals at the resting (sexual inactivity) stage was also carried out.     

The histology of mature gonads of Oreochromis (Nyasalapia) karongae (Trewavas)

Histology of gonads of Oreochromis karongae was undertaken to study internal cell characteristics during maturation. This study was necessitated by low spawning output of the fish species. Several oocyte stages, ranging from primary forms to vitellogenesis, suggest that the maturation was generally succesfully attained in the fish ponds. Pre‐vitellogenesis oocytes (oogonia to perinuclear stage) and more advanced vitellogenesis (primary vesicle to tertiary yolk vesicle) oocyte stages were all found in the same gonads. However, there were some discontinuities observed during stages 3 and 4, suggesting selective maturation. Failure of gonads to mature normally is attributed to an ecological crunch that was in a previous study associated with environmental factors. Atretic oocytes were also recorded in the same gonads, a sign that some oocytes failed to mature normally. This indicates insufficient stimuli for normal gonad development. Several stages of spermatogenesis (spermatocytes, spermatid and spermatozoa) were also found in the same gonads. Selective recrudescence was more pronounced in O. karongae because generally less oocytes attained final maturation stages compared to Oreochromis niloticus and other tilapias. This could be the main reason for low natural breeding that has been observed in both wild and captive stocks, and led to the abandonment of its use in aquaculture. This study corroborates findings of previous studies that depended solely on external gonad characteristics. Histology provides conclusive evidence from internal cell characteristics that other techniques are unable to show.     

Gonadal cnidocytes in the cubozoan Tripedalia cystophora Conant, 1897 (Cnidaria: Cubozoa)

Cubozoans have a complex lifecycle in many ways similar to the scyphozoan lifecycle. The sexual reproduction within cubozoans varies between species with one clade having copulation and internal fertilization and the release of planula larvae. This cubozoan clade, the family Tripedaliidae, includes three species, Copula sivickisi, Tripedalia cystophora, and Tripedalia binata. In a recent study, it was suggested that in C. sivickisi cnidocytes play a new and important role during the sexual reproduction. Male derived cnidocytes anchor sperm packages to the female gonads and female derived cnidocytes protect the externalized embryo strand. Here, we have examined the gonads and gametes of T. cystophora and our results reveal that the male produced spermatozeugmata have a high number of isorhiza type cnidocytes, which are transferred along with the sperm during copulation. This adds further support to our hypothesis that they are important for sperm anchorage. The female gonads are lacking cnidocytes all together showing that cnidocyte production is not just a default state of the epithelium in these animals.     

Differential expression of foxl2 and cyp19a1a mRNA during gonad developmental stages in great sturgeon Huso huso

This study aimed to determine the sex specificity and expression pattern of foxl2 and cyp19a1a genes in great sturgeon Huso huso gonads during gonadal sex differentiation and development. The results revealed that foxl2 and cyp19a1a mainly expressed in female gonads and during gonad development the foxl2 and cyp19a1a mRNA expression is required for ovarian development.     

Reproductive condition of Akodon montensis Thomas and Bolomys lasiurus (Lund) (Rodentia, Muridae) based on histological and histometric analyses of testes and external characteristics of gonads

The reproductive activity of two species of wild rodents was studied in the Serra do Rola‐Moça State Park (PERM), in the state of Minas Gerais, Brazil. From October 1998 to October 1999 specimens of Akodon montensis (Thomas 1913) were captured in an area of seasonal semi‐deciduous forest, while specimens of Bolomys lasiurus (Lund 1840) were captured in a cerrado area (a savannah‐like grassland). The determination of the reproductive condition was based on histological and histometric analyses of testes and external characteristics of gonads. The volume of the testes, diameter of the seminiferous tubules and depth of the seminiferous epithelium were measured. Akodon montensis showed a seasonal annual reproductive cycle divided into four stages (recrudescence, activity or proliferation, regression and rest) with the reproductive activity mainly occurring during the rainy season. In contrast, B. lasiurus presented reproductive activity during almost the whole year. For both species the volume of the testes was an effective indicator of their reproductive condition. We suggest that the histological and histometric analysis of the gonads of males, together with the observations of external characteristics of gonads of males and females, may assist in identifying the reproductive condition of these animals.     

Some aspects of the reproductive biology of Synodontis schall (Bloch-Schneider, 1801) from the White Nile near Khartoum

The biology of reproduction was investigated in 631 specimens of Synodontis schall taken from the White Nile near Khartoum. Morphological changes of the gonads were followed for twelve months and the results used to classify their different developmental stages and maturity. Water and ash content of the gonads varied slightly from month to month and this variation was more pronounced during the breeding season. Gonosomatic indices also varied in the same manner. Synodontis schall spawns from July to September and females are ripe at the early age of I. Absolute fecundity ranged from 10 000 to 90 000 eggs and was highly correlated with growth parameters such as length, weight and age. Variations in the diameter of the eggs during the breeding season were also followed.     

Bi-directional sex change and gonad structure in the gobiid fish <Emphasis Type="Italic">Trimma yanagitai</Emphasis>

Bi-directional sex change in the deep-water gobiid fish Trimma yanagitai was examined. The gonads of all individuals consisted of ovarian and testicular elements, and an accessory gonadal structure. In no gonads were both testicular and ovarian parts simultaneously active. Bi-directional sex changes occurred during the rearing experiments in aquaria under conditions of which there was co-existence of two males or plural females. The sex of individuals could be determined by their relative body size or social dominance: the largest individuals acting as male and the remainder as female.     

Interactions between immunocompetence,somatic condition and parasitism in the chub Leuciscus cephalus in early spring

Relationships between immunocompetence, somatic condition, parasitism and water temperature in a wild population of chub Leuciscus cephalus were investigated. The effects of a rapid temperature increase in early spring were studied for both sexes as water temperature affects immunocompetence. Investment in gonads and activity of mucus lysozyme were negatively correlated; lysozyme activity decreased as temperature increased. No correlations were found between lysozyme activity and parasitism or intensity of infection by monogeneans, the most abundant metazoan parasite group in L. cephalus. There was a positive correlation, however, between respiratory burst intensity and parasitism. Indices of investment in gonads and spleen were correlated, showing that energetic reserves allowed either investment in gonads and spleen, or that spleen investment, even if often used in other studies in immunoecology, was not always a significant indicator of immunocompetence during this period. This last proposition is supported by the lack of correlation between spleen investment and other factors linked to immunocompetence.     

Sexual reproduction in Hawaiian Acropora

Sexual reproductive maturity was evaluated in Acropora valida, Acropora cytherea and Acropora humilis at French Frigate Shoals, Northwest Hawaiian Islands during two consecutive summers. Acropora valida gonads matured at different rates in different habitats in both years. Spawning was inferred by the sudden disappearance of gonads of mature size. Histological sections of fertile polyps confirmed the maturity of gonads prior to spawning. An isolated colony of A. humilis spawned in early summer. Strong indications of sexually mature colonics of A. cytherea exist, but clear temporal patterns were not apparent. Lunar period of spawning in reef flat A. valida and A. humilis differed from that reported for these species from other regions. The three species did not overlap in time of spawning. Previous ideas concerning the allochthonous origin of larval recruits, as well as the absence of Acropora from high islands of the Hawaiian chain, are re-evaluated in light of new evidence for sexual reproductive capacity by native populations.     

Seasonal changes in the biochemical composition of the freshwater murrel,Ophicephalus punctatus Bloch

Summary Seasonal variations in various biochemical constituents in the tissues of Ophicephalus punctatus showed that. the fat content in the muscle was highest during November–January and lowest during June–October. Liver contained more fat than the muscle and its seasonal cycle was marked by two well defined peaks. Changes in the ovarian fat were also well defined seasonally. The moisture content in all the tissues varied inversely with the fat. Protein values in different tissues did not show as much fluctuations as fat. In muscle, protein remained high throughout the year except in January. In liver and gonads very low protein values were recorded during the winter months. Seasonal changes in the ash content were not very well marked in any of the three tissues.The seasonal variations in all the biochemical constituents seem related to the feeding intensity of the fish and the maturation of its gonads. Maximum and minimum values of fat fell in accordance with the high and low food intake. In the pre-spawning phase, more fat was stored in the muscle at first but subsequently the fat was mobilized in the liver and finally in the gonads. Peak ripeness was associated with an accumulation of greater protein and fat in the gonads (ovaries). During the spawning months the various constituents were depleted and the post-spawning phase of the fish was marked by minimal values of most of the biochemical constituents, excepting moisture and ash.     

Spindle-E is essential for gametogenesis in the silkworm,Bombyx mori

As a defense mechanism against transposable elements, the PIWI-interacting RNA (piRNA) pathway maintains genomic integrity and ensures proper gametogenesis in gonads. Numerous factors are orchestrated to ensure normal operation of the piRNA pathway. Spindle-E (Spn-E) gene was one of the first genes shown to participate in the piRNA pathway. In this study, we performed functional analysis of Spn-E in the model lepidopteran insect, Bombyx mori. Unlike the germline-specific expression pattern observed in Drosophila and mouse, BmSpn-E was ubiquitously expressed in all tissues tested, and it was highly expressed in gonads. Immunofluorescent staining showed that BmSpn-E was localized in both germ cells and somatic cells in ovary and was expressed in spermatocytes in testis. We used a binary transgenic CRISPR/Cas9 system to construct BmSpn-E mutants. Loss of BmSpn-E expression caused derepression of transposons in gonads. We also found that mutant gonads were much smaller than wild-type gonads and that the number of germ cells was considerably lower in mutant gonads. Quantitative real-time PCR analysis and TUNEL staining revealed that apoptosis was greatly enhanced in mutant gonads. Further, we found that the BmSpn-E mutation impacted gonadal development and gametogenesis at the early larval stage. In summary, our data provided the first evidence that BmSpn-E plays vital roles in gonadal development and gametogenesis in B. mori.     

Macroscopic and histological analyses of gonads during the spawning season of Chionodraco hamatus (Pisces,Channichthyidae) off Terra Nova Bay,Ross Sea,Southern Ocean

A macroscopic and histological analysis of gonads was carried out during the spawning season of the high-Antarctic channichthyid Chionodraco hamatus in the western Ross Sea. Samples were collected between December and February during several years in the coastal waters of Terra Nova Bay. Gonad maturity stages were described for males and females according to macroscopic and histological scales. Using multi-year data, the estimated length at first spawning of females was about 35 cm TL, very similar to that obtained indirectly for males. Similar to many other high-Antarctic fish, C. hamatus is a summer spawner. The greater part of the stock was indeed in spawning condition between December and February, although a large proportion of females large enough to spawn probably did not spawn in that season. The present data confirm that C. hamatus, as is typical for Antarctic fish, probably spawns a single batch of oocytes once a year. In addition, vitellogenesis is a slow process that extends over at least 1 year. Discrepancies between the macroscopic and histological appearance of gonads were found. These were associated mainly with spent and resting females (maturity stages 5 and 2, respectively). This study demonstrates the importance of histological analysis of gonads in order to confirm the results of the macroscopic analyses routinely carried out in studies of reproductive biology. This is of particular importance in determining size at maturity and spawning stock biomass, for assessment purposes.     

Metals in the tissues of the starry flounderPleuronectes stellatus from Nyiskii Bay (Southeastern Sakhalin)

We examined the concentrations of the heavy metals Zn, Cu, Cr, Pb, and Cd in the liver, gonads, and muscles of male and female starry flounderPleuronectes stellatus from Nyiskii Bay (off the northeastern coast of Sakhalin) in August 1996. It is shown that the accumulation of the metals was different in the organs and tissues of males and females. The greatest differences were recorded in the gonads. The concentrations of Zn and Cu were greater in the gonads of females, whereas the concentrations of Cd, Pb, and Cr were greater in male gonads. More Cd and Pb accumulated in the liver of females, whereas the concentrations of Zn and Cd were greater in the muscles of males. The results obtained seem to reflect the specific features of physiological processes in specimens of different sexes and the biochemical composition of the tissues of fish organs during the period of foraging and gonad development. The concentrations of metals in the muscles of starry flounder from Nyiskii Bay did not exceed the sanitary standards.     

Effect of Fixed Daylengths on the Photoperiodic Regulation of Gametogenesis in the Sea Urchin Strongylocentrotus purpuratus

Summary

The gametogenic response of the sea urchin Strongylocentrotus purpuratus was compared under treatments of different photoperiod regimes of fixed and seasonal changing daylength. Quantification of gametogenic activity in en- zymatically dissagregated ovaries and in histological sections of testes have shown that the sea urchin is sensitive to both fixed and variable daylengths. After one year at fixed short day (8L:16D) or fixed neutral day (12L:12D) the gonads were ripe and in active gametogenesis, the same as were gonads of animals reared at changing photoperiod and sampled during the short-day phase of the cycle. Under fixed long day (16L:8D) the gonads lacked significant amount of gametes and had the cell constitution found in gonads of animals reared at changing photoperiod and sampled during the long-day phase of the cycle. Measurement of a critical daylength related to the autumnal equinox seems to be part of the mechanism in the photoperiodic regulation of vitellogenic oocyte growth and spermatogenesis in these animals.     

Determination of temperature sensitive stages for sexual differentiation of the gonads in embryos of the turtle,Emys orbicularis

In order to determine the temperature sensitive stages for sexual differentiation of the gonads in Emys orbicularis, eggs of this turtle were shifted at different stages of embryonic development from the male-producing temperature of 25°C to the female-producing temperature of 30°C and reciprocally. Based on the series of developmental stages described by Yntema (′68) for Chelydra serpentina, temperature begins to influence sexual differentiation of Emys orbicularis at stage 16, a stage in which the gonads are still histologically undifferentiated. Its action lasts over the first steps of histological differentiation of the gonads. The minimal exposure at 25°C required for male differentiation of all individuals extends from stage 16 to somewhat before stage 21. For 100% female differentiation, incubation at 30°C must be longer, from stage 16 to somewhat before stage 22. Shorter exposures at 25°C or 30°C during these periods result in different percentages of males, females, and intersexes. Our results show that there is a critical stage (stage 16) which is the same for both male and female differentiation of the gonads. The thermosensensitive periods are rather long, corresponding to 11–12 days at 25°C and 30°C.     

Reproductive biology of a Gobiid fish Oxyurichthys tentacularis (Valenciennes, 1837) inhabiting Ashtamudi Lake,S. India

Reproductive traits of Oxyurichthys tentacularis, a most demanded fish in Ashtamudi Lake, S. India were studied from samples collected using gill net, cast net and dip net during 2013–2015. Sexes were separated by observing the urogenital papilla in males and the gonads. Five maturity stages were identified by examining the gonads. Though advanced maturity stages were encountered throughout the year, higher preponderance of ripe gonads was discernible during August to November and February to April. Gonadosomatic indices indicated same trend in both sexes. The length at first maturity was 86.67 mm in males and 80.17 mm in females. The absolute fecundity ranged from 5,112 (102 mm TL) to 52,431(175 mm TL). Fecundity established linear relationships with total length, body weight and ovary weight. Ova diameter studies revealed that spawning takes place in batches at regular intervals and the species is a multiple spawner. The ratio of males to females was found to be 1:0.7 (χ² = 10.8; p < 0.05). The pooled average for the whole period showed a perceptible dominance of male population in all of the months except in January (χ² = 2.3; p > 0.05) could be observed.     

Ontogenetic and tissue-specific expression of gonadotropin-inhibitory hormone (GnIH) and its receptors in Catla catla

Gonadotropin-inhibitory hormone (GnIH) is an RFamide peptide, and its role in reproduction is well studied from fish to mammals, but very few reports are available about the function of GnIH during larval development. In this study, we examined the GnIH and GnIH receptors (GnIHRs) expression from embryogenesis to adult stage and tissue-specific expression in adult Catla catla using quantitative real-time (qRT) PCR. The qRT PCR analysis of GnIH mRNA during ontogenetic development showed the increasing trend from early developmental stages to the adult stage with the highest expression in 24 months fish. However, the expression of two GnIH receptors, GnIHR1 and GnIHR2 also increased from larval stages to the adults with a peak at 17 days post-hatching, while GnIHR3 showed the higher mRNA expression during embryogenesis and then decreasing gradually. Tissue distribution analysis of GnIH showed the highest mRNA expression of GnIH in the brain, followed by gonads of both the sexes. GnIHR1 and GnIHR2 were also highly expressed in the brain and gonads of both the sexes, while GnIHR3 showed the highest expression in gonads of both the sexes without any expression in the brain. These results suggest that the brain is the primary site of action for GnIH, GnIHR1 and GnIHR2, while gonads for GnIHR3.

     

Nutrient allocation in the gonads of the sea urchin Arbacia dufresnii in different stages of gonadal development

This study reports nutrient allocation in different stages of gonadal development for two populations of the sea urchin Arbacia dufresnii off the Patagonian coast of Argentina (Nuevo Gulf and San Jorge Gulf). The biochemical composition of gonads was used to assess nutrient allocation by measuring ash, soluble protein, lipid and trichloroacetic acid-soluble carbohydrate concentrations, and absolute contents over a 24-month period. Reproductive output in terms of energy was calculated for females. Results were correlated with histological stage of the gonads. Soluble proteins were the main component for the Nuevo Gulf population while unmeasured organic material (i.e. insoluble proteins and nucleic acids, especially in testes) was prevalent in gonads from San Jorge Gulf. Soluble protein and lipid concentrations followed the gonadal cycle, while carbohydrate concentration was almost negligible, especially in the Nuevo Gulf population. The different patterns in the gonadal cycle in the two populations were reflected in the biochemical composition of gonads. Concentrations and contents of the biochemical components and reproductive output were higher in the population from San Jorge Gulf owing to the larger size of gonads and gametes. These findings contribute to the better understanding of the plasticity of the reproductive biology of A. dufresnii in different environments.