Effects of gonadectomy on the secondary sexual characters in the ganoid fish, Amia calva linnaeus (original) (raw)
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Journal of Experimental Zoology, 2001
Black porgy, Acanthopagrus schlegeli Bleeker, a marine protandrous hermaphrodite, is functional male for the first two years of life but begins to sexually change to female after the third year. Testicular tissue and ovarian tissue was separated by connective tissue in the bisexual gonad. This sex pattern provides a very good model to study the endocrine mechanism of sex change in fish. The annual profiles of plasma estradiol, vitellogenin and 11-ketotestosterone concentrations in males were significantly different from those in the three-year-old females. Significantly high levels of plasma estradiol during the prespawning/spawning season and low levels of plasma 11-ketotestosterone during the spawning season were observed in the inversing females. No difference of plasma testosterone levels was observed in males and females. Oral administration of estradiol stimulated high levels of gonadal aromatase activity, plasma gonadotropin II levels and sex change in the two-year-old fish. Exogenous estradiol administered for 5-6 months induced a reversible sex change in one-and two-year-old fish. The sensitive period for estradiol treatment of sex change is from early prespawning to spawning season. Implantation with testosterone for more than a year could not block the natural sex change in three-year-old fish. Exogenous aromatase inhibitors (1,4,6-androstatriene-3,17-dione or fadrozole) suppressed aromatase activity in the brain. Oral administration with aromatase inhibitors for a year further inhibited the natural sex change in three-year-old black porgy and all fish became functional male with spermiation. Estrogen receptor α gene in the ovarian tissue of bisexual gonad is significantly less expressed than that in the vitellogenic ovary of female on the basis of reverse-transcription polymerase-chain reaction. There was no difference in the annual profiles of the plasma gonadotropin II levels in the males and natural inversing females. Plasma gonadotropin II levels were significantly higher in estradiol-treated group than those in the control. It is concluded that estradiol, aromatase activity and estrogen receptor in the ovarian tissue play an important role in the natural and controlled sex change in black porgy. The association of gonadotropin and sex change in black porgy is not clear.
Zoological science, 2008
Primary males that function as males throughout their lives are often found among protogynous fishes such as wrasses and parrotfishes. However, the issue of whether the sexuality of primary males involves gonochorism or hermaphroditism remains uncertain. To clarify this, we implanted estradiol-17beta (E2) into the body cavities of primary males of two protogynous wrasses, Halichoeres poecilopterus and Halichoeres tenuispinis. At 51-63 days after implantation, primary males with E2 treatment in both wrasses were observed to develop ovarian tissues. These results suggest that primary males of Halichoeres wrasses potentially have the ability to change sex and that estradiol-17beta is related to gonadal transitions in primary males.
Macroscopic gonadal deviations and intersex in developing whitefish Coregonus lavaretus
Aquatic Biology, 2009
In Lake Thun, Switzerland, a significant number of whitefish Coregonus lavaretus were found to exhibit abnormal gonadal morphology. To determine the time at which the morphological deviations from a normal gonadal arrangement develop, we conducted experiments designed to: (1) examine whether the morphologic gonadal variations develop during or after gonadal differentiation, and (2) characterise the entire ontogenetic gonadal development in whitefish from hatching until maturity. For these experiments, whitefish were reared under controlled conditions with distinct water sources and temperature regimes (Lake Thun water: 4 to 22°C; spring water: 8 to 9°C). Gonadal development in the spring water group was clearly delayed with respect to age, but similar to the Lake Thun water group with respect to degree-days in Celsius (°D). Undifferentiated gonads were first seen at 65 d post-hatch and 491°D. Ovarian differentiation (starting from 1734 to 1820°D) preceded testicular differentiation (starting from 1989 to 3673°D). The first fish with mature germ cells were recognised at 8163 to 8356°D. Morphological gonadal deviations became evident during gonadal differentiation. Constrictions and asymmetries developed for the first time in the first (0+) or second (1+) year-of-life, at a body length of 13 to 18 cm. Aplasia and compartmentation were recorded in the third (2+) year-of-life at a body length of 16 to 18 cm. Intersex fish occurred at a frequency of 8 to 9% during gonadal sex differentiation. Because no evidence for the presence of exogenic endocrine active substances was revealed, we suppose that there is a naturally increased mosaic intersex condition in whitefish during the ontogenetic gonadal differentiation process.
Morphological Changes in Astacus Astacus Gonads During the Reproductive Cycle
Bulletin Français de la Pêche et de la Pisciculture, 2006
The reproductive cycle of Astacus astacus was described by the external observation of the gonads, recording changes in the gonadosomatic index (GSI) and by the histological analysis of the reproductive organs. A total of 37 males and 13 females of Astacus astacus were collected from the Vukovina gravel pit located at northwest Croatia from May 2003 until January 2004. All crayfish were mature with total body lengths between 7.84 and 13.7 cm and weights between 16 and 125 g. There was a pronounced difference between the GSI values of the sexes. GSI fluctuated within a very small range (between 0.2 and 1.5%) in males while in females it increased up to 12.3% during the mating season. The external appearance of the testes and ovaries during the reproductive cycle was compared with the histological sections of germ cells in the testes, the vas deferens and ovaries. Besides the germinative cells, the morphological changes in testis and vasa deferentia of A. astacus extended also to the connective tissue and secretory epithelium. The maturation of germinative cells was synchronized, both in testes and ovaries.
Ovary Differentiation and Activity in Teleostei Fish
Theriogenology
Teleostei fishes constitute a very large group among the vertebrates. They present several reproductive strategies, and many species are gonochoristics. During the gonadal differentiation, the gonadal primordium undergoes morphological changes giving rise to male or female gonads. Considering the lack of information about gonadal morphogenesis in Teleostei, especially in tangent aspects concerning the establishment of the germinal epithelium and its relation with the formation of the ovarian cavity, Tanichthys albonubes, Corydoras schwartzi, and Amatitlania nigrofasciata were taken as biological models to establish a comparative analysis of the female gonadal differentiation. In undifferentiated gonad, the epithelial cells associate with primordial germ cells and form germline cysts. These are distributed throughout the gonadal tissue; after the entrance of the oogonia into meiosis, the folliculogenesis occurs forming the first follicles, in a quite conserved process. However, the formation of the ovarian cavity is distinct. In T. albonubes and A. nigrofasciata, the lumen is formed by pleating and in C. schwartzi, it is formed by cavitation. The central lumen formed characterizes the cystovarian of Teleostei. Although there are differences in the chronology of the differentiation, the processes involved are quite similar and culminate in the formation of analogous structures.
Malaysian Journal of Science. Series B, Physical & Earth Sciences, 2021
The establishment and survival of a species population in their breeding ground can be attributed to reproductive behavior and adaptive capacity. The rice paddy eel Monopterus albus is an introduced fish in the Philippines. It is a protogynous hermaphrodite which has a natural ability for sex reversal. This study described the histomorphology of the different gonadal maturation stages and measured the concentration levels of the steroid hormones 17ßestradiol (E2) and testosterone (T) in the blood plasma during sexual development. This paper aimed to better understand the gonadal development and sex differentiation of the rice paddy eel as a hermaphroditic fish. Samples were collected randomly from farm ponds located in three provinces within the island of Luzon, Philippines. Then, the fishes were segregated by sex by observing the presence or absence of ovarian and testicular tissues. Histological analysis of the gonad showed that immature, maturing and mature female gonad exhibited oocytes at different stages. The immature ovaries consisted mainly of perinucleolar oocyte clusters in the previtellogenic stage, whereas the maturing ovaries contained oocytes in the cortical alveoli stage and early vitellogenesis phase. Meanwhile, the oocytes in the mature ovaries were mostly in the advanced vitellogenic stage with a few cortical alveoli and perinucleolar stages. On the other hand, the intersex gonad showed the existence of both ovarian and testicular tissues. The male gonads contained spermatogenic cells and testicular lobules. Enzyme-linked immunosorbent assay (ELISA) was used to determine the concentration levels of gonadal steroid hormones. Differences in the concentration levels of the two hormones were evident across all stages of gonad maturation, although there were no significant differences between the groups. The functional role of these hormones might be in vitellogenesis and spermatogenesis that lead to the development of sex-changing gonads. This reproductive characteristic may contribute to understanding the reproductive success of this hermaphroditic fish.
Copeia, 2014
In the bi-directionally hermaphroditic fish, Lythrypnus dalli, two distinct male phenotypes have been described. The more conspicuous parenting males are larger, establish breeding territories, and display courtship, mating, and parenting behaviors. The alternative males, called mini males, have been postulated to have a parasitic reproductive strategy, although the behavioral ecology of mini males is not well understood. The mini male morph has been characterized based on size and anatomical differences, including sperm-filled accessory gonadal structures (as opposed to mostly mucous in nesting males), consistent with parasitic male morphs in other gobiid species. Here, we determined the endocrine profiles of mini males to gain further insight into their phenotype. Systemic (water-borne) 17b-estradiol (E 2 ) concentrations were higher than testosterone (T), and 11-ketotestosterone (KT) concentrations were lowest. Mini males in L. dalli are similar to parasitic males of other species in having higher T:KT ratios than breeding males. In mini males, brain and reproductive tissue levels of T, E 2 , and KT were higher than in the muscle. Among all the steroids, E 2 levels were high in all three tissues in mini males. Data from relative hormone levels in different tissues will lead to a better understanding of the endocrine regulation of behavioral, physiological, and morphological correlates of male sexual polymorphism.