Molecular cloning, characterization, and expression analysis of a gonadotropin-releasing hormone-like cDNA in the clam, Ruditapes philippinarum
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Ruditapes
Hemolymph
Cloning (programming)
Gonadotropin
By observing the seasonal changes of gonad of live shellfish and the changes of gonad on histological sections,the yearly development of the gonad of the clam Paphia (Paratapes) undulata (Born) in the sea area of Beihai, Guanxi was studied.Taking the developmental status of the gametes in follicles as the main characteristics,the authors thought that the development of the gonad could be devided into six stages for both male and female,ie,resting stage,proliferating stage,growing stage,maturing stage,spawaing stage,and degenerating stage.Meantime,it was revealed that the gonadal development of the clam has only one cycle in a year in Beihai area. In addition, some precocity were found.
Developmental stage
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Although females grow 4-6 times faster and reach larger adult sizes than males in half-smooth tongue-sole,Cynoglossus semilaevis,male ratio is higher than female study culture conditions.Thus,it is necessary for us to make a detailed understanding of gonadal development,which provides a theoretical basis for sex control.What's more,water temperature is considered a very important modulator of reproductive activity in fish.Therefore,the principal purpose of the present work is to analyze the effects of different temperatures(19,21,23,25 and 27 ℃)on gonadal development in the half-smooth tongue-sole,which were reared for 67 days from 39 to 106 days post fertilization(pfd).And the temporal dynamics of germ cell growth and gonad development were examined during the experiment using light microscopy method.We found that the histological differentiation occurred firstly on pfd46 in the half-smooth tongue-sole reared at 19 ℃,as the gonad with the increasing primordial germ cells(PGCs)will develop into ovary.And the gonad without cavity will develop into testis in fish held at 19 ℃ on pfd82.At the same time,compared with fish kept at other temperatures,half-smooth tongue-soles maintained at 27 ℃ demonstrated increased oogonium proliferation in females and the spermatocyst size in males.And the ovaries of the fish reared at 27 ℃ were in stage Ⅱ on pfd129.Higher water temperatures triggered rapid germ cell differentiation and seminal vesicle growth,and relatively,lower water temperatures delayed,hence,not until pfd142,the ovaries of juvenile feeding at 23 ℃ and 25 ℃ were in stageⅡ.In addition,under higher temperature treatment,there were more oocytes in the ovarian lamella;in males,late-stage testis germ cells were predominated at this time,Especially in the juveniles rearing at 25 ℃,spermatozoa were distributed to almost all seminal lobules,even seminal vesicles and sperm ducts were filled with high density spermatozoa.All of these results suggest that higher water temperature favors gonadal development.
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The reproductive cycle of the small temperate dendrochirote holothurian Eupentacta chronhjelmi was studied in the intertidal zone of Aoshima Island, in the Seto Inland Sea of Japan, from July 1989 to January 1991. Reproductive status was assessed by the gonadal index method and histological analysis of the largest (tertiary) gonadal tubules. The primary and secondary tubules are cryptic and difficult to find, so no reference to the animal's annual cycle in terms of gametogenesis is made. The gonad wall was thickest in September for females and October for males, when the gonadal index was at its peak the rapid final stages of vitellogenesis in females (and completion of spermatogenesis in males) depleted reserves in the gonad wall, producing gametes that were spawned in October to December. When gametes were spawned in December the gonadal index and gonad wall thickness decreased. We suggest that the gonadal index reflects gonadal growth by oocyte production and an increase in gonad wall thickness. In the laboratory, spawning occurred from midnight to 04:00, at ambient seawater temperature (12 °C). Individuals elevated their anterior, oral end, waved their tentacles, and released gametes for about an hour. Based on its large egg size (300 ± 5 μm (mean ± SE) diameter) and low fecundity (1500 ± 10 ripe oocytes per individual), we infer lecithotropic development with an abbreviated larval stage.
Ovotestis
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The histological structure of the gonads was studied in yellow eels sampled from a coastal lagoon and from stocks reared in an aquaculture plant showing different sex ratios. Gonad development related to body size rather than to age and underwent an intermediate stage characterized by a structure of an early testis but containing oogonia and oocytes. This gonad was called the Syrski organ and the stage juvenile ambisexual. Ovaries were found in eels from 22–30 cm in length, possibly derived from undifferentiated gonads or from Syrski organs. Fully differentiated testes were found in eels >35 cm, derived from Syrski organs. These observations support the results of previous research. From elvers and in eels up to 15–16 cm in length, growth of the gonadal primordium is due to primordial germ cell migration. In eels > 15 cm multiplication of primordial cells begins. Oogonial clones were found in eels > 18 cm in length, whilespermatogonium B clones were observed in eels >30 cm in length. The dynamics of sex differentiation was different among stocks with different ultimate sex ratios: ovaries were found in shorter eels in stocks with a prevalence of females, in longer eels in stocks with a prevalence of males. This result supports the hypothesis of a metagametic (environmental) sex determination. The somatic cells in contact with germ cells and those in the interstitium appeared early during gonad development and preceded germ cell differentiation. This suggests that somatic cells are the targets of the environmental factors influencing sex differentiation.
Sexual Differentiation
Primordium
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The yellow catfish, Pelteobagrus fulvidraco, is a commercially important fish species. It is widely distributed in the fresh water areas of China, including rivers, lakes, and reservoirs. Like many other aquaculture fish species, people have observed significant size dimorphism between male and female yellow catfish and it shows a growth advantage in males.Here, at the first time, the time-course transcriptome was used to explore the various expression profiles of genes in different gonad developmental stages and genders. A total of 2696 different expression genes (DEGs) were identified from different stages. Based on these DEGs, 13 gonad development related genes were identified which showed time-specific or sex biased expression patterns.This study will provide the crucial information on the molecular mechanism of gonad development of female and male yellow catfish. Especially, during the different gonad development stages, these 13 gonad development related genes exhibit various expression patterns in female and male individual respectively. These results could inspire and facilitate us to understanding the various roles of these genes play in different gonad development stages and genders.
Sexual dimorphism
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During the peak period of its reproduction,external morphylogical features of gonad were under careful observation for diploid and triploid oyster,Ostrea cucullata, and with a comparison of mature oocytes and their nuclei in size. The results revealed that gonad in triploids showed poor development relative to diploids by appearances, the diameter of mature oocytes and their nuclei of triploids were 19.6% and 17.6% larger than those of diploids,and with 70.3% and 64.2% larger in volume.Histological sections presented that unlike diploids, gonadal development was retarded in triploids, of which the majority remained in stages of proliferation and spent,and only some of them developed to growth and mature stages and produce mature oocytes and sperm. Three hermaphrodites were observed in triploids sampled, which the sex ratio was female 7:male 1. In addition,retardation of gonadal development and hermaphroditic phenomenon of triploids are discussed in this paper.
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The processes of gametogenesis, development, and degeneration, together with the gonad fatty acids, of the pen shell Atrina pectinata were studied. The results showed that water temperature is the key factor affecting gonadal development. The gonad started to develop and differentiate at 6–7°C, with fast development of both the visceral mass and the gonad when the temperature increased to 11–12°C. The gonad index peaked at approximately 21°C, which suggested that 6–7°C is the threshold for gonad development and that 21°C is the optimum temperature at which broodstock will mature. The gonad fatty acid 18:1n-9 correlated remarkably with the condition and gonad indices, which might be indicative of the maturity of the gonad of A. pectinata. From the perspective of nutritional composition, Pavlova sp. and Chroococcus sp. were thought to be the most appropriate feed for A. pectinata broodstock cultivation.
Broodstock
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Manila clam,Ruditapes philippinarum,is one of the most important clam species cultured in China.By observing gonadal development of Manila clam from different areas under controlled water temperatures,we could forecast and control the spawning time.Manila clam was sampled in Dalian and Fujian in March ,2004.They were warmed up in indoor ponds to ripe with the same condition.Shell size and weight were measured.We researched the histology of its gonad develepment and the relationship between periodic variation of histology with gonad development and effective accumulated temperature.The gonads were fixed with Bouin's solution,and tissue sections were stained with H.E solution.Taking micrography pictures to show the gonad development of the Manila clam in Dalian was divided into five sections:spent stage ,early active stage,later active stage,mature stage,spawned stage.The gonad development of the Manila clam in Fujian was also divided into five sections:early active stage,later active stage,mature stage, spawned stage,degenerating stage.The relationship of gonad develepment with effective accumulated temperature was discussed in this paper.It indicated that the effective accumulated temperatures of gonad development of the Manila clam in Fujian and Dalian were 190.1℃·d and 331.8℃·d,respectively.
Ruditapes
Histology
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