Seasonal Changes In Gonads Research Articles

11beta-hydroxysteroid dehydrogenase complementary deoxyribonucleic acid in rainbow trout: cloning, sites of expression, and seasonal changes in gonads.

11beta-Hydroxysteroid dehydrogenases (11beta-HSDs) are important steroidogenic enzymes for catalyzing the interconversion of active glucocorticoid (cortisol and corticosterone) and inert 11-keto forms (cortisone and 11-dehydrocorticosterone) in mammals. In teleosts, 11beta-HSD also plays a role in the production of the predominant androgen, 11-ketotestosterone, in male fish. In this study we cloned cDNAs encoding rainbow trout 11beta-HSD (rt11beta-HSD) from testes and head kidney. The predicted amino acid sequence, hydrophobicity analysis, and transient transfection assays with rt11beta-HSD in HEK293 cells showed that rt11beta-HSD is a homolog of mammalian 11beta-HSD type 2. rt11beta-HSD transcripts are present in steroidogenic tissues and in a number of other tissues. Strong in situ hybridization signals for rt11beta-HSD transcripts were found in Leydig cells of testes, in thecal cells of the early vitellogenic ovarian follicles, and in thecal and granulosa cells of the midvitellogenic and postovulatory follicles. Weaker signals were also found in head kidney interrenal cells from juvenile rainbow trout. Seasonal changes in rt11beta-HSD transcripts in testes showed a pattern similar to that of stress-induced serum cortisol levels, but not to serum androgen levels. High levels of rt11beta-HSD transcripts were found in ovarian follicles from late vitellogenesis through ovulation. These results raise the possibility of a role for rt11beta-HSD in the protection of developing gonads from the inhibitory effects of stress-induced cortisol.

東京湾船橋地先におけるアサリの生殖周期

Seasonal gonadal changes were investigated by observation of oocyte diameter and histological examination in samples of Manila clam Ruditapes philippinarum collected from Funabashi waters in Tokyo Bay from May 1988 to September 1991. Gametogenesis was observed from January to November and gonadal maturation was bimodal, similar to southern areas of the Japanese Pacific coast, with peak periods occurring from April to June and from August to October. Gametogenesis in summer was less synchronous between individuals than in winter-spring and was characterized by the prolonged holding of a large number of matured gametes together with partial resorption and new growth of young gametes. Two annual peak periods in the condition factor, which conincided with gonadal maturation, were evident from April to May and August to September. The major spawning period of Manila clam in Funabashi waters was supposed to occur in spring, since gonadal maturation was highly synchronized and the condition factor reached its annual maximal value in this season.

Seasonal variations in growth, condition and gonads of Dormitator latifrons (Richardson) in the Chone River Basin, Ecuador

Growth in length, condition, and gonads of a food fish, Dormitator latifrons, were studied in the Chone River basin, Ecuador, in 1981. The river was bordered by floodplains in the upstream freshwater zone, and by mangrove swamps and shrimp farms in the downstream estuarine zone. The climate was marked by wet (January to April) and dry (May to December) seasons. During the dry season, an earth dam in the river prevented movement of water and fish between upstream and downstream zones. At the end of the dry season, most of the upstream floodplains were dry, and the main fish refuges were in downstream areas in deep pools in the river upstream. During the floods, fish migrated from downstream areas towards upstream floodplains. Growth rates and condition increased when water levels were high or salinity was low and decreased when water levels were low or salinity was high. Seasonal changes in gonads and abundance of juveniles indicated that reproduction occurred during the floods, but there was some reproduction in the dry season. Reproduction occurred in upstream and downstream zones and appeared to be stimulated by a complex of factors, including water levels, currents and salinity. The yield in flood plain sites was estimated as c. 115 kg ha−1 in 1981.

Seasonal gonadal changes in the clam, Paphia laterisulca

The seasonal gonadal changes in the edible clam, Paphia laterisulca, from the Kalbadevi Estuary at Ratnagiri were studied for the period from May 1972 to April 1973 with the help of fresh gonad smears and histological study. The observations of gonad smears revealed the probable commencement of spawning between September and April from the occurrence of spent gonads. Male and female clams were present in almost equal numbers throughout the year. Histological details revealed that the clam P. laterisulca has a prolonged spawning period extending from mid-September to the end of March with two peaks, the first in October–November and the second in February–March. Lysis of the ripe gametes in both sexes for 2.5 months preceding spawning was observed. The second spawning peak was followed by regression in the gonads. Active gametogenesis was observed in May and June (33.5°C and 30.0°C), and again in December and January (21.5°C and 26.0°C) in clams that had spawned during the first spawning peak. The spawning stimulus in Paphia laterisulca appeared to be the sudden increase in salinity (from 4.1 to 22.5‰) in September in the Kalbadevi Estuary.

Seasonal gonadal changes in adult freshwater mussel,Parreysia favidens var.Marcens (Benson)

1. Seasonal gonadal changes in adult mussels were observed. 2. The spawning starts in the month of March and continues up to October indicating a prolonged breeding period. 3. After the start of the spawning, lipid globules appear in the lumen of the follicles. 4. In the male, spermatocytical morulae appear after the start of the spawning. 5. No indeterminate sex condition or hermaphroditism is noticed.

Seasonal changes in the adenohypophysis of the vole ( Microtus agrestis)

The vole ( Microtus agrestis) is a seasonally breeding mammal. In the vole's adenohypophysis five different types of cell can be recognized by virtue of their shape and affinity for periodic acid-Schiff reagent (PAS), aldehyde fuchsin, or orange G. Of these five cell types, the supposed gonadotrops undergo marked cytological changes in synchrony with seasonal gonadal changes. During the breeding season, gonadotrops are filled with PAS-positive granules, but in the nonbreeding season the PAS-positive contents form the walls of otherwise unstaining large vesicles. Gonadotropic hormones could be detected (by the mouse uterus assay) in the hypophyses of males caught in the breeding season, but not in the hypophyses of males caught in the nonbreeding season.

Seasonal gonadal changes in the adult backwater oyster,Ostrea (Crassostrea) Madrasensis preston from ennur near madras

Seasonal changes in the gonads of lamellibranchs such as oysters, clams and teridinids have been studied in detail by various workers, viz., Coe (1932 b and 1936), Coe and Turner (1938), Loosanoff (1937 b, 1942 and 1953), Galtsoff (1937), Orton (1933), Roughley (1933) and Quale (1943). In commercially important forms these stud.ies have been of immense value in their culture and management.of the natural environments