This is a study of the reproductive biology and morphology of the pituitary gland of the osteoglossid fish Scleropages J O F~O S U S (Muller & Schlegel). The fish spawn in the Tasek Bera waterways of Pahang, Malaysia during the rainy season beginning in August. Young fish are incubated in the mouth of the male parent until free-swimming. Males mature in their 2+ year, when 30-45 cm in length. In mature specimens the testis is small, and little sperm is produced. Some females mature in their 2+ year, although at that time, most have only reached the stage of secondary oocyte production. The chorion and follicdar granulosa of secondary oocytes are deeply invaginated into the cytoplasm. All fish spawn in their 3 + year, when 45-60 cm in length. The single ripe ovary contains 20-30 ova, each 1.9 an in diameter. No fish of 41-years were caught, which may be the result of mortality or emigration, or due to extraneous causes such as selectivity in the fishing techniques used.The pituitary gland accords with the generalized teleost pattern and embryonic development. There is no saccus vasculosus. Adrenocorticotropic cells predominate in the proadenohypophysis, and somatotropic and luteotropic cells occur here. The mesoadenohypophysis contains gonadotropic and somatotropic cells; the former grow large in ripe specimens, so that the mesoadenohypophysis becomes much enlarged. The metaadenohypophysis contains relatively few cells, much neurohypophyseal ramification, and is deeply penetrated by the third ventricle of the brain.
The reproductive cycle of Coregonus luvuretus (L.) in Loch Lomond, Scotland, was investigated by monthly sampling. Spawing takes place during the first 3 weeks of January, on offshore gravel banks. Males congregate on the spawning-grounds throughout the spawning period, while ripe females cruise in unisexual shoals in deeper water. Individual females migrate to the spawning-grounds as ovulation takes place, spawn, and return to deep water. After spawning, the gonadosomatic ratio and somatic condition factor of both sexes decrease until June or July. Gonad recrudescence occurs in males between JulyandOctober, and in females between July and Deceniber. The somatic condition factor of both sexes rises from its minimum in June oi July to its maximum in September. Acompetitive protein binding assay was used to determine cortisol levels in 0.1 ml plasma samples of individual fish. The lowest cortisol levels occurred in fish caught by seine-netting and killed inimediately by anaesthesia in MS 222 (Sandoz). Seine-netting and killing by concussion induced higher cortisol levels, in the range of 3-5 pg/lOO ml. Cortisol levels in fish caught by @netting for 18 h were 3-6 times higher than in seine-netted fish, and the method of killing was immaterial in this case. The length of time spent in the gill-net had no significant effect on cortisol level, but maintenance of the fish in aquaria for 24-80 h elicited high cortisol levcls of over 50 pg/lQQ ml. Post-mortem delay before blood-sampling resulted in lowered cortisol levels. Seasonal variations in cortisol level were determined in gillnetted fish throughout the year, and in seine-nctted fish when available. Cortisol levels were high in both sexes in September; and very high in ovulating femdes caught on the spawning-grounds, though not in ovulating females caught off the spawning-grounds,
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