Age at maturity and dynamics of gonadal cycle vary among individuals in a standard population; the extent of that variability in a group of siblings is not known for any species. Therefore, the aim of the study was to find out how the differentiation of gonad development varies in a group of sibling fish. The study involved 176 seven-month-old sea trout parr (mean fork length of 11 cm) collected at a single time point during their first spawning season (late October) from the brook of Pniewa in Western Pomerania (Poland). Gonad maturation was determined from histological analysis which was interpreted according to specially developed criteria.
The stage and forms of gonad maturation were diverse in the sibling group studied. Gonads of 52.8% males were not maturing (Class I), with only spermatogonia A present. The remaining males (47.2%) had gonads differing widely in the development, from beginning of maturation to completion of the reproductive cycle (Classes from II to VIII). In addition to the classes described, some males were observed to feature attempted maturation. It is difficult to provide an unequivocal estimate of the proportion of precocious males (mature at a young age, prior to the first descent to the sea) in the first year of life because of difficulties in categorizing males in Class II. It was predicted that 32.4% of the population would complete the cycle during the first spawning season. The body length and weight of the maturing males was significantly smaller (P < 0.05) than that of the non-maturing males.
Three forms of gonad maturation were identified. Gonads of a large group of precocious males (70%) developed incompletely (only some germ cell developed during the reproductive cycle), some of those gonads assumed the form of attempted maturation and partial maturation. Testes of the remaining 30% of the males underwent complete maturation. Gonads that undergo attempted maturation do not spermiate.
It is only from microscope-aided analysis of the testes that the class of gonad development can be accurately evaluated and the extent of precocious maturation assessed, particularly in fish maturing for the first time. It is impossible to correctly identify maturing males of the underyearling sea trout on the basis of morphological examination of gonad appearance, abdominal massage to detect spermiation or gonadosomatic index value. 相似文献
The precocious trifoliate orange (Poncirus trifoliata [L.] Raf.), an early flowering mutant of P. trifoliata, has a short juvenile phase of about 14 months, significantly shorter than other citrus. In this report, using the stems of precocious trifoliate orange seedlings as explants, an improved protocol mediated by Agrobacterium tumefaciens was developed to evaluate regeneration and transformation frequency. The transformed plants continued to reveal the precocious trait of non-transgenic mature precocious trifoliate orange, and as such could prove to be an efficient system for the verification of gene function in the fruits/flower via genetic transformation in woody plants. 相似文献
