Premium
Fine structure of the free‐living parakeet pineal in relation to the breeding cycle
Author(s) -
Prasadan T.N. Krishna,
Kotak Vibhakar C.
Publication year - 1993
Publication title -
journal of pineal research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.881
H-Index - 131
eISSN - 1600-079X
pISSN - 0742-3098
DOI - 10.1111/j.1600-079x.1993.tb00518.x
Subject(s) - pinealocyte , biology , pineal gland , parakeet , endocrinology , medicine , golgi apparatus , ultrastructure , vesicle , endoplasmic reticulum , melatonin , anatomy , microbiology and biotechnology , zoology , biochemistry , membrane
Seasonal changes in the ultrastructure of the free‐living Rose‐Ringed Parakeet Psittacula krameri pineal were examined in relation to the sub‐tropical environment and seasonal reproduction. Dark and light pinealocytes of the presumptive neuroendocrine cell line predominated, while supporting cells, ependymal cells, myelinated and non‐myelinated nerve fibers with nerve endings, and regressed photoreceptor elements were also observed. Unlike in pineals of many animals, particularly mammals, the presence of dense‐core vesicles (DCVs) with varying core density, and absence of clear vesicles and vacuoles with flocullent material, indicate the involvement of DCVs in the synthesis and secretion of pineals principle/s. In November (pre‐breeding) when the day length registered a drop to LD 10:14, pinealocytes showed significantly decreased and smaller DCVs and mitochondria, nuclei with heterochromatin, and greater distribution of glycogen and lipid droplets, all indicating low pineal metabolic activity. During the shortest day regime from December to March, when the birds peaked breading, the number and size of DCVs and mitochondria increased, and Golgi body‐endoplasmic reticulum‐lysosome complex (GERL) was very well defined. Images of DCVs suggested possible secretion of pineal principle/s by dissolution, and exocytosis. Coincidence of these features with peak gonadotrophic (circulating LH) and spermatogenic and testicular endocrine activity described previously suggested an active turnover of pineal products during this short day length regime when parakeets breed. In contrast, during the post‐breeding season (April onwards), when the day‐length increased to LD 13:11 and hypophyseal‐gonadal function was down, nuclei and RER continued to show active profile, the Golgi body and associated complex were moderately seen, and the DCVs and mitochondria were significantly smaller and lesser. It is therefore probable that the pineal is an important relay to translate cues related to less drastic sub‐tropical environmental change into DCV‐linked neurohormones that in turn may be involved in modulating seasonal breeding in parakeets.