• P C Joshi

      Articles written in Proceedings – Animal Sciences

    • Structure and seasonal changes in the testes of a freshwater crab,Potamon koolooense (Rathbun)

      P C Joshi S S Khanna

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      The paired ‘H’-shaped testes ofPotamon koolooense show histomorphological changes during various stages of maturity. Seminiferous tubules show different stages of spermatogenesis. A few undifferentiated or resting spermatogonia supply a new crop of germ cells for the next breeding season. In a tubule the meiotic divisions occur more or less synchronously in all the primary or secondary spermatocytes. Sperm consists of a head and mitochondrial vesicle which encloses axial filament and distal centrosome. Spermatogenesis activity is seasonal. Spermatogenesis begins in January-February, progresses slowly through March, reaching its peak in April-May. However, all the tubules do not mature simultaneously. Spermiation occurs during May and June, the spermatogenesis ceases gradually, and by December the testes enter a brief period of rest.

    • Seasonal changes in the ovary of a freshwater crab,Potamon koolooense (Rathbun)

      P C Joshi S S Khanna

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      The ovaries ofP. koolooense which are paired H-shaped structures undergo seasonal morphometric and histological changes. A minute oviduct leads into the seminal receptacle which receives sperms during breeding season. Oogonia and young oocytes develop in the germinal zone, present in the centre of the ovary. The resting or residual oogonia which occur throughout the year divide shortly after ovulation and supply new crop of germ cells for the next breeding season. Five maturational stages of ova have been described on the basis of changes that occur in their nuclei and cytoplasm. They are oogonium, premeiotic oocyte, previtellogenic oocyte, vitellogenic oocyte and the ripe ovum. Spawning occurs during May or June. The weight of the ovaries, gonad index and ova diameter were minimum in June and reached a maximum value in April.

    • Population, biomass and secondary net production of aboveground insects in a temperate grassland

      B R Kaushal P C Joshi

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      Population, biomass and secondary net production of aboveground insects were studied in a temperate grassland from February 1986 to january 1987. The live shoot biomass varied from 12·4±0·67 to 84·8 g m−2 and the aboveground net primary production was 190·3 g m−2 yr−1. A total of 65 species belonging to 33 families of 10 insect orders were collected. Herbivores (77·6%) were the most dominant insects followed by Omnivores (12%), Predators (5%), Saprophages (5%) and Parasites (0·4%). Maximum population density and biomass were 9·8 m−2 and 254 mg m−2, respectively. Cumulative secondary net production was 1·144 g m−2.

    • Neurosecretion of brain and thoracic ganglion and its relation to reproduction in the female crab,Potamon koolooense (Rathbun)

      P C Joshi

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      The gonadotropic function of the neurosecretory system of brain and thoracic ganglion in the adult female crab,Potamon koolooense is examined. The type A-cells of brain and thoracic ganglion display marked annual cyclic changes of synthesis and release of cytoplasmic material in association with the ovarian cycle. Administration of the thoracic ganglion extract during early oogenesis induced oocyte growth and precocious vitellogenesis, with an increase in the ovarian weight or gonad index and oocyte diameter. However, the brain extract injection did not produce marked changes in the immature ovary. The results suggest that the ovarian activity, particularly growth and vitellogenesis, depend on the neurosecretion of the thoracic ganglion, especially on the activity of A-cells. The neurosecretion of A-cells of the brain seems to be involved in the process of mating and ovulation.

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