Reproductive system and spermatogenesis in the opisthobranch gastropod Retusa obtusa (montagu)

  • Berry A
  • Purvis J
  • Radhakrishnan K
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Abstract

The cephalaspidean opisthobranch Retusa obtusa has an ovotestis simultaneously producing eggs and spermatozoa. Reproductive organs are characterized by the hermaphrodite duct and seminal receptacle together joining the pallial glandular duct which is differentiated anteriorly to form the albumen' gland, membrane or capsule gland, and mucus gland. The duct of a copulatory bursa joins the common central chamber of this complex. Eggs presumably pass through extended tracts in the 3 glands to emerge at a hermaphrodite aperture in the right side of the mantle cavity. Spermatozoa also emerge at this aperture to a ciliated seminal groove along the right side of the head which, in turn, joins copulatory organs folded within the head and opening close behind the right cephalic tentacle: a muscular penial sac receives 4 elements of prostate gland. Spermatophores were never seen. Oocytes, surrounded by several thin follicle cells, reach 150-330 {micro}, m diameter in larger winter snails, mostly in the periphery of theovotestis. Spermatocytes and spermatids develop as clusters in association with accessory (Sertoli) cells. The acrosome appears in the centre of a dense anterior plaque, develops as a domed acrosome vesicle on a short peduncle and eventually becomes a terminal spike on the nucleus tip. The Golgi complex is seen sometimes near the early acrosome but more often behind the nucleus. Mitochondria aggregate first ahead of the nucleus but then form a mitochondrial derivative, with a glycogen helix, spiralled around the axoneme throughout the mid-piece of the tail. This region is marked off from the end-piece of the tail by the annulus. The nucleus becomes long, spiralled with a strong keel, and surrounds the centriolar derivative at the base of the axoneme.

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Authors

  • A. J. Berry

  • J. Purvis

  • K. V. Radhakrishnan

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