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Gayana (Concepción)

Print version ISSN 0717-652XOn-line version ISSN 0717-6538

Abstract

HUAQUIN, Laura G.; VELIZ, Dina  and  ARRATIA, Gloria. A COMPARATIVE STUDY OF THE OVARIES AND OOCYTE ENVELOPES OF FRESHWATER SILUROID CATFISHES FROM CHILE. Gayana (Concepc.) [online]. 2002, vol.66, n.2, pp.269-274. ISSN 0717-652X.  http://dx.doi.org/10.4067/S0717-65382002000200026.

Reproductive biology including the mode, timing and duration of spawning can be inferred from the ovarian structure of fishes. This study describes and analyses ovarian and oocyte structure of two siluroid species, the one Nematogenys inermis threatened with extinction, the other, Trichomycterus areolatus, the most abundant and widespread in Chilean continental waters. Histological sections (6 mm) of ovaries fixed in Bouins fluid were routinely stained with hematoxilin-eosin and some with trichromic (Azan) and Periodic Acid Schiff (PAS). Histologically the ovarian wall consisted of an external serosa, a median tunic and ovarian epithelia. The tunic reaches internally with leaflets of connective tissue comprising the ovaric strome. In mature ovaries of T. areolatus oocytes with several developmental stages were observed. This indicates asynchronous maturation with spawning taking place throughout the reproductive period. N inermis showed partial synchronisation indicating a single spawning activity in the reproductive cycle. In both species the immature oocytes are enveloped with the plasma membrane. Mature ova show well developed envelopes, a radiata zone, folicular epithelium with basal membrane and an external theca, with specific differences shown by the ovocytic envelopes

Keywords : histology; envelope oocytes; Siluriformes.

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