Abstract

VILLAMIL-MORENO, Ludy P.  and  ARIAS - CASTELLANOS, José A.. Otocinclus spectabilis fecundity. Orinoquia [online]. 2011, vol.15, n.1, pp.41-47. ISSN 0121-3709.

Fecundity is the estimated number of oocytes which a female could be expected to expel during one spawning; this is thus one of the most used indicators for evaluating fish species'reproductive potential and their farming potential. The ovaries of mature wild female fish were studied to contribute towards knowledge regarding this criterion. Fish and ovaries were weighted individually and the gonadosomatic index (GSI) was calculated. Each ovary was digested in Gilson's solution for 20 days and then screened through a 500 μm mesh; the retained oocytes were counted (by stereomicroscope) and fecundity was thus estimated. The relative fecundity to weight (RFW) ratio was also calculated and oocyte diameters were measured. Atenth part of five ovaries was processed by conventional histology (haematoxylin and eosion- H & E - stain) to study oocyte development and types of spawning. This led to 62 ± 8 oocytes / female fecundity and 91 ± 10 oocytes g-¹ total weight RFW being obtained; the GSI was 13.2 ± 1.1 % and mature ovaries'oocyte diameter was 1,366.5 ± 203.8 μm. Oocyte diameter frequency and the histological slides revealed two oocyte growth groups having greater than 500 μm, thereby leading to the observation that ovarian development was asynchronous and spawning was partial in this sample.

Keywords : gonadosomatic index; oocyte development; oocyte diameter; otocynclos; relative fecundity; spawning.

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