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Determination of limited histotrophy as the reproductive mode in Mustelus schmitti Springer, 1939 (Chondrichthyes: Triakidae): analysis of intrauterine growth of embryos

ABSTRACT

This work analyzed length-mass relationship, growth in length, mass variations and dynamic of yolk sac depletion of Mustelus schmitti embryos, extracted from females catched by the artisanal fishery acting off La Paloma (34°39'S, 54°10'W, Uruguay) during 2006 and 2007. Differences in total length and total mass between sexes were not significant. Embryos showed a negative allometric growth for both years with a slope change near the day 170 of the year, likely to be associated with the depletion of the external yolk sac. Gompertz and Von Bertalanffy curves were adjusted for each year. Parturition date was determined around the day 300 of the year. Yolk depletion followed a logistic dynamic Yt=1/(1+e(-13.749 + 0.072*t)) for 2006 and Yt=1/(1+e(-10.472 + 0.054*t)) for 2007. Embryos showed a mean increase in total dry mass of 5.4g in 187 days which, together with yolk depletion dynamics, indicates additional energetic supply, suggesting that M. schmitti presents limited histotrophy.

Keywords:
Embryo growth; Matrotrophy; Narrownose smoothhound; Reproductive mode; Southwestern Atlantic

Sociedade Brasileira de Ictiologia Neotropical Ichthyology, Núcleo de Pesquisas em Limnologia, Ictiologia e Aquicultura, Universidade Estadual de Maringá., Av. Colombo, 5790, 87020-900, Phone number: +55 44-3011-4632 - Maringá - PR - Brazil
E-mail: neoichth@nupelia.uem.br