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

Luis Orlando,Santiago Silveira,Laura Paesch,Inés Pereyra,Maria Cristina Oddone,Walter Norbis

doi:10.1590/1982-0224-20150001

Abstract

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.

Highlights

Chondrichthyans exhibit all major vertebrate reproductive modes (Dulvy & Reynolds, 1997), which can be broadly categorized in oviparity and viviparity
Viviparous strategies can be further categorized into lecithotrophy and matrotrophy, based on the magnitude and way nutrients are transferred from the mother to the embryos throughout their development (Wourms, 1981; Musick & Ellis, 2005)
This study aims to characterize the intrauterine growth cycle of M. schmitti embryos

Summary

Introduction

Chondrichthyans exhibit all major vertebrate reproductive modes (Dulvy & Reynolds, 1997), which can be broadly categorized in oviparity and viviparity. Viviparous strategies can be further categorized into lecithotrophy and matrotrophy, based on the magnitude and way nutrients are transferred from the mother to the embryos throughout their development (Wourms, 1981; Musick & Ellis, 2005). The nourishment of developing embryos by a source other than yolk is known as matrotrophy (Wourms, 1981). The known relevance of embryonic life history traits is increasing, as links between the length of gestation period and the neonate mass have been established on several taxa (Ricklefs, 2010)

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