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.

Reproductive biology and placentotrophic embryonic development of the smalleye smooth-hound shark, Mustelus higmani, from the south-eastern Caribbean

“…Within the genus Mustelus , placentotrophic and non-placentotrophic (previously referred to as ‘aplacental’) embryonic development strategies can be found (Teshima, 1981). Non-placentotrophic strategies in Mustelus include strict lecithotrophy (Yamaguchi et al ., 2000) and minimal histotrophy (Storrie et al ., 2009; Orlando et al ., 2015). The morphology of the yolk sac placenta of M. canis has been largely studied among Mustelus species (TeWinkel, 1963 a , 1963 b ).…”

Diversity of the egg tertiary membranes in some elasmobranch species and comments on the actual yolk-sac viviparous reproductive mode

“…This configuration is shared with other members of the Triakidae family (e.g., Mustelus antarcticus and M. schmitti which, as G. galeus, are confirmed viviparous species with limited histotrophy). In such species in spite of the presence of uterine compartments as in typical placentotrophic species (Hamlett & Koob 1999), no placenta is developed (Storrie et al 2009, Orlando et al 2015, Vooren & Oddone 2019). According to Musick & Ellis (2005) the line between yolksac viviparity and limited histotrophy may be difficult to discern without data on the organic content of the eggs and term embryos.…”

Bioenergetic Model of the Highly Exploited Shark Mustelus schmitti under a Global Warming Context

“…Unlike other models that employ fixed parameters, we opted for the use of sampling distributions for several point estimates (sensu [8,9,59]). These probability distributions were defined based on either assumptions about the distributions of input variables (from recommendations in [8,9,59]) or driven by the distributions observed in the data of M. schmitti compiled by the authors.…”

“…Unlike other models that employ fixed parameters, we opted for the use of sampling distributions for several point estimates (sensu [8,9,59]). These probability distributions were defined based on either assumptions about the distributions of input variables (from recommendations in [8,9,59]) or driven by the distributions observed in the data of M. schmitti compiled by the authors. The possible sampling distributions were (1) normal distributions, used for variables that are symmetrical around the mean (i.e., T, initial W, constants for S, E, and F); (2) log-normal distributions, used for right-skewed variables with a lower limit of zero and no upper bound (i.e., SMR, RMR, intercepts); and (3) uniform distributions, used for variables with an upper and lower limit, where sampling probabilities are constant between the limits (i.e., prey proportions).…”

“…Model estimates of growth were run 3000 times, each representing an individual M. schmitti being born on 1 January. To ensure realistic initial sizes, initial W was based on observed weight-at-birth information [26,31,59,60]. A mean and standard deviation (SD) of weight-at-birth was estimated and fed to a normal distribution, which provided values for each individual.…”