Evol Ecol Res 20: 317-329 (2019) Full PDF if your library subscribes.
Are superfetation and matrotrophy more prominent in small species?
Nabila Saleh-Subaie1 and J. Jaime Zúñiga-Vega2
11Programa de Doctorado en Ciencias Biomédicas, Universidad Nacional Autónoma de México, Ciudad de México, México, 22Departamento de Ecología y Recursos Naturales, Facultad de Ciencias, Universidad Nacional Autónoma de México, Ciudad de México, México
Correspondence: J.J. Zuñiga-Vega, Departamento de Ecología y Recursos Naturales, Facultad de Ciencias, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, 04510, Ciudad de México, México. email: jzuniga@ciencias. unam.mx
Background: Superfetation is the ability of females to simultaneously bear multiple broods of embryos at different developmental stages. Matrotrophy is the post-fertilization transfer of nutrients to developing embryos by the mother. In viviparous fishes of the family Poeciliidae there is wide interspecific variation in the degree of these two reproductive modes. Given that superfetating and matrotrophic females increase less in mass and volume when producing a particular number of embryos compared with females of species that lack these reproductive modes, we propose the hypothesis that their joint presence allows females to fit a relatively large number of embryos in any given volume of the reproductive tract. Thus, matrotrophy and superfetation should be more advantageous for small species, because their presence could compensate for the space restrictions of a small body size by maximizing their reproductive output.
Question: Do superfetation and matrotrophy compensate for the reproductive constraints imposed by a small body size, and thus are more prominent in small species?
Method: If kisspeptin and GnRH trigger the photoperiodic induction of maturation in fishes, they would be expected to be activated prior to, or at least no later than, the gonadotropins. The mRNA levels of brain gnrh2, gnrh3, kiss2 and its receptor, gpr54, as well as of pituitary lh-β and fsh-β, were measured in males under standard laboratory conditions [16 hours light/8 hours dark (L16/D8) or 8 hours light/16 hours dark (L8/D16)] after 3, 10, 19, and 29 days at 20°C.
Data description: Previously published data on female size, degree of superfetation, matrotrophy index, and total fecundity of 91 poeciliid species.
Analyses: We implemented phylogenetic generalized least squares regressions to examine potential effects of female size on superfetation and matrotrophy. In addition, we compared total fecundity among four categories of species that differ in the presence or absence of matrotrophy and superfetation, accounting for both phylogenetic relatedness and differences in female size among species.
Conclusions: We failed to find support for the hypothesis that superfetation and matrotrophy increase the total reproductive output of small species. Small species do not exhibit more pronounced superfetation and matrotrophy than large species. Therefore, these two reproductive strategies do not function as mechanisms to compensate for the physical restrictions of small body size.
Keywords: body size, comparative analysis, reproductive modes, Poeciliidae, viviparous fishes.
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