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RESOURCE AVAILABILITY AND PLASTICITY IN OFFSPRING PROVISIONING: EMBRYO NOURISHMENT IN SAILFIN MOLLIES
Author(s) -
Trexler Joel C.
Publication year - 1997
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.1890/0012-9658(1997)078[1370:raapio]2.0.co;2
Subject(s) - provisioning , ecology , biology , offspring , resource (disambiguation) , mutualism (biology) , pregnancy , genetics , telecommunications , computer network , computer science
I report evidence of plasticity in the mode of embryo nourishment by female poeciliid fish raised under contrasting environmental conditions. In two experiments, female sailfin mollies ( Poecilia latipinna ), raised on high and low levels of food, produced neonates of similar mass and percentage of fat by varying egg size and the amount of supplemental nourishment provided to embryos as they developed. In one experiment, females displayed plasticity in ovum size, but not neonate size; females raised in a low‐food and low‐salinity treatment produced larger eggs than those raised on higher food levels and at higher salinity. In a second experiment, the amount of nourishment provided to embryos, in addition to that in the egg yolk, was dependent on brood size and maternal food level. Females with small broods were less matrotrophic than those with large broods; female body size and brood size were highly correlated. The brood size at which egg mass equaled neonate mass was smaller for females raised on low levels of food than for females raised on a higher food level treatment. In the second experiment, females from two populations, different from the source of fish for the first experiment, were studied and found to differ in the amount of fat stores remaining after reproduction. Females from a population with low postparturition fat stores displayed greater brood reduction during gestation (via resorption or abortion) and fewer offspring per unit mass than females from the population with more fat. In sailfin mollies, matrotrophy appears to be an adaptation that diminishes the offspring size–offspring number trade‐off by permitting a reduction in ovum size and increase in fecundity without compromising neonate size. However, matrotrophic supplementation of yolk nourishment was greatest in relatively large females raised on a restricted food level. Thus, matrotrophy may incur some energetic cost that renders it inefficient for small females and for females with substantial or dependable energy reserves available for reproduction.