Allometric constraints and variables of reproductive effort in brachyuran crabs

Abstract

Allometric relationships of reproductive output were compared in 20 species from 7 families of brachyuran crabs from the east and west coasts of North America, using regression analysis of log reproductive parameters versus log body weight. Comparisons of crabs spanning 4 orders of magnitude in body weight indicated that female body size was the principal determinant of reproductive output: 95% of the variance in brood weight, 79% of the variance in the number of eggs per brood, 63% of the variance in annual brood weight, and 74% of the variance in annual fecundity were explained by body weight. Brood weight exhibited an isometric constraint to about 10% of body weight. Allometric limitations on space available for yolk accumulation in the body cavity appeared to be the main constraint on brood size. Ovum size increased significantly, but only slightly, with increasing body size. There was a significant trade-off between ovum size and the number of eggs per brood. There was no significant relationship between the number of broods per year and body size. The number of eggs per brood was significantly better than brood weight as a predictor of the number of broods produced per year by a species, indicating that demographic pressure on fecundity rather than energetic considerations is the primary selective mechanism influencing annual reproductive effort. Each of the 7 families of crabs exhibited trends toward distinct patterns for the suite of co-adapted reproductive traits. However, no interspecific reproductive patterns were apparent with respect to the variables of feeding type, salinity tolerance, habitat, and geographic range represented by the 20 species.

Population and reproductive features of the western Atlantic hermit crab Pagurus criniticornis (Anomura, Paguridae) from Anchieta Island, southeastern Brazil

“…According to HINES (1982), the egg size is the best reproductive variable to determinate if the spawn has numerous and small eggs or few and large eggs, resulting in large variation in fecundity between species. Larger eggs produce an offspring better adapted to the search for food and with greater competitive ability (BERTNESS, 1981).…”

Crescimento do caranguejo de água doce, Dilocarcinus pagei Stimpson (Crustacea, Brachyura, Trichodactylidae)

“…Caranguejos de água doce apresentam desenvolvimento direto, possuindo ovos de maior tamanho do que os caranguejos marinhos. Devido à correlação positiva entre o número de ovos e seu tamanho nos braquiúros (HINES 1982), pode-se supor que as fêmeas de caranguejos dulcícolas investem mais em crescimento somático (maior taxa de crescimento), atingindo a maturidade com um maior porte, com elavação de sua fecundidade.…”

Fecundity of Uca uruguayensis and Chasmagnathus granulatus (Decapoda, Brachyura) from the "Refugio de Vida Silvestre" Bahía Samborombón, Argentina

“…Total carapace widths (CW), wet and dry weight (60 °C, during 48 hours) were measured. The dry weights of the brooded egg mass and number of eggs per brood (extrapolated from the dry weight of a counted sub-sample of 1000 eggs) were measured in order to determine the brood size (Hines, 1982;Mantelatto and Fransozo, 1997;Luppi et al, 1997;Leme, 2004). Although some authors (Mantelatto and Fransozo, 1997) recommend the use of embryos in developmental stages from late blastula to early gastrula for fecundity analysis, to avoid effects of embryonic diameter swelling during late stages of development, we considered here (following Hines, 1982;Luppi et al, 1997;Leme, 2004) also those embryos in the intermediate stage of development, as determined by formation of eyes.…”