Abstract
A study on the relative growth was carried out in a population of the fiddler crab Uca uruguayensis from the mangrove of Garças River, Guaratuba Bay, Paraná State, southern Brazil. The dimensions analyzed were the length of the major chela (LMC) of males and width of the abdomen (AW) of females, because they are related to reproductive activities of waving (males) and egg incubation (females). The cheliped handedness in males was also analyzed. The LMC was measured in 480 males, the AW in 566 females, and all crabs had the carapace width (CW) measured that was considered as the reference dimension for both sexes. The inflection point in the graphs between each the dimensions and CW was calculated with the aid of the software REGRANS. The CW ranged from 2.33 to 8.33 mm in males and from 1.65 to 7.79 mm in females. The relationship between CW and LMC showed an inflection point at 4.14 mm CW among males, and between CW and AW at 3.52 mm CW among females. The allometric growth was positive for both dimensions throughout the entire ontogeny of both sexes, before and after the puberty. The equations describing the relationship between CW and LMC in males were: logLMC = - 0.695960 + 1.72.logCW for juveniles and logLMC = - 1.212513 + 2.5.logCW for adults. In females, the equations were logAW = - 0.519071 + 1.02.logCW and logAW = - 0.902874 + 1.73.logCW, respectively for juveniles and adults. The population of U. uruguayensis from Guaratuba Bay is composed of the smallest crabs, and it also attains morphological sexual maturity at smallest CW. The frequency of occurrence of right and left handed males was statistically the same (1:1) as in most population of fiddler crabs.
Highlights
Some somatic dimensions of an animal can grow at different rates than others which results in changes of the body proportion during its increase in size
The two dimensions that are usually analyzed in research among decapod brachyurans are the major chela length of males and the width of females abdomen, because they are secondary sexual characters closely associated with the reproductive activities of each sex and constitute elements of sexual dimorphism in adulthood (Hartnoll, 1982)
In the dispersion graph of the empirical dots between carapace width (CW) and length of the major chela (LMC) of males there was an inflection point at 4.14 mm CW that discriminated the subset of juveniles at left with 137 individuals, and that of adults at right with 343 individuals (Fig. 1)
Summary
Some somatic dimensions of an animal can grow at different rates than others which results in changes of the body proportion during its increase in size. This phenomenon is called relative or allometric growth (Hartnoll, 1978), and can be used as a tool to deduce the size c Published by Brazilian Crustacean Society, Ribeirão Preto, Brazil - July 2013 at which a species attains its morphological sexual maturity. Crabs of the genus Uca Leach, 1814 are widely studied on relative growth due to their apparent contrasting sexual dimorphism: the adult males giant cheliped readily allows distinguishing it from female. These animals were object of morphometric studies in several countries: Uca pugilator Bosc, 1802 in Massachusetts, USA (Miller, 1973), Uca subcylindrica Stimpson, 1859 in Texas, USA (Thurman II, 1984), Uca pugnax Smith, 1870 in New York, USA (Rosenberg, 1997), Uca lactea Haan, 1835 from various regions of Japan (Yamaguchi, 1977) and Uca arcuata Haan, 1833 from Kyushu, Japan (Yamaguchi, 2001; Yamaguchi and Henmi, 2001)
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