Relative growth of the male major chela and female abdome was studied in a population of the fiddler crab Uca leptodactyla Rathbun, 1898 from Itapoá, Santa Catarina coast, southern Brazil. Major chela length (CMQ) was measured from 191 males, and abdomen width (LAB) from 128 females. Carapace width (LC) was the reference dimension for both sexes, which ranged from 3.9 to 11.5 mm for males, and from 3.15 to 10.65 mm for females. Males grew bigger than females. Relationship between CMQ and LC showed a transition point at 8.35 mm LC in males, and between LA and LC at 7.10 mm LC in females. Growth was allometrically positive in the early ontogenesis and isometric after the puberal molting for both sexes. Regressions between LC and CMQ in males read as: logCMQ = -0,854536 + 2,19. logLC for empirical points at left of critical point and logCMQ = 0,063047 + 1,24. logLC for those at right. In females, this relation was logLAB = -0,603590 + 1,30. logLC and logLAB = -0,361464 + 1,07. logLC, respectively. These body dimensions were connected with reproductive activity of this species.

The reproductive biology of Aegla caslro Schmitt, 1942 from Buraco do Padre, Ponta Grossa, Paraná State, was analyzed. The sampling was done monthly, from February/97 to January/98 with aid of hand net and screens at three stations, under an effort of 120 minutes. The mean air temperature ranged from 15.0ºC (May, July, September and October) to 24.3ºC (December and January), and the water temperature from 15.8ºC (July) to 22.3ºC (December). The dissolved oxygen oscillated from 95.7% (March) to 100.2% saturation (August) and the pH from 6.1 (July) to 7.2 (September). A total of 827 specimens were obtained among which 384 males, 311 females and 132 juveniles. Males predominated over females, but the sex ratio followed the standard model of 1:1. Juveniles were found during all the study period, except in May and September. The peaks of their frequency curve occurred in April and December. The reproduction is discontinuous type with greater intensity in the colder months, from May to October. The females take part of the reproduction for two consecutive years and the species longevity was estimated in two years. The carapace length of the various development stages ranged as following: juveniles < 6.4 mm, immature females and males = from 6.5 to 12.2 mm and mature females and males = from 12.3 to 29.5 mm.

A study of the annual abundance fluctuation, temporal distribution and size composition of Aegla castro Schmitt, 1942 was carried out at the Buraco do Padre, Quebra-Perna River, Tibagi River Basin, in the municipality of Ponta Grossa, Paraná State. The samplings were done monthly, from February/97 to January/98 with the aid of a hand net and screens at three stations, under an effort of 120 minutes. The average air temperature ranged from 15.0ºC (May, July, September and October) to 24.3ºC (December and January), and the water temperature from 15.8ºC (July) to 22.3ºC (December). The dissolved oxygen oscillated from 95.7% (March) to 100. 2% (August) saturation, and the pH from 6.1 (July) to 7.2 (September). The water flow speed varied from 0.2 m/s to 1.2 m/s. Sulfates and phosphates had values less than 0.2 ppm and the ammonia values alternated from 0.1 to 0.6 ppm. A total of 827 specimens were obtained, among which 384 males, 311 females and 132 juveniles. The abundance of Aegla castro varied from 27 (July/97) to 204 (September/97). In the Station 1 higher number and larger specimens were obtained with predominance of males. Juveniles and adults of both sexes occurred in all three sites, but the proportion between juveniles and adults was different. So, these habitats are appropriate to the development of these animals. Males grow up larger than females, due to the reproductive effort of the last ones.