More common than reported: range extension, size–frequency and sex-ratio of Uca (Minuca) victoriana (Crustacea: Ocypodidae) in tropical mangroves, Brazil

Abstract

The fiddler crab Uca (Minuca) victoriana von Hagen, 1987 has been reported, until recently, only from the type locality at Vito´ria, State of Espı´rito Santo, Brazil. We report here, for the first time, the occurrence of U. (M.) victoriana in estuaries of the States of Bahia and Pernambuco, north-eastern Brazil, extending its distribution; as well as some aspects of its population biology. For the population study, four sites were defined in mangroves of the Mamucabas and Ariquinda´ Rivers, Pernambuco, on different types of substrate, and sampled monthly during spring low tide from April 2008 through to March 2009. A total of 41 specimens were obtained in June 2008 in the Arinquinda´ River, of which 25 were males, 16 nonovigerous females and 1 ovigerous female. In the Mamucabas River, 772 crabs were collected over the year, including 472 males, 300 non-ovigerous females and 2 ovigerous females. In both areas, the U. (M.) victoriana population showed a unimodal size –frequency distribution, with males and females (ovigerous and non-ovigerous) similar in size (7.46 + 1.60 mm for males and 7.09 + 1.45 mm for females; t ¼ 20.744; P . 0.05). The overall sex-ratio (1:1.57) differed significantly from the expected 1:1 proportion1 (x2 ¼ 38.32; P , 0.05). Study of material deposited in Brazilian carcinological collections revealed several misidentified specimens, especially as U. (M.) rapax and U. (M.) burgersi. Some morphological characters to distinguish among these species are presented.