http://dx.doi.org/10.1590/1519-6984.01913 Original Article Population biology and color patterns of the blue land crab, Cardisoma guanhumi (Latreille 1828) (Crustacea: Gecarcinidae) in the Northeastern Brazil Silva, CC.a,b*, Schwamborn, R.c and Lins Oliveira, JE.b aPrograma de Pós-graduação em Biologia Animal, Universidade Federal de Pernambuco – UFPE, Av. Professor Moraes Rêgo, 1235, Cidade Universitária, CEP 50670-420, Recife, PE, Brazil bLaboratório de Biologia Pesqueira, Departamento de Oceanografia e Limnologia, Universidade Federal do Rio Grande do Norte – UFRN, Av. Via Costeira, s/n, Praia de Mãe Luíza, CEP 59014-000, Natal, RN, Brazil cDepartamento de Zoologia, Universidade Federal de Pernambuco – UFPE, Av. Professor Moraes Rêgo, 1235, Cidade Universitária, CEP 50670-420, Recife, PE, Brazil *e-mail:[email protected] Received: March 11, 2013 – Accepted: July 07, 2013 – Distributed: December 31, 2014 (With 5 figures) Abstract The objective of this study was to analyze the population biology and color patterns of Cardisoma guanhumi Latreille, 1828 in a mangrove area in Natal, Rio Grande do Norte, Brazil. Crabs were collected monthly between February 2010 and January 2012 and totaled 1,837 individuals. Sex ratios were similar between males and females in the first year and differed in the second. Sex ratios by size class differed statistically in the extremes of the distribution, with an abundance of males in the large size classes. There was no difference (p > 0.05) in carapace width between males and females in the first year, but in the second year, males were larger than females (p = 0.003), showing the importance of considering interannual variation in such studies. Both sexes presented a unimodal distribution. The size of first maturing of the females was 6.00 cm. Asymptotic carapace width for males was 9.4 cm and females for 9.2 cm, using the Wetherall method. There was no defined modal progression, which made the determination of the Von Bertalanffy growth parameter K impossible. Juveniles were found throughout all months of the year, demonstrating that there was no defined period of recruiting, although slightly fewer juveniles were found in the dry season. Four color patterns were observed, the three first patterns were the same for both sexes, while the fourth pattern was observed in females only. The four color patterns identified could be clearly related to the stage of development (size) and sexual maturity of the animal. Keywords: blue land crab, colour pattern, sex ratio, size frequency distribution. Biologia Populacional e padrões de coloração do caranguejo terrestre, Cardisoma guanhumi (Latreille 1828) (Crustacea: Gecarcinidae) no Nordeste do Brasil Resumo O objetivo deste artigo foi analisar a biologia populacional e os padrões de coloração da carapaça de Cardisoma guanhumi Latreille, 1828 em uma área de manguezal em Natal, Rio Grande do Norte, Brasil. Os caranguejos foram coletados mensalmente entre fevereiro de 2010 e janeiro de 2012 e totalizaram 1837 caranguejos. A proporção sexual foi semelhante para machos e fêmeas (1:1) no primeiro ano e diferiu no segundo ano. A proporção sexual por classe de tamanho diferiu estatisticamente nas classes extremas da distribuição, com abundância de machos nas superiores. Não houve diferença (p ≥ 0,05) entre as larguras de carapaça de machos e fêmeas no primeiro ano, porém no segundo os machos foram maiores que as fêmeas (p = 0,003), revelando à importância de se considerar as variações interanuais nestes estudos. Ambos os sexos apresentaram distribuição unimodal. O tamanho de primeira maturação sexual das fêmeas foi 6,00 cm. A largura de carapaça assintótica para machos foi de 9,4 cm e para as fêmeas de 9,2 cm, usando o método Wetherall. Não houve progressão modal definida, o que impossibilitou a determinação do parâmetro de crescimento k de Von Bertalanffy. Foram encontrados juvenis ao longo de todos os meses do ano, mostrando não haver um período de recrutamento definido, embora a abundância de juvenis tenha sido menor na estação seca. Foram observados quatro padrões de coloração, três para ambos os sexos e um quarto padrão observado apenas para as fêmeas. Os quatro padrões de coloração da carapaça estão claramente relacionados ao estágio de desenvolvimento (tamanho) e à maturidade sexual do animal. Palavras-chave: guaiamum, padrão de coloração, proporção sexual, distribuição de tamanho. Braz. J. Biol., 2014, vol. 74, no. 4, p. 949-958 949 Silva, CC. et al. 1. Introduction The following hypotheses are tested: (a) the sex ratio differs according to size class, (b) carapace width and The blue land crab Cardisoma guanhumi (Latreille, growth differs between sexes and between the periods 1828) displays a wide distribution in the West Atlantic, studied, (c) there is a distinct seasonal recruitment period, ranging from Florida (U.S.) to Santa Catarina, southern and (d) the distinct color patterns are related to size, sex Brazil (Burggren and McMahon, 1988; Branco, 1991). and stage of maturation. As a semi-terrestrial species, even though most of its life cycle is in a terrestrial environment, where it feeds and 2. Material and Methods reproduces, it depends on the aquatic environment for dispersion and planktonic larval development (Bliss, 1979; Samples of C. guanhumi were collected, without the Burggren and McMahon, 1988). This species builds its reposition of the individuals, in a monthly interval over two galleries above the line of the high tide (Melo, 1996) in the years, from February 2010 to January 2012. The sampling upper mangrove fringe and in areas adjacent to mangroves area is located in the lower estuary of the Potengi river (Schaeffer-Novelli, 1989). It is an important socio-economic (5°47’22,8”S, 35°13’10,5”W), in a mangrove area of the resource in many countries in Latin America and in the Naval Base of the city of Natal, Rio Grande do Norte Caribbean (Feliciano, 1962; Taissoun, 1974; Wolcott, State, located in northeastern Brazil; thus, this is inside a 1988; Rodriguez-Fourquet and Sabat, 2009). military area with restricted access and negligible capture In Brazil, this species is a highly valued resource, of land crabs. especially in the coastal region of Northeastern Brazil, and The specimens were collected using cylindrical traps is frequently sold at indoor and outdoor markets or roadside with diameters of 40 mm (120 mm long) and 100 mm stands near mangrove areas, being a favorite ingredient (250 mm long). The traps were set up in all burrows in the regional cuisine (Oshiro et al., 1999; Botelho et al., occupied by crabs, determined by the presence of feces 2001). This demand for consumption has generated a strong in the entrance of the burrow. Sampling was initiated at pressure on crab populations, and is one of the contributing 9 am and stretched until 5 pm, with harvest intervals of factors of the significant decrease in stock size observed 1 and a half hours; where crabs were trapped, they were harvested and the traps were armed again. in Northeastern Brazil (Botelho et al., 2001). Besides the In the lab, the following parameters were determined: increase in consumption, the species also suffers from sex, color and width of the carapace (CW). The individuals impacts caused by the changes generated by direct or were classified as Juvenile (A – immature) or adults indirect devastation of their habitat, where the vegetation (B, C, D and E – mature), through a macroscopic analysis of the mangrove is destroyed to provide space, primarily of the stages of gonad development (Botelho et al., 2001), for the expansion of ports, industries, salt production and based on its shape, size, consistence and coloration. This shrimp farms (Vannucci, 1999; Duarte et al., 2008). species presents three color patterns for males and four Studies on C. guanhumi are extremely important, since for females (Silva and Oshiro, 2002). The patterns are there is an enormous lack of information, especially in classified as follows: pattern 1 – characteristic for the northeastern Brazil (Abrunhosa et al., 2000; Botelho et al., juvenile stage, when the dorsal part of the carapace is 2001; Shinozaki-Mendes et al., 2008; Shinozaki-Mendes et al., a yellowish brown and the sides are a light purple, the 2012a, b) related to the population biology; this information chelipeds and legs also have an orange or yellowish brown is essential for the proper management of this resource, to color; pattern 2 – corresponds to the transition stage, allow sustainable exploitation of the species, as its populations when the animals’ body has an intense bluish dark purple are already being overexploited (De Oliveira-Neto et al., tone; pattern 3 – represents the individuals with color of 2008; Firmo et al., 2012; Shinozaki-Mendes et al., 2012a). the carapace, chelipeds and legs lavender blue; pattern The lack of information about the species C. guanhumi 4 – is characterized by the whitish, yellowish or grayish is also reflected by the number of studies dedicated to color. This pattern is frequently found in adult females; classifying and quantitatively investigating the relationship according to Gifford (1962) and Fischer et al. (1978), it of the carapace color patterns: there are just two published is due to ovulation, and can also be observed in the male studies (Gifford, 1962; Silva and Oshiro, 2002). In semi- reproductive period, although rarely. terrestrial crabs, the color patterns are correlated to In the analysis of the sex ratio in each class of carapace variations in behavior and physiology (Reid et al., 1997; width, the test utilized was the chi-square test χ2 (α = 0.05); Silbiger and Munguia, 2008). to assess the differences in carapace width between the Thus, the objective of this study was to describe the sexes in the two years analyzed, the t test was used (Zar, population structure of this species in a mangrove area with 1999).