Redalyc.Seasonal Variation in Body Size and Diet of the Sea Star
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Revista de Biología Tropical ISSN: 0034-7744 [email protected] Universidad de Costa Rica Costa Rica Guilherme, Pablo D. B.; Rosa, Leonardo C. Seasonal variation in body size and diet of the sea star Astropecten marginatus (Paxillosida, Astropectinidae) off coast of Paraná, Southern Brazil Revista de Biología Tropical, vol. 62, núm. 1, mayo, 2014, pp. 59-68 Universidad de Costa Rica San Pedro de Montes de Oca, Costa Rica Available in: http://www.redalyc.org/articulo.oa?id=44931382006 How to cite Complete issue Scientific Information System More information about this article Network of Scientific Journals from Latin America, the Caribbean, Spain and Portugal Journal's homepage in redalyc.org Non-profit academic project, developed under the open access initiative Seasonal variation in body size and diet of the sea star Astropecten marginatus (Paxillosida, Astropectinidae) off coast of Paraná, Southern Brazil Pablo D. B. Guilherme1* & Leonardo C. Rosa2 1. Programa de Pós-Graduação em Ecologia e Conservação, Universidade Federal do Paraná. Centro Politécnico, Curitiba-PR, CEP 81531-990, Caixa Postal 19031, Brasil; [email protected] 2. Núcleo de Engenharia de Pesca, Universidade Federal de Sergipe. Av. Marechal Rondon, s/n. Bairro Jardim Rosa Elze, São Cristóvão-SE, CEP 49100-000, Brasil; [email protected] * Correspondence Received 25-II-2013. Corrected 07-IX-2013. Accepted 01-X-2013. Abstract: The sea star Astropecten marginatus has a neotropical distribution and is a highly abundant and frequent species in shrimp trawling by-catchin many places along the Brazilian coast. This has caused its threat to extinction and in addition, its bio-ecological aspects are poorly known. Thus, the main objective of this study was to analyze the seasonal variations of population length structure and feeding habits of the sea stars A. marginatus inhabiting off state of Paraná, Southern Brazil. The analyzed specimens were collected in February (summer), April (fall), June (winter) and October (spring) of 2008 from shrimp by-catch trawling. In the labora- tory, each individual had its length measured and then weighed on an analytical scale. Afterwards, the stomach contents of 10 individuals of each of two most frequent length classes were seasonally analyzed. The relative frequency and abundance for each prey category was determined and, then combined into an index of alimentary importance. A total of 994 individuals of A. marginatus were collected with length ranging from 7.0 to 56.2mm, but most individuals were in the 20.1-25mm length classes. Individuals larger than 40mm were only collected in the spring while a few recruits (<10mm) were found in fall and winter. The total weight of individuals ranged from 0.1 to 15.3g and the weight-length relationships showed a negative allometric growth (b<2.54). Regarding its food consumption, this sea star explored eleven food items, with cumaceans and mollusks as the most fre- quent items. High frequency of empty stomach was recorded at fall. Seasonal differences in the amount explored preys and ingested items as well as in the prey composition were also observed. Higher amount of explored prey categories and ingested items were recorded at winter-spring than summer-fall periods. Predominance in prey category changed from gastropods (summer and fall) to cumaceans (winter and spring). The importance of gastropods as main prey category at summer and fall should be carefully considered since it was coincidently observed with high frequency of empty stomach and low amount of ingested items. The observed seasonal dif- ferences in feeding behavior pattern were mainly associated to low prey availability and to changes in the sea star feeding rates, and probably reflected in some biological traits such as small body size of the population inhabiting waters off the Paraná coast, Southern Brazil. Rev. Biol. Trop. 62 (1): 59-68. Epub 2014 March 01. Key words: Asteroidea, Echinodermata, population length structure, food items, seasonal variation, prey availability. The seastars (Echinodermata, Asteroidea) communities (Jangoux, 1982; Ganmanee, Nar- are predominantly carnivorous generalists ita, Iidas, & Sekiguchi, 2003). (Sloan, 1980). They inhabit different types The order Paxillosida has ambulacral of substrates and have an important role as feet without suckers and an incomplete diges- high-level predator in intertidal and subtidal tive tract, morphological features considered Rev. Biol. Trop. (Int. J. Trop. Biol. ISSN-0034-7744) Vol. 62 (1): 59-68, March 2014 59 primitive (Jangoux, 1982; Blake, 1987, 1989), with extinction in many Brazilian coastal states although some molecular studies show the (MMA, 2004). Despite its abundance and opposite (Matsubara et al., 2005, Janies, Voight, importance, knowledge on the biology and & Daly, 2011; Mah & Foltz, 2011). Regarding ecology of A. marginatus is scarce. Some bio- their feeding habits, the paxillosids swallow metric and ecological information about this their prey whole digesting it inside the stom- species may be found in studies off the coast ach cavity and, this intraoral digestion reflects of Venezuela (Roa, 1967), Brazil (Tommasi, an adaptation to life in soft-bottom substrates 1970; Monteiro & Pardo, 1994), and Suri- (Blake, 1987; Ventura, 2013). name (Walenkamp, 1976, 1979). Furthermore, Members of the family Astropectinidae, species feeding habits had only been studied including the genus Astropecten (Gray, 1840), for populations off Venezuelan (Soto, 1984; inhabit tropical, subtropical and temperate Ortega, Martín, & Díaz, 2011) and Southeast- waters (Bitter & Penchaszadeh, 1983; Soto, ern Brazilian coasts (Monteiro & Pardo, 1994). 2000; Loh & Todd, 2011). This genus is exclu- The main objective of this study was to sively carnivorous and an active predator with analyze the seasonal variations in the popula- a generalist diet, and has negative effects on tion length structure and in prey composition the density of its prey (Jangoux, 1982). These of sea stars Astropecten marginatus inhabiting organisms are able to find and capture their off state of Paraná, Southern Brazil. preferred prey buried into the sediment (Wells, Wells, & Gray, 1961; Bitter & Penchaszadeh, MATERIALS AND METHODS 1983). The selectivity of its prey is influ- enced by several factors such as the prey size, The coast of Paraná is characterized by a which depends on its body size and constraints shallow continental shelf with a smooth topo- imposed by the mechanism of intraoral diges- graphic gradient (Veiga, 2005). The substrate is tion (Ventura, Grillo, & Fernandes, 2001). The mostly sand, mud and clay from continental and availability of prey also exerts influence on fluvial origin (Angulo, 1992; Lorenzi, 2004). the diet, as their distribution and abundance The climate is classified as Cfa, according to are determined by environmental conditions Köppen-Geiger (i.e., rainy temperate [C], rain- (McClintock & Lawrence, 1985; Beddingfield ing all year around [f] and average temperature & McClintock, 1993; Monteiro & Pardo, 1994; of the warmest month above 22°C[a]) (Maack, Gaymer, Himmelman, & Johnson, 2001; Gil & 1968; Vanhoni & Mendonça, 2008). Zaixso, 2008). The genus Astropecten is able The analyzed specimens of A. margin- to distinguish the “quality” of their prey using atus were taken from the by-catch of artisanal its chemo-receptive abilities (Sloan, 1980) and sea-bob shrimp Xiphopenaeus kroyeri (Heller, thus to select prey with higher nutritional qual- 1862) fishery carried out off the coast of ity and energy (Beddingfield & McClintock, Paraná. In this region, shrimp trawling are nor- 1993). As a consequence, it is the most special- mally carried out at depths ranging from five ized trophic group of asteroids (Jangoux, 1982). to 25m (Andriguetto-Filho, 1999). Samples Astropecten marginatus (Gray, 1840) has were collected in February (summer), April a neotropical distribution (Caribbean Sea to (fall), June (winter), and October (spring) of the extreme South of Brazil, the State of Rio 2008, by local fishers always at Shangri-lá Grande do Sul) inhabiting sandy substrates beach (25°37’20” S - 48°24’36” W). Speci- between depths of one to 130m (Tommasi, mens of A. marginatus were separated from the 1970; Jangoux, 1982; Clark & Downey, 1992). rest of the by-catch and immediately fixed in Due to its high frequency and abundance, formalin (10%). the species is considered an important item In laboratory, the length of each individual in shrimp by-catch fisheries (Kotas, 1998; was measured from the center of the disc to the Branco & Verani, 2006) and, it is threatened end of its longest arm with a caliper (0.05mm 60 Rev. Biol. Trop. (Int. J. Trop. Biol. ISSN-0034-7744) Vol. 62 (1): 59-68, March 2014 precision). Each specimen was dried on paper in which the ANOVA result was significant towel and then weighed with an analytical (p<0.05), Tukey’s multiple comparison test scale (0.1mg precision). The specimens of A. was applied to determine specific differences marginatus were grouped into different length (Underwood, 1997). The similarity in the A. classes at intervals of 5mm, which was deter- marginatus food items between two most fre- minate by Sturges’ Rule (Sturges, 1926). quent length classes and among sampling peri- The weight-length relationship was esti- ods were assessed by applying the Simplified mated by least square regressions with preced- Morisita index (Horn, 1966). A suitable coef- ing ln-transformation of dependent (weight in ficient for proportion analyses with little influ- g) and independent (length in mm) for each ence of the sample size (Krebs, 1999), on the season. Regressions coefficients were tested AI values of each item, where the results were for significant deviations from zero (ANOVA). displayed in the form of UPGMA clustering Slopes of different regression equations were method dendrogram. In a complementary way, compared with each other employing mul- a two-way PERMANOVA was used to test the tiple ANCOVA and, intercepts with the Y-axis null hypothesis of no difference in prey com- with an ANOVA (i.e., after removal of the position among length classes and sampling interaction term).