Consistent habitat segregation between sexes in the spider crabs <em>Maja brachydactyla</em> and <em>Maja squinado</em> (Brachyura), as revealed by stable isotopes

Abstract

Summary: Differences in the resource use patterns of males and females of the spider crab species Maja brachydactyla Balss, 1922 and M. squinado (Herbst, 1788) from several geographic areas (three in the Atlantic and two in the Mediterranean) were studied through the analysis of stable isotopes of carbon and nitrogen in the exoskeleton of post-pubertal (adult) specimens. Results confirmed that males and females from the same population usually did not differ in δ 15 N values and hence foraged at the same trophic level. In contrast, females were usually enriched in 13 C as compared with males from the same population, thus suggesting that females use shallower habitats than males before the terminal moult. The results reported here also indicate that stable isotopes can be useful for the traceability of commercial Maja species, but only if species and sex are incorporated in the analysis.Keywords: Maja brachydactyla; Maja squinado; stable isotopes; trophic level; sexual segregation; traceability. Segregación sexual del hábitat en los centollos Maja brachydactyla y Maja squinado (Brachyura) revelada mediante isótopos establesResumen: Se estudiaron mediante el análisis de isótopos estables de carbono y nitrógeno en el exoesqueleto de ejemplares adultos las diferencias en los patrones de uso de recursos de los machos y las hembras de los cangrejos Maja brachydactyla Balss, 1922 y M. squinado (Herbst, 1788) procedentes de varias zonas geográficas (tres en el Atlántico y dos en el Mediterráneo). Los resultados confirmaron que los machos y las hembras de la misma población, por lo general, no difieren de los valores de δ 15 N y por lo tanto se alimentaban en el mismo nivel trófico. En contraste, las hembras por lo general se hallan enriquecidas en 13 C en comparación con los machos de la misma población, lo que sugiere que las hembras ocupan hábitats menos profundos que los machos antes de la muda terminal. Los resultados aquí presentados indican también que los isóto-pos estables pueden ser útiles para la trazabilidad de las especies comerciales del género Maja, pero sólo si la identidad de la especies y el sexo del ejemplar se incorporan al análisis.Palabras clave: Maja brachydactyla; Maja squinado; isótopos estables; nivel trófico; segregación sexual; trazabilidad.Citation/Como citar este artículo: Guerao G., Rotllant G., Gisbert E., Uyà M., Cardona L. 2016. Consistent habitat segregation between sexes in the spider crabs Maja brachydactyla and Maja squinado (Brachyura), as revealed by stable isotopes. Sci. Mar. 80(1): 103-110. doi: http://dx

A beacon of dung: using lemming (Lemmus lemmus) winter nests and DNA analysis of faeces to further understand predator–prey dynamics in Northern Sweden

“…Additionally, trophic niche segregation between the different sexes has been noted in many species (Forero et al 2005;Mariano-Jelicich et al 2008;Tucker et al 2009;Guerao et al 2011;Kernaléguen et al 2015). Stoats and weasels, as many mustelids, are known to show evident sexual body size dimorphism (Moors 1980), which could lead to diverging trophic niches (Mcdonald et al 2000;Purdey et al 2004) or habitat use .…”

Isotopic Niche and Trophic Position of the Invasive Portunid Portunus segnis Forskål, (1775) in Elounda Bay (Crete Island, Eastern Mediterranean)

“…Noticeably, we observed significant differences in SEAc values, indicating that, independently from the number of specimens analyzed, females have a smaller isotopic niche than males. The occurrence of sex-or reproductive state-related differences in isotopic niche width or other metrics deserves to be addressed in the future, since the issue is unexplored for P. segnis as well as for other portunids, while isotopic studies focused on marine brachyurans have provided non-univocal, even contrasting results [15,[81][82][83].…”