Abstract
Crustaceans are a key component of the fauna living in rhodoliths, but patterns in their distribution and abundance remain largely unknown. This paper assessed spatio-temporal variability of Brachyura associated with rhodoliths. A seasonal study was conducted at three depth layers (18, 25, and 40 m), throughout two years (December 2015 to October 2017) at Gran Canaria Island (eastern Atlantic Ocean). A total of 765 crabs belonging to 10 species were collected. A larger abundance and richness of crabs at 25 m correlated with a larger biomass of epiphytic algae attached to rhodoliths. A seasonal pattern was also observed, where a higher richness of crabs occurred in the summer. The Xanthid crab, Nanocassiope melanodactylus, dominated the assemblage (83%); juveniles of this species were more abundant in deeper waters (40 m), while adults were more abundant on the shallower depth layers (18 m and 25 m). The species Pilmunus hirtellus was restricted to 25 m. Nevertheless, Pisa carinimana and Achaeus cranchii did not show any spatio-temporal pattern. In summary, this study demonstrated that two conspicuous crabs, N. melanodactylus and P. hirtellus, associated with rhodolith beds are bathymetrically segregated.
Highlights
Rhodoliths are nodules of individual non-geniculate coralline red algae (Corallinales, Hapalidiales, Sporolithales: Corallinophycidae) with a calcified thallus [1]
The present study has first evidenced that the assemblage of brachyuran crabs associated with rhodoliths in Gran Canaria Island is dominated by Nanocassiope melanodactylus
This study has contributed to the understanding of spatio-temporal variability of the brachyuran fauna associated with rhodoliths in the Canary Islands
Summary
Rhodoliths are nodules of individual non-geniculate coralline red algae (Corallinales, Hapalidiales, Sporolithales: Corallinophycidae) with a calcified thallus [1]. They form relatively stable three-dimensional structures and large heterogeneous beds of biogenic substrates [2,3,4,5,6,7]. Rhodoliths have relatively slow growth rates and a perennial life strategy; some thalli can even live >100 years [10] As they are not attached to a fixed surface, individual thalli are exposed to the action of waves and currents and have the potential to be rolled over or moved on the seafloor. In terms of area covered, rhodolith beds may be one of the
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