MEPS 320:161-167 (2006)  -  doi:10.3354/meps320161

Influence of ecological role on bathymetric patterns of deep-sea species: size clines in parasitic gastropods

Craig R. McClain1,3,*, Jennifer Crouse2

1Department of Biology, University of New Mexico, Albuquerque, New Mexico 87131, USA
2Department of Biology, University of Massachusetts, 100 Morrissey Blvd., Boston, Massachusetts 02125, USA
3Present address: Monterey Bay Aquarium Research Institute (MBARI), 7700 Sandholdt Road, Moss Landing, California 95039, USA

ABSTRACT: How an organism’s phenotype responds to both its biotic and abiotic environment is a complex interplay of selection pressures and adaptive tradeoffs. Bathymetric patterns of body size in deep-sea organisms should also reflect both ecological role and taxon-specific constraints, as exemplified in a variety of recent studies. Here, we examine bathymetric size clines in deep-sea ectoparasites, a group that has received little attention in the literature compared to other deep-sea groups. Specifically, we focus on body size in 3 families (21 species) of ptenoglossate gastropods from the deep western North Atlantic, conducting analyses both within and among species. Both quantile and linear regression models yielded non-significant relationships for body size and depth for the 3 most abundant species. Two of the 3 families exhibited positive size–depth relationships, but only in mean size. The findings indicate that resource availability/host size may control parasite density, but dislodgement and predation risk may set a hard upper boundary on body size in deep-sea ectoparasites. Moreover, this study stresses the necessity of understanding the ecological role of species in investigating body size trends.

KEY WORDS: Body size · Deep sea · Quantile regression · Ectoparasite · Gastropod · Western North Atlantic · Benthic · Parasitism

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