N. I. Selin - Structure and density of aggregations of the hermit crab Pagurus proximus Komai, 2000 in epibiosis of the brown alga <i>Costaria costata</i> (C. Agardh) De A. Saunders, 1895 in the sublittoral zone of Vostok Bay, Sea of Japan

BIOLOGIYA MORYA, 2017, Vol. 43, No. 6, pp. 430-435

Structure and density of aggregations of the hermit crab Pagurus proximus Komai, 2000 in epibiosis of the brown alga Costaria costata (C. Agardh) De A. Saunders, 1895 in the sublittoral zone of Vostok Bay, Sea of Japan

A.V. Zhirmunsky Institute of Marine Biology, National Scientific Center of Marine Biology, Far Eastern Branch, Russian Academy of Sciences, Vladivostok 690041

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A study of epibiosis of the brown alga Costaria costata in the sublittoral zone of Vostok Bay, Sea of Japan, during the spring and summer of 2016 showed that hermit crabs of the following four species accounted for about 85% of the total biomass: Pagurus proximus, P. minutus, P. brachiomastus, and P. middendorffii. Of them, the most abundant one (96.5% of the total number of hermit crabs) was P. proximus, the mean aggregation density of which on C. costata (429 ± 221 ind./m²) was an order of magnitude higher than that in the adjacent area of bouldery bottom. The size ranges of males and females of this species in aggregations on boulders and those on C. costata were similar, with a predominance of larger individuals on algae. In size-frequency distribution, three groups of individuals corresponding to three size-age cohorts were differentiated. The male-to-female ratio was 1 : 1.7. Hermit crab aggregations on C. costata are ephemeral; their existence is determined by duration of the period of algae development: from late spring to the middle of summer.

Key words: hermit crabs, Pagurus proximus, epibiosis, brown alga Costaria costata, competition, associated fauna, Peter the Great Bay, Sea of Japan.