| Summary: | Por (1964) suggested that deep-sea harpacticoids were adapted to an "epipelic way of life", by means of a "gradual elongation of limbs". To test this hypothesis I examined four closely related Arctic species to determine if such a predicted gradient of morphological characteristics exists with increasing depth. The deep-sea macrobenthos is highly diverse (Sanders & Hessler, 1969), and harpacticoid copepod assemblages follow this trend (Coull, 1972). Species and genera from the family Cerviniidae are often dominant members of deep-sea benthic copepod communities (Brodskaya, 1963; Por, 1964; Por, 1969; Coull, 1972; Dinet, 1977; Montagna & Carey, 1978). Thus, members of the Cerviniidae are especially good for testing hypotheses about the deep-sea. In general, deep-sea harpacticoids are found patchily distributed at cm and m scales (Thistle, 1978), in agreement with Jumar's (1975) ''grainmatching model". Disturbance/predation is probably also important in structuring these communities since harpacticoids are negatively correlated with the presence of sessile surface-deposit feeding polychaetes (Thistle, 1979). In this study I pro vide information about the nature of speciation in deep-sea harpacticoids.
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