Protists and detrital particles as prey for the first larval stage of the brachyuran crab, Hemigrapsus oregonensis

Newly-hatched larvae of the brachyuran crab, Hemigrapsus oregonensis, were raised in the laboratory on an autotrophic dinoflagellate (Prorocentrum mic ans), a heterotrophic dinoflagellate (Noctiluca milaris), a green alga (Dun aliella rertiolecta), an unfed control, and a fed control of Artemia sp. na uplii. Larvae also were fed preparations of seagrass detritus that had been cultured both to promote microbial colonization and to discourage it. Detr ital diets were used both alone and in combination with sub;optimal applica tions of Artemia sp. nauplii. Larvae raised on P. micans showed survival to zoeal stage II equal to those raised on the Artemia sp. nauplii control, a lthough development was delayed. Larvae raised on N. milaris showed substan tial (34.7%) survival to zoeal stage II; however survival was lower and dev elopment slower than for Artemia sp. nauplii-fed larvae. Survival on D. ter tiolecta was less than 3%. Larvae fed microbially enriched detritus showed a delay in mortality as compared to unfed controls. No larvae fed solely on detritus survived to zoeal stage II. When larvae were fed a sub-optimal di et of Artemia nauplii, supplemented by detrital particles, survival to zoea l stage II increased, although not to the level shown by Artemia-fed larvae in optimal application. Development was not accelerated over the sub-optim al diet in either treatment. The potential for larval crabs to utilize a wi de variety of potential prey immediately upon hatching is significant given their susceptibility to early starvation. Such omnivory also suggests a tr ophic link between carbon sources of the microbial loop and crab larvae. (C ) 1998 Elsevier Science B.V. All rights reserved.