Reprint Series No. 27

THE USE OF PROTISTS AND DETRITUS AS A DIET FOR THE FIRST ZOEAL STAGE OF THE BRACHYURAN CRABS CANCER MAGISTER AND HEMIGRAPSUS OREGONENSIS

Jason A. Lehto

August 1997

Bibliographic Citation
Lehto, Jason A. 1997. The use of protists and detritus as a diet for the first zoeal stage of the brachyuran crabs Cancer magister and Hemigrapsus oregonensis. Master of Science Thesis. Western Washington University, Bellingham, Washington. 81 pp. Washington State Department of Ecology (Publication No. 97-109), Padilla Bay National Estuarine Research Reserve Reprint Series No. 27.

Abstract
To determine whether protists contribute to the diet of larval crabs, first stage larvae from the brachyuran crabs Cancer magister and Hemigrapsus oregonensis were fed diets that included Noctiluca milaris, Prorocentrum micans and Dunaliella tertiolecta, alone and in combination with a sub-optimal diet of Artemia sp. nauplii.

Cancer magister larvae fed diets of Prorocentrum micans or Noctiluca milaris alone, had a delay in mortality compared to the unfed control. When the sub-optimal diet was supplemented with N. milaris or P. micans, survival increased and was comparable to the Artemia sp. control diet although stage duration increased in the protist fed treatments. Larvae fed a sub-optimal diet plus Dunaliella tertiolecta showed lower survival compared to larvae fed the sub-optimal diet alone.

Hemigrapsus oregonensis larvae fed diets of Prorocentrum micans and Noctiluca milaris alone showed survival to stage II of 81.8% and 34.7% respectively. The survival for larvae raised on a diet of P. micans was comparable to the Artemia sp. control, although the development time was longer on the P. micans diet. A few larvae survived to stage II when fed a diet of Dunaliella tertiolecta. Larvae fed a combination of protists and a sub-optimal diet of Artemia sp. followed the same trends as the protist diets alone.

To determine whether bacteria and detritus contribute to the diet of larval crabs, first stage larvae from the intertidal crab Hemigrapsus oregonensis were fed diets that included microbially colonized and uncolonized detritus alone and in combination with a sub-optimal diet of Artemia sp. nauplii.

Hemigrapsus oregensis larvae fed diets of microbially colonized and uncolonized detritus alone, had a delay in mortality compared to the unfed control. When the sub-optimal diet was supplemented with colonized and uncolonized detritus survival increased over the sub-optimal diet alone. The stage duration was similar among larvae fed the sub-optimal diet alone and those fed the sub-optimal diet plus colonized and uncolonized detritus. Larval weights were highest in the Artemia sp. fed control and lowest in larvae fed the sub-optimal diet plus uncolonized detritus.