ASPECTS OF THE LIFE HISTORY OF CARCINONEMERTES ERRANS (NEMERTEA: CARCINONEMERTIDAE), AN EGG PREDATOR OF THE CRAB CANCER MAGISTER

¹ University of California, Bodega Marine Laboratory, Bodega Bay, California 94923

1. Specimens of Cancer magister below 20 mm carapace width are not infested by Carcinonemertes errans. Worms infesting young-of-the-year crabs beyond this size would have been in the plankton for 8-9 months prior to host infestation.

2. Nemertean burden on crabs increases with the crab's time on the bottom, at least through the crab's early life. Worms move from the host's exuvium to its new exoskeleton upon host molting.

3. Juvenile specimens of C. errans were localized under the abdomen, near the copulatory appendages on male crabs. Juvenile worms were found in protected spots all over female crabs' exoskeletons.

4. Nemerteans migrate to the host egg clutch within a day or two of host ovipostion. They are peripherally distributed in the egg clutch through the early part of host brooding, but descend into the clutch to become more evenly distributed in the latter part of the brooding period.

5. All measurable growth occurs during C. errans' feeding period in the host egg clutch. Growth is inhibited as the density of worms per egg clutch increases.

6. Carcinonemertes errans matures approximately 60-70 days after host oviposition. Worms lay an average of 3.1 egg strings in the laboratory, each containing an average of 446 eggs. Fecundity per worm declines as worm density within the host egg clutch increases.

7. More than 99% of all specimens of C. magister are infested by C. errans in California waters. Numbers per host can range as high as 100,000.

8. Worms exhibit a contagious distribution among hosts, with the variance in density per host in excess of the mean density in all sample collections. The ratios of variance to mean increase as mean density increases.

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