LARVAL REARING, METAMORPHOSIS, GROWTH AND REPRODUCTION OF THE EOLID NUDIBRANCH HERMISSENDA CRASSICORNIS (ESCHSCHOLTZ, 1831) (GASTROPODA: OPISTHOBRANCHIA)

¹ Laboratory of Biophysics, Section on Neural Systems, Intramural Research Program, National Institute of Neurological and Communicative Disorders and Stroke, National Institutes of Health, Marine Biological Laboratory, Woods Hole, Massachusetts 02543

1. Hermissenda crassicornis is a subannual nudibranch species that reproduces year-round.

2. There is a significant positive relationship between adult weight, diameter of the egg mass, estimated number of eggs per egg mass, and average number of eggs per capsule.

3. There is a planktonic veliger stage of 34 days minimum at 13°-15° C.

4. Larvae metamorphose on at least three species of hydroids.

5. To develop in reasonable numbers to a state competent to metamorphose veligers require a diet that includes phytoplankton of larger cell size (10-11 µm) than the commonly used Isochrysis and Monochrysis (5 µm).

6. Although Hermissenda feeds on a wide variety of sessile invertebrate species in the ocean, a diet of tunicate alone (Ciona intestinalis) promotes good growth and survival in the laboratory.

7. Egg mass deposition is initiated only after first copulation, except in the last month of life, and continues from about one-month post-metamorphosis to death, at about four months post-metamorphosis. Generation time (egg-to-egg) may be as short as 2.5 months.

8. A laboratory strain of Hermissenda is being established to provide animals of known history for research on the neural correlates of behavior. Animals, at least initially, are being selected for fast growth rate.