| Summary: | Effects of long-term dietary conditioning on gonadal growth, lipid, and moisture content,
and on egg size, egg-energy content, larval morphometry, and larval development of the
green sea urchin Strongylocentrotus droebachiensis were studied in the laboratory. One
algal and seven artificial diets were tested over a nine-month period, coinciding with the
urchin’ s annual reproductive cycle. Formulated diets differed in protein level and in the
presence or absence of different supplements, such as algal storage carbohydrates
(mannitol and algin), cholesterol, and B-carotene. Diets were: 1)10% protein (LO-PRO),
2)10% protein+ mannitol (LO-PRO+M), 3)10% protein+algin (LO-PRO+A), 4) 20%
protein (HI-PRO), 5) 20% protein+cholesterol (HI-PRO+C), 6) 20% protein+B-carotene
(HI-PRO+B), 7) 20% protein+B-carotene+cholesterol (HI-PRO+C/B), and 8) dried
seaweed Nereocystis luetkeana (KELP). Urchins reared on the low-protein diet
formulations had significantly smaller gonad indices than urchins conditioned on the highprotein
and algal diets. Gonadal lipid and moisture contents varied significantly over time
but not among dietary treatments. Significant differences in egg sizes were observed.
HI-PRO produced the smallest eggs and HI-PRO+C the largest, while other diet groups
produced intermediate-sized eggs. Egg organic-carbon levels also differed significantly
with the largest amounts being present in HI-PRO+C/B, and the lowest in LO-PRO and
HI-PRO. Larvae cultured from eggs of selected diet groups (LO-PRO, HI-PRO, HI
PRO+B, HI-PRO+C/B, and KELP) showed significant differences in morphometry and
in rates of development. HI-PRO+B and HI-PRO+C/B were the first to reach the
feeding pluteal stage at 3 days and the 2-arm pluteus at 5-6 days. The feeding pluteal stage
was attained by LO-PRO and HI-PRO at 4 days and the 2-armed larvae at 7-8 days.
Larval development times for LO-PRO, HI-PRO, and HI-PRO+C/B were comparable by the 4-arm stage and remained so throughout development. HI-PRO+B larvae consistently
had the shortest development times, reaching the fully-formed 8-arm larval stage 3 days
earlier than larvae from other diet groups. HI-PRO+B larvae also had the highest rate of
metamorphosis success. They showed significantly higher diary band/body-length ratios
throughout all developmental stages, indicating greater larval feeding effectiveness and
suggesting that this was the key to their overall success. All larvae arising from adults fed
the artificial diets were competent; however, larvae from adults fed KELP showed severe
abnormalities and subsequent early mortality. With regard to an aquaculture program, I
conclude that HI-PRO+B is the best of the diets tested, in that it supported high gonathi
growth for the roe market, and produced healthy broodstock with resultant vigorous
larvae. === Science, Faculty of === Zoology, Department of === Graduate
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