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Laboratory Growth, Reproduction and Life Span of the Pacific Pygmy Octopus, Octopus digueti

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Title: Laboratory Growth, Reproduction and Life Span of the Pacific Pygmy Octopus, Octopus digueti
Authors: DeRusha, Randal H.
Forsythe, John W.
Hanlon, Roger T.
Issue Date: 1987
Publisher: University of Hawaii Press
Citation: DeRusha RH, Forsythe JW, Hanlon RT. 1987. Laboratory growth, reproduction and life span of the Pacific pygmy octopus, Octopus digueti. Pac Sci 41: 104-121.
Abstract: Octopus digueti Perrier and Rochebrune, 1894 was reared through
its life cycle at 25°C in a closed seawater system using artificial sea water. Two
field-collected females produced 231 hatchlings: 193 hatchlings were groupcultured
while 24 were isolated at hatching and grown individually to allow
precise analyses of growth in length and weight over the life cycle. All octopuses
were fed primarily live shrimps. Maturing adults fed at a rate of 4.7% of body
weight per day and had a gross growth efficiency of 48%. Growth in weight was
exponential for the first 72 days and described best by the equation: WW(g) =
.0405e•0646t. The mean growth rate over this period was 6.4% increase in body
weight per day (%/d), with no significant difference between male and female
growth. From 72 to 143 days, growth was logarithmic and described best by the
equation: WW(g) = (6.78 x 1O- 6) t3 .13. Females grew slightly faster than males
over this growth phase. During the exponential growth phase, mantle length
increased at a mean rate of 2.1% per day, declining to 1.1% per day over the
logarithmic phase. No attempt was made to describe mathematically the period
of declining growth rate beyond day 143. The primary causes of early mortality
in group culture were escapes and cannibalism. Survival was good despite high
culture density: 73% survival to date of first egg laying (day 111). Survival was
better among the isolated growth-study octopuses: 88% to the date of first egg
laying (day 130). Mean life span was 199 days in group-reared octopuses and
221 days in the growth-study octopuses. There was no significant difference
between male and female life span. Progeny of the group culture were reared at
similar stocking densities and fed predominantly fresh dead shrimp and crab
meat. This diet resulted in cannibalism, with only 6% survival to first egg laying
on day 128. Fecundity in this group was lower. Octopus digueti is a good
candidate for laboratory culture and biological experimentation because of its
small size, rapid growth, short life span, and good survival in group culture.
ISSN: 0030-8870
Appears in Collections:Pacific Science Volume 41, Numbers 1-4, 1987

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