Larval and early juvenile
development of Lithodes santolla (Molina, 1782) (Decapoda: Anomura:
Lithodidae) reared at different temperatures in the laboratory
K. Anger, G.A. Lovrich, S. Thatje, J.A. Calcagno-2004
Journal of Experimental Marine Biology and Ecology, 306(2): 139-272
Abstract:
The southern king crab, Lithodes santolla
Molina, is distributed in cold-temperate and subantarctic waters ranging
from the southeastern Pacific island of Chiloé (Chile) and the deep
Atlantic waters off Uruguay, south to the Beagle Channel (Tierra del Fuego,
Argentina/Chile). Recent investigations have shown that its complete larval
development from hatching to metamorphosis, comprising three zoeal stages
and a megalopa, is fully lecithotrophic, i.e. independent of food. In the
present study, larvae were individually reared in the laboratory at seven
constant temperatures ranging from 1 to 18 °C, and rates of survival and
development through successive larval and early juvenile stages were
monitored throughout a period of 1 year. The highest temperature (18 °C)
caused complete mortality within 1 week; only a single individual moulted
under this condition, 2 days after hatching, to the second zoeal stage,
while all other larvae died later in the zoea I stage. At the coldest
condition (1 °C), 71% of the larvae reached the zoea III stage, but none of
these moulted successfully to a megalopa. A temperature of 3 °C allowed for
some survival to the megalopa stage (17–33% in larvae obtained from two
different females), but only a single individual passed successfully, 129
days after hatching, through metamorphosis to the first juvenile crab
instar. At all other experimental conditions (6, 9, 12 and 15 °C), survival
through metamorphosis varied among temperatures and two hatches from 29% to
90% without showing a consistent trend. The time of nonfeeding development
from hatching to metamorphosis lasted, on average, from 19 days at 15 °C to
65 days at 6 °C. The relationship between the time of development through
individual larval or juvenile stages (D) and temperature (T)
was described as a power function (D=aTb, or log[D]=log[a]blog[T]).
The same model was also used to describe the temperature dependence of
cumulative periods of development from hatching to later larval or juvenile
stages. One year after hatching, the 7th (6 °C) to 9th (15 °C) crab instar
was reached. Under natural temperature conditions in the region of origin of
our material (Beagle Channel, Argentina), L. santolla should reach
metamorphosis in October–December, i.e. ca. 2 months after hatching
(taking place in winter and early spring). Within 1 year from hatching, the
crabs should grow approximately to juvenile instars VII–VIII. Our results
indicate that the early life-history stages of L. santolla tolerate
moderate cold stress as well as planktonic food-limitation in winter,
implying that this species is well adapted to subantarctic environments with
low temperatures and a short seasonal plankton production.
(Biologische Anstalt Helgoland, Stiftung
Alfred-Wegener-Institut für Polar-und Meeresforschung, 27498, Helgoland,
Germany, e-mail: kanger@awi-bremerhaven.de)