Does lunar cycle affect
clawed lobster egg hatching and moulting frequency of hatchery-reared
juveniles?
E.A.
Ferrero, N. Privileggi, T. Scovacricchi, G. van der Meeren-2002
Ophelia, 56(1): 13-22 (from Current Contents)
Abstract :
Evidence that lunar cycles entrain crustacean
biological rhythms is briefly reviewed, Egg laying and hatching undergo
semi-lunar and monthly rhythms that appear to depend on endogenous clocks.
Lunar cycles can be understood in terms of adaptation and life history.
Original data are presented for Homarus gammarus (L) post larvae (n=150)
hatched during March 1997 and reared artificially. Their moulting frequency
was monitored from day 112 (post-hatch) to day 204 (CL = 20mm. 1.5 SD).
Daily moults (n=253) -recorded individually during July, August and
September- showed an average duration for the first and the second
inter-moult interval of about 36.2 and 34 days, respectively. Daily moulting
frequency distribution showed a trend characterised by peak values around
the new moon weeks (n=75), and significantly lower values around the full
moon weeks (n=46). Individually reared berried-lobsters hatched eggs within
restricted periods in the weeks before and a-round new moon and full moon in
the absence of any tidal cue. The pattern for communally reared female
lobsters is more confusing, possibly due to inter-individual communication
and natural sea temperature affecting the rhythm. However, modal and moving
average values over 24 years sampling period support the presence of a
semi-lunar cycle. The cycle is maintained under laboratory conditions and in
sublittoral populations that are not subjected to large tidal excursions.
Therefore, the circa-lunar rhythm may represent a powerful clock that is
retained for synchronising events throughout the life history of
crustaceans. It results in reduced predation risks for hatchlings in dark
new moon nights and favours dispersal during spring tides due to tidal
currents, This may enhance mutual protection against cannibalistic habits
for simultaneously moulting juveniles.
(Univ Trieste; Dip Biol; Via Giorgieri 7; I-34127
Trieste; Italy, e-mail: ferrero@univ.trieste.it)