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Vol. 38 No. 1, 1999
Population Dynamics and Mantle Autotomy of the Figsnail Ficus ficus (Gastropoda:
Mesogastropoda: Ficidae)
Li-Lian
Liu* and Sheau-Ping Wang
Institute
of Marine Biology, National Sun Yat-sen University, Kaohsiung, Taiwan
804
Li-Lian
Liu and Sheau-Ping Wang (1999) Ficus
ficus, a member of the Mesogastropoda, exhibits a special
behavior of mantle autotomy as a defensive mechanism. This study was
conducted to characterize the population dynamics of F. ficus and the occurrence of
autotomic behavior in the field. Monthly collections of F. ficus were made between May 1992
and June 1993. A total of 2186 individuals were sampled with shell
lengths ranging from 28 to 95 mm. Small individuals with shell lengths
< 35 mm were found only between July and September 1992. Seasonal
variation in the abundance of figsnails was observed: while few
figsnails (less than 75 individuals) were collected from May to July,
abundant snails were obtained from November to February. Sexual
dimorphism in shell length (male < female) was also found. Sex
ratios varied from 0.3 to 2.3 in favor of females between March and
September. The male-biased sex ratios observed between October and
February indicate that egg-laying migration might exist. The autotomic
tissue weighed from 0.03 to 8.86 g and comprised 0% to 34% of the total
body weight. A negative correlation between the percentage of autotomic
tissue and shell length was observed (y = 30.88 - 0.27x; R2 = 0.35; p < 0.01). Figsnails with newly
regenerated tissue (indication of recent occurrence of defensive
autotomy) comprised < 1% of the total samples, with 0 to 3
individuals appearing in each monthly collection. The results indicate
that autotomized figsnails might be more vulnerable to predation than
are intact snails, or that the occurrence of defensive autotomy in
natural environments might be low.
Key words: Ficus
ficus, Figsnail, Population dynamics, Autotomy.
*Correspondence: Fax: 886-7-5255100. E-mail:
lilian@mail.nsysu.edu.tw
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