Memórias do Instituto Oswaldo Cruz Fundação Oswaldo Cruz, Fiocruz ISSN: 1678-8060 EISSN: 1678-8060 Vol. 89, Num. 2, 1994, pp. 225

RESEARCH NOTE

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Effect of Proctoeces lintoni (Digenea) on the Fecundity of Fissurella crassa (Archaeogastropoda)

Marcelo E Oliva, Andrea A Vega

Code Number: OC94047
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Instituto de Investigaciones Oceanologicas, Fac. Recursos del Mar, Universidad de Antofagasta, P.O. Box 170, Antofagasta, Chile

Key words: Proctoeces lentoni - Fissurela crassa - fecundity

The gonads of the key-hole limpet, Fissurella crassa, are greatly parasitized by the adult digenea Proctoeces lintoni (Fellodistomidae). High levels of prevalence and intensity of infection produce strong damage on these gonads, affecting the reproductive success of the host (M Oliva 1992 Mem Inst Oswaldo Cruz 87:37-42). However the quantitative impact of the parasite on the host fecundity, remains unknown. In this note, we present a first attempt to quantify such an impact.

During July-November 1991, and aperiodically, we hand collected 203 specimens of F. crassa from rocky shores near Antofagasta, northern Chile (23^o 25'S, 70^o 35'W). Key-hole limpets were carried alive to the laboratory and kept in aquaria at 20 oC. Spawning of adult limpets (=/> 40 mm total length) was induced by a thermic shock (30 oC) for 2 hr. Only females were considered in the analysis, because eggs are easier to count than sperm. Fifty female key-hole limpets (ranged 40-50 mm in total length) spawned; the number of eggs of each spawn was determined. Posteriorly, all female were sacrified and the size of infrapopulation of worm in the gonads was quantified.

The number of eggs spawned per milimeter of shell was negatively and significantly correlated with parasite number (r = - 0.81, P < 0.001, df= 48). Moreover, the Student "t" test shows that the average number of eggs spawned per milimeter of shell was significantly different between parasitized and non-parasitized key-hole limpet (3941.6 and 5812.4 respectively, "t"= 3.23, 0.002 P > 0.001, df=48 ). Mean size of parasitized and non-parasitized limpet, does not differ significantly (52.8 and 53.2 mm respectively, "t" = 0.136, P > 0.50, df=48). Ours results show that, as a consequence of the presence of P. lintoni, F. crassa has a loss of fecundity that in average, reach 32.2%. This value closely resembles those reported by D Rader (1982 Proceedings Echinoderm International Conference, pp. 395-401 Tampa Bay. In JM Lawrence and AA Balkema (eds) Rotterdam) and A Kabat (1986 Can J Zool 64: 267 - 270), for other invertebrates infected by castrators. The impact on the fecundity produced by the presence of P. lintoni in key-hole limpets, undoubtfully affects the re-productive success of the infected population. Compensatory mechanisms, such as those proposed by D Minchella (1985 Parasitol 90: 205-216) as a response to parasitic castration, are not aparent in this host-parasite system.

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Copyright 1994 Fundacao Oswaldo Cruz - FIOCRUZ

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