Sclerite growth and morphometric variation inGyrdicotylus gallieni Vercammen-Grandjean, 1960 (Monogenea: Gyrodactylidae) fromXenopus laevis laevis (Anura)

1573-5192

Springer Online Journal Archives 1860-2000

Biology

Medicine

Abstract The embryonic development of haptoral sclerites is described forGyrdicotylus gallieni, a viviparous gyrodactylid occurring in the oral cavity ofXenopus laevis laevis. Due to the protogynous life-history ofG. gallieni, two age classes of adult fluke can be distinguished by the presence or absence of a penis. Highly significant differences in the length of hamulus roots between younger and older worms indicated that some post-birth growth occurs. Dorsal and ventral root lengths also showed greater variability than other hamulus characters and were highly correlated, probably as a result of their late, simultaneous development. The allometric exponent of dorsal on ventral root length in worms without a penis was estimated to be 1.00, suggesting hamulus roots show isometric growth in youngerG. gallieni. However, in older worms with a developed penis (estimated allometric exponent = 1.29) the dorsal root increases in proportion to the ventral root (which may stop growing). Hamulus point length was significantly correlated with host body length, but there was no significant association between any hamulus character and infrapopulation size or time post-infection. Variability in haptoral sclerite measurements betweenG. gallieni from the Cape, South Africa raised on different host taxa (X. l. laevis, X. l. victorianus andX. gilli) was small, while limited data suggested that increasing environmental temperature (14, 20 and 25°C) did not produce any trend in morphometric variation. There was little qualitative variability in the morphology of sclerites from worms exposed to different hosts and temperatures, or from two distinct lineages ofG. gallieni maintained at 20°C onX. l. laevis (these also showed negligible morphometric differences). Present results indicate that environmentally-induced variability is relatively minor and that haptoral sclerite characters (with the exception of hamulus root lengths, which show considerable ontogenetic variability) should provide unambiguous information for studies of speciation inGyrdicotylus.

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