Consistent sexual differences in trunk spine growth between cystacanths and adults of two species of Corynosoma (Acanthocephala: Polymorphidae): do each sex exhibit a different strategy to attach to the definitive host?

HERNÁNDEZ-ORTS, J.S; CRESPO, E.A.; TIMI, JUAN T.; RAGA, J.A.; AZNAR, F.J.

Melbourne

Congreso; XII International Congress for Parasitology.; 2010

Australian Society for Parasitology, World Federation of Parasitologists.

  It is generally assumed that the proboscis and trunk armature (if present) of acanthocephalans are fully developed at the juvenile (cystacanth) stage in the intermediate / paratenic hosts. As the argument goes, primary investment in attachment devices would maximize the likelihood of an effective attachment just after recruitment to the gut of the definitive host. Extensive evidence suggests that armature patterning is determined prior to the adult stage, but whether or not growth of armature occurs in the definitive host is still an open question. In this presentation, we compared size differences of trunk spines between cystacanths and adults of two polymorphid species, Corynosoma australe and C. cetaceum collected from fish and marine mammals off the Argentine coast. Spines were measured at three points: the disk border, the anterior hindtrunk and the posterior hindtrunk. Our results revealed that (1) the trunk was significantly larger in adults than in juveniles of both species, regardless of sex; (2) no significant differences were found between the size of spines in juvenile and adult males of any species; (3) in females of C. australe, disk spines were significantly larger in adults than in juveniles and (4) in females of C. cetaceum, spines at the 3 points were significantly larger in adults. Adult females of Corynosoma live longer than males and carry the (presumably heavy) load of the offspring. Therefore, it is possible that females experience stronger selective pressures to develop more plastic responses to avoid dislodgment from the gut. Interestingly, the effect is more apparent in C. cetaceum, the species that lives in the habitat with most intense physical disturbance (i.e. the stomach).    J.S.H.O. benefits from a PhD student grant of the CONACyT, Mexican Government. Funded by BBVA project no. BIOCON 04 and CGL2007-63221 from the Ministry of Science and Innovation of Spain.