Static and ontogenetic allometry of trunk spines in two species of Corynosoma (Acanthocephala: Polymorphidae): attachment strategies to the definitive host may differ between species and sexes.

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

Anchorage, Alaska

Congreso; 86th Annual Meeting of the American Society of Parasitology; 2011

The American Society of Parasitologists

It is generally assumed that the holdfast of acanthocephalans is fully developed at the cystacanth stage as an adaptation to maximize the likelihood of successful attachment after recruitment to the definitive host. However, some acanthocephalan species are known to generate new holdfast devices (e.g., an inflation of the proboscis, neck or foretrunk) in the definitive host. Accordingly, less dramatic changes may also occur in typical holdfast features (e.g., the size of proboscis, hooks, or trunk spines). We tested this hypothesis by investigating patterns of static and ontogenetic allometry of trunk spines using cystacanths and adults of Corynosoma cetaceum and C. australe that were collected from fish and marine mammals from Argentine. Spines were measured at the disk border, and the anterior and posterior hindtrunk. In males of both species, the size of spines did not differ between cystacanth and adults, nor was there a significant correlation between spine size and trunk size within each development stage. In females of C. cetaceum, spine size of cystacanths did not differ from that of males. However, spines from adult females were significantly larger than that of cystacanths and adult males, and spine size was correlated with body size. In females of C. australe, only spines at the disk border were larger in adults than in cystacanths, and hidtrunk spines were significantly larger than that of males regardless of development stage. Sexual dimorphism in spine size did not result from body size differences between sexes. In summary, the final size of the trunk armature of males, but not of females, is reached at the cystacanth stage. Females of Corynosoma live longer than males and carry the offspring; therefore, larger spines could improve attachment efficiency. Females of each species apparently use different ways to adjust the size of the trunk armature to the microhabitat conditions they encounter (the stomach of dolphins in C. cetaceum and the intestine of pinnipeds in C. australe).