Ontogenetic development of the haptor of Neogrubea spp.: How to use your clamps, a practical guide for young mazocraeids.

HERNÁNDEZ J.S., F.E. MONTERO, M. DEL DEDO-GARCIMARTÍN, B. BERÓN-VERA, E.A. CRESPO & J.A. RAGA.

Viterbo, Italia.

Congreso; 7TH INTERNATIONAL SYMPOSIUM ON FISH PARASITES (ISFP VII); 2007

The ancestral structural design of the haptor of the species within the monogenean family Mazocraeidae appears to be formed by 2 ventral longitudinal rows, each row with 4 equal clamps and posterior larval hooks. This basic design varies in the different genera. Our communication presents comparative data on 3 members of the mazocraeid genera (Grubea, Kuhnia and Neogrubea) exhibiting different modes of attachment to the variable gill structures. These observations are related to comments on the ontogeny of Neogrubea stromateae from the gills of Stromateus brasiliensis from Patagonian waters. The haptor of Kuhnia scombri is apparently the closest to the original design: symmetrical with 2 rows of 4 small equal transversely oriented clamps. Each clamp is small enough to grasp secondary lamellae thus attaching the worm. N. stromateae possesses an asymmetrical haptor with 1 row of 4 small transversely oriented clamps and another row of 4 large longitudinally oriented clamps. Only the small clamps show the orientation and size needed to grasp secondary lamellae whereas the large clamps have the exact orientation and size to grasp the filament of the primary lamella. Finally, Grubea cochlear possesses one longitudinal row of 4 large clamps and 1 or 2 posterior small clamps on the opposite side, all transversely oriented. In this case these large clamps act rather as suckers than clamps adhered to the filament surface. Despite their different function, these ?sucker-clamps? do not show modifications in the inner skeleton although the surrounding parasite tegument is cup-like. Changes in size, orientation and function were also observed during the ontogenetic development of N. stromateae and includes the following milestones: (i) Early parasite stages attach to gills with the larval haptor; (ii) As parasites grow 4 pairs of transversely oriented equal clamps appear progressively, while hooks lose their function. At this moment the haptor´s aspect is quite similar to that in K. scombri and that of the hypothetical ancestral mazocraeid; and (iii) Later, one of the lateral clamp rows grows relatively faster while its clamps progressively rotate to their definitive longitudinal orientation. Looking at the evolution of mazocraeid clamps (and microcotyloid clamps in general) clamps appear to represent a very efficient mechanism for gill attachment. This is probably the cause of their conserved structure despite the functional differences and the great diversity of species.