ABOUT THE DIFFICULT SYSTEMATIC POSITION OF AN ACANTHOCEPHALAN OF THE ROUND SCAD, DECAPTERUS PUNCTATUS (CUVIER 1829) FROM BRAZIL

BRAICOVICH, PAOLA E.; LANFRANCHI, ANA L.; LUQUE; TIMI, JUAN T.

Viña del Mar

Simposio; VII International Symposium of Fish Parasites; 2011

A total of 152 acanthocephalans were recovered from the intestine of 18 round scad, Decapterus punctatus (Cuvier 1829), from the coast of Cabo Frio, Brazil on November, 2008. The specimens clearly fit the diagnosis of the palaeacanthocephalan Order Echinorhinchida and according to its morphological characters they represent a new taxon. However, its assignation to a family status within this order is difficult and problematic. The dorso-ventral asymmetry of the proboscis hooks, as well as the presence of a perfect circle of basal hooks in the proboscis, abruptly larger than anterior hooks and of four tubular cement-glands agree with the characteristics of the genus Rhadinorhynchus Luhe 1911 (Rhadinorhynchidae). However, by lacking trunk spines, their inclusion in this family is not possible. Otherwise, Neorhadinorhynchus Yamaguti 1939 was erected as a subgenus of Rhadinorhynchus to include species with trunk unspined. However, for this feature, it was transferred, as a genus, to Cavisomatinae Meyer 1932 (Echinorhynchidae), which in turn was later raised to family status (as Cavisomidae), including Neorhadinorhynchus. Despite all species of Neorhadinorhynchus have a basal ring of proboscis hooks, and only two of them show dorsoventral asymmetry in the proboscis, no species of Cavisomide have been described as having basal hooks abruptly larger than precedent ones, a typical rhadynorhynchid characteristic. At present, the taxonomy of Echinorhynchida is complex and unsatisfactory due to the lack of stable characters useful at family-level, as well as to the incomplete descriptions of many species. A major revision of echinorhynchidans, with the assessment of the relative value of trunk spines as diagnostic features at family level is necessary, before giving a generic and family status to the present species.