Fessisentis, a Genus of Acanthocephalans Parasitic in North American Poikilotherms

Abstract

Thirteen of 16 Siren intermedia collected in Union County, Illinois, were infected with from two to 49 specimens of Fessisentis fessus Van Cleave, 1931. There are no previous reports of identified specimens of Acanthocephala from Siren. This is also the first report of F. fessus since the original description and represents new host and locality records. Old siren harbor more and larger specimens than do young siren. Intensity of infection and host age do not, however, relate to variability of other morphological features. Two paratypes, the original description, and specimens from siren form the basis for redescription of Fessisentis fessus. It is now realized that the trunk of females may be up to 52 mm long and unlike all other species of the genus it possesses a subterminal genital pore. It is also known that lemnisci of males seldom reach the anterior testis and that proboscis hooks may be in as many as 21 longitudinal rows. Contrary to the original description, F. fessus possesses two retinacula. The proboscis receptacle departs from usual acanthocephalan morphology in consisting of 2 muscular layers of tubular bundles with contractile fibers at the periphery enclosing a central area of noncontractile cytoplasm. Fessisentis necturorum Nickol, 1967, and F. vancleavei Haley and Bullock, 1953, also possess 2 retinacula and have proboscis receptacles identical in construction to those of F. fessus. Fessisentis and Fessisentidae are redescribed to conform to this additional information. Acanthocephalus vancleavei Hughes and Moore, 1943, agrees with Fessisentis as redescribed with the exception of cement gland number. One male specimen was reported to have a cement gland number atypical of both Acanthocephalus and Fessisentis. It is felt that this deviation should not be emphasized to the point of obscuring unique features shared with species of Fessisentis. Because of transfer of this species to Fessisentis, a new name, F. friedi, is proposed for F. vancleavei Haley and Bullock, 1953. Richard Heard has collected Fessisentis necturorum near Athens, Georgia, from larval Ambystoma opacum. This represents additional knowledge of host and geographical distribution. In 1931, Van Cleave described Fessisentis fessus as a new species of Acanthocephala and named a new genus, Fessisentis, and a new family, Fessisentidae, to reflect its taxonomic position. He felt that the form of the proboscis receptacle (with a pouchlike thickening containing several prominent nuclei at the posterior end of the outer wall), form of the testes (filiform with indistinct boundaries and extending at least three-fourths the length of the trunk), possession of one retinaculum (rather than two), an unusual number of cement glands (four), and protonephridial organs associated with the uterine bell served as evidence of the distinctness of the Fessisentidae. Van Cleave later recognized that structures originally interpreted as protonephridia are pockets of the selector apparatus (Haley and Bullock, 1953). F. fessus was described from freshwater drum, Aplodinotus grunniens, collected at Money, Mississippi, and until the current paper there is no published record of additional collections. Hughes and Moore (1943) described Acanthocephalus vancleavei from neotenic, streamReceived for publication 3 August 1971. dwelling Eurycea tynerensis collected near Tahlequah, Oklahoma. For reasons discussed below, this species is now considered a member of the genus Fessisentis. The only other report of A. vancleavei was by Malewitz (1956), who tentatively identified specimens from E. multiplacata collected near Tahlequah, Oklahoma, as A. vancleavei. In 1953, Haley and Bullock described a new acanthocephalan, Fessisentis vancleavei, from sunfish, Lepomis gibbosus, collected at Durham, New Hampshire. Bullock has since collected F. vancleavei from other species of fish (see Materials section), and Fried and Koplin (1967) collected it from white sucker, Catostomus commersoni, taken in Northampton County, Pennsylvania. Nickol (1967) described Fessisentis necturorum from Necturus beyeri collected near Folsum, Louisiana. F. necturorum has since been collected from larval Ambystoma opacum (see Materials section). Golvan (1969) expanded the Fessisentidae to include all members of the superfamily Echinorhynchoidea with four cement glands, elongations of the middle egg membrane,