Constructional morphology and mode of attachment of the trunk of Corynosoma cetaceum (Acanthocephala: Polymorphidae)

Abstract

Dead specimens of Corynosoma cetaceum were used to describe the trunk musculature of this species and to infer the use of the trunk as a secondary holdfast. Inferences were based on trunk muscle arrangement, changes in trunk shape, size and distribution of spines, and geometry of tegument thickness. The foretrunk of C. cetaceum is swollen and forms a spiny disk that is bent ventrally. The disk is flattened by several groups of muscles not described previously, which seem able to finely adjust the disk surface over the substratum. Disk attachment appears to be accomplished by two dorsal neck retractor muscles specialized in pulling the anchored proboscis into the foretrunk. This mechanism has been described in other acanthocephalans, becoming surprisingly efficient when used with a flattened, armed foretrunk. The ventrally spined hindtrunk requires force to move downwards in order to attach. A single ventral neck retractor muscle seems specialized in pulling the posterior trunk forward, inducing a downward force due to the muscle's precise points of insertion. This mechanism necessarily generates ventral wrinkling that needs to be eliminated for the spiny surface to be functional. The trunk ventral muscles are apparently arranged so as to concentrate the "excess" of the tegument into a single fold, optimizing the use of the remaining surface for attachment. The size and distribution of spines, as well as the geometry of tegumental thickness, conform to these observations. Morphological changes, seemingly simple, such as structural bending, may have triggered a cascade of subtle modifications and new functions during acanthocephalan evolution, reflecting how morphological integration and novelty interact.

First description of an apical epidermis cone in Paratenuisentis ambiguus (Acanthocephala: Eoacanthocephala) and its phylogenetic implications

“…The body of adult acanthocephalans is anchored at the intestinal wall of their de®nitive hosts by the presoma (Taraschewski 1989a(Taraschewski , b, 2000Taraschewski et al 1989). Additionally, in some species the trunk serves as an organ of attachment (Aznar et al 1999).…”

Corynosoma australe Johnston, 1937 and C. cetaceum Johnston & Best, 1942 (Acanthocephala: Polymorphidae) from marine mammals and fishes in Argentinian waters: allozyme markers and taxonomic status

“…Specimens of C. cetaceum examined in the present paper agree in general terms with the characteristics that define the species; however, some differences in the number of proboscis hook rows (20-21 versus 18-9) and in the number of hooks per row (13-15 versus 12-13 or 14-16) were observed. The ventrally transverse folds delimiting a blunt lobe between the fore-and hind-trunks in the female, described by Aznar et al (1999bAznar et al ( , 2002b, were also observed in cystacanths in the present study.…”

Corynosoma cetaceum in the Stomach of Franciscanas, Pontoporia blainvillei (Cetacea): An Exceptional Case of Habitat Selection by an Acanthocephalan

“…Corynosoma hamanni was mostly found in the duodenum of Antarctic seals, but about 3% of the component population was found in the pyloric region of the stomach (Zdzitowiecki, 1984). On the other hand, adult Corynosoma cetaceum have repeatedly been reported from the stomach and duodenum of at least 3 species of cetaceans from the Southern Hemisphere (Brownell, 1975;Kagei et al, 1976;Figueroa and Puga, 1990;Torres et al, 1992;Aznar et al, 1994;Corcuera et al, 1995;Andrade et al, 1997;Aznar et al, 1999).The presence of adult acanthocephalans in the stomachs of marine mammals is puzzling because the digestive and absorptive functions in these hosts are well separated; the stomach is involved only in digestive functions as in other mammals (Gaskin, 1978;Berta and Sumich, 1999). This raises the question over whether Corynosoma reported from the stomach might represent recently recruited worms or worms located in an abnormal habitat (Crompton, 1973;Kennedy, 1985).…”

“…Corynosoma hamanni was mostly found in the duodenum of Antarctic seals, but about 3% of the component population was found in the pyloric region of the stomach (Zdzitowiecki, 1984). On the other hand, adult Corynosoma cetaceum have repeatedly been reported from the stomach and duodenum of at least 3 species of cetaceans from the Southern Hemisphere (Brownell, 1975;Kagei et al, 1976;Figueroa and Puga, 1990;Torres et al, 1992;Aznar et al, 1994;Corcuera et al, 1995;Andrade et al, 1997;Aznar et al, 1999).…”