Redescription of Neoechinorhynchus tenellus (Acanthocephala: Neoechinorhynchidae) from Esox lucius (Esocidae) and Sander vitreus (Percidae), among other Percid and Centrarchid fish, in Michigan, U.S.A

The only 2 published taxonomic accounts of Neoechinorhynchus tenellus are those of Van Cleave (1913) and Van Cleave (1919) from Esox lucius Linnaeus and Sander vitreus (Mitchill) (1⁄4Stizostedion vitreus (Mitchill)). While Van Cleave’s original description is adequate to identify N. tenellus, his description of proboscis armature, lemnisci, reproductive system in both sexes, and eggs was either not complete or in error. We studied the original type material and found their present state to be of little use for elucidating characters that were not already illustrated and described by Van Cleave. For that reason we studied newly collected, conspecific specimens to better document key morphological features of this species. Our description of the Michigan material from the same 2 fish species was compared with the original description and with Van Cleave’s cotypes (designated syntypes). Our revised description includes the following: (1) trunk of males and females is widest in anterior third tapering gradually at both ends. (2) Lateral anterior hooks are markedly larger than and set more posterior to the other 4 hooks of the same circle. Middle hooks not in perfect circle but alternate. (3) Middle and posterior hooks with discoidal bases. (4) Lemnisci are subequal. (5) Eggs have distinct polar prolongation of fertilization membrane, which places the species in the subgenus Hebesoma Van Cleave, 1928. New observations address sexual dimorphism, the larger size of specimens from S. vitreus than from E. lucius, the apical organ, giant nuclei, sensory pits on the proboscis, and details of the reproductive system in both sexes.