Acanthocephala from Lake Fishes in Wisconsin: Morphometric Growth of Pomphorhynchus bulbocolli (Pomphorhynchidae)

Abstract

The trunk, proboscis, basal proboscis hooks, neck (exclusive of bulb), bulb, basal hooks, anterior testis, and eggs of Pomphorhynchus bulbcolli Linkins in Van Cleave, 1919, were studied in 7 length classes of worms ranging between 2 and 16 mm. All structures, except proboscis hooks, showed progressive and continuous growth corresponding with increase i omomn worm length. Growth was most rapid in worms shorter than 6 mm including mostly immatures. Females smaller than 6 mm had no eggs. Eggs and proboscis hooks in worms longer than 6 mm were sufficiently stable to be of reasonable taxonomic value. Growth in bulb diameter and length of proboscis hooks and neck appear essential for the special attachment mechanism characteristic of P. bulbocolli. The small size of these structures in recently ingested immatures permits the freedom to disengage, move, and reattach. Within 2-3 wk, these structures reach considerable size in worms ca. 6 mm long. Once secured, maturation and reproductive activity become evident as growth slows down. The reported study provides a reference line against which a comparison with other species, e.g., P. rocci Cordonnier and Ward, 1967, may be made.