A Redescription of Gigantobilharzia lawayi Brackett, 1942

Abstract

Specimens of Gigantobilharzia collected from herring and Bonaparte's gulls in Manitoba during their fall migration are considered to be identical with Gigantobilharzia lawayi Brackett, 1942. Since the original description by Brackett is inadequate, being based on incomplete specimens, a redescription is given including measurements of eggs not previously described. Miracidia of the species failed to infect three local snail species: Lymnaea stagnalis, Stagnicola palustris, and Physa gyrina. During the summer of 1962 a survey was made of the schistosome fauna of Manitoba. Prior to this summer six species of avian schistosomes (McLeod, 1936, 1937, 1940) and one species of mammalian schistosome (Farley, 1962) had been recovered in the province. Adult worms belonging to the genus Gigantobilharzia were found in 2 of 7 herring gulls (Larus argentatus) and 6 of 16 Bonaparte's gulls (Larus philadelphia) examined. Based on the number of testes, position and size of the gynecophoric canal, and position of the ovary, the worms seem to be identical with Gigantobilharzia lawayi described originally by Brackett in 1942 from herring and ring-billed gulls (Larus delawarensis) of Michigan, USA. The description of the species by Brackett was inadequate, since examination of the type material revealed that the specimens were incomplete. Brackett also failed to locate any eggs, either in the uterus of the female or in the gut mucosa of the host. For this reason a redescription of the species is given, based on the examination of seven complete males, two complete females, and many fragments of both sexes. Gigantobilharzia lawayi Brackett, 1942 (Figs. 1 to 4) Specific diagnosis: Gigantobilharzia Odhner, 1910. Received for publication 4 February 1963. * Contribution from the Department of Zoology, University of Manitoba, Winnipeg, Canada. This investigation was supported by a Canadian Industries Limited Wildlife Fellowship. Male: Extremely long and thin with a distinct gynecophoric canal. Suckers absent. Body 21.25 to 38.5 mm (avg 28.9) in length by 0.06 to 0.1 mm wide anterior to the gynecophoric canal, 0.15 to 0.22 mm at the canal and 0.1 to 0.15 mm posterior to the canal. Posterior end of the body swollen but not spatulate. Gynecophoric canal with distinct anterior end 0.86 to 1.25 mm (avg 1.06) from the anterior end of body, 1.75 to 2.7 mm (avg 2.16) in length with the posterior part ending obscurely. Floor of canal with numerous (up to 50) thickened bands at right angles to axis of body, sharply defined anteriorly, becoming less pronounced posteriorly. Esophagus 0.3 to 0.44 mm long, paired ceca short, reuniting in region of the anterior part of the seminal vesicle. Common cecum extending to posterior end of body. Testes 345 to 545 (avg 460), extending from the posterior end of the gynecophoric canal to the posterior end of body, tandemly arranged, and reaching a diameter of about 0.09 mm. Seminal vesicle elongate and spiral, lying anterior to gynecophoric canal, and divisible into two portions: the anterior part or external seminal vesicle lying outside the cirrus pouch, and the posterior part or internal seminal vesicle lying enclosed within the cirrus pouch. External seminal vesicle 0.23 to 0.44 mm (avg 0.32) in length, commencing 0.38 to 0.54 mm (avg 0.43) from the anterior end of the body. Internal seminal vesicle 0.2 to 0.38 mm (avg 0.31) in length. Ejaculatory duct opens on papilla at anterior end of the gynecophoric canal. Female: Filamentous worm about 20 mm in length, with a constant width of 0.75 mm. Suckers absent. Esophagus 0.38 to 0.46 mm long; paired ceca reuniting immediately posterior to the seminal receptacle. Ovary coiled, 0.46 to 0.6 mm (avg 0.57) long, commencing 1.45 to 1.9 mm (avg 1.64) from anterior end of body. Seminal receptacle 0.18 to 0.2 mm in length, situated immediately behind the ovary. Oviduct from posterior end of ovary, receives a branch from the seminal receptacle, and immediately turns forward giving off Laurer's canal. Oviduct receives vitelline duct and opens into ootype 0.23 to 0.28 mm in front