A New Microphallid Trematode from the Blue Crab in the Northern Gulf of Mexico

Levinseniella (Monarrhenos) capitanea n. sp. is described from metacercariae on the hepatopancreas and gonads of Callinectes sapidus Rathbun from Louisiana and Mississippi. It can be distinguished from all other members of the genus by possessing 11–21 atrial pockets and an acetabulum larger than the oral sucker, not possessing a pharynx nor well-developed ceca, and being 1.9–3.6 mm in length. Heardlevinseniella Yamaguti, 1971 is considered a synonym of Levinseniella Stiles & Hassal, 1901. An easily visible microphallid metacercaria was found on the hepatopancreas and gonads of a few large specimens of the blue crab from the northern Gulf of Mexico. Over 1500 various-sized individuals of Callinectes sapidus Rathbun and over 500 of C. similis Williams from Mississippi Sound and adjacent waters taken between June 1970 and September 1971 were routinely inspected for obvious parasites. Of these crabs, only four from a sample of 41 C. sapidus in July and August 1971 from the vicinity of Raccoon Island, Louisiana, and one from 92 C. sapidus in August 1971 from Cat Island, Mississippi, had the metacercaria present. The mean width of the carapace of the infected crabs was 151 mm. Of the five, three were females in a stage between first and second ovulations and two were mature males. The species is described below even though it is a larval stage because its reproductive system is well developed and its characteristics are unusual. O V E R S T R E E T A N D PE R R Y , T R A N S A C T I O N S O F T H E A M . M I C R O S C O P I C A L S O C I E T Y 9 1 (1 9 7 2 ) 2 Materials and Methods The trematodes were fixed in hot AFA under slight pressure and stained with Van Cleave’s hematoxylin or studied alive with and without neutral red stain. All figures except Figure 2 were drawn with the aid of a camera lucida, and measurements are given in micra. Figures 1–5. Levinseniella capitanea (scale values are micra). Fig. 1. Holotype, ventral view. Fig. 2. Atrial pocket, illustrated from photograph of living specimen. Fig. 3. Terminal genitalia and associated structures of a paratype, ventral view. Fig. 4. Male papilla of different paratype illustrating variation in both the organ and the tip, ventral view. Fig. 5. Anterior end of holotype illustrating sensory papillae, ventral view. O V E R S T R E E T A N D PE R R Y , T R A N S A C T I O N S O F T H E A M . M I C R O S C O P I C A L S O C I E T Y 9 1 (1 9 7 2 )