First record of a digenean from invasive lionfish, Pterois cf. volitans, (Scorpaeniformes: Scorpaenidae) in the northwestern Atlantic Ocean.

Adults of Lecithochirium floridense (Digenea: Hemiuridae) parasitized the stomach in each of 22 necropsied lionfish, Pterois cf. volitans (Scorpaeniformes: Scorpaenidae) (prevalence  =  100%, mean intensity  =  11), captured in the northwestern Atlantic Ocean off Beaufort, North Carolina (34°14.83'N, 76°35.25'W). This is the first report of a digenean from the invasive lionfish and that of L. floridense from a species of Pterois. The leech specimen previously identified as Myzobdella lugubris from P. volitans in the northwestern Atlantic Ocean is re-identified as Trachelobdella lubrica based on a study of the original voucher specimen.

The swimbladder nematode Anguillicola crassus in American eels (Anguilla rostrata) from middle and upper regions of Chesapeake Bay.

The patterns of infection of American eels Anguilla rostrata, with the introduced swimbladder nematode Anguillicola crassus, in tributaries of middle and upper Chesapeake Bay are described. A total of 423 subadult eels was collected from 8 Bay tributaries from spring 1998 to fall 1999. Also, 30 elvers were collected from Ocean City, Maryland, in spring 1998. The numbers of juvenile and adult specimens of A. crassus in the swimbladder wall and lumen were counted. No elvers were infected. In subadult eels, prevalence of adult and juvenile stages combined ranged from 13% to 82%; mean intensity ranged from 2.6 to 9.0 worms per eel. Infection levels were highest for Susquehanna River eels (northernmost river) and lowest in the southernmost sites: St. Jerome's Creek and the Pocomoke River. Although eels from these 2 localities were larger, the low infection rates there are most likely due to reduced transmission in higher salinity water and not to eel size. Eels with both adult and juvenile stages of A. crassus were more common than expected by chance. This might be explained by inhibition of juveniles migrating into the swimbladder lumen when adults are already present there.

Gill parasites of mummichogs, Fundulus heteroclitus (Teleostei: Cyprinodontidae): effects of season, locality, and host sex and size.

I investigated the prevalences and densities of gill parasites in 4 seasonal samples of mummichog, Fundulus heteroclitus (n=242), from 2 creeks differing in salinity in central Chesapeake Bay. The parasites (and overall prevalence ranges) were: mobile (12-88%) and sessile (0-50%) peritrichs (Ciliophora); Myxobolus funduli (58-94%) (Myxozoa); Gyrodactylidae (0-94%) (includes Gyrodactylus sp. and Fundulotrema sp.) and Salsuginus sp. (74-100%) (Monogenea); metacercariae of Phagicola diminuta (75-100%) and Echinochasmus schwartzi (79-100%) (Digenea); Ergasilus manicatus (25-100%) (Copepoda); Lironeca ovalis (0-11%) (Isopoda); and cysts of unknown etiology, or CUEs (64-94%) (unknown taxon). CUEs were more abundant in fall and gyrodactylids in winter. The myxozoan, copepod, and 1 species of digenean were most abundant in spring. Except for gyrodactylids and CUEs, densities were greater in the less saline creek for all taxa. There were no significant differences between sexes except in 1 sample; digenean densities increased with host length for females but not males. There was a strong positive relationship of CUE density with host length and weaker positive associations of gyrodactylid and Salsuginus sp. densities with host length.

Sexual anomalies in the estuarine snail Ilyanassa obsoleta: imposex in females and associated phenomena in males.

The spatial distribution of the "imposex" phenomenon (the imposition of male characters on females) among populations of Ilyanassa obsoleta in southern Delaware, USA estuaries was studied. Imposex was most frequent among females in a segment of the Lewes and Rehoboth Canal (68%, n=376) and there was significant spatial heterogeneity of imposex frequencies (range=43-98%) even within this habitat. Two lines of evidence indicate that conditions which generated female imposex (organotin molecules in the water) also affected male sexuality: 1) healthy males normally lose the penis following reproduction but they tended to retain it where imposex-inducing conditions were strong; and 2) males parasitized by trematodes usually lose the penis but tended not to under strong imposex-inducing conditions. The altered biology associated with imposexinducing environments extends beyond female I. obsoleta to males and to other species. This must be recognized when studying organisms exposed to these conditions.