William A. Roumillat

Diamondback terrapins, Malaclemys terrapin, as a sentinel species for monitoring mercury pollution of estuarine systems in South Carolina and Georgia, USA

Total mercury concentrations were measured in diamondback terrapin blood and scutes collected from four sites in South Carolina, USA, and at a superfund site in Brunswick, Georgia, USA. There was a strong correlation between mercury concentrations in the two terrapin body compartments (Kendalls tau = 0.79, p < 0.001). Mercury concentrations in terrapin scute and blood and in salt marsh periwinkles, Littoraria irrorata, were significantly higher in Brunswick (scute x = 3810.2 ng/g, blood x = 746.2 ng/g) than from all other sites (scute x = 309.5 ng/g, blood x = 43.2 ng/g, p < 0.001). Seasonal fluctuations of total mercury in the blood and scutes of terrapins collected in the Ashley River, South Carolina, were significantly lower in August than in April, June, or October in blood (p < 0.001); however, scute concentrations did not vary seasonally. Overall, we found higher concentrations of mercury in the scutes of females than males (n = 32, p < 0.05). Larger females may preferentially prey on larger food items, like large periwinkles, which had significantly higher mercury levels in their body tissues than smaller periwinkles (p < 0.001). Methylmercury levels in terrapin scutes were measured, revealing that 90% of the total mercury stored in this compartment was in the organic form. A methylmercury biomagnification factor of 173.5 was calculated from snails to terrapin scutes, and we found that mercury levels in scutes were representative of the mercury levels in other compartments of the ecosystem. These findings show that terrapin scutes are good predictors of mercury pollution and that this species could be used as a bioindicator for assessing mercury contamination of estuarine systems.

Three new species of philometrids (Nematoda: Philometridae) from centrarchid fishes in the USA.

The following 3 new species of the Philometridae (Nematoda: Dracunculoidea) are described from freshwater centrarchid fishes (Centrarchidae: Perciformes) from eastern North America on the basis of museum and newly collected specimens: Philometra orbitalensis n. sp. and Philometroides aphanonaris n. sp. from the oculo-orbits and subcutaneous tissues of the head, respectively, of the largemouth bass Micropterus salmoides, and Philometroides wellborni n. sp. from the oculo-orbits of the bluegill Lepomis macrochirus (type host) and the redbreast sunfish Lepomis auritus. Whereas P. wellborni is described from both males and gravid females, the males of P. aphanonaris and P. orbitalensis remain unknown. The type locality of all 3 species is the West Point Reservoir, Alabama–Georgia; P. aphanonaris and P. wellborni have also been recorded from the Santee River in South Carolina. In contrast to other Philometra spp. parasitizing North American freshwater fishes, the gravid females of P. orbitalensis are characterized by large cephalic papillae of the external circle, yellowish body color, location (oculo-orbits) in the host, and by the host type (Centrarchidae). Philometroides aphanonaris and P. wellborni differ from North American congeners from freshwater fishes in the absence of esophageal teeth or a different embossment of the caudal end in gravid females; P. wellborni differs from P. aphanonaris in the absence of cuticular bosses from the caudal end of gravid females and in some other features (extent of embossment, body color, location, and host type).

Habitat use of Intertidal Eastern Oyster (Crassostrea virginica) Reefs by Nekton in South Carolina Estuaries

ABSTRACT The majority of recent studies investigating the habitat value of intertidal oyster reefs have compared the nektonic assemblages on natural oyster reefs, salt marshes, mud bottom, and subtidal oyster shell habitats using methods that involve some degree of habitat disturbance. The current study used a novel, non-destructive sampling approach involving the deployment of a drop net around study plots to compare the nektonic assemblages associated with intertidal oyster reefs (natural and enhanced) with those of neighboring soft sediment habitats at 3 sites in South Carolina. At each site, the nektonic organisms collected on a reef plot were compared with those collected on an adjacent control plot lacking a structurally complex habitat. Nekton abundance was significantly higher on the reef plot compared with the control plot at all 3 sites. Nekton abundance also varied among seasons, with the greatest numbers occurring during summer compared with spring and fall. Notably, grass shrimp (Palaemonetes spp.) were especially dominant on reef plots. A total of 60 taxa were identified, 57 of which were identified to species level. Reef plots exhibited significantly greater taxon richness than control plots. The number of taxa present also accumulated over time at a higher rate on the reef plots than on the control plots at 2 of the 3 sites. Among the 60 taxa collected, 36 were found on both the reef and control plots, whereas 14 taxa were unique to the reef plots. For data pooled across all sites and seasons, 33 taxa were more numerous on reef plots than control plots, 3 taxa occurred in equal numbers, and 24 taxa were more numerous on control plots. For taxa collected on more than 1 occasion, paired t-tests performed with Bonferroni-adjusted significance thresholds revealed that Alpheus heterochaelis and Palaemonetes spp. were significantly more abundant on the reef plots than on the control plots, whereas unadjusted analyses revealed the same pattern for Gobiosoma bosc, Menidia menidia, and Fundulus heteroclitus. In contrast, no taxa were significantly more abundant on the control plots at either significance threshold. Although nekton abundance was generally higher on the reef plots, measures of diversity were significantly higher on the control plots, regardless of season, site, or date. Greater abundance of a limited number of species on the reef plots accounted for lower evenness and therefore lower diversity measures for this treatment. Overall, community structure was driven more by site than by treatment, whereas the seasonal occurrences of certain species on the reef plots highlighted the importance of oyster reefs as essential fish habitat for the critical life stages of finfish species with complex life histories.

Histopathology of Two Philometrid Parasites of the Southern Flounder, Paralichthys lethostigma

The southern flounder Paralichthys lethostigma is host to two species of philometrid nematodes in the estuarine systems of South Carolina, USA. Histologic studies showed that all worms were hematophagous and that the host-parasite interface varied according to the worms location in the fish. Individuals of Philometra overstreeti associated with the teeth induced a degradation of the enameloid epithelium but elicited minimal host reaction, whereas those located in the branchial arches induced an intense inflammatory response. Individuals of Philometroides paralichthydis elicited no host reaction. Those associated with the bones of the buccal cavity were contained in a thick collagenous capsule, whereas those located between the depressor and erector muscles of each fin element displaced or thinned the fin inclinator muscles to the extent of eventually causing their complete atrophy. Often the bulk of gravid worms imposed upon uninfected adjacent fin element muscle groups. Damage induced by these worms are likely to affect feeding and swimming behavior of the infected flounder and thus, impact the population structure of this important fish species.

Stock identification of the sciaenid fish Micropogonias undulatus in the western North Atlantic Ocean using parasites as biological tags

Proper fisheries management of the Atlantic croaker Micropogonias undulatus is necessary in the United States due to the commercial and recreational importance of this fish species. Croaker stock structure in the western North Atlantic has been investigated in the past by various authors, with inconclusive results. In this study, macroparasites were used as biological tags to identify putative croaker stocks in the area between New Jersey and Florida, which encompasses the Mid Atlantic Bight and the South Atlantic Bight separated at Cape Hatteras, North Carolina. The macroparasite community of the fish was identified, showing the presence of 30 species in four phyla, of which several were new host records, and one species, a monogenean, was new to science. A canonical correspondence analysis was applied to determine the variables responsible for parasite species composition, to resolve the question of croaker stock structure in the western North Atlantic Ocean. This analysis showed that latitude was the deciding variable delineating the parasite community composition of the Atlantic croaker. Among the 30 parasites, 15 were identified as putative tags according to qualitative criteria, and then 10 out of those 15 were selected as being appropriate tags using quantitative criteria. These parasite tags support the presence of two stocks roughly separated at the known biogeographical barrier at Cape Hatteras.

Invasive swimbladder parasite Anguillicoloides crassus: infection status 15 years after discovery in wild populations of American eel Anguilla rostrata.

A year-round survey of American eels Anguilla rostrata was performed at 5 localities in South Carolina (SC), USA, 15 yr after the first infection by the nematode Anguillicoloides crassus was reported from Winyah Bay, SC. Infections by adult stages of A. crassus in the swimbladder lumen occurred with a prevalence of 45% (n = 479), a mean intensity (± SE) of 2.3 ± 0.2 worms per infected eel (range = 1-22), and a mean abundance of 2.0 ± 0.1 among all eels. Infections by larval stages of A. crassus in the swimbladder wall occurred with a prevalence, intensity, and abundance of 29%, 2.4 ± 0.3 (range = 1-15), and 0.7 ± 0.1, respectively (n = 471). Overall prevalence of the parasite (any stage) was 58%, with a mean intensity ± SE of 3.0 ± 0.2 and a mean abundance of 1.8 ± 0.2. Biomass of the adult parasite stage varied significantly with eel body length, but the direction of the effect depended on salinity. Prevalence and intensity of infection by adult nematodes varied by locality but not by eel total length, salinity, or season. Larval prevalence was significantly greater in the winter and spring and also differed among localities. The lack of seasonal effects on infection by the adult worm stage contrasts with studies from higher latitudes in North America and Europe and may be due to the warmer winter temperatures at southern latitudes. Significant variation in infection among localities reflects possible differences in abundance of intermediate and/or paratenic hosts. Overall, infection levels were higher than previous reports for eels in SC but comparable to more recent reports from other areas in North America.

Effects of a muscle-infecting parasitic nematode on the locomotor performance of their fish host

The southern flounder Paralichthys lethostigma, host to the nematode Philometroides paralichthydis that is embedded in place of the inclinator muscles of the dorsal and anal fin elements, is hypothesized to impair two aspects of locomotor performance (swimming and burying capacity). Peak swimming acceleration and both measures of burying performance did not differ between infected and uninfected fish, whereas swimming velocity of infected fish was significantly lower than that of uninfected fish. Smaller infected fish swam at significantly slower speeds than smaller uninfected fish, whereas there was no difference among larger fish. Neither the location nor the number of worms affected either swimming or burying performance. The decrease in swimming velocity observed in smaller infected fish may be sufficient in rendering them more vulnerable to predation and environmental stressors.

PHILOMETRIDS OF THE SOUTHERN FLOUNDER PARALICHTHYS LETHOSTIGMA: A MULTIDIMENSIONAL APPROACH TO DETERMINE THEIR DIVERSITY

Abstract Two species of philometrid nematode, Philometra overstreeti and Philometroides paralichthydis, infect the southern flounder, Paralichthys lethostigma. Individuals of P. overstreeti are located between the teeth and inside the bony part of the branchial arches of the fish. Individuals of P. paralichthydis are associated with the bones of the buccal cavity and among muscles that control the dorsal and anal fins. Sequencing of part of the cytochrome oxidase I gene revealed 4 distinct genetic clades, each corresponding exactly to the 4 respective locations of the parasites in the host, suggesting the need for taxonomic revision. We hypothesized that each clade represented a separate species and, because the worms are morphologically indistinguishable, compared population level parameters of the clades comprising each currently recognized species. For each currently recognized species, the presence of worms from 1 clade was negatively correlated with the presence of worms from the other. Results also indicated significant differences between the clades in prevalences relative to both biotic and abiotic factors. Results clearly indicated major differences in the ecology of the philometrids constituting each clade. Taken as a whole, molecular and ecological data support the contention that the 4 genetic clades are likely 4 distinct species.

Use of molecular tools in identification of philometrid larvae in fishes: technical limitations parallel our poor assessment of their biodiversity

The usefulness of the polymerase chain reaction with restriction fragment length polymorphism (PCR-RFLP) and partial sequencing of the cytochrome oxidase I (COI) gene was tested regarding the utility of these techniques in unraveling philometrid life cycles and, in particular, to determine putative paratenic host species. Our focus was to study three species of philometrids commonly found in the estuaries of South Carolina: Philometroides paralichthydis and Philometra overstreeti from the southern flounder, Paralichthys lethostigma and Philometra carolinensis from the spotted seatrout, Cynoscion nebulosus. A total of 473 fish in 19 species known to be potential prey of the spotted seatrout and the southern flounder were dissected. Of all nematode larvae found in the mesenteries of 53 fish of 10 species, 21 specimens were determined to be philometrids using PCR. The use of PCR-RFLP allowed the identification of larvae of P. carolinensis and P. overstreeti in the freshwater goby, Ctenogobius shufeldti, and P. overstreeti in mummichog, Fundulus heteroclitus. However, 12 RFLP profiles could not be matched to control species, thus demonstrating the limitation of this technique in areas where diversity of philometrids is not well known and higher than anticipated. Similarly, COI procedures provided unknown sequences that did not match those of nine philometrid species used as controls. We concluded that although both techniques showed some usefulness and promise, at this point, however, they demonstrate the need of increasing our knowledge of marine and estuarine philometrid biodiversity.

Sinuolinea infections in the urinary system of Cynoscion species (Sciaenidae) and phylogenetic position of the type species of Sinuolinea Davis, 1917 (Myxozoa: Myxosporea)

Graphical abstract Highlights ► Myxosporean infections in the urinary bladder of Cynoscion species are reported. ► Sinuolinea dimorpha (Davis, 1917) was diagnosed as the agent of infections. ► SSU rDNA sequences of the type species of SinuolineaDavis, 1917 were generated. ► Phylogenetic position of S. dimorpha and potential cryptic species was determined.