Richard W. Heard

MACROBENTHIC RESPONSES TO NATURAL AND CONTAMINANT‐RELATED GRADIENTS IN NORTHERN GULF OF MEXICO ESTUARIES

Effects of pollution on biotic integrity are difficult to identify when correlations occur between environmental gradients and contaminant effects, as they do in estuaries. In this broad-scale study, we used canonical correspondence analysis (CCA) to distinguish influences of natural and contaminant-related gradients on macrobenthic community structure among 319 sites from estuaries throughout the northern Gulf of Mexico. Natural gradients in salinity, depth, and sediment composition obscured the detection of macrobenthic responses to sediment contamination. After adjusting for natural environmental variability, however, partial CCA revealed important macrobenthic variation in relation to sediment contamination. A rotated principal component analysis (PCA) distinguished five composite environmental factors, each largely reflecting contaminant or natural variation. Two complex gradients in sediment contamination identified by the PCA diverged in partial CCA space and correlated with different macrobenthic indicator taxa. Contaminant gradients represented variation in two different classes of sediment contaminants: trace metals and organic chemicals. Dispersion patterns of CCA site coordinates enabled cross validation of implied contamination-related variation in community function and the utility of several interpretive or management metrics. Trophic diversity decreased with sediment contamination, linking shifts in macrobenthic community function and community structure along contaminant gradients. The CCA model complemented an earlier benthic index developed from these data to examine biotic integrity, but the benthic index could not discern macrobenthic responses to the different contaminant gradients. Neither was the benthic index useful for showing transitions in macrobenthic community structure commensurate with different levels of contamination. Ampelisca amphipod sediment bioassays were inadequate for identifying contaminant effects on biotic integrity, whereas Mysidopsis mysid sediment bioassays conservatively reflected sediment contamination and associated macrobenthic indicators.

Effects of Sediment Contaminants and Environmental Gradients on Macrobenthic Community Trophic Structure in Gulf of Mexico Estuaries

Macrobenthic communities from estuaries throughout the northern Gulf of Mexico were studied to assess the influence of sediment contaminants and natural environmental factors on macrobenthic community trophic structure. Community trophic data were also used to evaluate whether results from laboratory sediment toxicity tests were effective indicators of site-specific differences in benthic trophic structure. A multiple regression model consisting of five composite factors (principal components) was used to distinguish the effects of sediment contaminants and environmental variables on benthic community trophic structure. This model explained 33.5% of the variation in macrobenthic trophic diversity (p<0.001), a variable derived from the distribution of taxas among nine original trophic categories. A significant negative relatinship was found between principal components reflecting concentrations of sediment contaminants and macrobenthic trophic diversity.Detritivores including surface deposit-feeders (SDF), subsurface deposit-feeders (SSDF), and filter feeders (FF) were numerically dominant at 201 random sites, each group accounting for 25–30% of total macrobenthic abundance. The relative abundance of SDFs was considerably lower (12.1±2.9% to 17.1±4.4%) at sites where sediment contaminant concentrations exceeded minimum biological effects thresholds (ER-L values from Long and Morgan 1990 than at sites sampled at random (29.3±5.7%). SSDFs were proportionally more abundant at contaminated sites (42.0±7.7% to 63.6±10.3%) versus random sites (27.5±5.7%), and the relative abundance of SSDFs was positively correlated with concentrations of particular contaminants. Benthic trophic structure was also found to be a function of salinity, where the proportion of SSDFs was negatively correlated with salinity (p=0.035, r=−0.223, n=326). Silt-clay content loaded fairly strongly on the first principal component, but trophic structure parameters were not significantly correlated with sediment grain size or dissolved oxygen (perhaps due, in part, to covariation). Results from laboratory sediment toxicity tests with mysids were predictive of differences in macrobenthic trophic structure in situ (i.e., mysid survival was negatively correlated with %SSDF; p<0.001, r=−0.292, n=326). Results from laboratory sediment toxicity tests with ampeliscid amphipods were not indicative of site-specific differences in benthic trophic structure.Results from this study demonstrated that sediment contaminants can be quite important in structuring macrobenthic communities in soft-bottom estuarine habitats. The fact that macrobenthic trophic diversity decreased significantly with increasing sediment contamination indicates that important general differences in benthic community function may exist between contaminated and random sites. These data suggest that benthic trophic structure analysis may be an effective tool for assessing integrated community responses to chronic sublethal exposure and may be useful for assessing toxicological responses at ecologically relevant levels of organization.

ACANTHOCEPHALANS FROM CRABS IN THE SOUTHEASTERN U.S., WITH THE FIRST INTERMEDIATE HOSTS KNOWN FOR ARHYTHMORHYNCHUS FRASSONI AND HEXAGLANDULA CORYNOSOMA

Cystacanths of Hexaglandula corynosoma were discovered in the fiddler crabs Uca spinicarpa and Uca rapax collected in Mississippi and Florida. Adults were present in yellow-crowned night herons, Nyctanassa violacea, collected in Florida. Cystacanths are very similar to adults, varying only in size and state of development. This is the first record of H. corynosoma from the United States and the first record of an intermediate host for any species of the genus. Cystacanths of Arhythmorhynchus frassoni were present in U. rapax from Florida. The proboscis size, shape, and armature of the cystacanths are identical to those of adults from clapper rails (Rallus longirostris) collected in several southeastern states. This is the first report of an intermediate host for A. frassoni. Profilicollis altmani cystacanths were collected from mole crabs (Emerita talpoida) at Atlantic Beach, North Carolina. These specimens, together with adults obtained from shore birds in Louisiana and Mississippi, are consistent with the view that P. altmani, Profilicollis kenti, and Profilicollis texensis are synonyms, with P. altmani having nomenclatural priority.

Biomass Variations of Estuarine Macrobenthos Preserved in Ethanol and Formalin

Three preservative treatments were compared for their effects on biomass of macrobenthic species collected at Biloxi Bay, Mississippi. We tested the hypothesis that biomass did not differ among treatments once specimens were fixed in 10% formalin. Two commonly used analyses, wet-weight biomass and dry-weight biomass, were tested. Wetweight variations among treatments were compared over time. Dry-weight calculations were not possible on individuals over time because specimens could be dried only once, so ratios of dry weight to wet weight were calculated on specimens at the conclusion of each treatment. Specimens were fixed in 10% formalin for 2 wk, then transferred to either 1% formalin or 70% ethanol, or left in 10% formalin. Wet-weight biomass of the three treatments was determined weekly four times, and then specimens were dried for 72 h at 60°C for dry-weight determinations. Biomass of most taxa fixed in formalin and preserved in ethanol or formalin did not vary significantly in wet weight over time. Minor variations among the treatments occurred in dry-weight biomass. Whereas previous investigators found that ethanol effected biomass when specimens were not formalin-fixed, our results supported the premise that three commonly used preservative treatments did not differ in their effects on biomass of estuarine macrobenthos. Therefore, we propose that estuarine macrobenthos be fixed in formalin, then transferred to ethanol for biomass procedures in order to avoid exposure of laboratory personnel to carcinogenic formalin.

Trophic relationships of three sunfishes (Lepomis spp.) in an estuarine bayou

We examined ontogenetic, interspecific, and seasonal trophic patterns among sympatric sunfish species, redspotted sunfish,Lepomis miniatus; redear sunfish,Lepomis microlophus; and bluegill,Lepomis macrochirus, in an estuarine bayou. In particular we studied these feeding patterns in relation to relative abundances of prey from different benthic feeding habitats. All three sunfishes showed ontogenetic divergence in their trophic niches, reflecting different ecomorphological specializations. Small fishes depended on zooplankton, whereas larger fishes of all three species shifted their diets to benthic macrofauna. A potential for trophic resource partitioning was reflected by dietary differences among the three sunfish species. One impalied mechanism for resource partitioning was feeding habitat, as redear sunfish frequently used sediment-associated prey, while bluegill showed greater use of water-column-associated prey, and redspotted sunfish often used SAV-associated prey. However, all three sunfishes apparently used each feeding habitat to some degree; and, trophic differences were more clearly based on prey type than on feeding habitat. Redear sunfish, which can crush hard-shelled prey, exhibited the most distinctive diet. An apparent seasonal shift in feeding habitat occurred in autumn/winter, as indicated by increased overlap between diets and SAV. This shift was facilitated by changes in the relative abundances of several common prey types between benthic habitats. The relative abuandance and use of freshwater and estuarine-derived prey also varied seasonally, suggesting a possible trophic benefit of consistent prey availability in the estuarine bayou.

Taxonomy and biology of Phagicola nana (Digenea: Heterophyidae).

Phagicola nana is resurrected from synonymy and redescribed based on syntypes from the arctic fox, Alopex lagopus, and adults from an experimental infection in the Virginia opossum, Didelphis virginiana. Natural definitive hosts include the great blue heron, Ardea herodias; least bittern, Ixobrychus exilis; and possibly gannet, Morus bassanus. The Virginia opossum, northern raccoon, laboratory white mouse, Syrian hamster, and domestic chicken serve as experimental definitive hosts. Natural metacercarial infections by P. nana occurred in the largemouth bass (Micropterus salmoides), redear sunfish (Lepomis microlophus), bluegill (L. macrochirus), and orangespotted sunfish (L. humilis) collected in estuarine bayous and rivers of Mississippi, Florida, and Georgia. Metacercariae caused minor histopathological alterations in fish hosts by inducing formation of fibrotic host capsules. They encysted primarily in sites already containing fibroblasts. Phagicola nana may have broad host specificity for piscivorous birds and mammals inhabiting estuarine marshes. Moreover, humans probably may become infected with P. nana by ingesting raw or inadequately prepared centrarchid fishes. Phagicola nana (Ransom, 1920) was originally described from a single specimen of the arctic fox, Alopex lagopus (Linnaeus) (as Vulpes 1.). Cause of the foxs death in 1906 at the National Zoological Park, Washington, D.C., was diagnosed as intense purulent peritonitis and septic metritis. At necropsy, Dr. H. W. Graybill collected specimens of it and P. longa (Ransom, 1920), and Ransom (1920) described them both. Because the fox was born and lived its entire four years at the Park, we assume it acquired both heterophyids from raw fishes fed to it. Metacercariae of P. longa parasitize mullets (Edwards & Overstreet, 1976; Hutton, 1957; Hutton & Sogandares-Bernal, 1958, 1959, 1960; Skinner, 1975), and adults occur at least in Procyon lotor (Linnaeus) and birds along the Atlantic and Gulf of Mexico coasts (Harkema & Miller, 1962, 1964; Hutton & Sogandares-Bernal, 1960; Overstreet, 1978). This paper is the first to report metacercariae of P. nana, a species that we consider distinct from P. angrense (Travassos, 1916). We found metacercariae of P. nana commonly We thank Sybil Hamlet, Historian, National Zoological Park, Smithsonian Institution, Washington, D.C., for providing information concerning the type-host of Phagicola nana and John C. Pearson, University of Queensland, for commenting on the manuscript. Also, Dr. J. Ralph Lichtenfels loaned us type and voucher specimens of heterophyids from the USNM Helminthological Collection; Dr. Jeffrey M. Lotz and Mr. Larry Shults donated heterophyids collected from birds and mammals in Ocean Springs, Mississippi; Dr. Adrian Lawler provided laboratory-reared chickens and collected raccoons and opossums for us; and Ronnie Palmer, Joan Durfee, and John Lamb provided technical assistance. We acknowledge the University of Wisconsin-Eau Claire for providing a Faculty Improvement Grant to WFF. The study was conducted in cooperation with the U.S. Department of Commerce, NOAA, National Marine Fisheries Service, under PL 88-309 Project Nos. 2-382-R and 2-393-R. 2 Department of Biology, University of Wisconsin-Eau Claire, Eau Claire, Wisconsin 54701,

The Tanaid Hexapleomera robusta (Crustacea : Peracarida) from the Caribbean Manatee, With Comments on Other Crustacean Epibionts

The tanaidaceans are among the most conspicuous and ecologically relevant benthic microcrustaceans in the marine realm but there are only a few records of species of tanaids associated with other marine organisms. During a long-term survey on the biology and distribution of the Caribbean manatee Trichechus manatus manatus Linnaeus in Mexican waters, parasites and epibionts were collected from 47 individuals that were captured for tagging in two bay systems. Well-established epibiotic communities of the tanaidacean Hexapleomera robusta (Moore) were found on eight of these animals; this tanaid crustacean formed patches of tubes adhered to the skin surface. Patches were distributed in different parts of the body surface but mainly along the backbone depression, the caudal zone, and on the lateral margins; in some instances they were related to clusters of barnacles. Highly significant differences of infestation rates were revealed between Chetumal Bay and Ascension Bay, the latter representing better conditions (high salinity and hydrodynamism) for tanaid invasion and settlement on the manatee. It is speculated that the tanaid is a commensal; no visible damage was found in the host and its presence was not related to skin lesions. The tanaid probably captures suspended particles as the manatee feeds. This is the first confirmed record of a symbiotic association involving a tanaid and the Caribbean manatee. The tanaid species recorded ( H. robusta ) and the harpacticoid copepod Balaenophilus manatorum (Ortiz, Lalana & Torres), have both been recorded also as epibionts of sea turtles. The tanaid has been known from sea turtles for some time, but the copepod was first recorded from a manatee and was subsequently found on sea turtles a few years later.

The Occurrence and Food Habits of Two Species of Hake, Urophycis regius and U. floridanus in Georgia Estuaries

Abstract From 1967 to 1970 a total of 2,683 spotted hake, Urophycis regius and 470 southern hake, U. floridanus were collected and found to exhibit migratory patterns in Georgia similar to northern and Gulf populations of these fish. The food habits of inshore juvenile populations of these two species of hake collected from coastal salt marsh-estuarine areas near Sapelo Island, Georgia were examined. The 341 spotted hake and 192 southern hake examined contained identifiable food items. These were analyzed for the numbers of individual food organisms, percent frequency of occurrence, and percent biomass. The most important group in occurrence and biomass was the Crustacea with Macrura and Natantia most important gravimetrically, Amphipoda and Mysidacea most frequently occurring. These data when combined with the habits of the food organisms established these two hakes as species which use the estuary as “nursery grounds.”

Seasonal Variability in Morphology of Blue Crab, Callinectes sapidus, Megalopae and Early Juvenile Stage Crabs, and Distinguishing Characteristics Among Co-Occurring Portunidae

Abstract Declines in abundance of the commercially important blue crab Callinectes sapidus have led fishery managers to search for new management strategies. Assessing year-class strength at megalopal or early juvenile stages may contribute to this effort, but separation from co-occurring species is difficult in many areas because morphological characteristics vary with season and published descriptions do not adequately distinguish C. sapidus from C. similis and other related species. Callinectes sapidus and C. similis megalopae were collected monthly and cultured in the laboratory to a size at which positive identification could be made. Measurements on intact megalopae and early crab exuviae of both species revealed seasonal differences, with spring megalopae having larger carapaces, longer rostral spines and antennae and more setae on some mouth parts than fall megalopae. This seasonal pattern of morphological variability was verified through examination of samples collected from MS (1976–1979) and NC (2005) coastal waters. Rostrum length, total carapace length and rostrum length as a percent of total carapace length of NC megalopae were negatively correlated with water temperature 2–4 weeks prior to collection. Callinectes sapidus and C. similis megalopae can be rapidly separated within locations and seasons by: 1) the shape of the antero-lateral carapace margin, 2) rostral length as a percent of total carapace length, and 3) the combined length of the distal eight segments of the antenna. Such rapid separation is essential for fisheries studies requiring identification of large numbers of individuals. Molecular analyses or more detailed morphological analyses remain necessary for definitive separation regardless of season. Keys to common coastal portunid megalopae and first crab stages were compiled to aid investigators in separating C. sapidus megalopae and early juvenile stages from co-occurring portunids.

Microphallus fonti sp. n. (Digenea: Microphaliidae) from the red swamp crawfish in southern United States

A new species of digenean, Microphallus fonti, is described from the red swamp crawfish in Lousiania, U.S.A. It has a small pharynx and a rudimentary gut like M. opacus and a possibly related species from crayfishes, but it differs from them by its relatively large male copulatory papilla and a conspicuous metraterm.