Cyathura Polita Research Articles

A SCANNING ELECTRON MICROSCOPE ANALYSIS OF MORPHOGENESIS OF EMBRYOS AND JUVENILES OF THE DIRECT DEVELOPING ISOPOD, Cyathura polita (Stimpson, 1855)

Isopods are a species rich, morphologically diverse group characterised by direct development of young within a marsupium. Collectively, these traits make isopods excellent models for understanding the changes to morphogenesis that occur in the evolution of direct development, but the overall understanding of this process is limited by a lack of comparative data. We investigated morphogenesis in Cyathura polita, an isopod common in estuaries along the Atlantic coast of North America, from gastrulation to release of young as benthic juveniles, using Scanning Electron Microscopy. We found that early development of C. polita from gastrulation to hatching from the extraembryonic membranes was generally similar to that described by earlier work using sectioned material, but found that development through the manca stage to free living juveniles differed from previous studies. For instance, the embryonic dorsal organ differed from that described generally for isopods as the apical surface is covered by a sieve plate and the typically reported microvilli were not observed. Differences in timing were also noted: for example, segments appeared throughout the pereon and pleon well before the post-naupliar appendages, and not coincident with them as described previously for isopods. Limb development occurred simultaneously except that pereopod 7 did not form until the post-manca stages, as is typical for this group, suggesting there is non sequential (or suppression of) teloblast activity in postnaupliar development. Also, some broods contained young of different developmental stages (i.e., early embryos and late manca), indicating that spawning events are repeated and overlap, which is perhaps adaptive in the shortened reproductive season characteristic of our study population that is at the northern limit of the known range for this species. Mean brood size was 53.2 ± 18.9 young (range 4-108), the largest reported for Anthuridae (a family of isopod crustaceans).Key words: scanning electron microscopy, marsupium, manca, embryonic dorsal organ, direct development, crustaceans.

Modeling the Effect of Environmental Parameters on Feeding Ecology of the Shortnose Sturgeon in the Saint John River, New Brunswick

AbstractWe examined the effects of spatial, temporal, and environmental parameters on the feeding habits of the shortnose sturgeon Acipenser brevirostrum. We sampled sturgeon gut contents using colonic flushing, a new, low‐impact technique. We found that heavy feeding continued until at least November, when water temperature reached 8°C. In all seasons, foraging shortnose sturgeon used shallow water (2–8 m); however, in late fall this trend was even stronger, when 50% of the sturgeon were captured in less than 3 m depth. Over 60 families of prey items were identified from 166 colonic samples collected at four points between spring and late fall from seven locations throughout the lower Saint John River, New Brunswick. Samples from freshwater sites contained mainly Gastropoda, Sphaeriidae, Chironomidae, and Gammaridae. Samples from saline and brackish environments contained mostly Gammaridae, Corophiidae, softshell clam Mya arenaria, Cyathura polita, and Chironomidae. We used sensitivity analysis to determine the number of shortnose sturgeon required to obtain a representative sample of the diet. We found that 20–40 gut samples from sturgeons in both brackish and freshwater environments would suffice for a general description of the diet but that complete knowledge of the sturgeon diet and a comparison among several sites would require the sampling of hundreds of fish. The digestibility of prey varied from 77% of the ingested volume in a saline environment to only 6% in freshwater samples. Shortnose sturgeon from freshwater sites had higher ingested volumes and more prey per ingested volume than did those from brackish sites, which indicated further differences in feeding efficiency between the environments. Salinity was a significant parameter in the redundancy analysis of ingested prey items. In freshwater sites the significant factors were season, sturgeon length, ingested volume, number of ingested prey, and number of ingested taxa. In saline sites the significant factors were season, location, ingested volume, and the number of ingested prey. Our findings identified the spatial and temporal gradients in shortnose sturgeon foraging and provided insight into foraging efficiency in this species.

Life History of the Marine Isopod <em>Cyathura polita</em> in the Saint John River Estuary, New Brunswick: a Species at the Northern Extent of its Range

The marine isopod, Cyathura polita, inhabits estuaries on the east coast of North America from the Gulf of Mexico to the Bay of Fundy, Canada. We studied C. polita in the Saint John estuary to test for potential differences in life history that might occur because of the northern location of the population. In the Saint John, based on our interpretation from a six-month sampling program (May-October), the population exhibits a three-year life cycle, one year longer than more southern populations, and stretching over four summers. Our study supported the occurrence of protogynic hermaphroditism. After two summers as juveniles, individuals matured as females during their third summer, then displayed sex reversal by becoming males that fall, and finally reproducing as males in their fourth summer of life before death. Mean length of C. polita from the Saint John was greater than individuals from more southern populations (females, 13.8 ± 2.14 mm; males, 16.3 ± 2.41 mm). Annual brood release occurred in late July-early August. Mean fecundity of females was 53.2 ± 18.9 embryos per brood, which was greater than found in southern populations. Cyathura polita is rare in Canada and is known only from the Saint John and along the northern shore of the Bay of Fundy to the border of the United States.

Benthic Macrofaunal Community Structure along a Well-Defined Salinity Gradient in the Mullica River–Great Bay Estuary**

The benthic macrofaunal community of the Mullica River–Great Bay estuary in the Jacques Cousteau National Estuarine Research Reserve is characterized by both small-scale and large-scale distribution patterns that can be correlated to gradients in physicochemical parameters. Sediment composition is a major factor regulating the local distribution of benthic assemblages in the estuary, with the amount of silt-clay being particularly important. For example, one suite of benthic fauna (i.e., Ampelisca verrilli, Ensis directus, Haustorius arenarius, Pygospio elegans, and Oxyurostylis smithi) reported in the estuary has been found only in sediments with less than 20% silt-clay, whereas another (i.e., Acteocina canaliculata, Lumbrineris tenuis, Maldinopsis elongata, Tellina agilis, Turbonilla sp., and Unciola irrorata) has been observed only in sediments with more than 38% silt-clay. Other physicochemical factors (e.g., organic carbon content of the sediments, dissolved oxygen levels, bottom currents, and turbidity) might also influence the local distribution patterns of the fauna. On the estuary scale, environmental gradients from upriver to down-bay regions strongly affect the distribution of the benthos over broader spatial areas. Hence, four distinct regional assemblages of benthic invertebrates have been identified in the Mullica River–Great Bay estuary, including river-, bay-, lower bay–, and estuary-wide forms. The dominant assemblage—the estuary-wide forms distributed along the length of the estuary—consists of the most abundant populations with the widest salinity tolerances. Examples are Ampelisca abdita, Corophium cylindricum, Cyathura polita, Notomastus latericeus, Polydora ligni, Scoloplos robustus, and Turbonilla sp. Because Great Bay exhibits marked changes in sediment type from predominantly sands in the eastern perimeter to generally finer deposits along the western margin, the abundance, species richness, and species composition of benthic invertebrates vary considerably over relatively small spatial scales.

Genetic Transition between Northern and Southern Populations of the Estuarine Isopod, Cyathura polita, and the Discovery of a New Species of Cyathura

Previous work on the genetics ofCyathura polita populations along the Atlantic coast indicated that northern and southern populations have diverged significantly. We used starch gel electrophoresis to study the transition between northern and southern populations for gene frequencies at four enzyme loci.Cyathura from three sites in the Carolinas were compared with those from representative populations in the north (Massachusetts) and south (Florida).Cyathura polita from the northern and southern populations were fixed for different alleles at three of the four loci assayed.C. polita from a population in North Carolina had the northern electromorph for two loci and were polymorphic at theEst locus for the northern and southern electromorphs, whileC. polita from a population in South Carolina had the southern electromorphs for two loci and were polymorphic at theMdh-1 locus for northern and southern electromorphs. Thus, there appears to be gene flow between the genetically differentiated populations in the north and south. One population ofCyathura from North Carolina had unique electromorphs at the four loci assayed and appears to be a new species.

Widespread Distribution of Some Estuarine Crustaceans (Cyathura polita, Chiridotea almyra, Almyracuma proximoculi) in the Limnetic Zone of the Lower Hudson River, New York

From June through September 1983, a survey was conducted to document the occurrence, abundance and distribution of benthic macroinvertebrates in the main channel, Hudson River Estuary. The survey was restricted to a 118-km reach of the limnetic zone from just below Albany to New Hamburg, New York. Results indicated that two crustacean species,Cyathura polita (Stimpson) andChiridotea almyra Bowman, are widely distributed and common throughout the limnetic zone, including areas more than 100 km upstream from the northernmost(=most upstream) intrusion of ocean-derived brackish water.Almyracuma proximoculi Jones and Burbanck was much less common, but also was found in areas well removed from any brackish-water influences. All three species previously have been thought to occur primarily in estuarine waters with at least some salinity. We could find no evidence to suggest that non-ocean derived sources were supplementing the levels of dissolved ions in the river water or sediments. Therefore, it appears that all three species have established permant populations in a truly freshwater habitat.

Genetic Differentiation and Speciation in the Estuarine Isopods Cyathura polita and Cyathura burbancki

We investigated the electrophoretically detectable variation at nine protein loci in seven populations ofCyathura polita and one population of the closely relatedC. burbancki from the Atlantic coast of North America. The average proportion of the genome heterozygous per individual\((\bar H)\) inC. polita ranges from about 0% in New Brunswick and Massachusetts to 9.3% in a Georgia population.\(\bar H\) in the population ofC. burbancki was 2.6%. On the basis of our results,C. polita can be separated into two geographic forms,northern (New Brunswick, Massachusetts, and Maryland) andsouthern (Georgia and Florida). The genetic distances between the southern and northernC. polita are similar to the genetic distances reported between species of several other invertebrate groups. Our genetic data support the idea that the northern and southern forms ofC. polita andC. burbancki comprise a triad of species that diverged from each other 2–3 million years ago. Since we know nothing about the genetic structure of populations ofCyathura between Georgia and Maryland, this interpretation must be considered preliminary.

Occurrence and Biology of Cyathura Polita (Stimpson) (Isopoda, Anthuridae) in Canada

[A large reproducing population of Cyathura polita occurs in the Saint John River estuary, New Brunswick, Canada. This is the first record from Canada and represents a 180 km northeastward extension of the known range for this species. A large portion of the Cyathura population occupies deep (20 m), mesohaline (0.1-20‰) water on bottoms of moderate silt-clay content. The population exhibits protogynic hermaphroditism, a phenomenon common to cyathurans. This occurrence, disjunct from the main center of Cyathura polita distribution to the south, may be a result of an earlier widespread distribution during the Hypsithermal Period with a subsequent fracturing of the range during recent cooler climatic conditions., A large reproducing population of Cyathura polita occurs in the Saint John River estuary, New Brunswick, Canada. This is the first record from Canada and represents a 180 km northeastward extension of the known range for this species. A large portion of the Cyathura population occupies deep (20 m), mesohaline (0.1-20‰) water on bottoms of moderate silt-clay content. The population exhibits protogynic hermaphroditism, a phenomenon common to cyathurans. This occurrence, disjunct from the main center of Cyathura polita distribution to the south, may be a result of an earlier widespread distribution during the Hypsithermal Period with a subsequent fracturing of the range during recent cooler climatic conditions.]

Distribution and Breeding Cycle of Cyathura polita (Isopoda:Anthuridae) in a Juncus roemerianus Marsh of Northern Florida

Cyathura polita was the most common infaunal macroinvertebrate in a north FloridaJuncus roemerianus marsh. Density was 58 and 75/m2 in lower and upper marsh zones, respectively, during a 19 month study period. It was randomly distributed in both marsh zones, but density was greatest 200 m from low water. Population analysis indicated that reproduction occurred in April, young were common in May and these produced young the following April. Males matured first, and there was some evidence for possible protogynous hermaphroditism. Smaller body size, shorter maturation period and a different environment from previously reported populations ofC. polita suggest that we have described a new ecotype located in a distinctively different biotope.

Benthic and epibenthic macroinvertebrates of the Hudson River: I. Distribution, natural history and community structure

A 1972 benthic survey of the invertebrate fauna represented the first spatial and temporal investigation over a large portion of the Hudson River estuary. The benthic investigation was one segment of a team effort which included phytoplankton, zooplankton, ichthyoplankton and rooted aquatic plants. The 55 stations that spanned an 80-mile area from New York Harbor to Poughkeepsie were sampled four times with a modified Petersen dredge. One hundred and five taxa were identified. Ten groups accounted for 95% of the organisms found. These included 19 species of polychaetes, 13 genera of chironomids, 10 species each of bivalves and gastropods, 8 species each of amphipods and decapods and 6 species of isopods. Salinity was one of the most important measurable factors controlling species range and community boundaries. The number of species was highest in the polymesohaline zones and lowest in fresh water. Stations with the highest numbers of animals were located south of the Tappan Zee Bridge. Many of these stations contained an average of 10 000 organisms/m 2 or a peak total of 60 000/m 2. In stations south of Haverstraw Bay, the populations of benthic fauna equalled or exceeded those populations found in other estuaries throughout the world. The highest densities reflected the presence of 4 species, e.g. 2 polychaetes, Streblospio benedicti and Scolecolepides viridis, the isopod, Cyathura polita, and the bivalve, Mya arenaria. Faunal homogeneity analysis by Sanders' affinity index system indicates the presence of broad communities within the 80-mile sampling area. This conclusion may be obscured, however, by the presence of two large complexes, the oligochaetes and the chironomids, which were not identified to species.

A comparison of the physiology and ecology of the estuarine isopod Cyathura polita in Massachusetts and Georgia : Frankenberg, D. and W. D. Burbanck, 1963. Biol. Bull., 125 (1): 81–95

A comparison of the physiology and ecology of the estuarine isopod Cyathura polita in Massachusetts and Georgia : Frankenberg, D. and W. D. Burbanck, 1963. Biol. Bull., 125 (1): 81–95

Some observations on the isopod, Cyathura polita in Chesapeake Bay : Burbanck W. D., 1963. Chesapeake Sci., 4 (2): 104–105

Some observations on the isopod, Cyathura polita in Chesapeake Bay : Burbanck W. D., 1963. Chesapeake Sci., 4 (2): 104–105

A comparison of dorsal patterns of the estuarine isopods Cyathura polita of North America and C. carinata of Europe

A comparison of dorsal patterns of the estuarine isopods Cyathura polita of North America and C. carinata of Europe

A COMPARISON OF THE PHYSIOLOGY AND ECOLOGY OF THE ESTUARINE ISOPOD CYATHURA POLITA IN MASSACHUSETTS AND GEORGIA

1. Aspects of the physiology and ecology of two populations of the estuarine isopod Cyathura polita have been studied. One of the populations was located in a beach on Saelo Island, Georgia; the other, in an estuary in Marshfield, Massachusetts. The ecological aspects of the study included habitat observations; analyses of the density, animal size, dispersion and sex ratio of the populations; and investigation of the faunal associations. The physiological aspects included studies of osmoregulatory behavior and oxygen consumption rates. 2. Ecologically, the two populations were similar in a number of respects. They were both found in habitats which had sandy sediments, well aerated water, and wide fluctuations of temperature and salinity. The Sapelo Island population was less dense, and was niade up of smaller animals than the Marshfield population, but they both had clumped dispersion patterns and sex ratios which changed seasonally. The faunal associations were liniited, and although Cyathura polita, and Scoloplos fragilis, were the only species found in both areas, others were closely related. C. polita was one of the niost coninion animals in both associations. 3. The physiological studies showed that cyathurans from the two populations have similar osmoregulatory behavior and oxygen consumption rates. Cyathura polita maintains a body fluid concentration which is hypertonic to its environment at salinities between 1 and 28%o, but which becomes isosmotic with the environment at salinities between 28 and 42%o. The oxygen consumption rate of Cyathura polita is similar to that of other isopods. The rate increases at higher temperatures, but does not change significantly over a salinity range from 1 to 37%o. 4. The physiological similarity of the two populations seems to indicate that distinct physiological races have not developed within the species. This physiological homogeneity may be an example of the evolutionary conservatism of estuarine organisms.

Effects of Salinity and Temperature on Osmoregulation in Two Latitudinally Separated Populations of an Estuarine Isopod, Cyathura polita (Stimpson)

Effects of Salinity and Temperature on Osmoregulation in Two Latitudinally Separated Populations of an Estuarine Isopod, Cyathura polita (Stimpson)

Further Observations on the Biotope of the Estuarine Isopod, Cyathura Polita

A report made by Burbanck in 1959 gave the then known distribution and the typical habitat conditions of Cyathura sp., which has since been established as Cyathura polita (Stimpson, 1855) (Miller and Burbanck 1961). Further studies of the Atlantic and Gulf coasts of the United States have verified the continuous but disjunct distribution of this isopod, confirmed earlier characterization of the biotope and added information on substratum requirements, revealed new associates, and determined the limits of its range. Populations in 10 places not previously visited by the author were studied during 1960-61. Five of these which were in southeastern states were listed in 1961 by Miller and Burbanck, but the following populations have been visited since that listing:

An Ecological Study of the Distribution of the Isopod Cyathura Polita (Stimpson) from Brackish Waters of Cape Cod, Massachusetts

The isopod, Cyathura polita (Stimpson), was found at 40 of 62 estuaries and tidal marshes visited along the shores of Cape Cod, Massachusetts, and nearby areas. The habitats were studied at low tide and were characterized by a stable substrate with some sand present, water in motion, and were located within the range of tidal influehce,, The distance upstream from the mouths of the creeks and rivers vatied, but cyathurans were frequently located below tidal gates, dams, and bridges where the natural environment had been modified by man and at the level of the downstream limits of cattails in unobstructed water- ways. C. polita was usually found at a depth of 5-8 cm in concentrations of from 108/M2 to 1080/M2 and appears euryokous with respect to its chemical environment. No species of macroscopic animals were always associated with C. polita, but those most frequently recorded were Scolecolepides, Heteromastus, nereids, and gammarids. Of three at- tempts made to introduce C. polita into apparently suitable habitats where it did not naturally occur, one at Sandwich was successful and a population with a density of 432/M2 and a linear extent of about 30 m was observed three years after the initial transplant. Populations of C. polita were stable as to location and density over a period of five years, and it is suggested that the numerous populations on Cape Cod may have acted as sources of distribution of the species to more northern locations during the past ninety years. C. polita is at the first trophic level of the food chain and is known to be eaten by winter flounder, brook trout, and black duck. Possible reasons for the absence of C. polita in certain estuaries are given, and it is hoped that cognizance of such factors will aid in the preservation of natural estuarine habitats in the

The Disappearance of Cyathura Polita from the Ashepoo River, South Carolina, After Hurricane "Gracie" in 1959

The Ashepoo River in the state of South Carolina is a dark water river (Figure 1) which flows into the Atlantic Ocean about 30 miles south of Charleston. It is unusual in that it is quite short, being around 35 miles in length. The river is free of industrial wastes and, except for the extreme upper reaches of its headwaters, it is under tidal influence. Although the lower two-thirds of the river meanders, there is a strong current that sweeps the clay-marl sides of the river free of most debris. Dredging, however, showed an accumulation of soft, organic material in the bottom of the central channel.

SYSTEMATICS AND DISTRIBUTION OF AN ESTUARINE ISOPOD CRUSTACEAN, CYATHURA POLITA (STIMPSON, 1855), NEW COMB., FROM THE GULF AND ATLANTIC SEABOARD OF THE UNITED STATES

A new combination, Cyathura polita (Stimpson, 1855), is established for a burrowing anthurid isopod widely distributed along the eastern and southern seaboard of the United States. Although it has long been considered conspecific with C. carinata (Kr\g=fscr\yer), a predominantly European species, morphological comparisons together with zoogeographical considerations, show the American forms are a distinct species first described by Stimpson as Anthura polita. Its known geographical range extends from Louisiana to Maine, with populations found in estuaries, tidal marshes, intertidal areas, etc., where salt and fresh water mix. It apparently requires a relatively stabilized sandy substrate with the stabilizing factor varying with the latitude.