Obsoleta Say Research Articles

Additional comments on the types and nomina of several North American ratsnakes (Pantherophis obsoletus complex, Colubridae, Serpentes)

Here, we provide updates to our recent paper reviewing the taxonomy and nomenclature of the Eastern ratsnakes (Pantherophis obsoletus complex, Colubridae, Serpentes). Specifically, we clarify that Coluber alleghaniensis Holbrook, 1836 is a subjective, rather than objective, senior synonym of Elaphis holbrookii Duméril, Bibron & Duméril, 1854. Contrary to our statement that USNM 1733–4 were syntypes of Scotophis lindheimerii Baird & Girard, 1853, the former is the holotype and the latter is the paratype. The holotype is lost and the paratype is in poor condition, but no neotype designation is warranted at present. We note that USNM 248870, which we designated as the lectotype of Coluber obsoletus lemniscatus Cope, 1888, was originally cataloged as USNM 4710. This catalog number was shared with the type of the salamander Amblystoma tenebrosum Baird & Girard, 1852, and the snake was re-cataloged as USNM 248870 in 1985. Finally, we originally treated C. reticulatus La Cépède, 1789 and C. reticularis Daudin, 1803 as senior subjective synonyms of C. corais Boie, 1827, but here corroborate recent authors in designating it a senior subjective synonym of C. obsoletus Say in James, 1823. As the Commission suppressed C. reticulatus La Cépède, 1789 (an exoplonym), this subsequently rendered C. reticularis Daudin, 1803 (an exoploneonym) unavailable as well.

The effect of constant and fluctuating incubation temperatures on the phenotype of black ratsnakes (Elaphe obsoleta)

According to the maternal manipulation hypothesis, females manipulate the phenotypes of their offspring by selecting favourable incubation conditions. In oviparous black ratsnakes ( Elaphe obsoleta Say in James, 1823), females manipulate offspring phenotype through nest-site selection. This study aimed to determine whether the thermal mean and variance of the incubation regime affect fitness-related traits in hatchlings. We incubated 136 eggs in a split-clutch design at two thermal means (26 and 29 °C) and variances (constant and ±3 °C). Hatchlings incubated at higher temperatures hatched earlier, were longer, faster, and less defensive. Hatchlings incubated at constant temperatures hatched earlier and were longer. For athletic performance, there was a significant interaction between temperature mean and variance: hatchlings incubated at 29 °C swam faster, had a lower muscular strength, and righted themselves equally fast when incubated at constant temperatures, whereas hatchlings incubated at 26 °C were stronger, swam faster, and righted themselves more slowly. Overall, constant incubation temperatures produced hatchlings with phenotypes favouring higher survival than fluctuating temperatures, but the effect of thermal variance was not as pronounced as the effect of thermal mean. Therefore, we found some support for the hypothesis that black ratsnakes prefer communal over single-female nests because communal nests have higher, more constant temperatures.

How Does Habitat Patch Size Affect Animal Movement? An Experiment with Darkling Beetles

We used an experimental model system consisting of darkling beetles (Coleoptera: Tenebrionidae, Eleodes obsoleta Say) in a microlandscape to assess the effects of habitat patch size on the movement patterns of animals. The ratio of habitat area to nonhabitat in a 25-m2 “microlandscape” was held constant while the grain of patchiness (patch size) was varied in four treatments. Beetle movement pathways were electronically surveyed, and seven pathway metrics were used to quantify movement characteristics. ANOVA and Fisher’s Protected Least Significant Difference post hoc comparisons revealed that both the presence and the grain of spatial heterogeneity influenced how animals moved through landscapes. Intermediate patch sizes elicited the strongest behavioral responses, whereas movements were similar between finely patchy landscapes with small habitat patches and coarsely patchy landscapes with larger habitat patches. These results indicate that organisms may use landscapes that possess different configurations of habitat in similar ways. Predicting how organisms respond to spatial heterogeneity therefore requires an assessment of how organisms use landscapes, in addition to an assessment of the structural characteristics of landscapes, such as grain size.

HOW DOES HABITAT PATCH SIZE AFFECT ANIMAL MOVEMENT? AN EXPERIMENT WITH DARKLING BEETLES

We used an experimental model system consisting of darkling beetles (Coleoptera: Tenebrionidae, Eleodes obsoleta Say) in a microlandscape to assess the effects of habitat patch size on the movement patterns of animals. The ratio of habitat area to nonhabitat in a 25-m2 “microlandscape” was held constant while the grain of patchiness (patch size) was varied in four treatments. Beetle movement pathways were electronically surveyed, and seven pathway metrics were used to quantify movement characteristics. ANOVA and Fisher’s Protected Least Significant Difference post hoc comparisons revealed that both the presence and the grain of spatial heterogeneity influenced how animals moved through landscapes. Intermediate patch sizes elicited the strongest behavioral responses, whereas movements were similar between finely patchy landscapes with small habitat patches and coarsely patchy landscapes with larger habitat patches. These results indicate that organisms may use landscapes that possess different configurations of habitat in similar ways. Predicting how organisms respond to spatial heterogeneity therefore requires an assessment of how organisms use landscapes, in addition to an assessment of the structural characteristics of landscapes, such as grain size.

The effect of water flow on movement, burrowing, and distributions of the gastropod Ilyanassa obsoleta in a tidal creek

Small-scale population densities of tidal creek eastern mudsnails, Ilyanassa obsoleta Say (studied in 1986 and in 1992 at West Meadow Creek, Stony Brook, New York) corresponded more to variation in water flow velocity than to surface sediment chlorophyll a. Higher densities were found at low flow sites. Short-term behavioral responses are likely to be responsible for density variation. Experiments using laboratory flumes and field observations both demonstrated that the snails responded to strong flow by burrowing into the substratum. Burrowing may prevent dislodgment from the sediment surface, but it also appears to be disadvantageous since burrowed mudsnails have smaller amounts of food in their guts. Snails released in sites of periodic high flow conditions moved greater distances and were soon found near the quiet-water periphery of the creek, whereas snails released at the quiet-water periphery moved far less. It is not clear whether movement from the high flow site was through crawling or through hydrodynamic transport. Laboratory flume experiments demonstrated an active crawling movement towards areas of lower current velocity. This evidence suggests that strong bottom flow in the creek center results in a combined response of burial to avoid dislodgment and a net movement towards quiet water, which reduces exposure to the high velocity conditions of the creek center.

A Comparison of the Effectiveness of Tri-N-Butyltin Chloride and Five other Organotin Compounds in Promoting the Development of Imposex in the Dog-Whelk, Nucella Lapillus

Populations of the common dog-whelk Nucella lapillus (L.) are declining or have already disappeared at many sites on rocky shores around the United Kingdom (Bryan et al. 1986). There is conclusive evidence that this is caused mainly by tributyltin (TBT) compounds leached from ships' antifouling paints (Bryan et al. 1987). These compounds impose male sexual characters (or imposex) on female N. lapillus. Other stenoglossan gastropods including Nassarius obsoletus Say (Smith, 1981a) and Ocenebra erinacea (L.) (Féral & Gall, 1982) are similarly affected by TBT. The intensity of expression of imposex in N. lapillus can generally be related to the sea water concentration of TBT. The appearance of a small penis and the partial development of a vas deferens first occurs at TBT concentrations below 0.5 ng/1 (as tin), although reproduction appears to be unaffected at this level. At 1–2 ng Sn/1 penis size is markedly increased and in some females proliferation of vas deferens tissue overgrows the genital papilla, thus sterilizing the animal. At slightly higher concentrations virtually all females become sterilized and at around 10 ng Sn/1 oogenesis is suppressed and spermatogenesis initiated (Gibbs, Pascoe & Burt, 1988). Since development is direct and there is no planktonic stage, N. lapillus has a very limited capacity for dispersion: thus the sterilization of females heralds the almost certain decline of so affected populations (Gibbs & Bryan, 1986).

Heavy metal effects on cellular shape changes, cleavage, and larval development of the marine gastropod mollusk, (Ilyanassa obsoleta Say).

The spawning areas for many marine invertebrates are in intertidal zones which can be exposed to surface water run-off containing heavy metals. The cellular shape changes and cleavage patterns of Ilyanassa embryos greatly resemble those of bivalve mollusks, such as Mytilus edulis, that occur in the same intertidal areas. Determining the concentrations of heavy metals tolerated by the molluscan embryos inhabiting such clam and mussel beds therefore is of some economic significance. Moreover, such research may providedata on the heavy metal effects on the cytoskeleton. There is increasing evidence that components of the cytoskeleton, directly or indirectly, are targets for toxic agents. Polar lobe formation is a cellular shape change that resembles cytokinesis. It is seen in the fertilized eggs of many marine mollusks. Recent data with inorganic and organic Ca/sup 2 +/ antagonists suggest that both polar lobe formation and cytokinesis utilize Ca/sup 2 +/ released from sequestered, intracellular sites. Both of these cellular constrictions are associated with microfilaments and are preceded by activation steps requiring microtubules. The data presented below suggest that several heavy metals affect the microfilament-dependent steps.

Marine succession: The effect of two deposit-feeding gastropod species on the population growth of Paranais litoralis Müller 1784 (oligochaeta)

The hypothesis that persistent populations of the mud snails Hydrobia totteni Morrison and llyanassa obsoleta Say in salt marsh mud flats affect the population growth of a more ephemeral oligochaete, Paranais litoralis Müller is tested. Using experimental microcosms, we demonstrate that both snail species affect negatively the rate of population increase of the oligochaete. For Hydrobia, oligochaete population density eventually reaches the same approximate maximum, irrespective of snail density. This may relate to the penetration by worms of initially anoxic deeper sediments. For llyanassa, maximum population density is depressed with increasing snail density, which may relate to the complete sediment disruption caused by the latter snail species. Staggered cycles of population increase and decrease with changing snail density would make a consistent density effect nearly impossible to identify in normal field sampling. However, our results suggest that persistent snail populations may explain the relative rarity of polychaete population explosions in mud flats, except when the local persistent biota has been wiped out via disturbance or predation.

Male characteristics on female mud snails caused by antifouling bottom paints.

This study continues an investigation of an anatomical abnormality, named 'imposex', which consists of a superimposition of male characteristics on to a functionally normal female reproductive anatomy of the dioecious snail Nassarius obsoletus Say. Imposex is prevalent in natural populations living near yacht basins and rarely found distant from them. In the current study caged snails were transferred between a yacht basin and a distant 'clean' locality where the natural population of snails was normal. Imposex was induced in some normal snails kept at the marina and suppressed, but not lost in abnormal snails kept at the clean locality. A similar positive result was obtained in the laboratory by exposing normal snails to organotin-containing antifouling paints and abnormal snails to clean sea water. Results were negative in parallel tests of various marina-associated materials which did not contain organotin. The laboratory studies have thus identified a causative factor for the anatomical abnormalities common near yacht basins in the natural environment. They also provide a rare, if not unique, example of a chemical agent which causes the appearance of superfluous anatomical features in an animal.

Reproductive anomalies in stenoglossan snails related to pollution from marinas

Over 3090 snails of the dioecious intertidal species Nassarius obsoletus Say were collected from a total of 71 localities. Their reproductive anatomy was examined for a superimposition of male characteristics on to the normal female anatomy, an abnormality called 'imposex'. Imposex was rated numerically in terms of the fraction of the population affected and the intensity of expression in bearer snails. An initial survey of 22 localities in Fairfield and Westport, Connecticut, led to the hypothesis that imposex was related to a substance arising from marinas. This was tested at nine pairs of marina and control localities in Long Island Sound, as well as six pairs along a transect ranging from Rhode Island to Georgia. Imposex scores were significantly higher at the marina locality in every pair. Further confirmation was found in a detailed survey of the estuarine harbor at Southport, Connecticut, which showed that adjacent populations could differ in the amount of imposex to the extent that both the snails and the waters they lived in remained separated by natural or man-made barriers. Imposex has been found in populations of N. obsoletus ranging from Damariscotta, Maine, to Savannah, Georgia, and it has been reported from San Francisco Bay, California. Similar anatomical abnormalities have been reported in at least 27 other species of taenioglossan and stenoglossan snails, extending the range to the Atlantic and Mediterranean coast of Europe and the British Isles. Concern is raised regarding the possible existence of another global pollutant with novel effects on marina biota.

Etude par cytochimie ultrastructurale des corpuscules périnucléaires présents dans les jeunes oocytes de Ilyanassa obsoleta Say (Mollusca gastéropode)

ABSTRACT An ultrastructural cytochemical study of the perinuclear corpuscles found in young oocytes of Ilyanassa obsoleta Say (molluscan gastropod) Ultrastructural study of the perinuclear region of young oocytes of Ilyanassa obsoleta shows the existence of numerous corpuscles which we have called ‘perinuclear corpuscles’. These are composed of filaments, of variable thickness (15–45 nm) and frequently show contacts with the nuclear envelope. With the development of the oocyte, they scatter in the cytoplasm and then disappear. Treatment of ultrathin sections by pronase or by pepsin provokes the disappearance of the main part of the perinuclear corpuscle. The residual structures of these corpuscles are not digested either by RNase or by DNase. However, if a digestion is carried out with DNase and pronase together, it increases the contrast of the residual structures. On the other hand, the contrast of the perinuclear corpuscles is not altered by specific techniques for polysaccharides. The constitution and the role of the perinuclear corpuscles is discussed.

A Comparative Study of the Susceptibility and Response of Eight Species of Marine Pelecypods to the Trematode Himasthla quissetensis

Specimens of eight species of marine pelecypods, Crassostrea virginica, C. gigas, Mytilus edulis, Modiolus demissus, Ensis directus, Mya arenaria, Mercenaria mercenaria, and Tapes philippinarum, were individually challenged with 150 Himasthla quissetensis cercariae in order to study their susceptibility and reactions. Quantitative recovery rates are given. Metacercariae were found encysted in various tissues of all of the pelecypods except C. virginica and C. gigas. In C. virginica few metacercariae were found in blood vessel lumina. Except in T. philippinarum, when metacercariae were found in tissues, they were enveloped by a non-cellular, parasite-secreted inner cyst wall. In T. philippinarum, only those metacercariae found in the testes were enveloped by such a wall. In addition to the inner wall, an outer wall, comprised of host leucocytes and either myofibers or connective tissue fibers, surrounded encysted metacercariae in most instances. The fibrous constituent of the outer wall appeared to be dependent on the type of fibers available in the immediate proximity, while the leucocytes are believed to be attracted by the inner wall. Encysted metacercariae were found on the gill and mantle surfaces of C. virginica and C. gigas and on the palps of M. edulis. These are believed to be inactivated, and thus prevented from invading the molluscs, by some host-elaborated substance. Adults of the echinostomatid trematode Himasthla quissetensis (Miller and Northrup) were originally described by Stunkard (1937) from gulls, Larus argentatus Pontoppidan, which were experimentally infected with metacercariae in molluscs which had been exposed to Cercaria quissetensis Miller & Northrup, 1926, a larval trematode of the mud snail, Nassarius obsoletus Say, collected at Woods Hole, Massachusetts. In one abstract (Stunkard, 1934) and two papers (Stunkard, 1937, 1938), Stunkard reported the life cycle of this parasite. In these papers he recorded that seven species of marine molluscs, Mya arenaria L., Modiolus modiolus L., Mytilus edulis L., Cumingia tellinoides Conrad, Aequipecten irradians L., Ensis directus Conrad, and Crepidula fornicata L., were compatible second intermediate hosts into which the cercariae penetrated and encysted. He reported encystment in the mantle, gills, and foot of these molluscs. Uzmann (1951) reported that the soft clam, Mya arenaria, is an important second intermediate host of H. quissetensis in nature since he found 43 to 100% of the samples of this clam from Merrimac Bay, Plum Island Sound, and Annisquam River, Massachusetts, and 90% of 50 specimens of this clam from St. Andrews, New Brunswick, Canada, to harbor metacercariae of this trematode. During a recent survey of the parasites of Nassarius obsoletus in Narragansett

A Time Schedule of the Meiotic and Early Mitotic Stages ofIlyanassa

SUMMARY1. The characteristics and duration of the meiotic and mitotic stages during the early development of the prosobranch gastropod Ilyanassa = Nassarius obsoletus Say were studied. These were correlated with the external morphology of the egg and blastomeres.2. At 23±1°C. the duration of metaphase and anaphase, both meiotic and mitotic, is about 10 minutes. Telophase I lasts 10 minutes; telophase II, 30 minutes; and the mitotic telophases 25 minutes. Prometaphase II lasts 10 minutes as does the prometaphase before the first cleavage. Prometaphase before the second and third cleavage lasts 5 minutes. Interphase has a duration of 30 minutes and prophase a duration of 25 minutes.

Pelagic Larvae of New England Intertidal Gastropods. I. Nassarius obsoletus Say and Nassarius vibex Say

Pelagic Larvae of New England Intertidal Gastropods. I. Nassarius obsoletus Say and Nassarius vibex Say

THE SEASONAL INFESTATION OF NASSA OBSOLETA (SAY) WITH LARVAL TREMATODES

From the data resulting from the examination of almost nine thousand specimens of Nassa obsoleta Say it seems clear that there is a semi-annual rise and fall in the larval trematode infestation. In view of the fact that none of the adults of these larvæ are known it is difficult to explain these phenomena. In all probability migrations of the definitive hosts, and the degree of their infestation, affect the seasonal fluctuations; and other factors are probably the life span of Nassa, and the effect of parasitism upon it. The relative importance of these factors is not clear.