Regina Septemvittata Research Articles

Habitat Use and Niche Partitioning of Regina septemvittata and Nerodia sipedon in a Small Appalachian Stream in West Virginia

The common water snake, Nerodia sipedon, and the queen snake, Regina septemvittata are two species of stream-dwelling water snakes in the Family Natricidae native to the northern panhandle of West Virginia. Nerodia sipedon is a large-bodied generalist, ranging up to 140 cm in length and 400 g in mass, which feeds on many fish and amphibian species. Regina septemvittata is a smaller specialist, reaching only 92 cm in length and 100 g in mass, which primarily consumes freshly molted crayfish. In an ongoing study conducted by students at West Virginia University, I studied the habitat preferences of both of these species in the North fork of Short Creek as there has been little research done on habitat preferences in small streams. Morphological, environmental, and behavioral data on each snake that was captured. Qualitative habitat evaluation indexes (QHEI) were also collected to assess stream health in conjunction with presence and abundance of both species. No significant differences were found in the presence or abundance as it relates to QHEI, but trends show higher rates of presence and abundance in sites with lower QHEI scores. These results suggest that there is minimal interspecific competition of habitat present between N. sipedon and R. septemvittata, as well as support the hypothesis that both species thrive in more disturbed habitats.

The Microhabitat Preferences Based on Relative Density and Stream Assessment of Regina septemvittata in a small West Virginia Stream

Regina septemvittata is a slim-bodied water snake in the family Natricidae that is native to the northeastern United States. Being the only species to consume exclusively freshly molted crayfish, R. septemvittata is categorized as a specialist. The selectivity of prey suggests possible other narrow range preferences including refuge and hunting locations. This study is being conducted in the North Fork of Short Creek in Ohio County, WV. In addition, Nerodia sipedon sipedon is also found within the study stream system. N. s. Sipedon is a generalist water snake species that has been shown to be larger and more aggressive than R. septemvittata. Both species are captured throughout their activity period, April - November, starting in 2018. In addition to environmental and morphological data being recorded at the time of collection, qualitative habitat evaluation indexes (QHEI) were recorded at the initiation of the project. QHEI allows for a more standardized evaluation of the quality of the stream system. The combination of the quality of the stream in 100-meter sections of the stream in addition to snake location data can show relative preferences of R. septemvittata throughout the stream system. The current data suggests a greater preference for disturbed habitat as well as a higher frequency of hot spots in the stream as opposed to their generalist counterparts N. s. sipedon.

Corticosterone in three species of free-ranging watersnakes: Testing for reproductive suppression and an association with body condition

The potentially suppressive effects of the hypothalamic-pituitary-adrenal (HPA) axis on the hypothalamic-pituitary-gonadal (HPG) axis revolve around the central role that glucocorticoids play in mobilizing energy. As an individual's energy balance becomes negative, the HPA axis helps mobilize energy and shifts energy expenditure away from reproduction toward maintenance and survival. While there is evidence in support of these relationships, substantial species variability exists. Studies in a greater diversity of species promise to enhance our understanding of the interactions between these axes. In this field study we tested for relationships among body condition, corticosterone, and sex steroid concentrations in three species of closely related watersnakes: the common watersnake (Nerodia sipedon), the diamondback watersnake (Nerodia rhombifer) and the queen snake (Regina septemvittata). Snakes were sampled before and after a 30 min acute confinement stressor and body condition was estimated using the scaled mass index. All three species exhibited robust elevations of corticosterone in response to acute stress, but only plasma progesterone was elevated by the acute stressor in queen snakes. There was no evidence for a suppression of sex steroid concentrations in any of the species. Body condition was negatively associated with baseline corticosterone in queen snakes and with post-stressor corticosterone in both queen and common watersnakes. Overall we found fairly strong support for the proposed link between corticosterone and energetics in two of the three watersnake species, but no support for the hypothesis that acute stressors are associated with reproductive suppression, at least as measured by steroid concentrations.

Effects of snake fungal disease on short-term survival, behavior, and movement in free-ranging snakes.

Pathogenic fungi are increasingly associated with epidemics in wildlife populations. Snake fungal disease (SFD, also referred to as Ophidiomycosis) is an emerging threat to snakes, taxa that are elusive and difficult to sample. Thus, assessments of the effects of SFD on populations have rarely occurred. We used a field technique to enhance detection, Passive Integrated Transponder (PIT) telemetry, and a multi-state capture-mark-recapture model to assess SFD effects on short-term (within-season) survival, movement, and surface activity of two wild snake species, Regina septemvittata (Queensnake) and Nerodia sipedon (Common Watersnake). We were unable to detect an effect of disease state on short-term survival for either species. However, we estimated Bayesian posterior probabilities of >0.99 that R. septemvittata with SFD spent more time surface-active and were less likely to permanently emigrate from the study area. We also estimated probabilities of 0.98 and 0.87 that temporary immigration and temporary emigration rates, respectively, were lower in diseased R. septemvittata. We found evidence of elevated surface activity and lower temporary immigration rates in diseased N. sipedon, with estimated probabilities of 0.89, and found considerably less support for differences in permanent or temporary emigration rates. This study is the first to yield estimates for key demographic and behavioral parameters (survival, emigration, surface activity) of snakes in wild populations afflicted with SFD. Given the increase in surface activity of diseased snakes, future surveys of snake populations could benefit from exploring longer-term demographic consequences of SFD and recognize that disease prevalence in surface-active animals may exceed that of the population as a whole.

Crayfish Eating in Snakes: Testing How Anatomy and Behavior Affect Prey Size and Feeding Performance.

SynopsisQuantifying the performance of animals is a powerful methodology for determining the functional consequences of morphological variation. For example, snakes consume prey whole, and variation in the anatomy of their trophic apparatus directly affects gape and limits maximal prey size. However, for the foraging ecology of snakes and other systems, scant data exist regarding how often maximal capacities are taxed in nature. Hence, we quantified: (1) maximal gape, (2) the size of prey relative to maximal gape, and (3) how the type and relative size of prey affected behavior and prey handling times (HTs) for two species of natricine snakes that primarily eat soft- (Regina septemvittata) or hard-shelled (Liodytes alleni) crayfish. Liodytes alleni had significantly larger maximal gape than R. septemvittata with equal snout–vent length. The percentages of large prey (>60% maximal gape area) consumed in the field were low in both R. septemvittata (22%) and L. alleni (2%). However, R. septemvittata, especially juveniles, ate relatively larger prey than L. alleni. Strategies for dealing with the seasonal scarcity of small crayfish differed as juvenile R. septemvittata commonly removed and ate only chelipeds from crayfish too large to swallow whole, whereas juvenile L. alleni ate many small odonate nymphs. During laboratory trials, unlike R. septemvittata, L. alleni usually used its body to restrain prey with behaviors that depended on relative prey size and prey hardness. Liodytes alleni consumed soft-shelled crayfish significantly faster than R. septemvittata and significantly faster than hard-shelled crayfish. Several of the differences in gape, prey size, and prey HTs and behavior between the crayfish-eating snakes resemble those between two phylogenetically distant species of homalopsid snakes that consume either hard- or soft-shelled crabs. In both groups of crustacean-eating snakes, the decreased capture success in captivity and the rare consumption of relatively large hard-shelled crustaceans in the field suggest that the ability to capture this type of prey constrains prey size more commonly than maximal gape. Based on data integrating snake size and gape with the relative mass of intact prey, the predicted potential feeding performance R. septemvittata consuming intact prey exceeded that of the other three species.

Evaluating Snake Density Using Passive Integrated Transponder (PIT) Telemetry and Spatial Capture–Recapture Analyses for Linear Habitats

Many snake species are elusive and difficult to study in field settings. As such, little is known about their population ecology despite conservation needs for many species. Advances in field techniques and statistical methods can improve our understanding of snake ecology. We used passive integrated transponder (PIT) telemetry to track Nerodia sipedon (Northern Watersnakes, n = 94) and Regina septemvittata (Queensnakes, n = 119) in six low-order streams in central Kentucky, USA from June to October 2016. We assessed snake density, spatial scale of detection, and detection probability using PIT tag relocations and spatial capture–recapture methods for linear habitats. Specifically, we modeled population density as a function of individual stream and land cover type, spatial scale of detection as a function of sex, and detection probability as a function of sex and time-varying covariates. Individual streams were a better predictor of snake density than land cover type; density estimates ranged from 6 ± 3 N. sipedon/km (mean ± standard error) to 107 ± 17 N. sipedon/km and 6 ± 5 R. septemvittata/km to 63 ± 10 R. septemvittata/km. Female R. septemvittata had a larger spatial scale of detection (55 ± 4 m) than male R. septemvittata snakes (40 ± 4 m). Spatial scale of detection did not differ between sexes for N. sipedon (females: 40 ± 4 m; males: 35 ± 3 m). The combination of PIT telemetry and spatial capture–recapture analyses can effectively estimate population densities and other population parameters for snakes and other reptiles and amphibians associated with linear habitats.

Prey Selection in the Queen snake, Regina septemvittata, in Streams of the Northern Panhandle of West Virginia, U.S.A.

Regina septemvittata (Queen snake) is a semi-aquatic snake occurring throughout central and eastern North America that exhibits extreme dietary specialization, feeding almost exclusively on freshly molted crayfishes. Though it is known R. septemvittata forage on crayfishes, little is understood about prey preferences at the species and genus level. Because different crayfish species have varying life history patterns, and molting frequency is allied to life history attributes, it is not clear whether there is a preference based on crayfish species or prey availability based on molt state. To determine if R. septemvittata has preferences for species, we surveyed four streams in the northern panhandle of West Virginia for R. septemvittata and completed seasonal life history studies on crayfish species occurring in those streams from March through October 2018. Over the collecting season 101 Queen snakes were captured. From these, we recovered 24 prey samples that were subsequently identified using either polymerase chain reaction (PCR) or visual identification. Monthly crayfish sampling was used to determine molting frequency of the two available prey species in the study streams: Cambarus carinirostris and Faxonius obscurus. Preliminary results seem to indicate that freshly molted crayfish availability dictates foraging behavior in R. septemvittata, and a lack of specialization at the taxonomic level occurs in this species.

Ecology of Nerodia sipeodon (Common Watersnake) in North Fork Creek, Ohio County, West Virginia. Elijah Henderson, Dan Meyer and Zachary Loughman, West Liberty University, Dept. of Natural Sciences and Mathematics, West Liberty, WV

The ecology of Nerodia sipeodon (Common Water Snake) was studied concurrently with ecology of Regina septemvittata(Queen Snake) in North Fork of Short Creek, Ohio County, West Virginia. Snakes were captured via hand collection or aquatic funnel traps. All captured animals were measured, weighed, pit-tagged, and underwent gastric lavage when food boluses were present. Snake activity peaked in the spring, followed by a mid-summer brumation period. Activity reoccurred in mid-August through the fall. Trap captures outnumbered hand captures, though most juvenile animals were collected by hand. Frequently encountered food species included Black Nose Dace, Creek Chubs, and Long Nose Dace. Daily activity peaked in the morning hours, was reduced during the heat of the day, and began again in earnest during the late afternoon and early evening hours. Though concerted effort was undertaken to collect them, zero gravid females were collected with this study. Neonates appeared in the population beginning in late August. The most frequently encountered behavior was basking, followed by various defensive behaviors allied with capture. To date, close to 50 individual snakes have been PIT tagged and released at the study stream. Future efforts will focus on the use of radio telemetry, as well as the capture of gravid females.

Habitat requirements of two common aquatic snakes, Regina septemvittata and Nerodia sipedon sipedon

Regina septemvittata (Queen Snakes)and Nerodia sipedon sipedon (Common Watersnake) are semi-aquatic colubrid snakes that utilize streams for their primary source of prey. Both species are currently listed by the International Union for Conservation of Nature as stable. The goal of this study was to determine which specific habitat aspects affect the presence or absence of R. septemvittata and N. sipedon sipedon. Snakes were collected in the summer and fall of 2017 from August to October in North Fork of Short Creek, a 3rd order stream located just south of West Liberty, WV. Using the Ohio QHEI form to quantify stream quality and program PRESENCE to generate Logistic Regression Models, stream sub-habitat types were compared with occurrence data. Resulting models revealed which specific sub-habitat types were associated with positive occurrence. Univariate models selected for riparian zone determined by the width and predominant cover present with an AIC weight of 0.499. Multivariate models selected riparian zone with an AIC of 0.372 and riparian plus total stream health with AIC of 0.185. Our preliminary data indicates that snake presence is related to both riparian zone and water quality. This suggests that sufficient cover quality and stream health are required to maintain populations of Regina septemvittata and Nerodia sipedon sipedon.

Maternal investment and delayed feeding in neonatal Lake Erie watersnakes: a life‐history strategy

AbstractNeonatal growth can have lasting consequences on survival and reproduction. In many taxa, larger, faster growing neonates experience higher survival, reach sexual maturity more rapidly, and achieve higher lifetime fecundity. In contrast to their closest relatives, Lake Erie watersnakes grow slower, mature later, and may delay feeding until after their first hibernation. To determine if Lake Erie watersnakes do indeed delay feeding until after their first hibernation, we compared age class 0 (between birth and first hibernation) and age class 1 (emergence from hibernation and through the first full season) snakes in the field and in the laboratory. In the field, only 0.6% of pre‐hibernation neonates were found to contain prey, while 11.9% of post‐hibernation neonates contained prey. During captive feeding experiments, the probability of eating was positively correlated with age (binary logistic regression, Wald = 25.354, P < 0.001). To clarify the underlying mechanism for delayed feeding, we compared neonatal yolk and fat reserves among species with delayed feeding (Lake Erie watersnakes, Graham's crayfish‐eating snakes), species that commence feeding immediately after birth (common gartersnakes, Dekay's brown snakes) and a species falling between these extremes (queen snakes). Like Lake Erie watersnakes, Graham's crayfish‐eating snakes contained large energy reserves (yolk + fat body mass to carcass mass ratio = 0.39 and 0.24, respectively), common gartersnakes and Dekay's brown snakes lacked measurable reserves (0.00), and queen snakes contained intermediate reserves (0.17). Taken together, this evidence suggests that neonatal Lake Erie watersnakes do delay feeding until after their first hibernation and contain large energy reserves at birth to facilitate this behavior. While most snake life‐history studies have focused on the trade‐off between offspring size and number, Lake Erie watersnake females invest large amounts of energy in offspring condition.

Extending the latent multinomial model with complex error processes and dynamic Markov bases

The latent multinomial model (LMM) of Link et al. [Biometrics 66 (2010) 178–185] provides a framework for modelling mark-recapture data with potential identification errors. Key is a Markov chain Monte Carlo (MCMC) scheme for sampling configurations of the latent counts of the true capture histories that could have generated the observed data. Assuming a linear map between the observed and latent counts, the MCMC algorithm uses vectors from a basis of the kernel to move between configurations of the latent data. Schofield and Bonner [Biometrics 71 (2015) 1070–1080] shows that this is sufficient for some models within the framework but that a larger set called a Markov basis is required when errors are more complex. We address two further challenges: (1) that models with complex error mechanisms may not fit within the LMM framework and (2) that Markov bases can be difficult to compute for studies of even moderate size. We extend the framework to model the capture/demographic and error processes separately and develop a new MCMC algorithm using dynamic Markov bases. Our work is motivated by a study of queen snakes (Regina septemvittata) and we use simulation to compare estimates of survival rates when snakes are marked with PIT tags which have perfect identification versus brands which are prone to error.

Composition of native crayfish assemblages in southern Ontario rivers affected by rusty crayfish (Orconectes rusticus Girard, 1852) invasions – implications for endangered queensnake recovery

Orconectes rusticus (rusty crayfish) is an aggressive and prolific aquatic invader. Where introduced, it has caused dramatic ecosystem changes, including the replacement of native crayfishes. In Canada, it was first reported in Lake of the Woods in northwestern Ontario and a small number of south-central Ontario lakes during the 1960s. It has subsequently spread to other regions of the province. Its current expansion into southwestern Ontario rivers presents an unknown risk to the endangered queensnake (Regina septemvittata), an obligate feeder on freshly molted crayfish. We sampled 99 river sites across southern Ontario to: (i) describe crayfish assemblages within river reaches currently occupied by Queensnake; and, (ii) characterize the impact of O. rusticus on native crayfish assemblages. O. rusticus was caught at 41% of sites sampled, and was the only species at 24% of sites. The abundance, richness, and within-site distribution of native crayfishes were all significantly lower at sites with O. rusticus. Within the distribution of queensnake, crayfish assemblages were almost entirely dominated by O. propinquus, with O. rusticus being absent. However, O. rusticus was found along the lower Speed River, where only one dam separates it from Grand River queensnake populations. Given its past spread, O. rusticus will likely be introduced into areas used by queensnake and replace O. propinquus (the primary prey of queensnake). The adaptability of queensnake to prey upon non-native crayfish is unknown and requires investigation.

Operating Body Temperatures in a Snake Community of Northern Virginia

Thermal data were collected from 15 of 16 species of snakes found at the Mason Neck National Wildlife Refuge, Fairfax County, VA. Data recorded at each capture included the date, 24-hour military time, body temperature (BT), air temperature (AT), ground-surface temperature (ST), water temperature (WT) if in water, and the snake's activity (under cover, moving on land, basking, foraging, climbing, swimming, courting/mating). The purpose of this study was to determine the potential range of operating body temperature (OBT) of the individual species. The range of OBT is interpreted as the snake's operating temperature at its current environmental temperatures (ET), which can be used in comparisons with similar data from other North American regions, and represents the first such report from the Mid-Atlantic Region. The mean and ranges of BT, AT, ST, and WT are presented for the eight snakes with 20 or more records: Carphophis amoenus (n = 238), Coluber constrictor (204), Nerodia sipedon (67), Thamnophis sirtalis (55), Diadophis punctatus (54), Pantherophis alleghaniensis (43), Thamnophis sauritus (26), and Agkistrodon contortrix (24). New thermal records are reported for several of these species. The ranges of BT during activities are also reported. New temperature records are also reported for Virginia valeriae (n = 16 encounters), Storeria dekayi (12), Opheodrys aestivus (6), Lampropeltis calligaster (6), and Regina septemvittata (2).

INTER‐ AND INTRASPECIFIC VARIATION IN MERCURY BIOACCUMULATION BY SNAKES INHABITING A CONTAMINATED RIVER FLOODPLAIN

Although mercury (Hg) is a well-studied contaminant, knowledge about Hg accumulation in snakes is limited. The authors evaluated Hg bioaccumulation within and among four snake species (northern watersnakes, Nerodia sipedon; queen snakes, Regina septemvittata; common garter snakes, Thamnophis sirtalis; and rat snakes, Elaphe obsoleta [Pantherophis alleghaniensis]) from a contaminated site on the South River (Waynesboro, VA, USA) and two nearby reference sites. Total Hg (THg) concentrations in northern watersnake tail tissue at the contaminated site ranged from 2.25 to 13.84 mg/kg dry weight (mean: 4.85 ± 0.29), or 11 to 19 times higher than reference sites. Blood THg concentrations (0.03-7.04 mg/kg wet wt; mean: 2.24 ± 0.42) were strongly correlated with tail concentrations and were the highest yet reported in a snake species. Within watersnakes, nitrogen stable isotope values indicated ontogenetic trophic shifts that correlated with THg bioaccumulation, suggesting that diet plays a substantial role in Hg exposure. Female watersnakes had higher mean THg concentrations (5.67 ± 0.46 mg/kg) than males (4.93 ± 0.49 mg/kg), but no significant differences between sexes were observed after correcting for body size. Interspecific comparisons identified differences in THg concentrations among snake species, with more aquatic species (watersnakes and queen snakes) accumulating higher mean concentrations (5.60 ± 0.40 and 4.59 ± 0.38 mg/kg in tail tissue, respectively) than the more terrestrial species, garter snakes and rat snakes (1.28 ± 0.32 and 0.26 ± 0.09 mg/kg, respectively). The results of the present study warrant further investigation of potential adverse effects and will aid in prioritizing conservation efforts.

Behavioral Responses of a Dietary Specialist, the Queen Snake (Regina septemvittata), to Potential Chemoattractants Released by Its Prey

Queen Snakes (Regina septemvittata) are extreme dietary specialists, feeding nearly exclusively on freshly molted crayfish. To elucidate specific cues that mediate prey detection and foraging behavior in R. septemvittata, we examined the response of R. septemvittata and the dietary generalist Nerodia sipedon sipedon, to chemical compounds produced by crayfish during the molting cycle. Ingestively naive neonate snakes were presented with 20-hydroxyecdysone, ecdysone, methyl farnesoate, ponasterone A, xanthurenic acid, and distilled water. Their response was measured using a modification to the tongue-flick attack score. Regina septemvittata exhibited an elevated tongue-flicking response to ecdysone, whereas N. s. sipedon exhibited no differential responses to these same arthropod molting chemicals. In a second experiment, R. septemvittata showed a two-fold higher tongue-flicking response to intermolt crayfish extract that contained ecdysone than to intermolt crayfish extract alone, whereas N. s. sipedon demonstrated no differential response between these extracts. In a third experiment consisting of feeding trials, R. septemvittata was offered live intermolt crayfish with and without ecdysone. The presence of ecdysone increased the feeding scores of R. septemvittata. When ecdysone was present, crayfish were ingested in five of the seven trials, but when ecdysone was absent crayfish were not ingested in any trial. These results suggest that ecdysone may play a critical role in the interaction between R. septemvittata and their prey. With numerous stream contaminants known to imitate ecdysone and disrupt the arthropod molting cycle, this finding may have important implications for the conservation of R. septemvittata.

The interaction of food motivation and experience in the ontogeny of chemoreception in crayfish snakes

Precocial offspring are often required to recognize and acquire food without assistance. In addition, they must be able to respond to changes in prey availability. We studied two species of crayfish snake (Regina septemvittata and R. grahamii) to compare the effect of the availability of their preferred prey, freshly moulted crayfish, on the ontogeny of chemosensory response towards different prey types (fish, odonate larvae, intermoult crayfish and freshly moulted crayfish). A split litter design was used; within each species, litters were divided into three groups for testing at different ages (7, 14 and 21 days) and then within each age group, individuals were assigned to treatment groups that were fed or not fed prior to testing. The results of this study confirm that R. grahamii and R. septemvittata are born with chemosensory prey preferences that reflect their specialized diets. However, the ontogeny of these preferences is modified by food availability and available energy levels. Significantly, the pattern of development that emerged in the groups deprived of food differed between species. Regina septemvittata neonates had limited yolk and fat reserves and rapidly increased their interest in alternative prey types, whereas R. grahamii neonates, with significantly more reserves, did not increase their responses to alternative prey. These differences may reflect alternative survival strategies of newborn snakes that have different amounts of energy reserves at birth.

Feeding Ecology of Nerodia rhombifera in a Veracruz Swamp

In Mexico, the niche of non-venomous water snakes is occupied by two genera of thamnophiine snakes, Thamnophis (garter snakes) and Nerodia (water snakes). Both genera are widely distributed in Mexico, but are sympatric only in the coastal slopes (Conant, 1963, 1969). Nerodia rhombifera and T. proximus are found throughout the Gulf coast both at freshwater and brackish ponds, marshes, and swamps, mainly near river estuaries (Rossman, 1963; Conant, 1969). Recent ecological studies of these genera in Mexico have reported on single or mixed populations of garter snakes (T. eques, T. melanogaster, and T. rufipunctatus; Sosa, 1982; Drummond, 1983; Macias Garcia and Drummond, 1988; Drummond and Macias Garcia, 1989). The ecology of Mexican populations of Nerodia, whether allopatric or sympatric with Thamnophis, is largely unknown. Several studies have reported ecological differences between N. rhombifera and sympatric water snakes and queen snakes (Regina spp.) on the Gulf coast of the United States (Mushinsky and Hebrard, 1977a, b; Hebrard and Mushinsky, 1978; Mushinsky et al., 1980, 1982) related to diet, use of time, and microhabitat. Nerodia rhombifera is regarded mainly as a fish-eater (Clark, 1949; Mushinsky and Hebrard, 1977a; Mushinsky et al., 1982; Plummer and Goy, 1984), but also feeds on anurans (Clark, 1949). Our aim was to describe the use of microhabitats, daily activity patterns, and diet in Nerodia rhombifera werleri in Alvarado, Ve-

Description of the o�cysts of Eimeria septemvittata n. sp. (Apicomplexa: Eimeriidae) from queen snakes, Regina septemvittata (Serpentes: Colubridae), in Arkansas

Coccidian oocysts recovered from the feces of queen snakes, Regina septemvittata, from Arkansas, USA, were found to represent a previously unreported eimerian. Oocysts of Eimeria septemvittata n. sp. are spherical or subspherical, 14.6×14.0 (12–16×12–15) μm, with a thin, bi-layered wall; the shape-index (length/width) is 1.04 (1.00–1.17). The micropyle and oocyst residuum are absent but a large polar granule is present. The sporocysts are ovoidal, 11.3×5.6 (9.5–13.5×5–6) μm and possess a Stieda body; the shape-index is 2.02 (1.81–2.50). Each sporozoite contains a large, centrally located refractile body and a generally smaller, posterior refractile body.

Permeability and channel structure of reptilian skin.

A study of the permeability of shed epidermis from some terrestrial and freshwater snakes was conducted. Permeability to Br, Na, and K ions was very low and showed a higher influx than efflux in most cases. Permeability to the smaller water molecule was much greater, and in contrast efflux was higher than influx. Skins from aquatic snakes with larger water permeabilities also showed greater permeabilities to Na and K. The highly aquatic Regina septemvittata has the most permeable skin of any snake. Ethanol fluxes were higher than expected for a tracer of its size, perhaps due to its solubility in lipid. Na fluxes through whole live skins of Nerodia cyclopion floridana in vitro were not significantly different from those of the shed skin alone. Isolated hinge regions showed complete water impermeability, suggesting that channels through the skin are located only in the scale region. Dermal water efflux into dry air was considerably less than water-to-water efflux. Lipid extraction increased permeability markedly and eliminated the asymmetry of water and ion fluxes. Lipid replacement with linoleic acid restored half of the water impermeability lost during extraction. Protein extraction did not significantly increase membrane permeability but did eliminate the permeability difference between dry and hydrated skins. Two sizes of lipid-lined channels extending through a protein matrix are suggested as a possible model for snake skin. The diameter of the channels apparently varies in relation to the differing water, Na, and Cl concentrations on opposite sides of the skin, but the mechanism of this adjustment is unknown.

Serological Relationships among Some Colubrid Snakes

Sera of 22 species of colubrid snakes were studied by immunoelectrophoresis using antisera against serum proteins of Coluber constrictor, Elaphe vulpina, Natrix sipedon, Naja naja and Crotalus horridus to develop the preparations. Development of a snake serum with its homologous antiserum gives a pattern of seven or eight precipitin arcs. Some of these represent components widely shared among snakes, while others are more or less specific for closely related taxa. Two serological groups can be distinguished in our material. One consists of Elaphe (3 sp.), Lampropeltis (2 sp.) and Pituophis melanoleucus. The other group consists of Natrix (4 sp.), Thamnophis (2 sp.), and Regina septemvittata. Serologically these groups are as distinct from each other as they are from Naja and Crotalus. Coluber constrictor is somewhat intermediate between the two but closer to Elaphe. Three Old World colubrids, Coluber jugularis, C. ravergieri and Spalerosophis diadema, are serologically intermediate between Coluber constrictor and Elaphe. Malpolon monspessulanus and Psammophis schokari are also intermediate but slightly closer to Coluber. The affinities of Trimorphodon biscutatus are more nearly with Elaphe than with Coluber or Natrix. Leptodeira maculata and Heterodon platyrhinos do not fit the above groups nor do they appear to be closely related to one another.