Renal sexual segment of the Cottonmouth snake, Agkistrodon piscivorous (Reptilia, Squamata, Viperidae)

The seasonal variation of the renal sexual segment (RSS) of males of the Cottonmouth snake, Agkistrodon piscivorous, is described using light and electron microscopy. This study is the first to describe the ultrastructure of the RSS of a viper (Viperidae) and only the fourth on a snake. Renal sexual segments from males collected February to May and from August to November are similar in appearance. The cells are eosinophilic and react with periodic acid/Schiff procedure (PAS) for neutral carbohydrates and bromphenol blue (BB) for proteins. At the ultrastructure level, the cells contain large (2 microm diameter), electron-dense secretory granules and smaller vesicles with a diffuse material, and these structures abut against the luminal border and upon clear vacuoles continuous with intercellular canaliculi. Evidence was found for both apocrine and merocrine processes of product release. In June and July, the RSS are significantly smaller in diameter, largely basophilic, and have only scattered granules that are PAS+ and BB+. Cytologically, the RSS from June to July lack electron-dense secretory granules and the smaller vesicles with diffuse material. Numerous condensing vacuoles and abundant rough endoplasmic reticulum, however, indicate that active product synthesis is occurring. This is the first report of significant seasonal variation in the histology and ultrastructure of the RSS of a snake, although such reports exist for lizards. The seasons when the RSS is most highly hypertrophied correspond to the fall and spring mating seasons of A. piscivorous, as determined by other studies.     

PCR primers for microsatellite loci in the tiger rattlesnake (Crotalus tigris,Viperidae)

The tiger rattlesnake (Crotalus tigris) is found only in the Sonoran Desert of North America, where it inhabits rocky foothills that are increasingly being affected by urban encroachment. In order to continue a long‐term study of the demography and movements of tiger rattlesnakes around Tucson, Arizona, we identified six novel polymorphic microsatellite loci for this species. All loci exhibited high variability (five to 41 alleles). These markers are useful for studies of paternity, population structure, and assessing appropriate destinations for translocated animals.     

A New Species of the Genus Protobothrops(Squamata: Viperidae) from Southern Tibet,China and Sikkim,India

A new species of the genus Protobothrops Hoge Romano-Hoge, 1983, was described from Jilong County, southern Tibet, China, and Chungthang, northern Sikkim, India. It differs from congeners by the following characters: 1) relatively large body size(total length up to 1510 mm); 2) dorsal scale rows 25–25–19; 3) except for the smooth outermost row, dorsal scales are weakly keeled; 4) relatively high number of ventral(198–216) and subcaudal(65–76 pairs) scales; 5) 7–8 supralabials; 6) 11 to 13 infralabials; 7) dorsal head uniform dark brown, laterally a reddish-brown obscure postocular streak; 8) dorsum of trunk and tail olive, with distinct black edged red brown transverse bands across the body and tail; and 9) eye from bright brown and reddish brown to mildly brown. The new species was also observed from the Haa Valley in western Bhutan.     

Phylogeography of the bushmaster (Lachesis tnuta: Viperidae): implications for neotropical biogeography, systematics, and conservation

We used mitochondrial gene sequences to reconstruct phylogenetic relationships among subspecies of the bushmaster, Lachesis muta. These large vipers are widely distributed in lowland tropical forests in Central and South America, where three of four allopatric subspecies are separated by montane barriers. Our phylogeny indicates that the four subspecies belong to two clades, the Central American and South American lineages. We use published molecular studies of other taxa to estimate a 'reptilian mtDNA rate' and thus temporal boundaries for major lineage divergences in Lachesis. We estimate that the Central and South American forms diverged 18-6 Mya, perhaps due to the uplifting of the Andes, whereas the two Central American subspecies may have diverged 11-4 Mya with the uprising of the Cordillera de Talamanca that separates them today. South American bushmasters from the Amazon Basin and the Atlantic Forest are not strongly differentiated, perhaps due to episodic gene flow during the Pleistocene, when suitable habitat for this species was at times more continuous. Our results agree with previous evidence that genetic divergence among some neotropical vertebrates pre-dated Pleistocene forest fragmentation cycles and the appearance of the Panamanian Isthmus. Based on morphological, behavioral, and molecular evidence, we recognize three species of Lachesis. In addition to L. muta, the widespread South American form, the Central American forms are treated as distinct species (L. meknocephak and L. stenophrys), each deserving of special conservation status due to restricted distribution and habitat destruction.     

Integrating phylogeny,environment and space to explore variation in macroecological traits of Viperidae and Elapidae (Squamata: Serpentes)

We used eigenvector mapping in space and phylogeny to investigate the relationships among space, phylogeny and environment on body size and range size variation across two groups of venomous snakes – Viperidae and Elapidae – from the New World. Data on species geographic range sizes, maximum body sizes and phylogenetic relationships were compiled from the available literature. The distributional data were also used to calculate the latitudinal and longitudinal midpoint and the environmental centroids for each species. The eigenvectors extracted from the pair wise spatial and phylogenetic distance matrices were integrated with environmental variables into a method of variation partitioning where the variation in each trait was quantitatively attributed to ‘pure’ and/or shared effects of phylogeny, environment and space. Our results showed that variation in body size was predominantly determined by phylogeny in both groups of snakes. For Viperidae, we found that pure ‘effects’ of phylogeny were the strongest, indicating that most of the body size evolution that was phylogenetically determined in this group occurred independently of environment and geographical proximity. Regarding range sizes, pure phylogenetic influences were very low in both groups, whereas the largest single fraction of explained variation corresponded to overlapped influences of the three sets of predictors, especially for Elapidae. Along with this, we found evidence that niche conservatism is an important processes underlying variation in body size and range size in both groups of snakes.     

Elaphostrongylus rangiferi: Influence of temperature,substrate, and larval age on the infection rate in the intermediate snail host, Aarianta arbustorum

The infection rate of the first stage larval nematodes, Elaphostrongylus rangiferi, was studied experimentally, using the juvenile snail Arianta arbustorum as intermediate host. The nematode showed a linear, fivefold increase in infection rate within the temperature range of 4 to 28 C. The snails were exposed to the larval nematodes on three different substrates. The highest infection rate was recorded when snails were exposed in tap water and significantly slower infection rates were obtained when either lettuce or soil was used as the substrate. First stage larvae of E. rangiferi were infective for at least 2 months when stored at 12 C. Throughout this period, the infection rate showed a significant decline, while the motility of the larvae remained unchanged.     

The influence of prey-scent stimuli on predatory behavior of the North American copperhead Agkistrodon contortrix (Serpentes: Viperidae)

Viperid snakes strike, envenomate, and release mammalian preyto prevent being harmed by the prey; snakes must then trackprey in the process of strike-induced chemosensory searching.Because rattlesnakes prefer to track and consume envenomatedprey, it would seem that the scent of envenomated tissue iskey to the tracking process. After striking rodents, rattlesnakesalso retain a specific chemical search image of prey items.I examined this behavioral pattern in copperheads (Agkistrodoncontortrix) from three US populations with documented dietarybiases toward mammals (Kansas), lepidopteran larvae (Texas),and amphibians (Louisiana), respectively. Experiments were conductedto assess whether copperheads form a specific search image ofnon-envenomated mouse, hornworm, and frog prey items. Additionalexperiments tested the relative importance of envenomated tissueto prey scent. Results indicate that copperheads do not forma specific search image of prey items. Preference for non-envenomatedprey items is in the order mouse > hornworm > frog forall three populations; therefore, the innate behavioral preferencefor types of prey does not match the dietary biases noted inthe literature. Envenomated mice and hornworms were preferredto all nonenvenomated prey items, but most trials involvingenvenomated frogs did not suggest envenomated prey preference.Overall, these results suggest that when the snakes search forprey, envenomated tissue stimuli are more important to snakesthan scents arising from the prey itself. Searching and consumptionbehaviors seem to be independent, suggesting that strike-inducedchemosensory searching and consumption are more complicatedbehavioral processes than previously recognized.     

Effect of temperature on the expression of P-glycoprotein in the zebra mussel, Dreissena polymorpha

The multixenobiotic resistance (MXR) system is a defence mechanism which protects living organisms by actively extruding xenobiotics from cells. Membrane transporters responsible for this phenotype can be induced by numerous compounds, but also by physical stressors such as temperature. In order to better understand the contribution of temperature in MXR expression, the MXR system was studied in the freshwater bivalve, Dreissena polymorpha. Results showed that the zebra mussel possesses a gene closely related to the ATP-binding cassette (ABC) subfamily B, which is expressed as a 120-kDa protein. Moreover, gill cells can transport the model substrate Rhodamine B in a verapamil-sensitive manner, which is a good indication of MXR protein activity such as P-glycoprotein (Pgp). When bivalves were slowly acclimated to temperatures ranging from 4 to 20 °C (maximum temperature variation, 2–3 °C/day), no significant change in MXR protein expression could be immunochemically measured. Furthermore, the MXR transport activity did not show significant variation in this temperature range. Conversely, incubation of zebra mussel specimens in 20 μM Dacthal dramatically enhanced both protein expression and transport activity, thus indicating that temperature is not a major determinant in zebra mussel gill Pgp expression.     

Effect of several factors on the phototactic response of the oriental armyworm, Mythimna separata (Lepidoptera: Noctuidae)

Recently, light traps equipped with light-emitting diode (LED) lights have been used to monitor and control nocturnal insect pests. The oriental armyworm, Mythimna separata Walker, is an important cosmopolitan agriculture pest. The phototactic responses of nocturnal insects, including moths are influenced by abiotic and biological factors. The present study aimed to evaluate the phototactic response to different wavelength LED lights to determine the wavelength to which M. separata adults are most sensitive, and then identify the effects of several factors on the phototactic response. Our experiments revealed that M. separata adult moths had a significantly higher attraction rate to the green (520?nm) LED light compared with other LED lights, the green LED light was 1.28 times more attractive the moths than the commercial double-wave light used as a control. The phototactic response of the adult moths was significantly influenced by several factors, including adaption time in darkness, age, mating status and sexuality. These findings suggest that using a green LED light as a light source in trap could be effective in monitoring or controlling M. separata moths. Our results may provide a theoretical and scientific basis for improving the light trap technique for M. separata moths.     

Influence of oxygen and temperature on growth and metabolic performance of Paralichthys lethostigma (Pleuronectiformes: Paralichthyidae)

In this study, we apply Fry's classification of environmental factors to demonstrate the limiting effects of oxygen and its interaction with temperature on the growth of juvenile P. lethostigma. We also evaluated the properties of two metabolic indices, marginal metabolic scope (MMS) and limiting oxygen concentration (LOC), as indicators of metabolic scope. We found that oxygen limitation has its greatest impact near the optimum temperature for growth of the species. At 29 °C a reduction from 6.00 mg/L to 4.00 mg/L caused a 50% reduction in growth rate while at 27 °C the reduction had no significant effect on growth rate. The results are particularly relevant because these temperatures and oxygen concentrations are commonly observed in nursery areas during summer months. At all temperatures fish from the lowest oxygen treatment (1.75 mg/L) had negative growth rates. Comparisons between daily oscillating oxygen treatments and constant treatments failed to demonstrate significant effects. At temperatures past the optimum, growth rates between the 6.00 mg/L and 4.00 mg/L treatments were not statistically different. LOC was significantly affected by temperature, oxygen, and their interaction. Estimates were positively correlated with oxygen treatment (R² > 0.71) and negatively correlated with temperature at moderate and low oxygen concentrations (R² > − 0.84). MMS was significantly affected by temperature and oxygen and was significantly correlated with oxygen treatment (R² > − 0.91), but correlations with temperature were not as clear. In conclusion, oxygen and temperature interactions have significant effects on metabolic scope and growth rates of fish, well above the accepted hypoxia threshold of 2.00 mg/L and MMS has proved a useful estimator of the metabolic scope of the organism within an environment.     

Establishing species' environmental requirements to understand how the southernmost species of South American pitvipers (Bothrops,Viperidae) are distributed: A niche‐based modelling approach

Three Bothrops species are known to be present along an extensive and generally xeric band of the south‐eastern portion of South America. Yet, the environmental factors responsible for the maintenance of the structure of this community have remained undetermined. To have a better understanding of snakes' geographic range limits in Argentina, we modelled the ecological niche of Bothrops alternatus, B. ammodytoides and B. diporus to identify areas of their occurrence and sympatry. We used snakes presence records and pseudo‐absence data with topographic (altitude and slope), vegetation and 19 bioclimatic variables as predictors. These variables were evaluated for each species, using Multiple Logistic Regression Analysis. The distribution of B. alternatus was correlated with temperature, precipitation and vegetation; that of B. ammodytoides with altitude, slope, precipitation, temperature and vegetation; and that of B. diporus related only to precipitation and temperature variables. Five variables appeared in all three models (i.e. annual precipitation, precipitation seasonality, precipitation of the driest month, mean diurnal temperature range and temperature range), although with different effects in different species. Probable sympatry areas were identified, for B. alternatus – B. ammodytoides in a narrow area, for B. diporus – B. alternatus in a wide area and B. ammodytoides – B. diporus in a small area. While some factors constrain the distribution of the southernmost pitvipers community in South America to spatially non‐overlapping ranges, others facilitate sympatry by allowing spatial coexistence. We found high sympatry between phylogenetically distantly related pitvipers. Niche‐based Geographic Information Systems modelling allowed us to identify the environmental factors correlated with each pitviper range in Argentina and in its contact zones, and to understand species distributional limits.     

Response of cold-acclimated,farmed South African abalone (Haliotis midae) to short-term and long-term changes in temperature

In its natural environment, the South African abalone, Haliotis midae, occurs at average monthly water temperatures between 12 and 21 °C. In the present study we aimed to describe selected physiological and molecular responses of winter acclimated, cultured H. midae after acute and chronic exposure to 16, 19 and 22 °C.     

Microsatellite and major histocompatibility complex variation in an endangered rattlesnake,the Eastern Massasauga (Sistrurus catenatus)

Genetic diversity is fundamental to maintaining the long‐term viability of populations, yet reduced genetic variation is often associated with small, isolated populations. To examine the relationship between demography and genetic variation, variation at hypervariable loci (e.g., microsatellite DNA loci) is often measured. However, these loci are selectively neutral (or near neutral) and may not accurately reflect genomewide variation. Variation at functional trait loci, such as the major histocompatibility complex (MHC), can provide a better assessment of adaptive genetic variation in fragmented populations. We compared patterns of microsatellite and MHC variation across three Eastern Massasauga (Sistrurus catenatus) populations representing a gradient of demographic histories to assess the relative roles of natural selection and genetic drift. Using 454 deep amplicon sequencing, we identified 24 putatively functional MHC IIB exon 2 alleles belonging to a minimum of six loci. Analysis of synonymous and nonsynonymous substitution rates provided evidence of historical positive selection at the nucleotide level, and Tajima's D provided support for balancing selection in each population. As predicted, estimates of microsatellite allelic richness, observed, heterozygosity, and expected heterozygosity varied among populations in a pattern qualitatively consistent with demographic history and abundance. While MHC allelic richness at the population and individual levels revealed similar trends, MHC nucleotide diversity was unexpectedly high in the smallest population. Overall, these results suggest that genetic variation in the Eastern Massasauga populations in Illinois has been shaped by multiple evolutionary mechanisms. Thus, conservation efforts should consider both neutral and functional genetic variation when managing captive and wild Eastern Massasauga populations.     

Effects of water temperature change on immune function in surf clams, Mactra veneriformis (Bivalvia: Mactridae)

Surf clam, Mactra veneriformis is one of the crucial fishery resources in Korea. This study was performed to examine the immune functions of the surf clam under the stress of water temperature changes at 10 °C, 20 °C or 30 °C for 24 h. Viable bacterial counts (VBC), total haemocyte count (THC), phagocytic activity, lysozyme activity, NRR times and SOD activity were assessed in three different water temperature groups. Clams held at 10 °C decreased in THC, lysozyme activity and NRR times, but phagocytic activity was increased. The highest temperature (30 °C) significantly increased in THC, whereas it decreased in phagocytic activity, lysozyme activity and NRR times. In clams maintained at 20 °C, phagocytic activity, lysozyme activity and NRR times were increased whereas THC was somewhat decreased with respect to clams held at 30 °C. However, water temperature changes did not elicit any alteration of VBC and SOD activity. The present study demonstrates that acute water temperature change affects the haemocytic and haemolymphatic functions, reducing immunosurveillance in stressed surf clam, M. veneriformis.     

Effect of temperature and salinity on the energetics of juvenile gray snapper (Lutjanus griseus): implications for nursery habitat value

Gray snapper (Lutjanus griseus) encounter a wide range of temperatures and salinities in nearshore and estuarine juvenile habitats. The energetic response of juvenile gray snapper to temperature and salinity was measured in laboratory experiments to determine the influence of these physicochemical factors on the potential value of different juvenile nurseries. Maximum consumption and growth rates of juvenile (25-50 mm SL) gray snapper were determined in 12-day trials at 20 temperature/salinity combinations representing conditions in juvenile habitats. Ad libitum feeding level of individual fish was measured daily. Maximum weight specific feeding rate increased significantly with temperature and salinity; however, the effect of salinity was much less than that of temperature. Linear growth rate and specific growth rate both increased with temperature, and salinity did not have a significant effect on either. Gross growth efficiency (K₁, growth×consumption⁻¹*100) increased with temperature and was significantly lower at high salinities, indicating increased energetic costs. The higher K₁ at lower salinities has several implications for juvenile gray snapper in low salinity habitats: (1) they would need less food to achieve the same somatic growth as juveniles in high salinity habitats; (2) they would have higher growth at limited ration levels as compared to high salinity habitats; and (3) they would have less impact on prey populations than higher salinity habitats assuming similar gray snapper densities.