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Identifying sex of hatchling turtles is difficult because juveniles are not obviously externally dimorphic, and current techniques to identify sex are often logistically unfeasible for field studies. We demonstrate a widely applicable and inexpensive alternative to detect subtle but significant sexual dimorphism in hatchlings, using landmark-based geometric morphometric methods. With this approach, carapace landmarks were digitized from photographs of each hatchling, and shape variables were generated after variation in size, location and orientation were eliminated. These variables were then analyzed for sexual dimorphism, and used in discriminant function analysis to estimate sex of each hatchling. Using this approach on two species (Chrysemys picta and Podocnemis expansa), we found this method had high accuracy in assigning sex when compared with true sex (98% and 90%, respectively), and cross-validation revealed a correct classification rate of 85%. These correct classification rates were considerably higher than those found on the same species using linear distance measurements as data. We also explored two alternative statistical approaches for assessing sex (K-means clustering and multiple logistic regression) and found that these alternative approaches were accurate only 61% and 78% of the time, respectively, in C. picta and 69% and 77% of the time in P. expansa. These findings are similar to classification rates found for turtle species using approaches based on linear distance measurements. We also found that the observed sexual dimorphism differed between the two species. In P. expansa, males displayed relatively more expansion of the central region of the carapace relative to females, whereas in C. picta this pattern was reversed. We conclude that discriminant analysis of morphology quantified using geometric morphometrics provides researchers with a powerful tool to discriminate between male and female hatchling turtles.
The phylogenetic relationships of extant species of Esox were investigated using both morphological and molecular data. The complete mtDNA cytochrome b gene (cytb) and the second intron of the RAG1 gene were sequenced from multiple specimens of each species and analyzed using maximum parsimony and maximum likelihood. The resulting cladograms were compared with each other and to the morphological cladogram for congruence. Data from all three sources strongly support the monophyly of the genus, and the monophyly of the subgenera Esox (i.e., pikes) and Kenoza (i.e., pickerels). Our data support the sister-group relationship between Esox reicherti and Esox lucius (the Amur and Northern Pike, respectively). Incongruent results between the morphological and RAG1 data and the cytb data, with respect to pickerel interrelationships, suggest hybridization and introgression among pickerel species. Additional research is necessary to explore these results further. This study represents the first study to integrate both morphological and molecular data into a phylogenetic analysis of Esox. It aims to provide a better understanding of esocid evolution and lay the foundation for the interpretation of fossil material assigned to Esox. It also provides preliminary genetic evidence of hybridization among the pickerels.
We studied geographic variation in allozymes (22 loci), mitochondrial cytochrome b gene sequences (575 bp), advertisement calls (pulse rate, call duration, and dominant frequency), and snout–vent length among populations of Hyla wrightorum and Hyla eximia in the United States and Mexico. Calls were only available for H. wrightorum, and although populations varied in some advertisement call variables, there was no indication of species level differentiation. Allozyme variation was exhibited among the H. wrightorum populations, but no fixed differences were discovered, and the amount of genetic divergence among populations was small (Dm ≤ 0.0643). Seven mtDNA haplotypes were discovered among the H. wrightorum individuals included in this study. A single haplotype (G) was present in the Huachuca Mountains and was found only in this population restricted to southeast Arizona. Neither the Mogollon Rim nor the Sonora populations were exclusive, with some haplotypes in each being more closely related to haplotypes in the other population. Molecular data (allozymes and mtDNA), as well as the advertisement calls, support continued recognition of two species: H. eximia in central-southern Mexico and H. wrightorum, which consists of disjunct populations in the Sierra Madre Occidental of northern Mexico, the Huachuca Mountains of southeastern Arizona, and the mountains of central Arizona and western New Mexico.
Genetic surveys of widely distributed marine species often find previously undetected biodiversity. In the present study, populations of three species of Halichoeres were sampled across their entire geographical ranges: Halichoeres cyanocephalus and Halichoeres maculipinna were sampled on both sides of the Amazon freshwater outflow, the main biogeographic barrier in the tropical western Atlantic; and Halichoeres garnoti was sampled in the Caribbean and Bermuda. Genetic divergences between populations separated by the Amazon ranged from 2.3% in H. cyanocephalus to 6.5% in H. maculipinna. There is inconsistency between color differences and genetic partitions in the species surveyed. The color differences between populations of H. cyanocephalus and H. maculipinna correspond to deep genetic partitions at the cytochrome b locus. However, genetic similarity at this same locus was observed between populations of H. garnoti with striking color differences. Based on the combination of the observed genetic differences with diagnostic color differences, the Brazilian species Halichoeres dimidiatus (Agassiz) and Halichoeres penroseiStarks, 1913 are revalidated. In addition, a neotype is designated to H. cyanocephalus (Bloch, 1791), to clarify its taxonomic status and type locality. All species analyzed have a similar larval dispersal potential, but varying degrees of genetic divergences were observed, indicating that benthic stage ecology may also play a role in speciation in this group.
Introduction of nonnative species and consequent genetic introgression of native taxa is a primary conservation concern, particularly for endangered species. Our ongoing molecular study of the endangered Sonora Tiger Salamander, Ambystoma tigrinum stebbinsi (Lowe), has uncovered evidence of introgression by the Barred Tiger Salamander, Ambystoma tigrinum mavortium. We conducted both mitochondrial DNA sequencing and analyses of nine microsatellite loci to (1) evaluate the distinctiveness of A. t. stebbinsi from the two other tiger salamander subspecies in Arizona; and (2) test for introgression in A. t. stebbinsi. Two mitochondrial haplotypes were found. One was undescribed for tiger salamanders, and the other was identical to that found in nearby A. t. mavortium. Microsatellite analyses, including assignment tests, diagnostic alleles, and high genetic distances, supported distinctness of A. t. stebbinsi. Thirty-nine animals that were putatively A. t. stebbinsi had mtDNA haplotypes identical to those in A. t. mavortium. These 39 individuals were distributed among six ponds, where a total of 73 individuals were sampled for microsatellites and considered “unknowns” because of the shared haplotype with A. t. mavortium. Assignment tests and diagnostic alleles of microsatellite data indicated that five of these 73 individuals may be hybrids of A. t. mavortium and A. t. stebbinsi. Some salamanders within the geographic range of A. t. stebbinsi were morphologically similar to A. t. mavortium or intermediate between the two subspecies. Our results suggest that introgression from introduced A. t. mavortium may be altering the gene pool of A. t. stebbinsi, thereby raising concerns about continued management of this endangered species.
The deep-sea ceratioid anglerfish genus Phyllorhinichthys is revised on the basis of all known material. Two species are recognized: the type species Phyllorhinichthys micractis, now represented by nine specimens collected from all three major oceans of the world; and a new species described here on the basis of five specimens, all from the Atlantic Ocean. The new species differs from P. micractis in having a longer illicium, only a single anterior escal appendage, and a much longer distal escal appendage. Diagnoses and descriptions are given for all taxa, known distributions are plotted, and a key to the species is provided.
Information about animal movement patterns is critical to understanding their ecology, and such information is essential to the design of conservation plans for threatened species. Using radio telemetry, GPS, and ArcView GIS software, we examined seasonal activity, habitat use, movements, and home-range size of a southeastern population of Spotted Turtles (Clemmys guttata), a declining species. Data collected over three years revealed an annually repeated pattern of seasonal activity. Habitat use differed annually, seasonally, and between the sexes. Home ranges overlapped, and there was an area of concentrated overlap in early spring, indicating an aggregation of turtles, likely for breeding. Individuals showed annual fidelity to home-range areas. Home-range size (calculated using three methods) for males was smaller (∼5 ha) than that of gravid females (∼16 ha). Movement data did not fully support the reproductive strategies hypothesis. As predicted, gravid females moved greater distances than males during the nesting season. In contrast to the hypothesis, males did not move their greatest distances in spring at which time mating mainly occurs. That males did not make the predicted movements in spring can be explained by the fact that turtles aggregated at this time of year; thus, males do not need to travel to find mates. The current study is important because it provides information on the role of natural (“hurricane-tip-ups”) and anthropogenic (powerline rights of way, clearcuts) disturbances in maintaining habitat heterogeneity and the early-successional vegetative communities preferred by Spotted Turtles. A set of management recommendations is presented.
A new species of small-sized scorpionfish, Scorpaena cocosensis, is described on the basis of a single specimen collected from off Nuez Island, Cocos Islands, Costa Rica, eastern Pacific Ocean. The new species is similar to two eastern Pacific species of Scorpaena, Scorpaena russula and Scorpaena sonorae, in overall body appearance and in lacking a supplemental preopercular spine. However, it is distinguished from these two species by the following characters: eight dorsal-fin soft rays; well-exposed scales covering anteroventral body surface; interorbital ridges well developed, beginning just behind nasal spines, diverging anteriorly and posteriorly in dorsal view; lateral margins of frontal diverging posteriorly in dorsal view; upper posttemporal spine directed upward; posterior margin of maxilla just reaching level with posterior margin of pupil; posterior tip of pectoral fin reaching level with origin of third dorsal-fin soft ray; large head length (48.8% SL); large orbit diameter (16.9% SL); wide interorbital space between supraocular spine bases (9.2% SL).
We describe a new species of high-elevation rain-forest tree frog (genus Platymantis) from New Britain in the Bismarck Archipelago, Papua New Guinea. It is characterized by moderate body size (males 27.4–30.7 mm), widely expanded finger and toe disks, smooth dorsal skin, a distinct reticulate dorsal color pattern, and numerous spectral and temporal characteristics of the advertisement call. The new species inhabits shrub layer vegetation in canopy gaps in primary montane rain forests of the Nakanai Mountain Range above 1500 m. We compare the new species to all known Platymantis from New Britain and to other morphologically similar species from the Bismarck archipelago, Solomon Islands, and Fiji. We also redescribe Platymantis macrosceles from the holotype and two new specimens from the Nakanai Mountains. We suspect that anuran species diversity on the large and topographically complex island of New Britain is currently underestimated.
Tilapia, in general, are known for their plasticity in growth, reproduction, and age- and size-at-maturity that not only make them an excellent aquaculture taxa but also allow them the ability to invade and become established in nonnative environments. We investigated aspects of reproductive biology and recruitment of the nonindigenous Nile Tilapia, Oreochromis niloticus, collected in the Pascagoula River watershed and from Simmons Bayou, a small tidal system of Biloxi Bay, Mississippi, over a 16-month period. Males ranged from 32.6–430.0 mm total length (TL) and females from 31.7–349.0 mm TL. The Gonadosomatic Index (GSI) for males or females indicated year-round reproduction with increased spawning intensity in spring (March to May) and in late summer (August to September). Small juveniles (≤ 25 mm TL) were collected every month of the year except March, and multiple size classes were collected suggesting successful recruitment of young. The smallest female with mature oocytes was 79.9 mm TL, and the size class where 50% of the females were mature was 113 mm TL. Batch fecundity (BF) ranged from 30–2603 oocytes for females, and there was a significant relationship between log10-BF and log10-TL and log10-BF and log10 EBW. Relative fecundity ranged from 0.89–11.75 oocytes/g EBW. Although Nile Tilapia have low fecundity, parental care essures that the majority of their eggs will survive to the juvenile stage. Low fecundity is further offset by the ability to spawn multiple broods throughout their year-round reproductive season. These reproductive characteristics may give the species a competitive advantage over native fishes. We expect Nile Tilapia to further invade and spread in these coastal watersheds.
We provide descriptions for two new cryptic species belonging to the Liolaemus alticolor group from northern Argentina and northeastern Chile. The new species were previously considered conspecific with either Liolaemus walkeri in northeastern Chile or L. alticolor in northwestern Argentina and adjacent Chile. However, the new species differ from these taxa, and all other members of the alticolor group, in a number of characteristics. Liolaemus chaltin n. sp. differs from L. alticolor from the type locality (Tiahuanaco, Bolivia) in the following ways: this new species has a larger body size; a fragmented vertebral stripe; and a pigmented subocular (white in L. alticolor), and is one of just three members of the alticolor group that is oviparous. Liolaemus puna n. sp. differs from all other members of the alticolor group in that male L. puna lack paravertebral markings and dorsolateral and vertebral stripes. Females, however, are similar to other members of the alticolor group but can be distinguished from them by several meristic characters. Liolaemus puna is widely distributed throughout the high-elevation (3680–4400 m) Puna regions (a flat or gently sloping steppe dominated by perennial bunch grasses and small shrubs) in northwestern Argentina and northeastern Chile. Liolaemus chaltin is known only from the Puna of central Jujuy Province, Argentina (3400–3750 m). Based on examinations of the type series of L. alticolor and L. walkeri, we determined that virtually all northern Chilean populations of Liolaemus previously considered to belong to either of these two species should be assigned to L. puna. Thus, the range of L. alticolor is restricted to Bolivia and southern Perú, and the range of L. walkeri is restricted to central and southern Andean Perú. Liolaemus chaltin is oviparous, and L. puna is viviparous, and because both are morphologically similar to L. alticolor, some investigators have suggested that some populations of L. alticolor may be reproductive bimodal. Our studies, however, indicate that these populations represent sympatric populations of the cryptic species described herein. A diagnostic key is provided for the currently recognized members of the alticolor group.
A new species of cyprinid, Notropis calabazas, is described from the Río Calabazas, a small tributary of the Río Verde in the Río Pánuco basin in San Luis Potosí state, central México. It belongs to the Notropis calientis complex, which is defined primarily on the occurrence of reduced and interrupted cephalic and lateralis sensory canals. Notropis calabazas is unique in having 17 or more gill rakers on the second gill arch versus 16 or fewer. Notropis calabazas can also be distinguished from the other three members of the complex by its relatively high numbers of gill rakers on the first arch, total lateral line scales, pored lateral line scales, body circumferential scale rows and caudal peduncle circumferential scale rows, and its relatively low numbers of supraorbital and infraorbital cephalic sensory pores. Notropis calabazas is uncommon within its limited range and warrants official designation as a protected species.
Trichomycterus pseudosilvinichthys, new species, is described from midelevation drainages in the Provincia de La Rioja, Argentina. The new species is distinguished from other members of the apparently nonmonophyletic genus Trichomycterus by having the insertion of the first proximal dorsal-fin pterygiophore at, or posterior to, vertebra 20 to 22; the presence of the pelvic fin and girdle; a fronto-lachrymal tendon bone with a lateral expansion but an incomplete laterosensory canal segment; the absence of a portion of the supraorbital laterosensory canal running between the frontal and nasal bones with the resultant loss of pore 3; the possession of 17–19 ribs; a first pectoral-fin ray that is not prolonged as a short filament; and the tip of the pelvic fin falling short of the anus.
Mystus armiger, a new species of estuarine bagrid catfish, is described from the mouth of the Kelantan River in the northeastern part of the Malay Peninsula. Mystus armiger resembles Mystus wolffii, both species easily distinguished from congeners by their uniform color without any dark markings, approximately equal lengths of adipose- and anal-fin bases, and long maxillary barbels that reach at least to the base of the caudal fin. Mystus armiger differs from M. wolffii in having a broader snout, smaller eye (17.5–22.8% HL vs 22.8–27.0), and fewer larger serrations on the pectoral spine.
The subdivision Elopomorpha, united by the possession of a leptocephalus larval stage, is a diverse group of primarily tropical fishes that contains many rare species. In this paper, six leptocephalus types collected from the waters around Barbados are described, including the muraenid, Echidna catenata, two ophichthid types, and one nettastomatid type that are most likely the larvae of species that have not been collected and described as adults, and an additional ophichthid type and muraenid type that cannot be matched to a species. Based on this work and previous descriptive work on both adult and larval ophichthids, western North Atlantic species richness in this family is evaluated.
The eggs, embryos, and tadpoles of Spicospina flammocaerulea are described. The free-swimming tadpole has a distinctive body form among described Australian genera but shares morphological similarities with the myobatrachid genera Taudactylus and Uperoleia. The egg capsules have an unusual semiopaque outer envelope that is similar to a firm gelatinous envelope present on egg capsules of some species of Uperoleia. The embryos are unique among described Australian genera in that they do not develop visible adhesive organs. Spicospina and Taudactylus and some Uperoleia larvae share a narial flap. Both Spicospina and Uperoleia have large nares that open in a dorsal direction. Larvae of S. flammocaerulea can be readily distinguished from other sympatric species by a combination of features of the oral disc and nares, position of the spiracle and eyes, and the low tail fins.
Dietary analysis of a population of the glassfish Chanda nama from a wetland in southwestern India revealed facultative scale feeding (lepidophagy). In addition to fish scales, microcrustacea and aquatic insects were consumed by all size classes, with juvenile diets containing larger fractions of invertebrates. More scales were consumed during the wet season, the period when abundance of juvenile fishes was greatest. Aquarium observations revealed how the glassfish uses stealth and ambush tactics. Scales are dislodged by raking the extended lower jaw, distally armed with four curved conical teeth, across the flanks of prey.
Flicker electroretinography (ERG) was used to examine the in situ photopic (cone-photoreceptor based) spectral sensitivities of Green and Loggerhead Sea Turtles. Both species were responsive to wavelengths from 440–700 nm, and both had peak sensitivity in the long wavelength portion of the spectrum (∼580 nm). For Loggerhead Sea Turtles, no measurable responses were obtained below about 440 nm, whereas reliable signals were seen for Green Sea Turtles at wavelengths down to 400 nm. Both species exhibited significant declines in sensitivity below 500 nm. The overall shapes of the spectral sensitivity functions were similar for the two species. These results support previous findings that sea turtles have well-developed photopic visual systems. The characteristics of these spectral sensitivity functions indicate that both species possess multiple cone photopigment types, and these, in conjunction with the presence of colored oil droplets, strongly imply a capacity for color discrimination. Comparative evaluation suggests that these turtles have modified their visual pigments from those of their terrestrial relatives to better suit the ambient conditions present in the shallow water, submarine environments that they typically inhabit.
We examined the effect of nest guarding by the male Fringed Darter (Etheostoma crossopterum) on egg predation by the Bluntnose Minnow (Pimephales notatus), the Southern Two-Lined Salamander (Eurycea cirrigera), and a species of crayfish (Orconectes margorectus). When male E. crossopterum were removed from nests, both P. notatus and O. margorectus consumed a greater percentage of eggs than when the male was present. Although E. cirrigera consumed eggs during one trial, results suggest that this species may not be as consistent a predation threat as are the minnow and crayfish. These results indicate that male E. crossopterum provide parental care to developing embryos in the form of defense against predators and provide support for a previously untested hypothesis for nest guarding darters.
Theoretical and empirical studies of habitat selection suggest that reptiles should use “fixed” structural features (perch diameter, vegetation) or light intensity (sun and shade) to select thermally suitable microhabitats. But how do nocturnal species select thermally suitable diurnal retreat sites at night in the absence of visual cues? To investigate this question, we studied habitat selection by two sympatric nocturnal snakes, the endangered Broad-Headed Snake Hoplocephalus bungaroides and the common Small-Eyed Snake Cryptophis nigrescens. In the field, we investigated whether snakes selected diurnal retreat sites nonrandomly with respect to vegetation structure and rock temperature. In the laboratory, we offered snakes a choice between rocks with different crevice sizes, temperatures, and degree of shading. In the field, rocks used by snakes received significantly higher levels of incident radiation intensity (and therefore had higher temperatures) than random rocks but had similar levels of canopy cover. This apparent paradox reflects differences in the position of canopy gaps relative to the path of the sun, the most important determinant of a rock's diurnal temperature profile. In the laboratory, snakes chose rocks with narrow crevices but did not discriminate between shaded and exposed rocks. Snakes consistently chose hot rocks over cold rocks, even though the nocturnal temperature difference between the two retreat sites was less than 4 C. Our results show that these nocturnal snakes use a fixed structural cue (crevice size) to select potential retreat sites but then use a temporally variable cue (substrate temperature) to choose among potential retreat sites.
The genus Sebastes contains over 110 species, an unusually high level of species diversity for marine fishes. Many of the 70 species that occupy the northeast Pacific Ocean coexist during parts or all of their life cycle. Although allopatric speciation explains much of this diversity, the presence of many closely related species within the same locations suggests that other isolating mechanisms may play a role. Sebastes carnatus and Sebastes chrysomelas are a sympatrically distributed pair of sister species having no morphologically distinguishing characteristics other than color: S. carnatus has pinkish spots on a brown background, and S. chrysomelas has yellow spots on a black background. In this study, seven nuclear microsatellite DNA loci were employed to assess relatedness of 111 S. carnatus and 91 S. chrysomelas sampled from three locations spanning the species' range. Analysis of the seven microsatellite loci provided evidence of genetic divergence between color morphs (FST = 0.046, P < 0.0001). Furthermore, magnitude of genetic divergence between the color morphs was consistent among geographic locations. Divergence between S. carnatus and S. chrysomelas was low relative to that detected among other species within the genus, suggesting that the two morphs represent reproductively isolated incipient species.
Rana sylvatica (Wood Frog) tadpoles subsist as microphagous suspension feeders but opportunistically prey on macroinvertebrates and embryos of Ambystoma maculatum (Spotted Salamander). We conducted two mesocosm experiments to determine whether breeding phenology and presence of Rana affect the growth, time to metamorphosis, and survival of Ambystoma (Experiment 1) and whether Rana density and access to Ambystoma embryos affect the growth, duration of larval period, and survival of both species (Experiment 2). Rana did not affect Ambystoma embryonic survival in either experiment. In Experiment 1, seasonal time of oviposition did not affect the overall response of Ambystoma larvae; however, Rana presence decreased larval survival and prolonged time to metamorphosis. In Experiment 2, relatively high tadpole density significantly reduced Ambystoma survival and decreased Rana survival, growth, and development. The results of this and other studies suggest that R. sylvatica may adversely affect A. maculatum through an array of context-dependent interactions, including indirect food web alteration, direct competition for benthic macroinvertebrates and zooplankton, and consumption of embryos. We provide a conditional interpretation of community organization that encompasses bottom-up and top-down effects generated by Rana on community members.
We redescribe Stenocercus erythrogaster based on examination of the holotype, eight additional Colombian specimens, and five Venezuelan specimens. We report S. erythrogaster from two localities in the Serranía de Perijá, Zulia, Venezuela. Although widespread in Amazonia and among the northern Andean countries of South America, Stenocercus has not been reported previously from Venezuela. Earlier reports of Enyalioides sp. from the Serranía de Perijá were based on a misidentified specimen of S. erythrogaster.