Similar morphology and confused historical taxonomy of Hybognathus hankinsoni (brassy minnow) and Hybognathus placitus (plains minnow) have made determination of their historic distributions and conservation status unclear in eastern Colorado basins. We developed logistic regression models from morphometric measurements to predict species identity of Hybognathus collections from Colorado and adjacent counties (n = 1154 specimens in 134 lots). A model based on orbit diameter, standard length, and eye position correctly predicted 98% of the specimens examined and 100% of the museum lots. Hybognathus hankinsoni have larger eyes centered on a horizontal line through the tip of the snout, whereas H. placitus have smaller eyes centered above the tip of the snout. The two species were historically sympatric in the Platte, Republican, and Smoky Hill River basins, whereas H. placitus was allopatric in the Arkansas River basin. The taxonomic characters defined here will allow accurate identification of future collections to determine the status of these native fishes.

Studies of diet overlap of insectivores, especially lizards, have been important for the development of much ecological theory. However, measures of overlap, usually based on dietary volumes, vary widely among studies. Most researchers estimated the volumes of prey in stomach contents subjectively or attempted to reconstruct the volume of individual prey items from linear measurements of length (L), width (W) and/or height (H), or from mass. We studied the relationship between indices of volume based on indirect measures and direct measures of volume by fluid displacement for a collection of arthropods that simulated the diet of a generalist lizard. For each individual arthropod, we calculated the proportional error [(measured volume—estimated volume)/measured volume)] for each estimation method. For individual large insects, there were significant differences between orders in the proportional error for all methods. The methods based on linear measurements had only weak relationships (r² ≤ 0.4 in all cases) with measured volume. Mass had a stronger (R² = 0.9), but curvilinear relationship with measured volume. For the combined masses of all arthropods in each diet category from stomach contents of four species of lizards, there were also significant differences in the proportional error between arthropod orders for all methods (P ≤ 0.018 in all cases), except for mass (P = 0.126). Because most indices of overlap are based on proportions, errors in estimation for any one category affect the degree of overlap for all other categories found in that stomach. Cluster analysis of different indices based on the same data indicated differences of up to 10% in proportional overlap. Such large differences for identical diets mean that it is extremely difficult to compare studies that used different methods of volume estimation. We conclude that the use of general formulas to reconstruct the volumes of arthropods are not appropriate for most studies of diet overlap and that extreme care should be exercised in attempts to perform meta-analyses on studies that purportedly measured prey volumes.

Catfishes of the genus Ameiurus are a well-known component of the North American ichthyofauna. J. G. Lundberg estimated phylogenetic relationships among species of Ameiurus according to morphological variation. Two clades containing the extant species were recovered: the natalis clade (Ameiurus natalis, Ameiurus melas, and Ameiurus nebulosus) and the catus clade (Ameiurus serracanthus, Ameiurus catus, Ameiurus platycephalus, and Ameiurus brunneus). Original nucleotide sequence data were collected from mitochondrial (cytochrome b) and nuclear (recombination activation gene 2) genes and used to test the predictions of the hypothesis based on morphological data. The monophyly of both natalis and catus clades was rejected by the nucleotide dataset and an alternative phylogenetic hypothesis is provided.

The structure and dynamic history of a mosaic hybrid zone are investigated using an analysis of morphometric variation to determine the extent of interbreeding between the species involved in different regions. The hybrid zone between the toads Bufo americanus and Bufo fowleri is geographically widespread. Natural hybrids occur in Ontario at Long Point but not along the nearby Niagara peninsula although the species are sympatric in both places. Discriminant analysis of variation in 27 morphological characters from 286 preserved museum specimens of male toads and putative hybrids was compared with previous allozyme genetic characterization of the same specimens. Reference samples from allopatric populations were used for comparison. Bufo americanus from Long Point were significantly different from other samples of the same species, demonstrating introgression in the direction of sympatric B. fowleri. Long-term hybridization in this region has been confined to Long Point despite sympatry elsewhere. Thus, the hybrid zone between these toads does not conform to gradient or “tension zone” models. Rather, it is a mosaic in that hybrids appear at some times and in some places but not in others and it conforms to the concept of a “localized sympatric” hybrid zone.

Activity patterns, diet, and shelter site use were compared between two species of moray eels, the spotted moray, Gymnothorax moringa, and the purplemouth moray, Gymnothorax vicinus, in the shallow backreef habitat of the Belize Barrier Reef. We tracked eels tagged with acoustic transmitter tags, analyzed stomach contents, and surveyed shelter sites in a 150-m by 250-m survey area of patch reefs and coral rubble. The study site supported primarily subadult to early adult eels (379–947 mm TL). We made 490 G. moringa and 344 G. vicinus sightings in 74 census days. Shelter site use was similar for both species. Gymnothorax moringa left shelters nearly twice as often as G. vicinus (62.5% of nights vs 36.4%). Both species moved primarily at night and ranged less than 10 m to approximately 100 m from shelter for periods less than 1 h to more than 9 h. Forays were mainly in the open grassbed away from patch reefs, rubble, or other shelter. Gymnothorax moringa fed nearly twice as often as G. vicinus (39.4% empty stomachs versus 70.0%), consistent with the difference in activity patterns of tagged fish. Prey included fishes (primarily wrasses), small crabs, and octopus; however, G. moringa specialized on small crabs, and G. vicinus specialized on fish. Gymnothorax vicinus moved and fed primarily on nights with inclement weather, whereas G. moringa did so on both calm and inclement nights. Fish consumption increased on inclement nights for both species, and crab consumption increased on calm nights. Piscivory by G. vicinus appears to have been enhanced by their feeding on inclement nights.

Polyphenisms (environmentally cued polymorphisms) are ubiquitous, yet the specific proximate mechanisms producing alternative morphs are generally not well known. We tested hypotheses for the role of large heterospecific prey in the cannibalistic polyphenism within larval tiger salamanders, Ambystoma tigrinum nebulosum, to determine whether heterospecific prey directly or indirectly influence the production of cannibal morphs. Field surveys suggested, and laboratory experiments confirmed, that macroinvertebrate prey induce cannibals via an increase in body size variation within larval salamander populations. Dietary data and laboratory foraging experiments revealed that cannibals preferred conspecifics even when their capture success was greater on macroinvertebrates. Typical morphs, in contrast, consumed only macroinvertebrate and other prey and never successfully cannibalized conspecifics. Our results support the indirect hypothesis that cannibals are induced via increased body size variation within a population of larvae, as a result of differential consumption of large heterospecific prey, and do not rely on consumption of heterospecific prey once they are cannibals. The cannibalistic polyphenism is one example of phenotypic plasticity in which the functional significance and the proximate mechanisms producing the two morphs are becoming clearer, allowing further study of the molecular and physiological basis of the alternative phenotypes.

Caracanthus typicus and Caracanthus unipinna are small, obligate coral-dwelling, scorpaeniform fishes (F. Caracanthidae). In the majority of individuals in these two species, the male gonad is an ovotestis with several ovarian features, including an apparently nonfunctional gonadal lumen and the frequent presence of healthy-appearing oocytes. In addition, it has a feature typical of secondary testes in the form of peripheral sperm sinuses located within the ovotestis wall. These features collectively suggest that males in these two species arise secondarily from females. Males and females of both species also have an unusual gonad architecture in which the gametogenic tissue is almost entirely surrounded by a peripheral lumen for much of its length. Among females, maturing oocytes project into the ovarian lumen on stalks of stromal tissue and the periphery of the gonadal lumen is lined with a distinctive tall columnar epithelium consistent with a secretory function. Such ovarian features present in three other scorpaeniform species are associated with the release of eggs that are bound together in a gelatinous matrix to form floating egg masses. The presence of such features in female C. typicus and C. unipinna suggests that Caracanthus may have a similar mode of reproduction.

The current literature reports divergent conclusions on the patterns of body size change in island snakes. I reviewed body size data in the published literature and tested the effects of island biogeographic variables on such changes. I found that none of the physiographic variables (island area, island age, distance to mainland, and latitude) was important in determining changes in size of island snakes. Additionally, a current hypothesis of phylogenetic history had no effect on changes in body size. Rather, the proportional change in body size of island snakes was bimodal, consistent with a diet alteration hypothesis that suggests that snake body size is principally influenced by prey size and that island snakes encounter prey that are larger or smaller in size compared with those on the mainland. Also, snakes that became small on islands did so to a relatively greater degree than those that became large. Ontogenetic changes in foraging strategies appeared to explain this pattern. The distribution of gigantic and dwarf snake populations on islands differed significantly between the families Viperidae and Colubridae. The foraging style of colubrids, specifically nest-robbing behavior, may predispose these species to become larger on islands. Numerous colubrid (and one elapid) species attain their largest sizes on islands that also support nesting seabirds, whereas dwarfed populations consume mainly squamates.

The genus Emblemaria presently includes 14 species, five in the eastern Pacific and nine in the western North Atlantic. Several individuals of an undescribed species of this genus were obtained by trawling along the northeastern Brazilian coast in 1981, in depths between 10 and 30 m. This new Emblemaria species best agrees with Emblemaria pandionis in counts and morphometrics, but differs in the number of palatine teeth and in the height of the first dorsal fin spine. The only other Atlantic species having an elongated first dorsal fin spine is Emblemaria hyltoni, but it differs from the new species mainly by having only two obvious segmented pelvic fin rays, and also by having a much longer first dorsal fin spine. Emblemaria australis sp. nov. is sexually dimorphic in several characters. This new species is found mostly over sand and rubble bottoms of the northeastern Brazilian continental shelf.

Understanding the spacing patterns of individuals in a population of animals is important for establishing the specific functions of territorial behavior. Here, we couple a comprehensive analysis of home range with demographic information and focal behavioral observations of Sceloporus undulatus (eastern fence lizard) to investigate (1) spacing patterns, (2) the determinants of home range, and (3) the functional significance of territorial behavior and traits related to territorial behavior (body size, color). Male home-range area is an order of magnitude larger in the New Jersey population of S. undulatus described here than in other populations, whereas female home ranges are comparable in area to other populations of this species. Home-range area is positively correlated with body size in adult males, although this relationship is not found within age classes, and males share about 50% of their home range with other males. After removal of the effect of body size, residual home-range area is smaller in two-year olds (first breeding season) than in older males. Home-range area increases as a function of the number of overlapped females, even after the effect of body size is statistically removed, and the sightings of males within their home ranges are tightly clustered in and near the home ranges of females. Males courted females in 60% of focal behavioral observations and contested other males in 14%, always in close proximity to a female. Relative body size, color, and behavior were displayed by contest “winners” and “losers” in the same manner as previously characterized in captive lizards. Of the three status traits examined, only body size explained variation in home-range area, apparently reflecting the ability of males to court increasing numbers of females as they get older and larger. The winners of contests gained access to the nearby female, but contests had no lasting influence on the locations where males subsequently were sighted. Thus, the size and shape of male home ranges are determined largely by the number and locations of females with whom males interact. Females themselves and not specific sites or home-range area are the contested resources. Plasma corticosterone was correlated with the area of a male's home range overlapped by female home ranges. Because this measure of overlap may reflect the frequency of interactions between lizards and assuming that elevated corticosterone reflects a stress response, social interactions including contests between males and courtship of females appear to be stressful in free-living male S. undulatus.

To test functional hypotheses about home-range variation, it is necessary to compare the fitness of individuals whose home ranges are characterized by measurable differences in vital resources such as mates and food. In the present study, we compare measures of reproductive success of male lizards estimated from field observational data with results from DNA fingerprinting of the same individuals. Observational data included both male and female home-range overlap and proximity of actual sightings. Because home ranges can function for access to mates, and males with larger home ranges can overlap a greater number of females, we tested the hypothesis that males with larger home ranges have higher reproductive success. We also tested to see whether females were most likely to mate with males that overlapped their own home range. We found a positive correlation between male home-range area and the number of females overlapped by a male. Male reproductive success was not significantly correlated with home-range area but was positively associated with the number of females overlapped by a male home range, even after the effect of body size had been statistically removed. Despite this relationship, only about 40% of our observational estimates of reproductive success were confirmed by DNA fingerprinting in this population. Thus, many females had mates whose home ranges did not overlap their own, and proximity of a male to a particular female did not accurately predict paternity.

A new labrid fish, Halichoeres socialis is described from specimens collected in mangrove islets off Belize at depths from less than 1 m to 7 m over coral, sand, rubble, or seagrass substrata. This species feeds in small aggregations on zooplankton and forms evasive schools when threatened. Its small size (largest, 36.4 mm SL, with mature females as small as 27.4 mm) at maturity and at maximum length is unique for the genus. Halichoeres socialis is similar to juveniles of Halichoeres pictus, but it differs in having a black ocellus on its caudal fin base, which is absent in juvenile and female H. pictus.

The sand vipers of the genus Cerastes vertically burrow into the soft sand of the Saharan desert. The mechanics of vertical burrowing in Cerastes cerastes and Cerastes vipera were explored using a combination of morphology, videography, radiography, and experimental manipulation. The results suggest that the key to vertical burrowing is localized unilateral rib abduction. The ribs terminate in expanded calcified costal cartilages, which, when abducted, aid in scraping sand from below the snake and transporting it laterally. The transport of the sand is enhanced by long-axis torsion of the vertebral column. The specialized lateral scales of Cerastes do not appear to function in vertical burrowing.

Sexual selection via female choice is assumed to be common in darters despite few studies demonstrating the phenomenon. This study examines the breeding behaviors of the rainbow darter, Etheostoma caeruleum, and addresses the following four questions: Do females exhibit mating preferences? Which behavioral variables are good measures of female mating preferences? Which male behaviors are used in the context of mating? How do female choice and male competition affect mating success? In dichotomous choice tests, where females could choose between males from two different populations, females performed a precopulatory behavior (nosedigs) significantly more often in front of males from Prairieville Creek than they did in front of males from Seven Mile Creek. However, no pattern of choice was detected when preference was measured as the amount of time spent associated with each male. When the animals were allowed to interact freely, males competed aggressively over the female by chasing and attacking each other. Group spawns occurred where two males mated simultaneously with the female. Male spawning success was positively correlated with male guarding ability (the ability to prevent a competing male from coming between himself and the female). However, there were no significant correlations between overt aggression (chases and attacks) and male spawning success or between female preference (measured in dichotomous choice tests) and male spawning success. Male interactions, in the form of guarding, appear to play a larger role in determining male mating success than does female choice.

The Sardinian brook salamander, Euproctus platycephalus, is an endemic newt restricted to the internal and mountainous regions of Sardinia (Italy). We study the age structure and the morphometric sexual dimorphism in one of the known largest breeding populations of this species. It takes both sexes a minimum of four years to reach maturity, and the period of immaturity often extends to six years. At the breeding site, males are significantly older than females, but we do not know whether these differences are because of a sex-biased longevity or to sex- and age-dependent differential activity patterns. Independently of age, sexes differ in both body size and body shape. Males are longer and heavier than females and show proportionally longer and larger heads, shorter cloacas, and longer hind limbs. Most of these between-sex differences might be explained in the light of the brook salamander's mating behavior, in which males capture females and directly force their spermatophora into the female cloaca.

The existence of temperature-dependent sex determination (TSD) and its latitudinal variability among populations were examined experimentally in Menidia peninsulae. Along the Florida coast, TSD was detected only in a northern population (Apalachee Bay: 29°55′N), wherein the proportion of females declined dramatically with increasing rearing temperature. In lower-latitude populations (New Smyrna Beach: 29°05′N, Vero Beach: 27°46′N, and Grassy Key: 24°45′N), however, offspring sex ratios were temperature-independent and approximated 1:1 at all temperatures examined (17–32 C), indicating genetic sex determination (GSD). The shift from TSD to GSD with decreasing latitude in M. peninsulae occurs coincidentally with a shift from annual to semiannual breeding and life cycle patterns. Combined with the previous studies of the northern congener Menidia menidia (∼32–47°N), the level of TSD in the genus Menidia is generally highest at intermediate latitudes (∼32–38°N), whereas nearly pure GSD is displayed at the northern and southern extremes. This pattern of latitudinal variation across two species confirms that TSD is adaptive in Menidia only in annual life histories wherein temperature during larval development serves as an accurate predictor of length of growing season and hence relative adult body size.

I sampled movements and amount of area used by boreal toads (Bufo boreas) between June and October for 3 yr. Females were found farther from the breeding site than were males, and mean home ranges, as calculated by the adaptive kernel method, were four times larger for females than for males. Temperature and snow accumulation were comparable over the study, but data collection was hampered by mortality of animals caused by an outbreak of amphibian chytridiomycosis in yr 2. These data provide insight into use of habitat by boreal toads in undisturbed areas but may not be typical of a completely healthy population.

Three species of the genus Megaelosia (Megaelosia massarti, Megaelosia boticariana, and Megaelosia lutzae) were studied karyotypically using conventional Giemsa staining, C-banding, and NOR techniques. Megaelosia lutzae had 2n = 32 chromosomes, a new diploid number for this genus and for the subfamily Hylodinae. Two morphotypes of B-chromosomes were found in two specimens of M. massarti. C-banding patterns and NOR location varied among the species. Nevertheless, some chromosome pairs, as well as the NOR-bearing secondary constriction and the large pericentromeric C-block on the short arm of chromosome 10, were consistent among the three species. Megaelosia differs markedly from other Hylodinae and Dendrobatidae in terms of karyotype.

The development of the anterior vertebrae were examined in late larval and early juvenile Chanos chanos, with a focus on character states that have been used in ostariophysan systematics such as the expansion of dorsal cartilages of the anterior neural arches. In Chanos, these changes take place in juvenile fishes beginning at about 12.0 mm SL. This contrasts sharply with the ontogeny of the otophysan Weberian apparatus, which occurs in early to midlarval stages. A supraneural space is present in Chanos, between neural arch 1 and the occiput. It is into this space that the cartilages of neural arch 1 and the supraoccipital expand. We also found paired nodular cartilages are present in the supraneural space but are incorporated into the supraoccipital cartilage by about 15.5 mm SL. These cartilages may represent an accessory neural arch (ANA).

The mechanisms that underlie the diversity of cichlids in the East African Great Lakes are poorly understood. Sexual selection through female choice based on male body coloration has often been suggested as a driving force behind the speciation of these fishes. The objectives of this study were to investigate, through mate choice trials, the cues that guide species-isolating female choice. In a group of sympatric Lake Malawi mbuna (rock-dwelling fish), we investigated both visual and chemical cues that might guide female choice by giving gravid females a choice between a heterospecific and a conspecific male. Visual cues, in contrast to olfactory cues, were sufficient to stimulate courtship and thus guide female choice of males. Furthermore, in contrast to other studies on related species, we found that females courted only with conspecifics even if color was not a cue. Species-isolating female choice is likely based primarily on visual information.

Ostracion knorrii Walbaum, 1792, is shown to be a senior synonym of the antennariid anglerfish Antennarius striatus (Shaw and Nodder, 1794). Conditions exist, however, to allow “reversal of precedence” of the two names, as provided by Article 23.9.1 of the International Code of Zoological Nomenclature. Thus, A. striatus (Shaw and Nodder, 1794) is regarded as valid, qualifying as a nomen protectum, whereas the name O. knorrii Walbaum, 1792, is recognized as invalid, qualifying as a nomen oblitum.

Movement behavior and timing of mating vary between populations of snakes. Here I present data on movement and mating behaviors of adult male Crotalus oreganus concolor in southwestern Wyoming and compare the results to other populations. Male C. o. concolor make short, infrequent movements. I found no evidence of migratory behavior or shifts in areas used during the monitoring period. Mating behavior was limited to 5–17 July, shorter in duration than for any other population of C. oreganus. Male snakes located and courted females prior to shedding of the females; however the only successful copulation was between a pair that had recently shed. One instance of male-male combat was observed, during which the larger male displaced the smaller male.