The Middle American killifish genus Profundulus occurs in most Pacific and Atlantic drainages from the Mexican state of Guerrero to the Chamelecón River in Honduras, with highest species diversity in southern Mexico. In this study, we describe a new member of the genus, Profundulus parentiae, new species, from the Mexican state of Oaxaca. It is distinguished from P. guatemalensis and P. kreiseri by having rows of dots on the sides of the body. Profundulus parentiae, new species, can be distinguished from P. oaxacae by having 33 lateral scales, versus 29–31 in P. oaxacae. Profundulus parentiae, new species, can be distinguished from P. balsanus, P. oaxacae, and P. mixtlanensis by the presence of long epiotic processes that extend beyond the epipleural ribs of the first vertebra, versus short epiotic processes not reaching the epipleural ribs of the first vertebra. Profundulus parentiae, new species, can be differentiated from P. punctatus by the presence of a dorso-ventrally compressed Meckel's cartilage with a relatively straight medial process and a narrow and strongly concave sesamoid articular, versus a dorso-ventrally expanded Meckel's cartilage with concave medial process and a wide and moderately concave sesamoid articular. Based on the phylogenetic analysis of molecular sequence data, the new species is recovered as the sister taxon to P. balsanus. The discovery and description of this new species in southeastern Mexico, raises the number of species from this region to five and suggests that this area has been an important center for diversification within this lineage of killifishes.

The conservation of imperiled species often depends upon conserving their prey. Graptemys flavimaculata (Yellow-blotched Sawback) is an imperiled turtle endemic to the Pascagoula River system of Mississippi, USA. We investigated diet variability of G. flavimaculata relative to site geography, sex, seasons, and size. We captured individuals from May to October in 2007 and 2008 at two distant sites. One site is an inland freshwater tributary (Leaf River, LR) and the other site is coastal and tidally influenced (Pascagoula River, PR). Feces from males (n = 68) and females (n = 74) were collected and analyzed. Using the Index of Relative Importance (IRI; 0–100 scale, 100 = only item present in all samples), we found that G. flavimaculata are primarily sponge specialists for both males (IRI_LR = 85, IRI_PR = 91) and females (IRI_LR = 84, IRI_PR = 65). For both sexes, between-site differences were more varied than within-site differences; for the latter, prey items were typically similar for males and females at a single site, but importance varied. Seasonal comparisons suggest that both LR and PR females shifted diets towards mollusks during the spring and fall, possibly associated with increasing energy and calcium for reproduction. Based on the frequency of wood fragments in feces, submerged deadwood appears important for prey species, and therefore, managers should conserve deadwood along riverbanks (i.e., mature riparian corridors). If channel maintenance is needed, deadwood should be moved toward banks rather than removed to conserve structure for prey species colonization.

We describe a new frog species of the genus Guibemantis, subgenus Pandanusicola, from Marojejy National Park in northeastern Madagascar. Guibemantis milingilingy, the new species, exhibits high genetic divergence from all other described species of Guibemantis based on DNA sequences of a fragment of the mitochondrial 16S rRNA gene. This new species inhabits Pandanus plants like the majority of other members of this subgenus, but is found at much higher elevations (2026 m a.s.l.). It differs from its closest relative, G. punctatus, by the lack of speckled or spotted dorsal patterns and by the presence of a distinctly dark tympanum. As a high-elevation species, it is likely to be a species sensitive to climate change, similar to other montane endemics in Madagascar.

Physiological color change in animals is a rapid process involving the redistribution of pigments within chromatophores, and may have roles in camouflage, communication, or thermoregulation. Although observed in other ectotherms, it has not previously been documented in crocodilians. Using wild and captive Sunda gharials (Tomistoma schlegelii), we confirm rapid ventral color change in juveniles, as evidenced by significantly darker ventral scales in illuminated vs. dark environments. We also found that color varied significantly with body size, with larger individuals losing the ability to change color, and by testing environmental factors potentially triggering color change—temperature, ambient light, background color, or stress—we report that illumination was the only factor observed to explain the change. Our results reveal an unusual trait not corresponding to established countershading patterns, which provides a basis for further research not only into crocodilian behavioral ecology and physiology, but also into animal camouflage and convergent evolution. These results add further evidence to Tomistoma being an evolutionarily distinct lineage of crocodilian, confined to the threatened peat swamp habitats of Southeast Asia.

The Mayan Cichlid (Mayaheros urophthalmus) is usually considered to be a complex of 18 subspecies, most of which are endemic to the Yucatan Peninsula and were diagnosed by phenetic analyses based on traditional morphometrics and color pattern. However, morphological differences can be due to environmental conditions rather than taxonomic distinctiveness. We evaluated, by means of a geometric morphometric analysis, two hypotheses for shape differences in 20 natural populations of M. urophthalmus, including five subspecies recently raised to species status: M. alborus, M. cienagae, M. conchitae, M. mayorum, and M. zebra. The geographical distribution and three types of aquatic environment (River, Lagoon or Pond, and Cenote) were used as classificatory variables. In addition, a molecular analysis of two concatenated fragments of mitochondrial DNA (mtDNA), cytochrome b (cytb) and cytochrome oxidase subunit I (COI), showed genetic differentiation among some populations (F_ST = 0.36). Whereas the geometric morphometric analysis found significant differences among all aquatic environments, patterns of body shape of M. urophthalmus are more consistent with ecophenotypic variation than with genetic differentiation due to geographic isolation by distance. We think that there is currently no evidence to raise the traditionally recognized subspecies of M. urophthalmus to the species level.

Three cyprinids often referred to as the Gila robusta complex, G. robusta, G. nigra, and G. intermedia, are morphologically similar and genetically indistinguishable at the currently recognized species level. Current taxonomy is based on purported morphometric and meristic differences that are detailed in a classification key; however, the ability of the key to reliably distinguish the species has recently come into question. Chubs were collected from locations in Arizona, and two analysis methods were used to predict species' identification success using the key: 1) correct assignment to species using cluster analysis and multinomial logistic regression; and 2) observer identification success by species. Cluster analysis and multinomial logistic regression correctly assigned only 62% and 74% of fish, respectively, to the assumed species designation. Identification success using both analysis methods was most successful for G. robusta (82% cluster; 82% regression), followed by G. intermedia (53% cluster; 80% regression), and G. nigra (49% cluster; 58% regression). Overall observer identification success was 54%, led by G. intermedia (68%), followed by G. robusta (63%) and G. nigra (33%). The high level of misidentification appears to be due to overlap in morphometric and meristic characters among assumed species groups. Although the three species are currently considered allopatric, sympatry was found in 88%, 76%, and 100% of locations in the cluster analysis, regression analysis, and observer analysis, respectively. These results indicate that the morphometric and meristic characters in the key do not consistently distinguish the three putative chub species. Because independent genetic analyses also fail to support the delineation of the three species, we consider G. robusta as a single polymorphic species a viable hypothesis. Furthermore, a recent formal taxonomic review of the three species conducted by the American Fisheries Society–American Society of Ichthyologists and Herpetologists Committee on Names of Fishes concluded the available morphological and genetic data (including a pre-publication version of this study) support recognition of only one species, G. robusta.

Ram ventilation, which is characterized by the production of a respiratory water current over the gill by locomotory effort, widely occurs among pelagic sharks. However, the process by which the juvenile starts this respiratory mechanism remains largely unknown. The captive birth of a Tiger Shark (Galeocerdo cuvier) at the Okinawa Churaumi Aquarium on 23 March 2017 permitted the examination of the parturition process and behavior of newborn juveniles of this species. Sonographic examination of the pregnant female showed that, unlike adult Tiger Sharks, embryos used buccal pumping, revealing that Tiger Shark shifts its respiratory mechanism from buccal pumping to ram ventilation after birth. Our observation also showed that ram ventilation of the neonate was not continuous, and buccal pumping was also used when the neonate intermittently rested on the bottom of the tank. We speculate that this behavior is the transitional phase in the shift from buccal pumping to ram ventilation in neonates, and continuous ram ventilation may be established after the development of continuous and fast swimming abilities.

We describe Oryzias dopingdopingensis, a new species of ricefish, from Doping-doping River, a river in Malili in central Sulawesi, Indonesia. The new riverine species is distinguished from lacustrine congeners in Malili Lakes by a combination of 33–36 scales along the lateral midline and body depths of 20.3–25.5% standard length (SL). Oryzias dopingdopingensis, new species, is also distinguished from all other Sulawesi Oryzias by a combination of 8–9 dorsal-fin rays, caudal peduncle depths of 10.2–11.4% SL, eye diameters of 8.5–9.9% SL, and maximum SL up to 35.8 mm. In breeding males, 5–8 black blotches or bars appear along the lateral midline. Analyses of mitochondrial ND2 sequences revealed that O. dopingdopingensis, new species, carry distinct haplotypes from those of the Malili lacustrine species, suggesting no hybridization between them, although Doping-doping River shares an estuarine region with the Malili Lake system. Instead, O. dopingdopingensis, new species, is in a monophyletic group with O. sarasinorum and O. eversi in western Sulawesi. However, unlike these two pelvic brooders, we observed that females of O. dopingdopingensis, new species, deposit eggs soon after spawning and exhibit no maternal care.

Amphibious fishes moving over land between aquatic habitats likely encounter abrupt changes in a number of environmental conditions, including salinity. This study characterized the 1) spatial heterogeneity in salinity in the mangrove forest habitat of the self-fertilizing, amphibious mangrove rivulus (Kryptolebias marmoratus), 2) metabolic cost and behavioral response to acute exposure to novel salinity, and 3) repeatability of individual responses to acute changes in salinity. In mangrove habitats on Long Caye, Belize, salinity varied widely over short distances from 20.9–41.7‰ over a 90 cm distance. In the lab, fish were exposed to an acute change in salinity of Δ10, 20, or 30‰. Oxygen consumption significantly decreased in response to a 10‰ decrease in salinity and increased when salinity was elevated by 30‰. Activity levels significantly increased with an increase in salinity (Δ20 and 30‰). Individuals showed repeatable differences in both oxygen consumption rates and activity levels. Together, our data show that K. marmoratus is highly responsive to abrupt increases in salinity. Thus, movements made by K. marmoratus between temporary pools in the mangrove forest will acutely alter behavior and possibly metabolism, with many potential ecological consequences.

This study identified nursery habitat, recruitment patterns, the planktonic larval duration (PLD), size and age at settlement, and growth rate of the young-of-the-year (YOY) Giant Sea Bass (GSB), Stereolepis gigas, off Southern California. A total of 160 YOY GSB were sighted on 150 transects over a three-year period. Young-of-the-year GSB were relatively rare (maximum density of 40/ha) and recruitment was limited to a few areas. In 2014–2015, densities of YOY GSB were significantly higher at six locations off sandy beaches nearest the heads of submarine canyons off Redondo Beach, Newport Beach, and La Jolla, California. The vast majority of occurrences of YOY (73%) were within 500 m of the heads of submarine canyons. Three color phases of YOY were discovered ranging (smallest to largest individuals) from black to brown to orange. Recruitment occurred from July through February with peak abundances occurring in the late summer months from August through October. YOY occurred at depths from 2 m to nearly 10 m. Overall, size of YOY GSB increased with depth in the shallow sand riffle zone. YOY grew rapidly at 1.23 mm/day (n = 23) with collected individuals ranging from 31 to 84 d old based on daily ring increments in otoliths. The planktonic larval duration was estimated to be about one lunar month (26.8±2.4 d) based on the presence of the first settlement check and size of earliest settlers. Size at settlement was estimated to be 14.4±3.0 mm TL (10.6±2.5 mm standard length [SL]). This information adds substantially to our knowledge of early developmental processes and recruitment patterns of Giant Sea Bass that are crucial to our understanding of their life history and to making informed decisions regarding fisheries management policies and conservation efforts.

The family Leptotyphlopidae comprises about 120 species allocated in 12 genera including Siagonodon, the latter with four currently recognized species. Here we propose new diagnostic characters for the genus Siagonodon based on the analysis of variation of external morphology and comparisons with related taxa. In order to evaluate the diagnostic characters of the genus Siagonodon, representatives of other genera of the tribe Epictini occurring in South America were also analyzed (Epictia, Rena, and Trilepida). We examined 14 species of the family Leptotyphlopidae and analyzed 67 characters of external morphology. We propose six new diagnostic characters for the genus Siagonodon, including: rostral scale with enlarged base, terminal spine reduced or absent, and straight snout in lateral view. Furthermore, we provide new data on morphological variation and geographical distribution of the poorly known Siagonodon cupinensis, expanding the diagnosis of this taxon and improving comparisons with congeners.

Oocyte development and staging is described from histological preparation of the ovaries of field collected specimens of the Florida Bass, Micropterus floridanus. Oocyte development in Florida Bass progresses through six stages beginning with oogonial proliferation and ending with ovulation, the release of eggs. The stages are based on mitosis and meiosis, the core processes of Adaptable Oocyte Staging. After ovulation, the postovulatory follicle complex produces a mucus-like fluid with unknown function; we speculate that it protects the eggs immediately upon ovulation and upon their release into freshwater during spawning. Atresia is rare in the ovaries of reproductive Florida Bass. The release of cortical alveoli after fertilization follows a unique, extended time-release sequence. Oocyte development in the freshwater perciform Florida Bass follows precisely a pattern that has been documented for marine perciform fishes that produce positively buoyant, pelagic, non-adhesive eggs. The eggs of Florida Bass are morphologically like these pelagic eggs in that they have a single large oil globule and no attachment filaments. Yet Florida Bass eggs have small, clear yolk globules and an adhesive egg envelope and are functionally demersal. Thus, classification of an egg as pelagic or demersal should consider its morphology as well as its function, especially if egg type is to be used to interpret phylogenetic relationships or evolutionary patterns. The clearing of yolk due to the uptake of water during the development of actinopterygian eggs, as they progress from a demersal to a potentially pelagic phase, may be a general mechanism of oocyte maturation in teleost fishes.

A new species of Cyphocharax (Characiformes: Curimatidae) is described from the lower Rio Tapajós basin, including its tributary, the Rio Arapiuns, Pará, Brazil. The new species is diagnosed from congeners by a combination of characters that includes overall body light-colored, with a silvery hue, lacking any pattern of stripes or blotches, a distinctly straight body profile, and some meristic and morphometric features. Comparisons with similar congeners as Cyphocharax festivus, Cyphocharax leucostictus, Cyphocharax nigripinnis, and Cyphocharax plumbeus, some of which occur sympatrically with the new species, are presented.

The submerged continental shelf of Onslow Bay, North Carolina, preserves hardbottom limestone scarps with underlying clays as small isolated exposures in progressively deeper water seaward from the modern-day shoreline. These scarps formed as a result of wave- and current-driven erosion, transport, and redeposition of bottom sediments due to glacioeustactic sea level cyclicity and the migration of the ancestral shoreline since the Pliocene. Fossiliferous lag deposits containing an abundance of lamniform and carcharhiniform teeth, including those belonging to megatoothed sharks, occur adjacent to these scarps. These specimens include teeth from: Alopias grandis, Carcharhinus falciformis, Carcharhinus priscus, Carcharias cf. C. taurus, Carcharodon carcharias, Carcharodon hastalis, Galeocerdo aduncus, Galeocerdo cuvier, Hemipristis serra, Isurus oxyrinchus, Negaprion brevirostris, Otodus chubutensis, Otodus megalodon, Parotodus benedinii, Physogaleus contortus, and Rhizoprionodon sp. Comparison of biostratigraphically significant lamniform and carcharhiniform taxa from the submerged shelf with those from land-based assemblages along the Atlantic Coastal Plain of the USA indicates that the shallower shelf (≈25 m deep) exposes the Miocene Pungo River Formation and intermediate and deeper shelf (≈30–35 m deep) expose the Pliocene Yorktown Formation. Many of the Onslow Bay lamniforms and carcharhiniforms also occur in Miocene and Pliocene shallow marine assemblages around the world and reinforce the migratory abilities of these chondrichthyans in the late Cenozoic and the utility of lamniform and carcharhiniform teeth in biostratigraphic and chronostratigraphic analyses.

Variation in habitat across the landscape can limit dispersal between populations and influence the diversity and degree of genetic structure of populations. This effect may be larger in small aquatic species with low vagility, specific habitat requirements, and that inhabit lotic systems where dispersal may be biased by the unidirectional movement of water downstream. Darters offer a unique perspective to understand these influences because they have variable life histories and habitat requirements, and evidence suggests that certain life history characters may affect gene flow. Data were collected from a combination of microsatellite loci from 825 individuals to compare genetic structure and differentiation of three species of darters (Ammocrypta beanii, Etheostoma swaini, and Percina nigrofasciata) with differences in life histories and habitat requirements in the Pearl River basin. Our analyses reveal low, but interesting, patterns of population subdivision. Genetic subdivision among populations was highest for E. swaini, intermediate for P. nigrofasciata, and lowest for A. beanii. This pattern suggests a difference in dispersal, influenced by the variation in available habitat required for each species. Further investigations are warranted for small, benthic, and especially threatened species in the Pearl River basin as the main channel has undergone a significant shift in geomorphology and habitat diversity since the construction of reservoirs and low-head dams along its course.