The White Shark (Carcharodon carcharias) is a top predator cosmopolitanly distributed and heavily protected worldwide. Identification and information pertaining to White Shark nursery areas is limited yet crucial for the protection of sharks during their most vulnerable life stages. Here, we present morphometric, skeletal, and haplotypic characteristics of the smallest free-living White Shark reported to date (1066 mm TL). These characteristics correspond to a newborn White Shark smaller than those previously reported in an embryonic state but displaying the same number of rows of functional teeth as an adult. The individual was caught incidentally by an artisanal fishery operating along the Pacific coast of Baja California, near the international border between Mexico and the United States (USA). We found no genetic divergence between Isla Guadalupe and central California, two aggregation sites that have been proposed as a possible source for newborn sharks in this area. The newborn White Shark displayed the most common haplotype present among individuals at both aggregation sites. These findings provide evidence suggesting the presence of an extended nursery habitat in the Northeast Pacific, a transnational region between Mexico and USA.
In southern Florida, Gopher Tortoises (Gopherus polyphemus) occupy mesic flatwoods and Florida scrub communities where habitat and climatic conditions differ from other portions of the species' range. Both of these habitats appear suboptimal for tortoises due to saturated soils in mesic flatwoods and low forage abundance in scrub. Nonetheless, these habitats support large numbers of tortoises in southern Florida, albeit at low intensities. We assessed influences of elevation and microtopography on the spatial distributions of tortoise burrows and examined burrow use patterns within six sites at Avon Park Air Force Range in south-central Florida. The six sites differed in dominant soil types and vegetation communities, allowing comparisons of burrow distributions among mesic flatwoods, Florida scrub, and mixed flatwoods-scrub habitats (two replicate sites each). Point-process modeling identified significant influences of microtopography on burrow intensities that superseded the effects of site-wide elevation trends in five of the six sites. The effects of microtopography were most pronounced in flatwoods, suggesting greater reliance on areas of slightly higher elevation in mesic habitat, presumably in response to saturated soils and frequent flooding. Burrow use patterns during an exceedingly wet year also suggested that tortoises respond behaviorally to unsuitable hydrology by moving frequently among burrows that were flooded with groundwater. Microtopographic variation may be an important predictor of small-scale habitat use for fossorial reptiles, especially in mesic soils, which could be readily explored using increasingly available LiDAR-derived elevation data combined with the modeling approach demonstrated here.
Vast differences in available resources between habitats can have profound influences on aspects of an organism's life history, such as reproductive investment. Our study investigated how differences in nutrient availability affect sperm size in Diamond-backed Watersnakes (Nerodia rhombifer). We compared body size and sperm morphometrics between two populations with differing nutrient availability: a naturally occurring lake and a commercial fish farm. We hypothesized that prey availability affects sperm morphometrics. Our null hypothesis was that there would be no significant difference in sperm morphometrics between populations, whereas our alternative hypothesis was that the snakes from the fish farm would have significantly longer sperm. We measured total sperm length, sperm head length, sperm tail length, and snout–vent length (SVL). We then used two-tailed t-tests and AIC model selection to test our hypotheses. SVL was not correlated with sperm size. Furthermore, none of the sperm morphometrics were significantly different between the two populations. Finally, a nearly 1:1 correlation between sperm tail length and total sperm length was found. AIC model selection corroborated these results by choosing only sperm head length and sperm tail length as significant predictors of total sperm length. This is the first published study to explicitly compare sperm morphometrics between two populations of the same snake species. Additional studies of this nature are required to corroborate whether lack of significant differences in sperm morphometrics among snake populations are common.
A new species of Hyphessobrycon from a tributary of the Rio Paru do Oeste (Rio Trombetas basin), at the lower Amazon basin draining the Guiana Shield region in Pará State, Brazil, is described. The new species presents a unique combination of an irregularly-shaped humeral blotch, a broad diffuse midlateral stripe, and a roughly triangular caudal peduncle blotch. The new species is herein included in the Hyphessobrycon agulha species-group, and comparisons with species belonging to this group and to a similar-looking non-congener, Hemigrammus bellottii, are presented.
Information about the life history of larval fishes can be sparse, especially at the edges of typical geographic ranges and among fishes for which there is no commercial fishery. We report a new observation of larval Arctic Shanny (Stichaeus punctatus) far south of their typical geographic range in the western North Atlantic. Only two previous records of adult of S. punctatus have been documented in this region, and there has only been one previous report of larvae in US Atlantic waters. From May through July 2018, we observed large numbers of larval S. punctatus by night-lighting off a dock at Shoals Marine Laboratory on Appledore Island, Maine, in the Gulf of Maine. We include approximations of catch per unit effort (number of larvae per ten-minute sampling interval) throughout the sampling period and information regarding identifying features. The high number of larvae seen could indicate that the Isles of Shoals is a spawning locality for this species and could indicate a future increase in their abundance in the southern Gulf of Maine.
