Biological invasions are driven by the transport, release/escape, establishment, and spread of organisms across bio-geographic boundaries. While actions that prevent transportation and release/escapement are most efficient at thwarting the establishment of new invasions, control of existing evasions requires insight into ecological mechanisms that promote organism spread. The Western Mosquitofish (Gambusia affinis) is introduced globally because of its presumed benefits as a mosquito control agent, but the resulting invasions into nearby ecosystems have negative effects on native biota. Females of Western Mosquitofish have the ability to store sperm for multiple weeks, so movement of a single inseminated female could lead to secondary spread and new population establishment. Consequently, the global invasion success and secondary spread of Western Mosquitofish might be linked to greater movement ability among females, but we know little about female dispersal ability because existing studies are heavily biased toward evaluating males. Here, we investigate how six morphological traits linked to fish dispersal ability differ between male and female Western Mosquitofish. Our results reveal that traits correlated with movement capacity differed between males and females, with males having a perceived advantage for two traits (longer relative peduncle length and shorter relative body height) and females having a perceived advantage for three traits (larger caudal-fin aspect ratio, larger total length, and greater caudal-peduncle throttling). These findings suggest that females have greater capacity for dispersal relative to males and that future investigations on Western Mosquitofish and other ecologically and morphologically similar species should give greater focus to female movement ecology.

Females of highly iteroparous, oviparous species must mate multiply and potentially choose mates hundreds to thousands of times throughout their lifespan. Theory indicates that costly female mating preferences may favor low levels of preference in species that have to mate repeatedly. One potential cost of mating preference is overripening, which occurs in some external fertilizers when females ovulate but do not spawn their eggs. Overripening may create a tradeoff between the benefits of mate choice (i.e., rejecting males of poor quality) and egg viability. This study tested for overripening as a cost of delayed mating and determined its effects on female mating preferences in the Bluefin Killifish, Lucania goodei. Female L. goodei often mate multiple times each day across multiple days when gravid. Females were divided into three treatments: mate every day, mate every two days, and mate every four days. In the first experiment, females were paired with either a red or a yellow conspecific male on spawning days. In the second experiment, females were paired with either a conspecific male (L. goodei) or a heterospecific male (L. parva) on spawning days. In both experiments, the eggs were retrieved following spawning, and their viability (i.e., survival) was monitored for five days. Females that were forced to ‘hold onto’ their eggs for extended periods had smaller clutch sizes and lower egg viability, demonstrating that costs to rejecting males potentially exist. In the first experiment, there was no evidence of female choice for red versus yellow males. In the second experiment, female preference for conspecifics versus heterospecifics declined when females could only mate once every four days, but the differences among treatments did not reach statistical significance. The results of this study illustrate a potential cost to female mate choice and suggest that the benefits of mate choice may not outweigh the costs due to egg overripening.

We describe the olfactory chamber and histology of the olfactory epithelium in the auchenoglanidid catfish, Parauchenoglanis punctatus. Unlike the olfactory anatomy of non-auchenoglanidid catfishes, in all auchenoglanidids the olfactory rosette is elevated on a membrane suspended over the anterior portion of a large accessory sac. Scanning electron microscopy and histology show an array of long non-sensory cilia are present, likely maintaining flow of water over the rosette. Microvillar and ciliary sensory cells are regionalized in the folds of the lamellae. Combining dissection with reconstruction of the olfactory chamber, membrane, rosette, and accessory sac using contrast-enhanced CT scanning of soft tissue and supporting osteology suggests a novel “sniffing” mechanism may represent the primary means of drawing water and odorants into the olfactory chamber, and that specializations of the olfactory anatomy in this family function in flow augmentation into and around the olfactory chamber, maximizing the entrainment of odorants over the olfactory epithelium.

Females of the diandric, protogynous species Thalassoma bifasciatum release a single all-or-nothing explosive burst of eggs in a once-a-day spawning event. The mechanism controlling egg release is unknown but must provide proper spatiotemporal distribution of eggs, i.e., for successful fertilization, one that conforms sufficiently to the corresponding externally released sperm cloud geometry. This is particularly important in pair spawns, where one female releases eggs approximately simultaneously with the sperm release of a single male in a rapid, highly synchronized spawning rush. In order to determine how egg release is controlled, we examined the surface and internal morphology of the urogenital region of mature females using in vivo light microscopy, histology, and scanning electron microscopy. In anesthetized females, manual pressure to the abdomen distended the epidermis between the anus and urinary papilla until it ruptured and eggs burst outward en masse. Females captured before or after natural spawning, and with or without manual pressure applied under anesthetic, consistently exhibited a path for egg release from the oviduct(s) that was a caudoventrally descending irregular sinus within a loose connective tissue mass, which opened with the exterior where the epidermis ruptured; there was no distal duct, surface gonopore, or sphincter. This pathway was immediately rostral to, and separate from, the urinary papilla, its urinary duct, and urinary pore, which had no communication with the oviduct(s). We suggest that the egg load expands the sinus and distends the epidermis until it ruptures due to increased internal pressure, rapidly releasing hundreds of eggs. These results are consistent with a burst-release mechanism that occurs during the pelagic spawning event, perhaps optimizing spatiotemporal mixing of gametes.

Accurate estimation of the abundance of many snake species is often compromised by their secretive and elusive nature, which lowers the probability of recapturing marked individuals. However, urban-dwelling populations of Dekay's Brownsnake (Storeria dekayi) often congregate at high densities in fragmented edge habitats, making them unusually good models for estimating abundance using mark–recapture techniques. We used a mark–recapture modeling approach to estimate the population size of S. dekayi in two roadside greenspaces at an urbanized site in central New Jersey, USA. We applied a robust design sampling scheme and incorporated temporary emigration and trap responses into our a priori candidate models. Snakes occurred at high densities in both sites, with constant capture probabilities in the early activity season, but with some evidence of trap-shy behavior. This study provides a useful guideline for monitoring and assessing the population size of snakes, especially abundant species in urban environments.

Morphological adaptations of individuals are determined by different environmental and/or genetic factors. Depending on locality and sex, these adaptations may vary in different ways. Therefore, the objective of this study is to evaluate some morphological (morphometric) traits over time in different populations of Sceloporus mucronatus, a species endemic to Mexico with a high risk of extinction. The results showed significant differences at the intrapopulation level, male-biased in size, head, jaw structures, and limbs; however, females showed a greater interaxillary distance, although the difference was not significant in all populations and years. Among populations and years, significant differences were recorded in the size of the males. In females, the differences were in the size and the interaxillary distance. A significant and positive relationship was found between snout–vent length and temperature, precipitation, and elevation in females, and between snout–vent length and elevation in males; however, the association was very low. The morphological variation observed among populations of S. mucronatus suggests that this species has a wide degree of phenotypic plasticity, and therefore could adapt to different environmental conditions. However, the morphological variation recorded in this study is not strongly associated with some of the environmental variables analyzed; therefore, it is necessary to carry out further studies (behavior, thermal ecology, and diet, among others) to understand how this species is responding to environmental changes, mainly those generated by humans.

Ecdysis is a defining feature of all squamate reptiles, occurring at least annually in snakes. Shedding occurs at irregular and unpredictable intervals, inhibiting studies of the importance of ecdysis to life history. To date, limited information on the endocrine mechanisms controlling ecdysis has been used to induce sheds via endocrine gland removal. However, whole-gland removal is often lethal, limiting the scope of any conclusions drawn from these studies. We used data from the literature and reports of the natural timing of shed events in rattlesnakes to design a novel, non-invasive method for inducing ecdysis in the laboratory. Temperature manipulations following simulated brumation periods were used to induce ecdysis. Temperature trials were successful in inducing ecdysis in 63% of treated animals (28 of 44). Efficacy of the induction of ecdysis via temperature manipulation was related to body condition and time since previous shed cycle (with high body condition animals that had not shed in the three months prior being most likely to shed). The timing of ecdysis (Immediate or Delayed) relative to temperature manipulation was related to days since last shed but not body condition, with those who had not shed > 5 months prior to manipulations being most likely to shed immediately after warming from brumation temperatures (10°C). Temperature manipulation shows potential for use in the lab-based induction and study of ecdysis, particularly in high body condition animals that have not shed in several months. A reliable method to induce ecdysis in the laboratory provides a novel opportunity to investigate the physiological and ecological implications of an under-studied but ubiquitous function in squamates.