The Widemouth Blindcat, Satan eurystomus Hubbs and Bailey 1947, was the second of four stygobitic species of Ictaluridae discovered in the subterranean waters of southern Texas and northeastern Mexico. The skeletal anatomy of Satan has been scarcely known from a few, dated radiographs. Using additional radiographs and high resolution CT-datasets for two well-ossified specimens, we applied high-resolution X-ray computed tomography (HRXCT) to visualize, illustrate and describe the bony skeleton of Satan. We also provide an online archive of still and animated tomographic images of the skeletal anatomy of this little-known species. The skeleton and soft anatomy of Satan are distinctive. Twelve skeletal autapomorphies are described that singularly distinguish Satan within Ictaluridae and, probably in combination, from all other catfishes. Some of these are reductive losses or simplifications of skull bones (e.g. loss of one infraorbital bone; reduced ornamentation of the pterotic bone) and joint complexity (e.g. simple overlapping frontal-lateral ethmoid articulation; loosely ligamentous interopercle-posterior ceratohyal joint). Some of the autapomorphies are anatomically and perhaps developmentally complex (e.g. a novel series of three midline joints closing a middle span of the posterior cranial fontanel; a deeply excavated temporal fossa and an unusually enlarged interhyal bone). The tiny dorsal-fin spinelet (first lepidotrich) of Satan has a novel peaked and twisted shape. Ten apparent and exclusive synapomorphies within Ictaluridae gathered from this and previous studies suggest that Satan and Pylodictis are closest relatives. Most of these are functionally related to prey detection and suction feeding: fusion of the symphyseal mandibular sensory pores and increase in the number of preoperculo-mandibular canal pores; depressed, flattened heads and wide transverse mouths; prominent posterior process of the lateral ethmoid alongside and below the frontal bone margin; vertical and blade-like supraoccipital posterior process; unique arrangement of the parasagittal and occipital muscle-attachment crests on the skull roof; large triangular panel of integument within the operculum framed by the opercle, preopercle and interopercle bones; elongated posterior ceratohyal; and, form of the fourth supraneural and loss of its anterior nuchal plate. In contrast, fifteen synapomorphies recovered by Arce-H. et al. 2016, are confirmed suggesting that Satan is one of the four stygobitic ictalurids comprising a “Troglobites” subclade within the family: (Trogloglanis, Satan, Prietella phreatophila, P. lundbergi). These features include three stygomorphic and reduction apomorphies that are exclusive within Ictaluridae: loss of fully developed eyes and pigmentation, and simplification of the fifth vertebra and its joint with the Weberian apparatus. Twelve other synapomorphies shown by the Troglobites are also apparent homoplasies of character states shared with various other ictalurids. These include reductive characters such as shortened lateral line canal, reduced infraorbitals and underdeveloped or incomplete ossifications of the pterotic, supraoccipital, hyoid arch bones and transcapular ligament. Also, the Troglobites and various other ictalurids have: an adnate adipose-caudal fin, foreshortened anterior cranial fontanelle, reduced ventral wings of the frontal bone, replacement of bone by cartilage in hypohyal joints; incompletely ossified transcapular ligament, and consolidation of some hypural bones. Completing a full morphological character dataset across the Troglobites has been impeded by incomplete specimen preparations and study of P. lundbergi and to a lesser extent, P. phreatophila and Trogloglanis.
Sex-bias in gene expression is a widespread mechanism for controlling the development of phenotypes that differ between males and females. Most studies on sex-bias in gene expression have focused on species that exhibit traditional sex-roles (male-male competition and female parental care). By contrast the Syngnathid fishes (sea horses, pipefish, and sea dragons) are a group of organisms where many species exhibit male brooding and sex-role reversal (female-female competition for mates and paternal parental care), and little is known about how patterns of sex-bias in gene expression vary in species with sex-role reversal. Here we utilize RNA-seq technology to investigate patterns of sex-bias in gene expression in the brain tissue of the Gulf Pipefish (Syngnathus scovelli) a species that exhibits sex-role reversal. Gene expression analysis identified 73 sex-biased genes, 26 genes upregulated in females and 47 genes upregulated in males. Gene ontology analysis found 52 terms enriched for the sex-biased genes in a wide range of pathways suggesting that multiple functions and processes differ between the sexes. We focused on two areas of interest: sex steroids/hormones and circadian rhythms, both of which exhibited sex-bias in gene expression, and are known to influence sexual development in other species. Lastly, the work presented herein contributes to a growing body of genome data available for the Syngnathids, increasing our knowledge on patterns of gene expression in these unusual fishes.
Desert ecosystems are particularly susceptible to anthropogenic influences. This is especially true for desert aquatic systems where limited water resources can be easily impaired by excessive water mining depleting the underlying aquifers. Although the aquatic environments and their associated native fishes are declining throughout the Chihuahuan Desert, we will focus on examples from the Big Bend region, the Balmorhea Springs Complex, the Pecos River region, and the Devils River region. Ongoing and impending land use and water consumption patterns suggest even further reductions in the near future. Even though numerous conservation activities are underway, archaic Texas water laws must be revisited and reformulated if the desert aquatic systems are to be truly conserved for more than the immediate future.
Discovery of the Mexican blindcat, Prietella phreatophila, in Texas in 2016 generated interest in the species, which had previously only been known from Mexico but is listed as a foreign endangered species in the US. Consequently, an effort was undertaken to conduct a conservation status assessment of the fish using standardized methods developed by NatureServe. These assessments aim to determine the extinction risk of species and produce conservation ranks, which can be used to inform listing statuses and policy decisions and to determine conservation priorities. The rank is determined by assessing factors in three main categories: rarity, threats, and trends. Here we used three rarity and one threat factor in the NatureServe rank calculator to determine the global conservation rank of P. phreatophila. Known occurrences were compiled, and the online tool GeoCAT (geospatial conservation assessment tool) was used to determine range extent and area of occupancy. Number of occurrences (e.g., populations) was estimated based on the spatial distribution of observations and their proximity to one another. Threat comprised scope, which was assessed in ArcGIS by intersecting the total area covered by a given threat with the known occurrence area of P. phreatophila, and severity, which was estimated based on expert opinion. The resulting conservation rank was G2 (globally imperiled; roughly equivalent to IUCN’s Vulnerable rank); however, complete data were not available for any factor thus motivating the need for further study. When new data are available, the rank can be easily updated with this new information using the rank calculator.
Mexican blindcat, Prietella phreatophila, described in 1954 from a cave system near the town of Múzquiz in central Coahuila state, and considered a Mexican endemic, was listed by the U.S. Fish and Wildlife Service as a foreign endangered species (protected "wherever found") in 1970. Explorations in the 1990s discovered many new localities extending nearly to the international border, and in 2016 the species was discovered in Amistad National Recreation Area (ANRA) in Texas, just north of the international border near Del Rio. Not only does the discovery support the aquifer of this fish being an internationally shared resource, but the stygobitic invertebrate biota found with the fish indicates a potentially large extent of the aquifer, and thus possibly the fish, in Texas. Invertebrate faunal connections (historic or current) extend from the Amistad Lake area of the new occurrence west into the Trans-Pecos region and east into the Edwards Aquifer of central Texas. We explore implications of this for both water management and evolutionary history of this and other blind ictalurids, and suggest that population genetic studies of both stygobitic fishes and invertebrates could help hydrogeologists better define often difficult to map aquifer extents and interconnections. While NPS is continuing to support the cave explorations of ANRA that produced the Texas discovery, we propose a broader bi-national sampling effort for both the fish and invertebrates extending well beyond the current known distribution of P. phreatophila. We also pointed out questions about phylogenetic relatedness of P. phreatophila and P. lundbergi further south, as well as the possibility of a monophyletic clade of blindcats, including those of the Edwards Aquifer, Satan and Trogloglanis. If substantiated, that evolutionary history would imply broader historic inter-aquifer connections ranging from the San Antonio area as far south as southernmost Tamaulipas. Finally, we report establishment of a small captive population of Prietella phreatophila at San Antonio Zoo for research and possibly eventual conservation applications.
The endangered Mexican blindcat (Prietella phreatophila, Carranza 1954) is one of only fourstygobitic ictalurid catfish in North America. Members of two monotypic genera (Satan
eurystomus and Trogloglanis pattersoni) are known from the Edwards Aquifer in Texas and, until
recently, Prietella (represented by P. lundbergi and P. phreatophila) was only known to occur in
Mexico (northern Coahuila to southern Tamaulipas). The recent discovery of P. phreatophila in
a cave on the Amistad National Recreation Area in Val Verde County, Texas is the result of
decades of sporadic effort on both sides of the US/Mexican border and has stimulated a renewed
effort to investigate the distribution, ecology, evolutionary history, and conservation status of this
species. Collaborative efforts among The San Antonio Zoo, The University of Texas at Austin,
Zara Environmental and The National Park Service are currently focused on habitat surveys in
Texas as well as captive husbandry and propagation. Future efforts will include collaborators from
the Comisión Nacional de Áreas Naturales Protegidas, Área de Protección de Recursos Naturales
Sabinas, and the Laboratorio de Genética para la Conservación, Centro de Investigaciones
Biológicas del Noroeste, La Paz to conduct expanded fieldwork in Mexico, hydrogeologic studies,
and surveys using environmental DNA.
Satan eurystomus Hubbs & Bailey 1947, the widemouth blindcat, is endemic to the deep Edwards Aquifer below San Antonio, TX. Monotypic Satan is one of four subterranean ictalurids, Trogloglanis pattersoni, Prietella pheatophila and P. lundbergi, that all exhibit common features of stygomorphs: loss of eyes and pigmentation, hypertrophy of some chemo and mechanosensory systems, small size, and variously reduced musculoskeletal system. Each species is distinctive in its own ways, and hypotheses about their phylogenetic positions range from separate ancestries of each scattered among the lineages of epigean ictalurids to exclusive monophyly of a strictly subterranean clade. Specimens of Satan are rare, thus we used highresolution CT scans to develop the first detailed, richly illustrated descriptive and comparative study of its skeleton. Satan exhibits typical and singular reductive features plus complex structures, e.g. 3 novel symphyses closing the posterior cranial fontanel; an unusually deep temporal fossa; and an ornately shaped dorsal fin locking spinelet. Satan shares 15 synapomorphies with other ictalurid troglobites: the stygomorphisms plus bone and joint reductions. Satan shares 11 synapomorphies with Pylodictis, including increased numbers of cephalic sensory pores and paired fin rays, and several features associated with predatory suction feeding: wide gape, depressed head, expanded branchiostegal and opercular membranes and anterior extension of epaxial muscle. Incomplete character information, including lack of molecular data for Satan and Trogloglanis, poor quality of available skeletal preparations for Trogloglanis and Prietella, and uncertain identifications of some specimens of Prietella impede construction of a complete dataset for phylogenetic analysis.
Mexican blindcat, Prietella phreatophila, was described in 1954 from a single locality in Northern Coahuila, México. Long listed as endangered by the Mexican federal government, it was listed by the U.S. Fish and Wildlife Service as a foreign endangered species in 1970, and the most recent (1996) update of its assessment for the IUCN Red List considers it endangered as well. Explorations in the late 1990s discovered many new localities extending nearly to the international border, and a captive population established provided insights into the species’ basic biology and behavior. In 2016 the species was discovered in a cave in the Amistad National Recreation Area (ANRA), just north of the Río Grande in Texas. The 1970 listing instantly gave the TX population full protection under the U.S. Endangered Species Act. The species’ subterranean and mostly inaccessible habitat endows it with extremely low detectability and its actual range is likely broader than physical sampling of specimens has revealed. We review all prior and new knowledge of the species and its habitat to provide an updated international reassessment of its overall conservation status and threats, which most notably include aquifer depletion and contamination in both the Mexican and U.S. portions of its known range. A live captive population of two specimens collected in 1997 in Coahuila and one Texas specimen is now at the San Antonio Zoo, we are working with NPS to further explore ANRA caves and hope eventually to return to Coahuila to more fully update the species’ conservation status.
Assessments of growth can provide information needed to understand how fish populations respond to changing environmental conditions and management actions, including ecosystem experimentation. We estimated growth rates and parameter uncertainty from otoliths of endangered Humpback Chub Gila cypha from the Colorado River in Grand Canyon, Arizona. We then compared growth of Humpback Chub \textless age 2 that were 1) occupying the mainstem Colorado River during a period of variable discharge and cooler water temperatures (1980–1998; epoch 1), 2) occupying the Colorado River during a period of moderate discharge variability and warmer water (2001–2011; epoch 2), and 3) occupying the unregulated Little Colorado River. Because growth rates of juvenile Humpback Chub (\textless age 2) may be more sensitive to changes in environmental conditions than adult fish, we used analysis of covariance and linear models to compare growth of juvenile fish (slopes) between epochs and capture sites (mainstem Colorado River vs. Little Colorado River). Our analysis of covariance results were ambiguous (age × epoch × site interaction; P = 0.06). However, individual linear regressions of size and age by epoch and site suggest biologically important differences in growth, as evidenced by slower growth in the Colorado River in epoch 1 than in epoch 2, and slower growth in the Colorado River compared with the Little Colorado River for all time periods. Overall our results 1) provide information on growth and growth variability useful for parameterizing models to assess population viability and 2) provide empirical information on how growth of juvenile and adult Humpback Chub growth may respond to changing environmental conditions.
Compilation of basic occurrence records of American Eel in Texas revealed not only a general paucity of data, but also biases of different sources, and overall, inaccessibility of many different sources of useful records. Methodical searching, mining, normailization and basic data cleaning across a diversity of resources provided a much better picture of temporal and spatial occurrences of the species than had readily available sources. Similar data mining and sharing by all researchers and managers could greatly improve overall understanding of the species in the GoM and its tributaries, and help focus monitoring and research efforts.