Huffmanela cf. huffmani (Nematoda: Trichosomoididae) infecting swim bladder, peritoneum, and gonad of variable platyfish, Xiphophorus variatus (Cyprinodontiformes: Poeciliidae) and eastern mosquitofish, Gambusia holbrooki (Poeciliidae) in Florida; taxonomy, phylogenetic analysis, and pathological changes

Variable platyfish, Xiphophorus variatus (Meek, 1904) (Cyprinodontiformes: Poeciliidae) and eastern mosquitofish, Gambusia holbrooki Girard, 1859 (Poeciliidae) from earthen ponds in west central Florida were examined for parasitic infections. At necropsy, we observed myriad nematodes (adults and eggs), which we identified as Huffmanela cf. huffmani, infecting the swim bladder, gonad, and visceral peritoneum. Nucleotide sequences (small subunit ribosomal DNA, 18S) of H. cf. huffmani from variable platyfish and eastern mosquitofish were identical; likewise for newly obtained 18S sequences of Huffmanela huffmani Moravec, 1987 from the swim bladder of red breast sunfish, Lepomis auritus (Linnaeus, 1758) (Centrarchiformes: Centrarchidae) and warmouth, Lepomis gulosus (Cuvier, 1829) from the San Marcos River (type locality for Huffmanela huffmani Moravec, 1987), Texas. The sequences of H. huffmani and H. cf. huffmani differed by 7 (1%) nucleotides. Pathological changes comprised proliferation of the tunica externa of the swim bladder in low-intensity infections in addition to inflammation, proliferation, and tissue necrosis of swim bladder, peritoneum, and gonad in high-intensity infections. The lesion was severe, affecting the cellular constituents of the swim bladder wall and reducing the size of the swim bladder lumen; potentially reducing swim bladder physiological efficiency. The present study is the first record of a freshwater species of Huffmanela Moravec, 1987 from beyond the San Marcos River, first record of a species of Huffmanela from a livebearer, first nucleotide sequences and phylogenetic analysis for Huffmanela, and first evidence that an infection by a species of Huffmanela causes pathological changes that could impact organ function.

The complete mitochondrial genome of the Variable Platyfish Xiphophorus variatus

We present the complete mitochondrial genome sequence of the Variable Platyfish, Xiphophorus variatus (Meek 1904) (Cyprinodontiformes: Poeciliidae). The genome consists of 16,624 bp which encodes 13 protein-coding genes, 22 transfer RNAs, 2 ribosomal RNAs, and 1 control region. Genome-wide nucleotide composition is 27.79% adenine, 31.11% cytosine, 15.63% guanine, and 25.48% thymine. The X. variatus mitochondrial genome shares similar GC content and identical gene order and gene strand location with other members of Poeciliidae. The sequence presented herein will be of utility for future phylogenetic and biomedical research and for designing primers for species detection from environmental DNA samples.

Drainage basin checklists and dichotomous keys for inland fishes of Texas

Species checklists and dichotomous keys are valuable tools that provide many services for ecological studies and management through tracking native and non-native species through time. We developed nine drainage basin checklists and dichotomous keys for 196 inland fishes of Texas, consisting of 171 native fishes and 25 non-native fishes. Our checklists were updated from previous checklists and revised using reports of new established native and non-native fishes in Texas, reports of new fish occurrences among drainages, and changes in species taxonomic nomenclature. We provided the first dichotomous keys for major drainage basins in Texas. Among the 171 native inland fishes, 6 species are considered extinct or extirpated, 13 species are listed as threatened or endangered by U.S. Fish and Wildlife Service, and 59 species are listed as Species of Greatest Conservation Need (SGCN) by the state of Texas. Red River drainage basin was the most speciose with 120 fishes. Rio Grande & Pecos drainage basin had the greatest number of threatened or endangered fishes (N = 7) and the greatest number of SGCN fishes (N = 28). We revised drainage basin occurrences for 77 species. Drainage basin checklists and dichotomous keys provide finer resolution of species distributions within the geopolitical boundaries of Texas and can reduce probability of errors in fish identification errors by removing species not occurring within a natural boundary.

On the occurrence of three non-native cichlid species including the first record of a feral population of Pelmatolapia (Tilapia) mariae (Boulenger, 1899) in Europe

Thermally influenced freshwater systems provide suitable conditions for non-native species of tropical and subtropical origin to survive and form proliferating populations beyond their native ranges. In Germany, non-native convict cichlids (Amatitlania nigrofasciata) and tilapia (Oreochromis sp.) have established populations in the Gillbach, a small stream that receives warm water discharge from a local power plant. Here, we report on the discovery of spotted tilapia (Pelmatolapia mariae) in the Gillbach, the first record of a reproducing population of this species in Europe. It has been hypothesized that Oreochromis sp. in the Gillbach are descendants of aquaculture escapees and our mtDNA analysis found both O. mossambicus and O. niloticus maternal lineages, which are commonly used for hybrids in aquaculture. Convict cichlids and spotted tilapia were most probably introduced into the Gillbach by aquarium hobbyists. Despite their high invasiveness worldwide, we argue that all three cichlid species are unlikely to spread and persist permanently beyond the thermally influenced range of the Gillbach river system. However, convict cichlids from the Gillbach are known to host both native and non-native fish parasites and thus, non-native cichlids may constitute threats to the native fish fauna. We therefore strongly recommend continuous monitoring of the Gillbach and similar systems.