A new species of stone loach of the genus Mustura (Teleostei: Nemacheilidae) from Chindwin River drainage, Manipur, north-eastern India

Mustura taretensis, a new nemacheilid loach, is described from the Taret River, a tributary of the Yu River, Chindwin River drainage, Manipur, India. The new species is distinguished from all its congeners by a unique combination of the following characters: body with 12–13 irregular dark-brown blotches or bars on flank, alternating with 11–16 irregular dark-brown saddles on the back; dorsum of head with a distinctly visible rhomboid dark-brown mark encircling a pale oval area on the nape; dorsal fin with 9½­ or 10½ branched rays; lateral line complete; a well-developed free posterior chamber of air bladder, the halves of air bladder capsules connected by a manubrium; poorly developed processus dentiformis; suborbital flap present in males; and body depth 12.8–16.0 % SL. The generic status of Mustura chindwinensis, M. dikrongensis, M. tigrina and M. tuivaiensis are also discussed in the paper.

Revalidation of the Spanish stone loach Barbatula hispanica (Lelek, 1987) (Teleostei, Nemacheilidae) according to morphological and mitochondrial data

This study revalidates Barbatula hispanica, previously considered a junior synonym of B. quignardi. This species is found in the Ebro drainage and in Cantabria (Spain) as well as in the Adour drainage (Southwestern France). It is characterized by an upper lip with a well-marked medial incision and an interorbital width 18.5–33.7% of the HL. The species delineation is corroborated by the cytochrome oxidase subunit 1 molecular marker. We provide the sequence of 12S rDNA (950 bp) as reference for environmental DNA studies, and discuss also the taxonomy of B. quignardi which would be restricted to the Lez River.

One size does not fit all: inter- and intraspecific variation in the swimming performance of contrasting freshwater fish

Artificial barriers cause widespread impacts on freshwater fish. Swimming performance is often used as the key metric in assessing fishes’ responses to river barriers. However, barrier mitigation is generally based on the swimming ability of salmonids and other strong swimmers because knowledge of swimming ability for most other freshwater fish is poor. Also, fish pass designs tend to adopt a ‘one size fits all’ approach because little is known about population or individual variability in swimming performance. Here, we assessed interspecific and intraspecific differences in the sustained swimming speed (Usus) of five freshwater fish with contrasting body sizes, morphologies and swimming modes: topmouth gudgeon, European minnow, stone loach, bullhead and brown trout. Significant Usus variation was identified at three organizational levels: species, populations and individual. Interspecific differences in Usus were as large as 64 cm s−1, upstream populations of brown trout showed mean Usus 27 cm s−1 higher than downstream populations, and species exhibited high individual variation (e.g. cv = 62% in European minnow). Sustained swimming speed (Usus) increased significantly with body size in topmouth gudgeon, European minnow and brown trout, but not in the two benthic species, bullhead and stone loach. Aerobic scope had a significant positive effect on Usus in European minnow, stone loach and brown trout. Sustained swimming speed (Usus) decreased with relative pectoral fin length in European minnow and brown trout, whereas body fineness was the best predictor in stone loach and bullhead. Hence, swimming performance correlated with a diverse range of traits that are rarely considered when predicting fish passage. Our study highlights the dangers of using species’ average swimming speeds and illustrates why a ‘one size fits all’ approach often fails to mitigate for barrier effects. We call for an evidence-based approach to barrier mitigation, one that recognizes natural variability at multiple hierarchical levels.

Schistura syngkai, a new fish species (Teleostei: Nemacheilidae) from Meghalaya, northeast India

Schistura syngkai, a new stone loach, is described from the Twahdidoh Stream of Wahblei River (Surma-Meghna drainage) in Meghalaya, northeast India. It is unique among its Indian congeners in having a prominent dark-brown to blackish mid-lateral stripe about an eye diameter or more in width, overlain on 12–18 vertically-elongate black blotches on a golden-brown to amber body. Additionally, the species possesses an incomplete lateral line and a slightly emarginate caudal fin, and exhibits no apparent sexual dimorphism.

Paraschistura kermanensis, a new stone loach species from southeastern Iran (Teleostei: Nemacheilidae)

Paraschistura kermanensis from the endorheic Kerman-Naein basin in Iran is distinguished from its closest congeners (P. abdolii, P. delvarii, P. kessleri and P. naumanni) by lacking scales on the flanks anterior to the dorsal-fin origin, having scales on the caudal peduncle, and having the pelvic-fin origin situated anterior to or below the vertical through the dorsal-fin origin. It is also characterised by six fixed diagnostic nucleotide substitutions and a K2P nearest neighbour distance of 4% to P. abdolii in the mtDNA COI barcode region.

Malacosporean myxozoans exploit a diversity of fish hosts

Myxozoans are widespread and common endoparasites of fish with complex life cycles, infecting vertebrate and invertebrate hosts. There are two classes: Myxosporea and Malacosporea. To date about 2500 myxosporean species have been described. By comparison, there are only five described malacosporean species. Malacosporean development in the invertebrate hosts (freshwater bryozoans) has been relatively well studied but is poorly known in fish hosts. Our aim was to investigate the presence and development of malacosporeans infecting a diversity of fish from Brazil, Europe and the USA. We examined kidney from 256 fish belonging variously to the Salmonidae, Cyprinidae, Nemacheilidae, Esocidae, Percidae, Polyodontidae, Serrasalmidae, Cichlidae and Pimelodidae. Malacosporean infections were detected and identified by polymerase chain reaction and small subunit ribosomal DNA sequencing, and the presence of sporogonic stages was evaluated by ultrastructural examination. We found five malacosporean infections in populations of seven European fish species (brown trout, rainbow trout, white fish, dace, roach, gudgeon and stone loach). Ultrastructural analyses revealed sporogonic stages in kidney tubules of three fish species (brown trout, roach and stone loach), providing evidence that fish belonging to at least three families are true hosts. These results expand the range of fish hosts exploited by malacosporeans to complete their life cycle.