Nemacheilus pullus: A new species of Stone Loach from central Laos.

Stone Loaches, Nemacheilidae, are freshwater Cypriniform Fish found throughout Eurasia, with one genus occurring in Ethiopia. They favour fast moving stretches of small streams, but are occasionally found in larger rivers, and even caves. The group currently contains about valid 790 species in 53 genera, with new species being described on a regular basis, particularly from Southeast Asia. The genus Nemacheilus currently includes 36 species from the Chao Phraya, Mae Khlong, and Mekong river drainages, the Malay Peninsula, and the islands of Sumatra, Java and Borneo. Members of this genus tend to be found in streams and rivers with slow to moderate flows and sand, gravel, or pebble bottoms.

In a paper published in the Raffles Bulletin of Zoology on 20 February 2023, Maurice Kottelat of the Lee KongChian Natural History Museum at the National University of Singapore, describes a new species of Nemacheilus from central Laos.

The new species is named Nemacheilus pullus, where 'pullus' is intended to mean dark yellow to blackish. The species is described from populations living in the Nam Ngiep and Nam Xan watersheds of the the Mekong drainage in central Laos, which were previously assigned to the species Nemacheilus platiceps.

Nemacheilus pullus, Laos: Mekong drainage: Nam Ngiep watershed; (a) CMK 27518, paratype, male, 37.7 mm; (b) MHNG 2787.091, holotype, male, 41.5 mm; (c) CMK 27518, paratype, female, 64.1 mm. Note that in b the specimen is slightly tilted laterally and the eye appears more distant from the dorsal profile than in reality. Kottelat (2023).

Nemacheilus pullus shares with Nemacheilus platiceps an incomplete lateral line, whereas in almost all other members of the genus the lateral line is complete. However Nemacheilus pullus lacks the clear flank bars of Nemacheilus platiceps, instead being a plain yellowish grey in colour (juveniles, and some adult females, do have faint bars, but these are much less clear than in Nemacheilus platiceps). 

Nemacheilus platiceps; (a) CMK 21392, 27.8 mm; Laos: Mekong drainage: Xe Kong watershed; (b)–(d) CMK 7927, Vietnam: Dong Nai drainage, 36.2 mm, (b) reversed) 40.8 mm, 54.4 mm, (d) reversed; and (e) NRM 15095, holotype, 40.1 mm; Vietnam Dong Nai drainage (reversed). Kottelat (2023).

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Homatula guanheensis: A new species of Stone Loach from Henan Province, China

The Stone Loach genus Homatula includes a number of small, benthic Fish, which live in the drainage basins of the Yellow, Yangtze, Pearl, Lancang, Nujiang and Red rivers. They are sometimes considered to be a part of the genus Paracobitis, which is morphologically similar, but the two are generally considered separate, due to their different distributions, with Homatula known only from China, and Paracobitis found only in western Asia. Studies based on the morphology of Homatula have suggested that there is more diversity that the current number of species (19-20), but to what extent this reflects variation within species rather than the presence of undescribed species remained unclear, until scientists began to apply genetic identifications to the genus.

In a paper published in the Biodiversity Data Journal on 16 June 2021, Chuanjiang Zhou, Wenwen Ma, Xi Wang, Yongtao Tang, Xiaoling Meng, and Guoxing Nie of the Engineering Technology Research Center of Henan Province for Aquatic Animal Cultivation at Henan Normal University, describe a new species of Homatula from the Guanhe River, in the HanJiang River drainage (a tributary of the Yangtze River),  in Xixia County, Henan Province.

The new species is named Homatula guanheensis, where 'guanheensis' means 'coming from Guanhe', in reference to the Guanhe River where it was found living in cave environments. Like other Stone Loaches, the new species is an elongate, slender Fish. The known specimens range from 76.9 to 109.26 mm in length, and are cylindrical, and flattened towards the rear. The head is short and flattened, and lacks scales. The snout is short, with nostrils closer to the eye than the tip. The eyes are oval, and located towards the top of the head. The lips are thick, and cover the jaw; there are three pairs of barbels. 

 

Homatula guanheensis (holotype, HNU 010048, 99.6 mm SL). (A) Lateral view; (B) Dorsal view; (C) Ventral view; (D) Mouth characters; (E) Intestine form; (F) X–ray (lateral view). Zhou et al. (2021).

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Nothobranchius furzeri: Extremely rapid maturation in an African Annual Killifish.

African Annual Killifish are small Cyprinodont Fish found in ephemeral pools on the savannas of Africa. They spend most of their lives as diapausing embryos (embryos in a state of suspended development) buried in dry sediment, emerging when seasonal, but unpredictable, rains lead to the formation of small ponds, which can persist from a few weeks to several months. This has led to the Killifish developing an extremely rapid life-cycle, as they attempt to grow and reach sexual maturity before the pools disappear. One species, the Turquiose Killifish, Nothobranchius furzeri, has been shown in the lab to reach sexual maturity in as little as twenty days, but this is generally thought to be better than they can achieve in the wild, where conditions are likely to be more ideal than they are in the wild.

In a paper published in the journal Current Biology on 6 August 2018, Milan Vrtílek of the Institute of Vertebrate Biology of the Czech Academy of Sciences, Jakub Žák, also of the Institute of Vertebrate Biology of the Czech Academy of Sciences, and of the Department of Zoology at Charles University, Martin Pšenička of the Bohemian Research Center of Aquaculture and Biodiversity of Hydrocenoses at the University of South Bohemia in České Budějovice, and Martin Reichard, again of the Institute of Vertebrate Biology of the Czech Academy of Sciences, publish the results of a study in which Turqoise Killifish in ephemeral pools in southern Mozambique were monitored and sampled on a daily basis, to understand their maturation rate in the wild.

Vrtílek et al. monitored eight separate pools across the region, sampling the Fish daily over a three week period from when they first filled with water. They found that, contrary to expectations, the Fish could reach sexual maturity in fourteen days (a week faster than achieved in captivity). The Fish also reached their maximum size (17–43 mm in females and 17–54 mm in males) in 14-15 days, with the largest Fish encountered, at 63 mm, being 17 days old.

Adult Turquoise Killifish (Nothobranchius furzeri) and its natural habitat. (A) Site ‘D’ on 27 January 2016 when it contained at least 27 adult Fish estimated to be 16–17 days old. (B) Two 14-day-old male Nothobranchius furzeri from site ‘A’. Vrtílek et al. (2018).

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Oreonectes daqikongensis: A blind Stone Loach from a cave system in Guizhou Province, China.

Stone Loaches, Nemacheilinae, are freshwater Cypriniform Fish (the group that includes other Loaches as well as Carp and Minnows) found across Eurasia and Africa. They favour fast moving upland streams, with many species having colonised cave systems (an essentially similar environment), where they often lose their eyes and pigmentation.

In a paper published in the journal ZooKeys on 28 November 2016, Huaiqing Deng and Huamei Wen of the School of Life Sciences at Guizhou Normal University, Ning Xiao of the Guiyang Nursing Vocational College, and Jiang Zhou, also of the School of Life Sciences at Guizhou Normal University describe a new species of blind Stone Loach from a cave system in Guizhou Province, China.

The species is placed in the genus Oreonectes, which includes sixteen species, all from underground karst limestone caves in East Asia, and given the specific name daqikongensis, meaning 'from Daqikong', the species having been been described from specimens washed out of a limestone cave at the Daqikong Scenic Area following heavy rain in January 2011. This cave contains a pool connected to a subterranean river which forms part of the Dagou River System, but which has not previously produced any Fish or other aquatic cave animals. The Fish were blind and colourless, and ranged from 31.28 to 70.96 mm in length.

Oreonectes daqikongensis, live specimen. Deng et al. (2016).

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