Tarumania walkerae

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Tarumania walkerae
Systematics
Sub-cohort : Ostariophysi
Otophysa
Order : Tetras (Characiformes)
Family : Tarumaniidae
Genre : Tarumania
Type : Tarumania walkerae
Scientific name of the  family
Tarumaniidae
de Pinna , Zuanon , Rapp Py-Daniel & Petry , 2017
Scientific name of the  genus
Tarumania
De Pinna et al., 2017
Scientific name of the  species
Tarumania walkerae
De Pinna et al., 2017

Tarumania walkerae is a small freshwater fish of the order Characins (Perciformes), which is endemic in small bodies of water in the area of the underflow of the Rio Negro in the central Amazon basin occurs. The only previously known sites, 60 km apart, are the Rio Tarumã-Mirim, a tributary of the Rio Negro near the megacity of Manaus, and the Anavilhanas archipelago , a large river island archipelago in the lower Rio Negro. The very hidden fish was first scientifically described in August 2017.

features

Tarumania walkerae is elongated and the only tetra with an eel-like body shape. The body diameter is on average only 9% of the standard length . The fish are dark brown, the belly side is only slightly lighter than the rest of the body. The specimens examined so far had standard lengths of 4.5 to 15 cm. In cross-section, the body is oval, the tail stalk, which is higher than the body, is strongly flattened laterally. The small head that is not detached from the body is about 15% of the standard length. The snout is short and ends in a slightly upper mouth, the lower lip of which is longer than the upper lip. The mouth extends backwards to below the rear edge of the eye. The eyes are small and are located in the front fifth of the head. The distance between the anterior and posterior nostrils is greater than the diameter of the eye, the anterior ones are just above the upper lip. The Branchiostegalmembranen have grown together. The maxillary is covered with two rows of conical or slightly curved teeth.

The short-based dorsal fin is lanceolate and is found at the end of the middle third of the body. The anal fin lies between the dorsal and caudal fin; their base is about twice as long as that of the dorsal fin. The pectoral fins are short and about half the length of the head. The pelvic fins are large and lie far back but in front of the dorsal fin. The caudal fin is elongated to lanceolate. An adipose fin is missing. The whole body and a large part of the head are covered by very small, equally large scales arranged in regular rows. Only the lips and the top of the head are unscanned. The head scales, which overlap like roof tiles, resemble the body scales, but have a different orientation. Their free ends are directed forward and the base of the scales lies behind them. At the transition between the scaling of the head and the trunk, the scales are oriented upwards or downwards. Tarumania walkerae has 64 to 65 vertebrae, of which 21 to 22 are caudal vertebrae. On the first gill arch there are 11 or 12 gill rakes . The swim bladder extends from the head end to the beginning of the anal fin just below the spine. It is divided into eleven chambers by constrictions. The chambers are of different sizes, the first is wide, the most voluminous and the thickest-walled. All others are narrower.

Way of life

Tarumania walkerae lives in riverside forests deep in the leaves at the bottom of small, isolated ponds. Some of these pools barely have a water column above the leaves, while others have a height of up to 70 cm. In the rainy season, these pools are connected to the rivers and allow the fish to change their location and colonize new habitats. The only other fish species that commonly occurs with Tarumania walkerae is an undescribed catfish species from the genus Phreatobius . In rare cases other fish species have also been found, especially juvenile fish. It is Microsternarchus bilineatus , Brachyhypopomus beebei , an indefinite Apistogramma species such Aequidens pallidus , Scoloplax dolicholophia , Microphilypnus amazonicus , an indefinite Curimatopsis -Art, an indefinite Brycon -Art, C. punctatus , Nannostomus eques and Copella cf. nattereri . Tarumania walkerae feeds on small invertebrates. Small shrimp from the genus Euryrhynchus were found in the digestive tract of specimens caught . Tarumania walkerae can swim forwards as well as backwards and move the two pelvic fins independently of each other. In addition to gill breathing, the fish also take in air with their mouths. Tarumania walkerae can bend its head a little to the side from the body, a skill that only the Australian salamander fish ( Lepidogalaxias salamandroides ) has among fish .

Systematics

The species was already known 15 years before it was first described through a young but poorly preserved specimen. This took place in August 2017 after further specimens, including fully grown ones, were caught. The species was named in honor of the limnologist Ilse Walker, who caught the first specimen, the genus name Tarumania was derived from the Rio Tarumã-Mirim, where the first specimen was caught. Since the species shows so many unusual characteristics (single eel-shaped tetra-like, forward-facing scales on the head and 11-chambered swim bladder) it was placed in an independent, monotypical family, the Tarumaniidae. A phylogenetic analysis showed that this is the sister group of the predatory tetra (Erythrinidae).

Individual evidence

  1. a b c d e Mário de Pinna, Jansen Zuanon, Lucia Rapp Py-Daniel, Paulo Petry (2017): A new family of neotropical freshwater fishes from deep fossorial Amazonian habitat, with a reappraisal of morphological characiform phylogeny (Teleostei: Ostariophysi) . Zoological Journal of the Linnean Society , XX: 1-31. doi: 10.1093 / zoolinnean / zlx028
  2. Arcila, D., Petry, P. & Ortí, G. (2018): Phylogenetic relationships of the family Tarumaniidae (Characiformes) based on nuclear and mitochondrial data. Neotropical Ichthyology, 16 (3): Epub Oct 11, doi: 10.1590 / 1982-0224-20180016 .

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