Research Article |
Corresponding author: Marcelo Loureiro ( marcnagual@gmail.com ) Academic editor: Peter Bartsch
© 2018 Wilson S. Serra, Marcelo Loureiro.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Serra WS, Loureiro M (2018) Austrolebias queguay (Cyprinodontiformes, Rivulidae), a new species of annual killifish endemic to the lower Uruguay river basin. Zoosystematics and Evolution 94(2): 547-556. https://doi.org/10.3897/zse.94.29115
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In this article we describe a new species of the annual fish genus Austrolebias from the lower Uruguay river basin. The fusion of the urogenital papilla to the first anal fin ray in males and the pigmentation pattern, indicates a close relationship with the clade formed by A. bellottii, A. melanoorus, and A. univentripinnis. The new species can be differentiated from those by the following combination of characters: presence of well-defined light bands contrasting with the sides of the body, the distal portion of the anal fin dark gray, pelvic fins dark bluish green and bases united at about 50–80% on their medial margins, pectoral fins with iridescent blue sub-marginal band, and general coloration of body bluish green. The new species can only be found in wetlands of the Queguay river, an area included in the Uruguayan protected areas system and represents so far the only annual fish species endemic to the lower Uruguay river basin.
Austrolebias bellottii species group, Systematics, La Plata basin
Austrolebias, one of the most specious annual fish genus in the family Rivulidae, is composed of 47 valid species and is distributed in Bolivia, Paraguay, southern Brazil, northeast Argentina, and Uruguay, in the La Plata, Patos-Merin, and southwestern Amazon basins (
Afterwards, based on another morphological phylogeny,
In spite of the low statistical support of A5 and the unnamed clade in morphological analyses (
In this article we describe a new species of Austrolebias from wetlands of the Queguay river (lower Uruguay river basin), that shares similar morphological traits to the clade formed by A. bellottii, A. melanoorus, and A. univentripinnis.
Specimens analyzed and comparative material are deposited in the Fish Collections of Facultad de Ciencias, Universidad de la República (
Austrolebias
sp. in
Uruguay: Paysandú: MHNM 3728, 2 males 29.9–33.6 mm SL, 2 females 27.4–33.3 mm SL, Río Queguay, 32°08’21”S, 57°26’19”W, M. Loureiro, A. Duarte, M. Zarucki, J. Bessonart and D. Hernández, Sep. 2011. MHNM 3729, 1 male 34.0 mm SL, 1 female 31.0 mm SL, same data of the holotype.
The new species differs from all the other species of the genus except Austrolebias bellottii, A. univentripinnis and A. melanoorus, by the presence of the urogenital papilla attached to the anal fin in males (vs. free from the anal fin). It differs from A. bellottii and A. univentripinnis by the presence of well-defined light blue bands contrasting with the sides of the body in adult males (vs. vertical rows of light blue dots) (Fig.
A. Austrolebias queguay sp. n. paratype male (ZVCP 11620); B. A. queguay non type male (32°07’26”S, 57°30’45”W), not preserved (right side, photo flipped); C. A. bellottii non preserved male; D. A. univentripinnis male (
Morphometric data in Table
Morphometric data of Austrolebias queguay sp. n., Standard length is expressed in mm; measurements numbered 2–13 are percentage of standard length; subunits of head measurements (numbered 14–18) are percentage of Head length. Ranges presented for males include the holotype.
Character | Holotype | Males | Females | ||||||||
N | Low | High | Mean | SD | N | Low | High | Mean | SD | ||
1. Standard length (mm) | 39.4 | 54 | 22.8 | 39.4 | 31.0 | – | 88 | 21.2 | 40.1 | 29.2 | – |
2. Body depth | 37.4 | 54 | 32.8 | 39.5 | 36.5 | 1.75 | 88 | 30.0 | 40.0 | 34.7 | 2.09 |
3. Head lenght | 27.2 | 54 | 23.9 | 29.6 | 27.1 | 1.28 | 88 | 22.6 | 30.2 | 27.7 | 1.36 |
4. Caudal peduncle depth | 14.6 | 54 | 11.6 | 15.6 | 13.7 | 0.77 | 88 | 11.3 | 15.8 | 13.1 | 0.83 |
5. Caudal peduncle length | 11.5 | 54 | 6.5 | 17.3 | 11.5 | 2.16 | 88 | 12.1 | 26.4 | 16.0 | 2.25 |
6. Pre dorsal length | 50.6 | 54 | 43.1 | 54.3 | 50.3 | 2.37 | 88 | 43.1 | 64.8 | 59.9 | 2.81 |
7. Dorsal-fin base length | 42.3 | 54 | 34.8 | 47.7 | 40.6 | 2.79 | 88 | 22.4 | 32.6 | 27.3 | 2.42 |
8. Pre anal-fin length | 50.5 | 54 | 46.7 | 60.2 | 51.9 | 2.39 | 88 | 52.6 | 67.1 | 60.4 | 2.65 |
9. Anal-fin base length | 44.8 | 54 | 35.5 | 46.1 | 42.4 | 2.19 | 88 | 21.8 | 30.9 | 26.3 | 2.07 |
10. Pre pelvic-fin length | 45.9 | 54 | 41.3 | 48.8 | 45.3 | 1.51 | 88 | 46.3 | 61.1 | 51.9 | 2.38 |
11. Pectoral fin length | 20.2 | 54 | 18.8 | 27.7 | 23.5 | 2.10 | 88 | 20.2 | 30.4 | 24.4 | 1.74 |
12. Pelvic fin length | 9.6 | 54 | 6.7 | 11.9 | 9.2 | 1.01 | 88 | 9.2 | 14.9 | 12.3 | 1.11 |
13. Caudal fin length | 20.5 | 54 | 15.3 | 28.5 | 24.5 | 2.39 | 88 | 22.6 | 30.8 | 26.7 | 1.88 |
14. Head width | 65.1 | 54 | 59.9 | 77.2 | 67.7 | 3.95 | 88 | 60.8 | 90.3 | 75.3 | 6.28 |
15. Head depth | 112.3 | 54 | 92.1 | 125.7 | 110.3 | 6.70 | 88 | 88.5 | 133.7 | 104.7 | 7.33 |
16. Interorbital width | 51.7 | 54 | 39.8 | 58.0 | 47.6 | 4.50 | 88 | 39.5 | 54.1 | 45.9 | 3.17 |
17. Eye diameter | 30.9 | 54 | 25.0 | 37.7 | 30.3 | 2.83 | 88 | 25.7 | 35.7 | 30.9 | 2.12 |
18. Snout length | 27.6 | 54 | 16.7 | 29.5 | 21.9 | 2.10 | 88 | 16.4 | 25.5 | 20.2 | 1.98 |
Posterior end of anal and dorsal fins rounded; presence of short filaments in distal margin of anal-fin in males. Anal fin in females triangular shaped (anteromedian rays prolonged forming anterior lobe). Caudal fin rounded. Pectoral fin elliptical, posterior margin on vertical between 2nd to 5th anal-fin ray bases in males, and between pelvic-fin origin and urogenital papilla in females. Pelvic fins medially united between 50–80%, with posterior tip reaching between urogenital papilla and base of 4rd anal-fin ray in both sexes. Urogenital papilla in males partially attached (only tip of papillae free) to anal fin. Base of dorsal-fin origin anterior to the anal-fin origin in males, between 8th to 11th vertebrae and 7th to 10th neural spine; in females usually vertical to posterior to the anal fin origin, between 12th to 14th vertebrae and 10th to 13th neural spine. Origin of anal fin between pleural ribs 8th to 9th and vertebrae 10th and 12th in males: between pleural ribs 9th and 12th and vertebrae 12th and 15th in females. Dorsal fin rays 22–25 in males and 17–20 in females; anal-fin rays 24–27 in males and 21–24 in females. Caudal fin rays 20–25; pectoral fin rays 11–13; pelvic fin rays 5.
Scales cycloid. Trunk and head scaled, except ventral surface of head. Longitudinal series of scales 28–33, regularly arranged; transversal series 11–16 (N=29 and one specimen with 21 scales); circumpeduncular series 13–20. Anal-fin base without scales; caudal fin with three rows of irregularly arranged scales. Contact organs present in all analyzed males, 1 to 8 contact organs per scale (usually 1 or 2); contact organs present in first 6 upper rays of pectoral fins; no contact organs on unpaired and pelvic fins.
Cephalic neuromasts: supraorbital 13–23, parietal 0–4, anterior rostral 1–2 (usually 1), posterior rostral 0–2 (usually 1), infraorbital 1–3 + 18–27, preorbital 2–4, otic 2–5, post-otic 1–5, supratemporal 1–3 (usually 1), median opercular 1–2 (usually 1), ventral opercular 1–3, preopercular 19–29, mandibular 11–15, lateral mandibular 3–7.
Basihyal cartilage anteriorly widened, about 50–60% of total length of basihyal; anterior margin of cartilage usually concave or with little commissures. Second pharyngobranchial with 3–8 teeth and 3rd with 17–37. First branchial arch with 3–4 epibranchial spines and 10–12 hypobranchial. Dermosphenotic ossifications present only in 5 % of specimens analyzed; proximal radials 3–5 (usually 4); ventral process posttemporal well-developed. Total vertebrae 27–30.
Males (Fig.
Females (Fig.
Canonical variate analyses discriminated A. bellotti specimens from the other species along Root 1 (84.7 and 83.7% of total variation in males and females respectively, Figs
The specific name, queguay, is in reference to Queguay river basin, the type locality of the new species, treated as a noun in apposition to the generic name.
Austrolebias queguay is endemic to the wetlands of middle Queguay river basin (30 meters above sea level), Paysandú Department, Uruguay, which flows to the lower Uruguay river (Fig.
Geographic distribution of Austrolebias queguay sp. n. (orange dots, Uruguay river basin), A. bellottii (yellow dots, Paraná and Uruguay river basins), A. melanoorus (red dots, Negro and Yaguarón river basins), and A. univentripinnis (green dots, Yaguaron river basin). Orange star indicates type locality.
All its known locations are within “Montes del Queguay”, a permanent protection reserve under the control and regulation of the Uruguayan government, with an area of about 200 km2, but without a management plan (
As many species of the family Rivulidae, A. queguay presents an annual life cycle which includes drought resistant eggs and diapausing embryos. All species of Austrolebias are obligate annuals (
The new species described in this article presents all diagnostic characters for the genus Austrolebias proposed by
Differences with the other species of the clade concern pigmentation pattern in males. This kind of variation is common among species of other Austrolebias clades, such as the “A. affinis” species group, where A. juanlangi and A. paucisquama present well-defined clear bands (in different degree) over a darker background coloration, vs. vertical rows of light blue dots in the other species (
Additionally, A. queguay differs from of A. bellottii, A. melanoorus, and A. univentripinnis, by the disposition of black spots on the central area of the flanks in females, when present horizontally aligned vs. when present, usually not aligned, from A. bellottii by dermosphenotic ossifications usually absent (95% of the A. queguay specimens analyzed) vs. usually present in A. bellottii (91% of specimens analyzed), and from A. melanoorus by the number of anterior rostral neuromasts, usually one pair (85 % of specimens analyzed) vs. usually two pairs in A. melanoorus (90% of specimens). Although these characters cannot be used as diagnostic, they support the idea of genetic isolation of the new species from the others, particularly from the nearby located populations of A. bellottii.
According to a recent morphological and molecular phylogenetic analysis the new species (Austrolebias sp; figs 9–12,
The lower Uruguay and Paraná rivers have suffered the effect of sea level changes associated to the glacial cycles since the Pleistocene. The last transgression is hypothesized to have occurred around 6 thousand years ago where the sea level rose five meters above actual level (
Four species of Austrolebias had been recorded in the lower Uruguay river: A. bellottii, A. nigripinnis, A. alexandri, and A. elongatus (
Austrolebias bellottii: ARGENTINA. Buenos Aires. MHNM 2425, 13 males 18.6–41.6 mm SL, 52 females 17.5–40.1 mm SL, Santa Teresita, 36°32’S, 56°43’W, R. Taberner, 31 Oct. 1975. MHNM 2801, 5 males 27.8–35.8 mm SL, 18 females 30.1–39.8 mm SL, road between La Plata and Magdalena, 35°03’S, 57°37’W, J.R. Casciotta, Nov. 1986.
Austrolebias melanoorus: BRAZIL. Rio Grande do Sul.
Austrolebias univentripinnis: BRAZIL. Rio Grande do Sul.
Austrolebias vandenbergi: PARAGUAY. Boquerón. MHNM 2557, 1 male 46.8 mm SL, 6 females 25.0–52.3 mm SL, 100 km al SW de Filadelfia, 12.6 km de la Estancia Heisseque del Dr. Durán, Servicio Forestal Nacional, 13 Jun. 1981.
We are grateful to Daniel Hernández, Matías Zarucki, Alejandro Duarte, and José Bessonart for his assistance in the fieldwork; to Luiz Malabarba, Juliano Ferrer, Matheus Volcan, Luis Lanés, for providing the comparative material from Rio Grande do Sul (Brazil) and photographs of live specimens; and to Mark Sabaj for the loan of specimens from The National Academy of Sciences, Philadelphia. We also thank Wilson Costa and Matheus Volcan for their reviews that improved the quality of the original manuscript. This study was supported by the Agencia Nacional de Investigación e Innovación (POS_NAC_2014_1_102765), by Fondo Clemente Estable (FCE_1_2011_1_6884) and by the Programa de Desarrollo de las Ciencias Básicas (PEDECIBA) de la Universidad de la República, Uruguay; ML belongs to the Sistema Nacional de Investigadores.