Neotoca bilineata

Neotoca bilineata
Neotoca bilneata
Neotoca bilineata
Neotoca bilineata
Neotoca bilineata
Neotoca bilineata
Neotoca bilineata
Neotoca bilineata
Neotoca bilineata
Neotoca bilineata
Neotoca bilineata
Neotoca bilineata
Neotoca bilineata
Neotoca bilineata
Neotoca bilineata
Neotoca bilineata
Neotoca bilineata
Neotoca bilineata
Neotoca bilineata
Neotoca bilineata
Neotoca bilineata
Neotoca bilineata
Neotoca bilineata
Neotoca bilineata
Neotoca bilineata
Neotoca bilineata
Neotoca bilineata
Neotoca bilineata
Neotoca bilineata
Neotoca bilineata
Neotoca bilineata
Neotoca bilineata
Neotoca bilineata
Neotoca bilineata
Neotoca bilineata
Original Description: 

  BEAN, T. H. (1887): Descriptions of five new Species of Fishes sent by Prof. A. Dugès from the Province of Guanajuato, Mexico. Proceedings of the United States National Museum 10: pp 370 - 375

Etymology: 

  The species-name is derived from the Latin and means "with two lines", a colouration detail, this species shows mainly in preservation.

Holotype: 

  Collection-number: United States National Museum, Cat. No. USNM-37832.

  The Holotype is an adult female of 44.9mm total length, collected by A. Dugès, collection date unknown.

English Name: 
Twoline Skiffia
Mexican Name: 
Tiro de dos rayas
Synonyms: 

Characodon bilineatus Bean, 1887

Skiffia bilineata Meek, 1902

Goodea bilineata Regan, 1907

Karyotype: 

  The Karyotype describes the number and appearance of chromosomes during the phase of condensation, classified by the position of the centromere (Levan et al., 1964).

The following abbreviations are employed:

 

M = large metacentric chromsome (a result of Robertsonian fusion)

m = small metacentric chromsome (centromere at medium position)

sm = submetacentric chromsome (centromere at submedian position)

smst = submetacentric-subtelocentric chromosome (continous series)

st = subtelocentric chromosome (centromere at subterminal region)

stt = subtelocentric-acrocentric chromosome (continous series)

t = acrocentric chromosome (centromere at terminal region)

 

The Karyotype of Neotoca bilineata, following Uyeno, Miller & Fitzsimons, 1983:

2n = 48    4m/ 2sm/ 34st/ 8t  

Size: 
The maximum known SL is 42mm (Miller et al, 2005).
Terra typica: 

The Holotype comes - following Bean - from the "Province of Guanajuato".

Status : 

   International Union for Conservation of Nature (IUCN): not assessed

 

  Conservation status and population trends of Mexican Goodeids (Lyons, 2011): critically endangered/declining – Historically, this species was reported from three distinct areas: Lake Chapala and adjacent portions of its outlet, the upper Santiago River; the Lerma River and its tributary the Laja River and Lake Yuriria in the middle Lerma River basin; and the endorheic Lake Cuitzeo/Grande de Morelia River basin near the city of Morelia (Miller et al. 2005). The Lake Chapala area records are from the early 1900’s, and no individuals have been collected there for at least 60 years (Lyons et al. 1998). The last middle Lerma basin records are from the 1990’s, and recent surveys have not encountered any specimens (Soto-Galera et al. 1998; Mercado-Silva et al. 2006). The only remaining populations are in the Lake Cuitzeo/Grande de Morelia River basin (Domínguez-Domínguez et al. 2005b). Pollution and habitat modifications had eliminated the species from Lake Cuitzeo and from most of the Grande de Morelia River drainage by the 1990’s, leaving only four surviving populations (Soto-Galera et al. 1999). Two of these have since disappeared, and the long-term survival of this species in the wild is highly uncertain (de la Vega-Salazar 2003a; Domínguez-Domínguez et al. 2005b).

 

  NOM-059-SEMARNAT-2010: Categoría de riesgo (Category of risk): P - En Peligro de Extinción (in danger of extinction)

Distribution and ESU's: 

  This species comes from the Pacific Slope and inhabits the ríos Lerma-Grande de Santiago basin and the endorheic Río Grande de Morelia basin in the states of Guanajuato, Jalisco and Michoacán.

 

  ESU ist short for Evolutionarily Significant Unit. Each unit expresses an isolated population with different genetic characteristics within one species.  ESU's can be defined by Molecular genetics, Morphology and/or Zoogeography and help in indicating different phylogenetic lineages within a species. The abbreviation for an ESU is composed of the first 3 letters of the genus, followed by the first 2 letters of the species name and an ongoing number in each species.

 

  In Neotoca bilineata, we distinguish between the (probably) extinct populations from the Lagode Chapala drainage (Neobi1) and those from the other locations, encompassing the Lago de Cuitzeo drainage and the middle Río Lerma populations (ríos Guanajuato and Turbio). Those are named Neobi2.

Habitat: 

  The habitats are quiet, turbid to muddy waters of lakes, sloughlike channels, ponds, ditches and canals. They can be found in depths of less than 1m over mud, silt, sand, clay and rocks, prefering currents of none to slight. The vegetation comprises green algae, water haycinths, Potamogeton, Chara, Typha and Scirpus.

 

Lago de Cuitzeo ILago de Cuitzeo II

 

Lago de Cuitzeo IIILago de Cuitzeo IV

Colouration: 

  Both sexes are coloured silvery gray with a bluish or yellowish glimmer. Like in most Goodeid-species, the upper side is darker than the lower side. Males develop a black dorsal and anal fin, the caudal fin a bit brighter. The other fins are clear. Some populations can show white or whitish fins instead of black ones (e. g. Río Querendaro). On the sides are 10  to 15 irregular, but thin vertical stripes visible. Usually, they become broader posteriorly. The first stripe is settled near the origin of the pectoral fin, the last on the caudal base. Some specimens show reddish or orange pigments in the fins and on the caudal peduncle. Females may be coloured purplish or yellowish and show a silvery longitudinal stripe, extending from the eye posteriorly to the caudal base. All fins are clear. They show a black gravity-spot in the anal region, varying in size.

Biology: 

  This species can tolerate low temperatures and produces offspring in water with a temperature of 10°C. Captures of young and observations of females carrying embryos indicate that the reproduction occurs from early March to late May.

Diet: 

The gut is about 1.5 times the length of the fish, and herewith shorter than in Skiffia species. Both rows of teeth are bifid, so all in all, this species seems to be omnivorous (prefering maybe small invertebrates).

Remarks: 

  Neotoca bilineata was thought to belong to the genus Skiffia since 1902 (Meek). Though Hubbs & Turner showed even in 1937, that this species differs in many characters, like dentition, jaws, mouth, intestine length, colouration and sexual characters associated with the anal fin (Gonopodial suspension), many authors till in our days do not accept the genus Neotoca and place bilineata furthermore in the genus Skiffia. Recent studies (Webb, Dominguez) using phylogenetic methods place this species not in the nearest vicinity of Skiffa (though of course being related), but near Girardinichthys (an indication may be the black dorsal and anal fins of this species and Girardinichthys viviparus)

 

Neotoca bilineata has been imported to Europe even in 1935, but died out during the second World War.

 

In captivity and in combination with higher temperature, this species stays rather small, reaching sometimes not even 3cm TL (in the wild: more than 6cm TL  in females). Males might then reach not more than 1.5cm in total.

 

Netoca bilineata is a kryptic species in the wild, hiding in vegetation and being distributed in particular habitats. It may be overlooked many times, but nevertheless, it has to be denoted as one of the most endangered species of Goodeids. It seems to persist at only 5 sites, 4 of them small and being tributaries to the Lago de Cuitzeo and a fifth one, a spring tributary to the lower Río Laja, a tributary to the upper Río Lerma. From the degraded Lago de Cuitzeo, it was said it wasn't reported anymore since the early 1990s, but when a survey group of the GWG was there in November 2014, we could sample hundreds of them in a few minutes.

Taking in consideration the details given by Hieronimus in 1995 (his personal data and from Radda, both from the years 1984 and 1989) as "stocks are save for foreseeable future", it may be seen, how fast species or populations might disappear.