"Xenotoca" lyonsi

Xenotoca lyonsi
Xenotoca lyonsi
Xenotoca lyonsi
Xenotoca lyonsi
Xenotoca lyonsi
Xenotoca lyonsi
Xenotoca lyonsi
Xenotoca lyonsi
Xenotoca lyonsi
Xenotoca lyonsi
Xenotoca lyonsi
Xenotoca lyonsi
Xenotoca lyonsi
Xenotoca lyonsi
Xenotoca lyonsi
Original Description: 

Domínguez-Domínguez, O., Bernal-Zuñiga, D.M. & Piller, K.R. (2016): Two new species of the genus Xenotoca Hubbs and Turner, 1939 (Teleostei, Goodeidae) from central-western Mexico. Zootaxa 4189 (1): pp 081–098

Etymology: 

  The name of the species, an adjective, is derived from the name of the prominent North American ichthyologist, Dr. John Lyons, who has made substantial contributions to our understanding of the distribution, ecology, diversity, and conservation status of fishes in Mexico, and to Goodeids in particular.

Holotype: 

  Collection-number: Colección de Peces de la Universidad de Michoacán, Cat. No. CPUM-9590, CPUM-T-41522.

  The Holotype is an adult male 55 mm SL, collected 12the of July (2015?). 

English Name: 
Tamazula Redtail Splitfin
Mexican Name: 
Mexclapique de Tamazula
Synonyms: 

Characodon eiseni    Rutter, 1896

Characodon variatus    Regan, 1907

Xenotoca eiseni    Fitzsimons, 1972

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 "Xenotoca" lyonsi has not been ascertained, but is presumably similar to the one of "Xenotoca" eiseni.

Size: 
The maximum standard length is 50mm
Terra typica: 

  The type location is the Río Tamazula, Coahuayana drainage, just 5 km Northeast of the town of Tamazula de Giordano, Jalisco (19°43’24.9’’ N 103°12’05’’ W).

Status after IUCN: 

  not assessed

Status following other sources: 

  not assessed; after Domínguez et al. (2016): Critically endangered

Distribution and ESU's: 

The species is endemic of the Coahuayana River drainage, being reported only in the middle and upper part of the drainage, in the Tuxpán and Tamazula rivers at altitudes more than 1000 meters above the sea level, all localities within the state of Jalisco, Mexico. The type locality is in a highly seasonally changed Tamazula River, approximately 5 km northeast of the town of Tamazula town (19°43’24.9’’ N 103°12’05’’ W). The new species also has been reported in other locations along the Tuxpán and Tamazula rivers near Ferreria, Soyatlan de Afuera, San Rafael, Tuxpán and Atenquique villages, but most of these localities no longer harbour "Xenotoca" lyonsi and it is presumed to be locally extirpated.

 

  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 "Xenotoca" lyonsi, it is not possible to distinguish different ESU's, so there is only one recognized: Xenly1 (before: Xenei3).

Habitat: 

  The type locality for "Xenotoca" lyonsi is an area with high seasonal changes in water clarity and volume, from a turbid and deep high flow running water in the rainy season to clear and low flow water other times of the year, sometimes reduced to a few shallow pools in the dry season. The bottom primarily is composed of mud and gravel, and water plants are only evident in the stream bed, which seems to change in composition and coverage depending on the season. The area is totally surrounded by sugar cane plantations. Other fish species collected in the area were "Xenotoca" melanosoma (now extirpated), Ilyodon whitei (Meek 1904), Poecilia butleri (Jordan 1889), Allodontichthys tamazulae (Turner 1946), Allodontichthys cf. hubbsi and Astyanax anaeus (Günther 1860), as well as the introduced Cyprinus carpio and Oreochromis sp.

 

Río Tamazula I

Río Tamazula II

 

Río Tamazula III

Río Tamazula IV

Colouration: 

  When alive, the coloration varies with respect to the age and sex of the organism. Mature females show a general brownish coloration with a dark pigmented strip along the body, from the opercle to the hypural plate region that varies in intensity and width. Dark blotches are not evident in big females, but being more evident in the posterior half of the body when present. Scales are frequently rounded in their exterior margin by small black spots. A black blotch is present in the posteroventral region, between the pelvic and anal fins, which varied in depth and width. Juveniles have the same coloration than females, but as they reach ±20 mm they start to differentiate to adult coloration. Juveniles show a brownish translucent coloration with small darkblotches along the body. The fins are clear and unpigmented. Males show a coloration that varies depending on the size and reproductive stage, but in general the posterior half of the caudal peduncle has an orange coloration that extends to the caudal fin, and sometimes some iridescent blue scales are present. The anterior half of the caudal peduncle sometimes possesses blue iridescent scales that frequently extend anterior to the anal fin in the ventral region and to the middle of the dorsal fin, the intensity and coverage of each color is highly variable. Anal, pectoral and dorsal fins can show some pigmentation, being orange to dark coloration. The anteroventral portion of the body is normally with a brown to white coloration, the dorsal region is brownish in coloration, with blue iridescent scales in some males. Sometimes the dark blotch just up to the pectoral fin is present, and also is highly variable in intensity and size, and is less evident than in "Xenotoca" doadrioi. Blue iridescent coloration is often present on the opercle. The coloration of preserved specimens varies with respect to fixative and time since fixation, but in general, specimens preserved in 5% formalin show, for females, clear brownish coloration. The blotches are sometimes present along the body, but in bigger females are more evident in the dorsal half of the body, in young females are frequently present along the body. The ventral region is clear. Some females possess silver to dark stripe along the middle part of the body, being more evident in the posterior half. The opercle shows a silver coloration. Fins are unpigmented. Males lose all coloration, the ventral half of the body, including the head and preventral region, and the posterior half of the peduncle show a clear brownish to beige coloration, the rest of the body shows a brownish dark coloration with the darkest coloration around the external part of the scales. Normally fins clear and unpigmented.

Biology: 

  Nothing is known about its biology in nature. Concerning the closely related "Xenotoca" eiseni, we have the following information: Young are produced at least in March and April and probably over a long reproductive period. In aquatic stocks, broods have appeared in all months of the year, maintained  at 24 - 27°C.

 

  On a survey in February 2016, Koeck et al were able to find "Xenotoca" lyonsi east of the city of Tamazula de Giordano. The fish were inhabiting quiet parts of the clear and fast flowing Río Tamazula, but in low numbers.

 

Diet: 

  Adults have got strongly bifid teeth in the outer row and conic teeth in the inner row. Following Fitzsimons (1972), the closely related species "Xenotoca" eiseni is omnivorous, although plant material forms the greater volume of food. The gut is as long or sligthly longer than TL. Besides plant material, they feed also from worms, crustaceans, spiders and aquatic insects.

Remarks: 

  "Xenotoca" lyonsi is known only from a few sites along its original distributional range, and is reported to been extirpated from approximately 60% of the historical localities where it has been reported (Pedraza-Marron 2011). All the areas where the species originally occurred are highly impacted by human activities, being totally modified for agricultural purposes, with sugar cane plantations demanding high water resources and discharging polluted water from the production process. Also, un-treated urban waste water is a substantial ecological problem in the area. In several recent surveys for the species, it was never located downstream of the village waste water discharges, and, when found, it was always upstream of the discharge sites. Also, the species is not abundant in the few localities from where it is currently known to exist. This species should
be considered as endangered of extinction.

Husbandry: 

  Looking on the habitats of "Xenotoca" lyonsi, they suggest the species is not in need of a special habitat structure as many of the locations show no or little vegetation but murky water. Nevertheless, it may prefer dense vegetation and roots (in the aquarium even dense artificial staff) to hide. In the wild, the species occurs in rivers, prefering the quiet parts with little current, so it won't be necessary in the aquarium to have strong current. In the aquarium, the fish rarely hide in the shelter, but courting and impressing males as well as fighting fish of both sexes can often be seen in the open water. Fry is eaten in some cases, in others not, so it may depend on the quantity and quality of food and on the number of space to hide. When several different stages of juveniles occur, fry is often neglected, so it makes sense to add separate brought up fry to the group with a size of 1.5 or 2cm to provide these stages and get a flock breeding colony.

  The recommended tank size is at least 100 liters, bigger ones are better for sure. Dense vegetation combined with many roots and wood and free space areas for the males to impose and fight make sense. The current should be low.

  In the wild, the species seem to feed as a typical omnivore from small invertebrates, aufwuchs, algae, organic matter and insects from the surface. "Xenotoca" lyonsi can be fed in the aquarium with food of different sources, composed of different small frozen or freeze dried invertebrates (Daphnia, Bloodworms, Artemia), small livefood (e.g. Nauplia, Cyclops, Daphnia) and good flake food or tablets respectively granulat food. Fish of the "Xenotoca" eiseni - complexe feed from more vegetarian sources than representatives of the "Xenotoca" melanosoma - complexe.

   Concerning water quality, this species is in need of greater water changes (60 - 80% every week), so an automatic water changing system can be helpful. Otherwise, in combination with constant temperatures higher than 24°C, fish may get sick, lose resistance against diseases and burn themselves out. So, mainly for keeping the strain healthy and strong, give the fish a rest during winter time with temperatures lower than 20°C for 2 or 3 months so they stop producing fry. In spring, when the temperature slowly increases, they will start spawning at 20 or 21°C and won't stop until it gets colder again or gets too warm (25°C?).

  This species does very well when is kept in the open from spring to fall, starting when the temperature exceeds 17°C water temperature and cold periods are no longer expected. During the warm summer, reproduction will stop and may occur again in fall. Bring the fish in before the temperature goes below 15°C water temperature and keep them cool for the first days, then slowly raise the temperature but try to stay below 20°C over the winter time.

 

 

Locations