Allodontichthys polylepis

First Describer: 
Rauchenberger, 1988
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Original Description: 

  RAUCHENBERGER, M. (1988): A new Species of Allodontichthys (Cyprinodontiformes: Goodeidae), with comparative Morphometrics for the Genus. Copeia 1988 (2): pp 433 - 441

Etymology: 

  The name “polylepis” can be derived from the Greek and means: "with many scales", as this species has between 10 and 20% more scales in the lateral line than its congeners: πολύς (polýs = many) and λέπις (lepis = scales)

Holotype: 

  Collection-number: University of Michigan Museum of Zoology, Cat. No. 213951.

  The Holotype is an adult male of 42mm standard length, collected by R. R. Miller et al., 23.02.1973.

English Name: 
Finescale Splitfin
Mexican Name: 
Mexclapique de escama
Synonyms: 

  Allodontichthys sp.   Fitzsimons (1981)

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 Allodontichthys polylepis, following Uyeno, Miller & Fitzsimons, 1983:

2n = 48    2m/ 2sm/ 44stt  

Size: 
The maximum known standard length is 50mm (Miller et al, 2005).
Terra typica: 

  The original citation from the description says, that the Holotype was caught in the Río (Arroyo) Potrero Grande (Río Ameca drainage), 9.6km east of Ameca on the road to Guachinango in the state of Jalisco. This is defintely a mistake because the type location is about the same distance west of Ameca. Maybe the spanish word for west, oeste which is similar to east, este caused the mistake.

Status after IUCN: 

  not assessed

Status after J.Lyons (2011): 

  Status: Extinct in the wild?

  Population development: No records since 2000

Distribution and ESU's: 

  Allodontichthys polylepis is  - or better was - endemic to the upper (southwestern) tributaries of the Río Ameca west of Ameca on the Pacific Slope in Jalisco. There are only three collection sites known (2 of them very close to each other) and all of them do not inhabit this species any more, probably as a result to the big drought at the change of the millenium, that dried up the known habitats of the Finescale Splitfin.

 

  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 Allodontichthys polylepis there is morphologically no difference between both populations to detect, so they are treated as only one ESU, Aldpo1, but this is doubtful as both representatives differ in colour and other features. Phylogenetically, the type population has never been examined, but should be done by the end of 2015, so we have to wait for further results. Though the Río Potrero Grande and the Río de las Bolas are separated by only about 15km beeline, following the waters it is more than 150km to go, so we should absolutely be careful by treating them as one ESU.

Habitat: 

  The Finescale Splitfin lived in clear streams with riffles and pools over substrates of sand, gravel, rocks, boulders and some silty mud. The vegetation comprised green algae on rocks or floating. The currents were slight to none in the dry season, the depths usually less than 0.5m.

Colouration: 

  Here the original citation by Mary Rauchenberger, 1988: "In ethyl alcohol, the body is dark brown dorsally, lighter on the ventral half of flanks and cheek; dorsolaterally, edges of scale pockets are blackened, giving a flecked appearance; scapular blotch dark and prominent; 8 – 11 medium brown vertical bars from behind the pectoral fin onto the caudal peduncle; lateral bars may be obscured by a general darkening in larger males; dorsum with irregular spotting in juveniles and females; pectoral and pelvic fins relatively pale; dorsal fin in fish 20 – 40mm with a basal row of spots followed distally by 1 or 2 more irregular rows of larger spots; spotting in dorsal and anal fins sometimes obscured in larger fish, especially males, by dusky-dark pigmentation on basal three-fourths of the fin."

Biology: 

  Mary Rauchenberger noted, that none of the collections she used for her description (both localities: March 1957, February 1970 and 1976) contained gravid females, but Miller (2005) reported small young and gravid females from late February to early March.

Diet: 

  The diet is probably the same as in related species like Allodontichthys tamazulae. Miller found large insect larvae in its guts. In general, Allodontichthys species have short guts (0.67 - 1-20 % of the total length) and (except in A. hubbsi) the outer-jaw teeth shouldered or "incipiently tricuspid".

Remarks: 

  The Finescale Splitfin had been discovered in 1957 by R. R. Miller & M. Miller in the Río de las Bolas, a tributary of the Río Atenquillo (Ameca basin). However, it took scientists more than 30 years to describe this species. Its habitats are distant in distribution with respect to its congeners, making it to the only known representative of this genus in the Mesa Central.

 

  The fatal decline of this species seemed to happen by the end of the millenium. The population from the type locality, the Río Potrero Grande, disappeared in the late 1990's, probably due to a series of bigger droughts. The last confirmed collection for the Río de las Bolas dates back to 1998, but Brian Kabbes, who thought who was visiting the type location, but indeed had been at the Río de las Bolas, detected the species in deep pools in the nearly dried out river next to the town of Estancuela in December 1999. The population in the nearby Río Davalos existed at least until 2001, but a major drought dried the river completely between 2001 and 2003. However, such drought events also happened in the past (Dominguez, pers.), but maybe this time they simply were too severe for the Finescale Splitfin to deal with. All in all, the reason for the disappearance of Allodontichthys polylepis in the wild is not cleared completely, but seem to have its roots in this series of droughts. The Finescale Splitfin is probably extinct in the wild.

 

  In 2008, O. Domínguez started a semi-captive conservation program with the help from the Fish Ark Mexico Project. An artificial pond on the area of the Botanical garden of the Faculty of Biology from the University of Morelia was built and stocked with Neotoca bilineata and Zoogoneticus tequila in April, as well as with Allotoca goslinei and  Allodontichthys polylepis in August. In contrary to the other three species, all catches in the years thereafter did not reveal any specimen of the Finescale Splitfin and so it obvious, that this program failed finally.

 

  In 2011, the number of Allodontichthys polylepis in captivity from two surviving locations (the population from the Río Davalos has to be treated extinct) encompassed only about 30 or 40 specimens and it was said to be the rarest fish in the world. The number of individuals from the type location went down to eight adults and a handfull of juvenile fish, and from the Río de las Bolas population, there was only one female existing with a dozen of young fish she had been given birth to. Thereafter, the GWG and the Aqualab in Morelia started a breeding and distribution program with this species. Four years later in 2015, this species is still very rare but no more in immediate danger of extinction encompassing a few hundred fish from the Río de las Bolas and nearly two hundred from the Río Potrero Grande. While the number of specimens of the Río de las Bolas population is simply monitored to have an eye on the development of the strains, all individuals of the type location population are part of a breeding program including two zoos and three hobbyists at the moment (July 2015). Property, distribution, membership and more details are strictly regulated to be most successful in increasing the number of fish.

Husbandry: 

  Looking at the former biotopes of Allodontichthys polylepis, they suggest the species may prefer a habitat with moderate to swift current, structured with gravel, rocks and boulders. This species is probably not as aggressive as Allodontichthys hubbsi, nevertheless there is a lot of aggression between the adult fish, so the tank set up should prevent the fish from seeing each other most of the time. Fry is eaten in most of the cases, but 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 may be 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 150 liters, bigger ones with a generous base and little height (25cm are enough) are better for sure. With rocks well structured tanks combined with some roots and/ or wood seem to do best with this species. The current should be moderate or swift. 

 

 In the wild, the species seemed to feed from small or middle - sized invertebrates like bloodworms or insect larvae, so feeding with the same food, Daphnia, Mysis and other food from animalistic sources will be best for this predatory fish.   

 

 Concerning water quality, this species is in need of greater water changes (60 - 80% every week) like most of the Goodeids, especially river inhabiting species, 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 is doing very well when kept in the open from spring to fall, starting when the temperature exceeds 15°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 10°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.