Allodontichthys hubbsi

Allodontichthys hubbsi
Allodontichthys hubbsi
Allodontichthys hubbsi
Allodontichthys hubbsi
Allodontichthys hubbsi
Allodontichthys hubbsi
Allodontichthys hubbsi
Allodontichthys hubbsi
Allodontichthys hubbsi
English Name: 
Whitepatch or Whitepatched Splitfin
Mexican Name: 
Mexclapique (erronously: Mexcalpique) de Tuxpán
Original Description: 

  MILLER, R. R. & T. UYENO (1980): Allodontichthys hubbsi, a new species of Goodeid fish from Southwestern Mexico. Occasional Papers of the Museum of Zoology University of Michigan No. 692: pp 1-13

Holotype: 

  Collection-number: University of Michigan Museum of Zoology, Cat. No. UMMZ-200221.

  The Holotype is an adult male of 48.3mm standard length, collected by R. R. Miller and J. T. Greenbank on March the 8th, 1955.

Terra typica: 

  The Holotype was collected in a tributary (Arroyo San José de Tule or Río La Trampa) of the Río Tuxpán at the HW 110 bridge at Crucero del Tule 8km north of the city of Pihuamo in the state of Jalisco.

Etymology: 

  Citing Miller and Uyeno in the original description: "The species is named after the American ichthyologist Carl L. Hubbs (1894-1979), whose early studies on Goodeids set the stage for subsequent understanding of this compact but highly diversified family."

Synonyms: 

  none

Distribution and ESU's: 

  The Whitepatch Splitfin is endemic to the Mexican federal state of Jalisco, historically known from the Río La Trampa (Arroyo San José de Tule, type location) and the Río El Terrero, both Río El Tule drainage, and from the Río Tamazula and further downstream from the upper Río Tuxpán, both names for consecutive sections of the Río Coahuayana, to approximately the town of Tuxpán. Furthermore, the distribution encompasses two affluents of the Río Tamazula: a nameless creek east of La Garita and the Río Contla. Though the Río El Tule is an affluent of the Río Naranjo, the name for the river section of the Río Coahuayana following the Río Tuxpán, the Arroyo San José de Tule and the Río Tamazula collection sites are separated by about 120 river kilometres and 40km beeline. From the affiliation to two different drainages, two subpopulations can be inferred: the Río El Tule subpopulation (type subpopulation) and the Río Tuxpán subpopulation. The underlined names are the ones officially used by the Instituto Nacional de Estadística y Geografía; nevertheless, other ones might be more often in use or better known and therefore prefered. The species is absolutely rare in the wild, usually associated with its congener Allodontichthys tamazulae.

 

  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 three letters of the genus, followed by the first two letters of the species name and an ongoing number in each species.

  In Allodontichthys hubbsi, it is possible to distinguish two different ESU's, according to the two different subpopulations. Aldhu1 encompasses the northern populations of this species from the Río Tamazula and its affluents like the Río Contla and a nameless creek east of La Garita, and populations down the course of the Río Tamazula and the following river section, the (upper) Río Tuxpán, where Miller collected in 1955. The second ESU is named Aldhu2 and this abbreviation is used for the south-eastern populations north of Pihuamo (Río El Terrero and Arroyo San José de Tule), fish of the type location and areas in the geographic vicinity of it belong to this ESU.

Status : 

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

  Conservation status and population trends of Mexican Goodeids (Lyons, 2011): endangered/stable – This species is known from only four areas in the upper Coahuayana River basin (Lyons and Mercado-Silva, 2000). Two of these populations are small, but two, Contla Stream and the nearby upper Tamazula River, are fairly large. None of the populations have shown major changes since the late 1990s (Domínguez-Domínguez et al., 2005).

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

Habitat: 

  Like all known Allodontichthys - species, the Whitepatch Splitfin is a bottom-dwelling and riffle-inhabitating  species. As expected from this behaviour, Miller & Uyeno found a considerably smaller swimbladder than in Ilyodon. It extends only to between the fourth and fifth rib (versus to the first in Ilyodon). The fish live around and under stones and boulders of rocky riffles of generally clear streams, usually from 3 to 8m wide (up to 30m in the main stem Río Tuxpán, where it is scarce). It is associated with abundant green algae on rocks and along stream margins, often with trees (including Salix) shading part of the habitat. The currents are moderate to fairly swift in the dry season, no doubt torrential during the wet summer months. Its habitats are similar to those of the North American darters (Percidae, genus Etheostoma) living among and under rocks in shallow waters. At the Río Terrero, the long rocky riffles are separated by pools up to 8x20m in major dimensions. Miller found the water clear, but quite easily muddied because of the silt amongst the rocks and boulders. He described the water temperatures on several visits to the Río Terrero and to the type locality varying from 18 to 22°C, with the air temperature generally higher (24-28°C). The depth of the water varies from 2.5 to 0.15m.

 

  On a survey in 2016, a group of members of the GWG found this species together with Allodontichthys tamazulae and Ilyodon whitei close to the bridge at Contla in the Río Contla in very shallow (about 20cm deep) water in swift current. Both Allodontichthys species were easy to catch by lifting rocks (where the fish were under), and putting a dipnet over the place. The river had a width of about three to four meters in this dry season, the broad pebbly river bank sugested a width of about eight to ten meters in the rainy season. The survey revealed good stocks of this species with nearly the same number of individuals as of the Peppered Splitfin. We were able to find this fish additionally in the Río Tamazula at the east end of the town of Tamazula de Giordano, together with the same species of Goodeids and "Xenotoca" lyonsi in sligthly deeper water and swift current. On a survey of the same place in November 2018, the river was a murky fast flowing river, wide up to 8 or 10m and deep to 120cm at some places. Only few Whitepatched Splitfins could be found this time, including fry. A survey of the Arroyo San José de Tule revealed the species above the town of San José de Tule near the aqueduct, whereas in the town, only Allodontichthys tamazulae could be found. All Allodontichthys at all surveyed locations were in poor health condition probably due to a higher pressure through parasites.

 

  The Whitepatched Spitfin occurs sympatric with Allodontichthys tamazulae in the headwaters of the Río Tuxpán, but no more in the warmer and slow flowing parts of the river, where the Peppered Splitfin seems to be the only representative of the genus. Maybe this species is more tolerant against slightly higher temperatures or poorer water quality.

Arroyo Contla IArroyo Contla II

Río Tamazula IRío Tamazula II

 

Río Tamazula IIIRío Tamazula IV

Biology: 

  The species is probably sparsely distributed in riffle habitats. It was found to be abundant at Arroyo Contla (12km north-east of Tamazula) in February 2000 (John Lyons, 2002). In the original description, Miller noted that in aquarium observations (by Dolores Kingston) this species showed an aggressive behaviour with males killing each other and females when confined to small aquaria. He postulated that indicates this species is solitary. He observed a peculiar swimming of juveniles (that differed from the sympatric congener A. tamazulae) on riffles at Río Terrero that resembled a slow-moving tadpole. They hugged the bottom, hovering close to rock surfaces. He saw no adults there, so he thought, they may not venture far from rock cover much at the time.

 

  A survey of the GWG in 2016 found a decent number of hellgrammites, huge larvae of Dobsonflies (subfamily Corydalinae) covering in the mud of the Río Contla and hunting for fish, especially Ilyodon, but for Allodontichthys as well for sure. 

Diet: 

  The tricuspid and pointed fork-like teeth and the short gut indicate carnivorous feeding habits. The examinations of Turner found the guts of the related Allodontichthys tamazulae containing large insect larvae. In general, Allodontichthys species have short guts (0.67 - 1-20 % of the total length). Compared with all other respresentatives of this genus, the tricuspid teeth of the Whitepatch Splitfin are obviously stronger forked, so maybe they are better adapted to capture animalistic prey like Mayfly-larvae, Amphipods or Bloodworms.  

Size: 
The maximum known standard length is 61mm (Miller et al., 2005).
Colouration: 

  Citing Miller and Uyeno: "In preservative (ethanol), the dorsal fin of males has 3 to 5 irregular rows of dark spots, often strongly developed, that extend from near the base to well out onto the fin. The other fins are clear. There are as many as 9 to 11 bars on the upper half of the body that are broad and distinct posteriorly but become narrow and irregular in advance of the dorsal fin; they are more conspicuous in smaller males. The bars are often disrupted between back and midside to form lateral spots or blotches, especially in smaller males; in these specimens the back has a strongly mottled appearance. Barring is often indistinct in larger males. Females have 1 to 3 irregular rows of dark spots, generally along the lower half of the dorsal fin, that are usually less conspicuous than those in the male. The other fins are clear except that one fish shows a few, weak dark dashes on the interradial membranes of the caudal fin near its midbase. There are 5 to 8 irregular bars, blotches, or spots along the midside, from caudal base to about dorsal origin, that are generally discontinuous with the irregular barring and spotting on the back. In smaller females and juveniles there is a tendency for the spots along the midside to coalesce into a lateral stripe.

 

  In both sexes there are narrow to broad dark crescents outlining the posterior margins of the scales along the upper sides, most prominent in males. Near the midside and slightly below, dark pigment tends to be centred on the scales to form irregular longitudinal rows of spots. The lower sides and venter are light. A prominent, dark scapular bar or blotch, often crescent-shaped, occurs above and just behind the base of the pectoral fin in both sexes. In life, no bright colours were noted.

Remarks: 

  This is the only Goodeid species and one of only few known fish species at all with multiple sex chromosomes, 2n = 41 in the male and 2n = 42 in the female (Miller & Uyeno, 1972). Both authors thought of the sympatric congener Allodontichthys tamazulae to be the closest relative, but later phylogenetic results (Cytochrome c oxidase subunit I and mitochondrial control region, Webb, 2002) and morphological features (Rauchenberger, 1988, e.g. it differs from its congeners having only 3-3 versus 4-4 mandibular pores in the acustico-lateralis system, a longer base of the anal fin and the dorsal fin placed more anteriorly) heavily supported the position of Allodontichthys hubbsi at the basis of the genus as the most distinct representative. Latest phylogenetic studies (Cytochrome b gen, Dominguez-Domínguez et al., 2011) however place the Whitepatch Splitfin again next to Allodontichthys tamazulae as its closest relative. Nevertheless some inconsistencies remain: Why is it possible, that two closely related species of one genus are able to develop in one river system, and how can it happen, that both persist next to each other? Here the emergence of different sex chromosmomes in Allodontichthys hubbsi could be the answer. But how can the morpholgical distinct features between hubbsi and its three congeners be explained? Maybe the relationship is not that narrow and the Whitepatch Splitfin is really the most basic species of Allodontichthys, but former hybridisation processes between Allodontichthys hubbsi and tamazulae may be pretending narrow relationship in the cytochrom b gen, so for the moment, the position of the species in the genus Allodontichthys is not clearly resolved.

  However it is also possible, that both species have not clearly separated ecologocal niches and that Allodontichthys tamazulae is on the way to substitute Allodontichthys hubbsi in the future as this species is becoming absolutely rare. In some habitats, it seems to have disappeared throughout the decades and been replaced completely by Allodontichthys tamazulaeAllodontichthys hubbsi is restricted to the upper Río Coahuayana basin and is reported from only 6 sites (Lyons & Mercado-Silver, 2000). In total, only 264 have been sampled for Museums throughout the last six decades. From the Río Tuxpán are reported 14 individuals out of 1955, in 1964 and 1969 only A. tamazulae was found. A tributary to the Río Tamazula northeast of the city of Tamazula de Giordano revelealed also only the Peppered Splitfin in 1978, though in 1955 there were at least a few Whitepatch Splitfins (2 individuals collected). From the Río El Terrero are reported 84 A. hubbsi in collections from 1970 to 1976, but no more thereafter until 1995. Last surveys (2018) revealed two extant populations: A small one from the Arroyo San José de Tule and a relatively large one from the Río Contla. Both populations are subject to stream desiccation and municipial pollution.  

 

   J. Lyons and N. Mercado-Silva (2000) wrote, that in the field, the easiest possibility to distinguish A. hubbsi from tamazulae is by the colour of the back. While the Peppered Splitfin shows black or brown spots, the Whiteptach Splitfin doesn't have clear markings. Mary Rauchenberger (1988) described the dorsal body pigment of A. hubbsi as reduced in places, giving the fish a blotchy appearance. Additionally, she remarked pale fins in contrast to the other species.

Husbandry: 

  Looking on the biotopes of Allodontichthys hubbsi, they suggest the species may prefer a habitat with moderate to swift current, structured with gravel, rocks and boulders. Some breeders of the population from the Arroyo San José de Tule observed a high level of aggression between the adult fish, so the tank set up should prevent the fish from seeing each other most of the time. The population from the Río Contla doesn't show that level of aggression. 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 seem to feed from small or middle-sized invertebrates like bloodworms or insect larvae, so feeding with similar food, with Daphnia, Mysis and other food from animalistic sources will be best for this predatory fish. In aquarium, it feeds also well from flake food, granulate and even tablets, additionally given Nauplia of Brine Shrimps are eaten greedy and the species is not acting shy at all.  

  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 age too fast. So 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 when it gets too warm (25°C?).

  This species may do very well when is 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.

Locations