Characodon lateralis GÜNTHER, 1866

Rainbow Characodon

Etymology

Characodon: from the genus name Charax and Ancient Greek ὀδούς (odous), meaning ‘tooth’, in reference to the presence of a row of villiform teeth behind the incisors, this being reminiscent of characiform dentition.

lateralis: from the Latin lateralis, meaning ‘lateral, belonging to the side’, in reference to the lateral stripe on the body.

Classification

Order: Cyprinodontiformes Family: Goodeidae

Distribution

Putatively restricted to a series of small habitats below the waterfall known as ‘El Saltito’ in the upper Río Mezquital basin, Durango state, central Mexico. It was previously considered to occur throughout much of the upper Río Mezquital in both Durango and Coahuila states, but genetic analyses suggest otherwise and have resulted in taxonomic confusion (see ‘Notes’).

Known localities include ‘Los Berros’, ‘La Constancia’, ‘Amado Nervo’, ‘San Juan’, and ‘Nombre de Díos’, although additional populations are thought to exist (M. Köck, pers. comm.).

The precise type locality is unknown, being given simply as ‘Central America’.

This species is endangered in the wild, with its abundance and distribution having declined considerably due to pollution, abstraction of groundwater, introduction of invasive species and other forms of habitat alteration.

Habitat

Mostly inhabits springs and their outflows a an altitude around 1800 m AMSL, and displays a preference for shallow water with little to no flow and abundant aquatic vegetation. The water may be clear or turbid, with substrates varying from sand, gravel and rocks to mud, silt and clay.

At El Ojo de Agua (literally ‘the Eye of Water’) de San Juan the habitat comprises a clear water spring measuring approximately 100 m x 20 m with abundant aquatic vegetation. The El Ojo de Agua de Los Berros population also inhabits a fairly large modified spring containing transparent water, while at La Constancia the species is restricted to a tiny spring located on private property. At Amado Nervo the species has been collected from a tiny polluted stream with green algae and no aquatic plants, but this population may now be extinct with no specimens collected since 2011. The Nombre de Díos population also seems to have disappeared.

C. lateralis occurs sympatrically with Dionda sp. and Astyanax mexicanus at some localities, with introduced fish species including Xiphophorus hellerii, Oreochromis spp. (tilapia), Micropterus salmoides, Gambusia spp. and Lepomis macrochirus. Aquatic plants include representatives from the genera Myriophyllum, Ceratophyllum, Potamogeton, Nymphaea, and Scirpus.

Maximum Standard Length

55 – 65 mm. Females grow larger than males.

Aquarium SizeTop ↑

An aquarium or container with minimum base dimensions of 120 ∗ 30 cm or equivalent is recommended.

Maintenance

It is essential to provide sufficient cover, ideally in the form of aquatic plants or filamentous algae, in order to restrict aggressive interactions between rival males and provide refuges for fry. A lack of strong flow and regular partial water changes are essential.

Water Conditions

Temperature: 18 – 24 °C

pH: 6.0 – 8.0

Hardness: 90 – 268 ppm

Diet

Probably an omnivore feeding on small invertebrates, diatoms and algae in nature. In the aquarium it should be offered small live foods such as Daphnia and Artemia, plus some vegetative material in the form of filamentous algae, Spirulina or blanched spinach. High quality dried foods are also accepted but should not form the basis of the diet.

Behaviour and CompatibilityTop ↑

Should ideally be maintained alone for breeding purposes, but can be kept alongside other species provided space is not limiting.

Males are territorially aggressive but can coexist provided the aquarium is set up correctly (see ‘Maintenance’).

Sexual Dimorphism

Males are more colourful than females and possess a modified anal-fin known as the andropodium which is used for sperm transfer during copulation. Females grow larger than males and are heavier-bodied when gravid.

Reproduction

A matrotrophic livebearer that produces fully developed juveniles, which are supplied with nutrients through a placenta-like structure, the trophotaenia, prior to birth. In Characodon this is relatively simplified, consisting of just a pair of elongate, unbranched ‘ribbons’.

In the wild reproduction occurs over a period of several months between March and September, with courtship initiated by the male.

Incubation is generally 50-55 days with brood sizes of 10-20 fry per female normal. The young fish are quite large and immediately able to feed on small, motile live foods such as Artemia nauplii.

NotesTop ↑

In aquarium literature this species is also known as ‘rainbow goodeid’ and ‘red prince’, although by current thinking these names have also been applied to some populations of the congener C. audax which is also endemic to the upper Río Mezquital (see below).

Traditionally, C. lateralis was thought to occur throughout the upper Mezquital basin, both above and below the El Saltito waterfall, with C. audax restricted to affluent springs of Laguna El Toboso, an ephemeral lake. This view has been called into question since at least 2004, however, with genetic analyses suggesting all populations above the waterfall to represent C. audax, and those below it C. lateralis, the two species having been split approximately 1.5 million years ago (Doadrio & Domínguez-Domínguez, 2004; Domínguez-Domínguez et al., 2006). This conclusion has not been widely accepted, ostensibly due to confusion over the type locality of C. lateralis, lack of a more extensive analysis including a greater number of populations, and absence of morphological evidence, but it has been followed by some authors (Kempkes et al., 2013). A taxonomic review, including designation of a neotype for C. lateralis, is required in order to determine precisely how many species are involved and their respective distributions.

Individual populations display distinct phenotypic variation in both colour pattern and morphology, varying in body depth,  caudal peduncle proportions, head shape, and the length of the anal and dorsal fin bases. They should be considered as distinct evolutionary units and maintained separately in aquaria in order to prevent hybridisation and maintain genetic lineages. In addition to the known natural populations there also exists an aquarium strain of unclear origin which should never be mixed with wild fish.

Characodon represents the most basal lineage of the subfamily Goodeinae within the family Goodeidae, having diverged from other goodeids approximately 10-15 million years ago. In addition to C. lateralis and C. audax a third species, C. garmani Jordan & Evermann 1888 is known only from a single female specimen collected from a spring draining into Laguna de Mayrán of the endorheic Río Nazas basin in Coahuila state, some distance from the extant Characodon populations in the upper Río Mezquital. C. garmani is considered extinct in the wild since it has not been collected since the early 1880s, and Laguna de Mayrán has been almost entirely dry since the mid-twentieth century due to construction of dams on its principal affluent.

The family Goodeidae is typically divided into two subfamiles. The more primitive Empetrichthynae is distributed in the southwestern United States and can be characterised by a reproductive strategy involving external fertilisation, oviparity, and lecithotrophy. In contrast, the subfamily Goodeinae occurs in highland regions of central Mexico and members display internal fertilization, viviparity, and matrotrophy. Members of the Goodeinae are sometimes referred to as ‘splitfins’ due to the presence of the andropodium in males giving the anal-fin a somewhat divided appearance. Many goodeid species are at risk due to habitat loss, pollution, and introduction of endangered species, with some already extinct and others existing only in captive populations.

For further information about this species and its conservation, please visit the Goodeid Working Group website.

Thanks to Michael Köck.

References

1. Günther, A., 1866 - Catalogue of fishes in the British Museum v. 6: i-xv + 1-368
   Catalogue of the Physostomi, containing the families Salmonidae, Percopsidae, Galaxidae, Mormyridae, Gymnarchidae, Esocidae, Umbridae, Scombresocidae, Cyprinodontidae, in the collection of the British Museum.
2. Doadrio, I. and O. Domínguez-Domínguez, 2004 - Molecular Phylogenetics and Evolution 31(2): 416-430
   Phylogenetic relationships within the fish family Goodeidae based on cytochrome b sequence data.
3. Domínguez-Domínguez, O., I. Doadrio and G. Pérez-Ponce de Léon, 2006 - Journal of Biogeography 33(8): 1437-1447
   Historical biogeography of some river basins in central Mexico evidenced by their goodeine freshwater fishes: a preliminary hypothesis using secondary Brooks parsimony analysis.
4. Fitzsimons, J. M., 1972 - Copeia 1972(4): 728-756
   A Revision of Two Genera of Goodeid Fishes (Cyprinodontiformes, Osteichthyes) from the Mexican Plateau.
5. Howell, D. C., M. Martin and S. A. Webb, 2008 - Georgia Journal of Science (Abstract Issue) 66(1)
   Molecular phylogeography of Characodon (Goodeidae) from the Mexican high plateau.
6. Kempkes, M., M. Köck and R. Stawikowski, 2013 - Westarp Wissenschaften-Verlagsgesellschaft mBH: 368 pp.
   Beiträge zur Biologie und zum Artenschutz der Hochlandkärpflinge.
7. Miller, R. R., 2005 - University of Chicago Press: xxvi + 1-490
   Freshwater fishes of México.
8. Smith, M. L. and R. R. Miller, 1986 - American Museum Novitates 2851: 1-14
   Mexican Goodeid Fishes of the Genus Characodon, with Description of a New Species.
9. Tiedemann R. L., 2009 - Georgia Journal of Science (Abstract Issue) 67(1): 20-21
   Morphological status and taxonomy of Characodon (Goodeidae) from the high plateau of central Mexico.
10. Tobler, M. and N. Bertrand, 2014 - Journal of Fish Biology 84(2): 283-296
    Morphological variation in vanishing Mexican desert fishes of the genus Characodon (Goodeidae).
11. Webb, S. A., J. A. Graves, C. Macias-Garcia, A. E. Magurran, D. O. Foighil, and M. G. Ritchie, 2004 - Molecular Phylogenetics and Evolution 30(3): 527-544
    Molecular phylogeny of the livebearing Goodeidae (Cyprinodontiformes).