BIOTOPES AND BEHAVIORS OF KILLIES

Killifishes, or Cyprinodonts (Cyprinodontiformes), live in reclusive waters (usually creeks, temporary pools, overfloods, and margins of lakes and rivers), primarily in coastal lowlands, but also in highlands, where they are quasi exclusive : they are then very different from the standard ichthyofauna that lives in rivers, such as Cichlids, Barbs, Characids, Loricariids, etc.

Killifishes show very adaptative and specialized behaviors :

  • Kryptolebias marmoratus-ocellatus, a selfish hermaphrodite, inhabiting mangroves from the Florida panhandle, U.S.A. to south of the Sao Paulo latitude in southeastern Brasil ;
  • At least 2 gynogenetic species (producing all-females clones), result of natural hybridization in the wild, one named, in genus Poecilia (formosa), the others un-named, in genus Poeciliopsis (because speciation is not finalized), as complex of species, such as lucida-monacha or monacha-occidentalis or monacha-viriosa ;
  • Cyprinodon diabolis, restricted to a single cave in Devil's Hole (the smallest range of any fish in the world), in western desert of U.S.A., with the smallest population of a fish species (around 500 specimens up to 2000, but severely declining since… just a few dozen in 2007 and today… but with safe strains in artificial refuges, not far) ;
  • more than 2 hundreds of species, in tropical Africa and America, are annual species, living in seasonal biotopes only filled with water during the rainy season and dry otherwise, and spawning eggs that needs several weeks or months to incubate in dry mud, i.e. without water ;
  • Several hundreds of species that are livebearers, either truly viviparous (mother feeding embryos and larvae during internal development) like relict Splitfins (Goodeinae), with about 40 species, living in a dry plateau of central Mexico, or ovoviviparous (mother feeding only embryos, and not always, during internal development), with about 200 species (Poeciliinae) living all over America having in male a complete modification of Anal fin into various types of gonopodiums as intromittent copulatory organs ;
  • Nothobranchius furzeri, one of these annual species, having the shortest lifespan of all vertebrate animals, in total less than 6 months in the wild from egg hatching to death by aging ;
  • some annuals are even divers, then they cannot be seen during spawning and bury their eggs well into the substratum;
  • schooling Killifish or lampeyes, because they bear a lightning spot on eye, with members of the genera Lamprichthys, Procatopus, or Plataplochilus, spawning in rock holes ;
  • intermediate species between oviparous and viviparous fishes with internal fertilization but external development, like for Campellolebias species or Tomeurus gracilis ;
  • egg-stranding, aestivating and jumping-out-of-the-water species, like most Rivulus species (in a large sense), able to wander several hundred meters or spring several dozens of centimetres to better catch the insects for food or simply look for better opportunities;
  • cannibalizing species, that feed on their smaller congeners, like all Belonesox, Cynolebias, Megalebias or Paranothobranchius species ;
  • a unique parental caring species in a monotypic genus, Jordanella floridae ;
  • adaptative species to extreme conditions moving in estuaries along strong ebb flows with a unique modification of eye structure divided into one pair for vision of inside water, the other pair for air vision of outside water in genus Anableps ;
  • adaptative species to extreme conditions in waters with very high sulfuric contents (Aphanius) or in high altitude waters with very low oxygen dissolved (Orestias) with strong reduction of the number of scales on sides and head, some being even completely naked (with no scale at all) such as Aphanius asquamatus, Aphanius furcatus, Orestias minutus, Orestias minimus ;
  • adaptative species to extreme conditions, such as hypersaline reefs like some Cyprinodon or Aphanius species, as high altitude Andes lakes like Orestias species, with a speciation similar to that encountered in the Rift African Lake Cichlids, or, as desert permanent creeks, like some other Cyprinodon, with water temperatures above + 55°C as peak (unique, for fish in the world);
  • and most species feeding on mosquitoes and their larvae, hence being the sole natural weapon against the malaria disease which kills millions and millions of men and women and kids, each year on earth.

Typical biotopes:

legend

legend

legend

legend

Typical behavior: 

legend

legend

legend

legend

Annual egg:  Austrolebias wolterstorffi © J. Kadlec (annual, with surface hair)

legend

Breeding behavior:

legend

legend

legend

legend

legend

legend

Discover more on Killies? 

  • What are they? INTRODUCTION to Killies
  • Their color patterns, their morphs and variability? BEAUTIES of Killies
  • The list of all taxa with their current names, compared to previously USED names
  • The huge knowledge base with thousands of pages, photos and maps and with dozens of lists and statistics on all Cyprinodontiformes is only accessible to K-D-I members, after free REGISTRATION