What are KILLIES?

Origin of the name Killifish.

Killifish are secondary freshwater fishes, i.e., primarily living in freshwaters today but originating from marine coastal waters in the remote past.

Their common name, Killi (plural, Killies) stems from an old Dutch name, used by immigrants of USA in the seventeenth century to qualify fishes living in small channels, the "kills", that reminded them their home country.

Progressively, the name has been extended to other groups of related fishes from northern America, Mediterranean countries and finally tropical countries, when aquarists of the twentieth century became passionately interested by these fishes.

Systematics of Killifish.

Scientifically speaking, Killifish are Teleosts (vertebrate fishes), members of the superorder Atherinomorpha, of the order Cyprinodontiformes, with current relatives in related orders Beloniformes (Oryzias), Atheriniformes (Atherinids).

Cyprinodontiformes -or shortly Cyprinodonts- are split artificially into oviparous species, properly Killifish (770+ valid species), and viviparous groups (about 300 valid species), properly livebearers, featuring Guppies, Xiphos, famous aquarium fishes, or the beautiful Goodeids, or Anableps (4 eyed-fish), or Gambusies, (unfortunately) planted all over the world, for mosquito control.

Killifish, the common name for oviparous cyprinodontiformes fishes, are currently classified into 10 families (Huber, 2005):
- Aplocheilidae, only from India and Madagascar;
- Nothobranchiidae from Africa but Madagascar with 2 subfamilies: Nothobranchiinae and Epiplateinae;
- Rivulidae from Central and South America with 3 subfamilies: Rivulinae, Cynolebiinae and Kryptolebiinae;
- Fundulidae;
- Profundulidae, monotypic (which may be included also in Fundulidae as a subfamily or in Goodeidae as a subfamily, depending on authors);
- Goodeidae, with 2 subfamilies: Empetrichthyinae, oviparous and Goodeinae, viviparous;
- Valenciidae, also monotypic (which may be included also in Fundulidae as a subfamily, depending on authors);
- Cyprinodontidae, with 2 subfamilies: Cubanichthyinae and Cyprinodontinae (with the latter in 3 tribes, Aphaniini, Cyprinodontini and Orestiadini);
- Anablepsidae, with 3 subfamilies: Anablepsinae, viviparous, the monotypic Oxyzygonectinae, oviparous, and Jenynsiinae, viviparous;
- Poeciliidae, with 2 subfamilies: Poeciliinae viviparous (except the monotypic subtribe Tomeurina -or tribe as Tomeurini, depending on authors-, oviparous) and Aplocheilichthyinae oviparous (in 3 tribes, Aplocheilichthyini and Procatopodini in the Old World and the monotypic Fluviphylacini in the New World).
These 10 families are also accepted in international data bases on all fishes, such as Eschmeyer's Catalog and Fishbase, to ensure coherence and universality. The lower levels depend more on authors : a consensus view is selected herein.

Unlike other fish such as Characoids or Percomorphs which inhabit fresh water and yet show great morphological range, the egg-laying and live-bearing Cyprinodonts (gonopodium apart!) form a remarkably homogeneous entity; alongside this morphological homogeneity has been demonstrated an extreme heterogeneity in genotype and in male color pattern, which can be translated into genera comprising fifty or more species. In addition, here and there, an atypical species, often dwarf, often relict, differs from the homogeneous norm and is given its own genus name (or subgenus, depending on the author). There are not less than 31 monotypical genera or subgenera today out of a total of 104 genera or subgenera deemed valid. These important genera are today very difficult to place in the suprageneric phylogeny of Cyprinodonts.

Biogeography, habitat, and behavior of Killifishes.

Killifishes, or oviparous Cyprinodonts, occur all over the world, in tropical and temperate regions of Africa, America and Eurasia, except in northern and eastern Europe (today, but fossils are known) and in Australasia, east of the Wallace line. Then, they can be found all over Africa (except generally in the desert of Sahara and neighbouring regions, and of the extreme southwestern Africa), all over South America (except Patagonia and the south-western Pacific coastal plain), all over Central America, all over North America, including Canada (except its polar regions), all over Mediterranean countries and the Middle East (except deserts), and from Pakistan to Vietnam and Indonesia, up to Lombok (or New Papua if not artificially introduced).

Killifishes, or oviparous Cyprinodonts, 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 (photos in BIOTOPES): they are then very different from the standard ichthyofauna that lives in rivers, such as Cichlids, Barbs, Characids, etc.

Killifishes, or oviparous Cyprinodonts, feature some of the oddest fishes, such as:
- Kryptolebias marmoratus, a selfish hermaphrodite, inhabiting mangroves from the Florida panhandle, U.S.A. to the Sao Paulo latitude in southeastern Brasil;
- Cyprinodon diabolis, restricted to a single cave in Devil's Hole, in western desert of U.S.A., with the smallest population of a fish species (around 500 specimens);
- annual species (more than a hundred species, in tropical Africa and America), 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;
- divers, which cannot be seen during spawning and bury their eggs well into the substratum: these annual killifishes became famous as "instant fish" in the 1950'ies when a consumer goods company offered to their customers a small bag with eggs that became fish within a few minutes when put in water;
- schooling fishes or lampeyes, because they bear a lightning spot on eye, 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, able to wander several hundred meters or spring several dozens of centimetres to better catch the insects for food or simply look for better biotopes;
- cannibalising species, that feed on their smaller congeners, like Cynolebias, Megalebias, Moema or Paranothobranchius species;
- 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;
- and many other oddities that are to be discovered in a small gallery of their BEHAVIORS, within the database for each species and in the answers to each individual QUIZ scattered throughout the website.

Interesting Killifishes.

Killifishes, or oviparous Cyprinodonts, can be interesting, depending on the view point:

Killifishes, or oviparous Cyprinodonts, are among the most beautiful freshwater aquarium fishes: look to the few photos of their BEAUTIES (there are 1750 photos in the data base!) and you will understand why they are so attractive to aquarists.

Killifishes, or oviparous Cyprinodonts, besides combine, for aquarists, the unique qualities of being diverse in their characteristics, of needing at least 2 weeks of incubation, and even more for annual species (exchanging eggs by post mail is easy) and of living in small amount of waters (creating a fish room or "Killiarium", holding several dozens of small aquariums at room temperature, is easy). And aquarists, also nicknamed Killi-hobbyists or Killiphiles, are grouped in national ASSOCIATIONS (listed in the website) to exchange their experiences and fishes.

Killifishes, or oviparous Cyprinodonts, are among the most difficult fishes for ichthyological research, because most of their explosive evolution stems from the latest period of Earth history, and biologists, behaviourists, aging specialists, geneticists, molecularists, morphologists, osteologists, palaeontologists combine their efforts and discoveries to ensure scientific progress wherever they are amateurs or professionals in INSTITUTIONS (listed in the website).

This is the whole story of Killi-Data:
to ensure community efforts to gather knowledge on these fishes, 
just as Killifishes, or oviparous Cyprinodonts, develop community strategies to face stringent constraints and survive into their highly adverse and fragile environment.

Prospects on Killifishes.

No doubt Killifishes are in every way very different from the standard river fishes and opposite by major traits:
- independent micro-populations of sympatric congeners in reclusive fragile biotopes where they are quasi-exclusive;
- explosive recent genotypes and typified color patterns, together with an amazing basic morphological stability (only 5 basic morphotypes, 3 in Aplocheiloids, 2 in Cyprinodontoids);
- probable recurrent extinction episodes except in refugia, from where a brand new expansion process started again.

By combining data of palaeogeography, palaeoecology, vicariance, endemicity, diversity, internal and external characters of extant phylogenetic lineages, it is possible to hypothesize their centres of origin as well as plausible scenarios of the long term history and migration patterns of Cyprinodonts, since their birth more than 150 million years ago.

However, the explosive evolution of the tropical Cyprinodonts, is to be found in the near past. Apart from the very old development of the few distinguished morphotypes linked to major Earth events (continental drift), most of the evolution spur is hypothesized to be recent, linked to climatic fluctuations and especially to the late glacial maximums of the Pleistocene-Holocene. The evolution of these fishes, pushed by similar and severe constraints, is playing with a limited number of options. The many similarities between their characteristics in the Old and the New Worlds, or between those of Eurasia and North America plus the Andes, change then somewhat the picture from a purely haphazard convergence into the disclosure of very few options, variably combined as much as possible.