Introduction to It Rains Fishes

Frans Vermeulen - Aruba.

The Killiís of the Lost World:

The first book in a series of 4 with the title "The Killi's of the Lost World" is sold out. I am working on volume 2 now.

To all visitors of this site:

Welcome to "It Rains Fishes."

Frans Vermeulen, a Dutchman on Aruba who created and maintained the site, is glad you have visited and hopes you will find the information it contains useful and valuable to you.

All areas of the site are accessible without the need for any registration or membership. The site is intended for hobbyists and scientists alike who would like to know more about the Killifishes of Central- and South America. It follows the most recent nomenclature views as presented by Dr. Jean Huber in "Killi-Data Online." The information has also been derived from such literature as "A World of Killies" by the late R.H. Wildekamp. Additionally, historical and contemporary manuscripts and publications from scientists worldwide have been consulted as additional information sources.

The name of the site, "It Rains Fishes," is based on indigenous Indian tribes' folklore. This "event" was their explanation of the truly natural wonder of juvenile fishes appearing, often within an hour after the first seasonal rains, where there had been no water, and indeed no fish, for long periods of the year.

Navigation of the Site:

You will find listed most genera of the Killies inhabiting South- and Central America at the left column of each page. Additional genera will be added as time goes by and events warrant. By clicking the mouse on a genus name, a list of the species it contains will appear. Species names followed by an asterisk are considered defunct but have been retained for ease of search. Moving the mouse and clicking on "introduction" or a species' name will cause the appropriate information to appear.

If a genus name in the left side menu is underlined, several subgenera names are assigned to that genus. These subgeneric names are often circulating or considered full genus names, but these changes are not followed herein. The search for, let us say, Anablepsoides also starts with the choice "Rivulus" and then find Anablepsoides or other subgenera from the genus Rivulus.

Within the information pages, clicking on images will enlarge them and provide information about the content of the image and the author's name or source. Clicking the image again will shrink the image back to its standard size. To enlarge maps to a larger size, please right click and choose "open in a new window." (This is not ready for most maps yet! – I am working on this)

Menu's at the top of the species pages will take you to the indicated type of information, such as a short history, information on reproduction and breeding of the species, interactive maps, available images of the species' habitat, and known variations of the species, meristics, publications. If literature is freely available online, a blue "PDF" symbol will be present, and you can download/open it in a new window by clicking on the symbol.

At the top of the main page, links give access to the other sections of this site. For example, you may be interested in the field trips I have made in attempts to locate known species and new undescribed species in their habitats. For example, there is a link called <Expeditions>.

You may also have questions not answered on the site or comments you wish to send. You might also like to help me make the site more comprehensive by providing PDF files containing additional general information, species information, images of species or population variations, images of biotopes, or publications of which I may not be aware. Please e-mail me by selecting the <Contact me> link for any of the above, and I will respond promptly.


Many biogeographic areas do not have sufficient rainfall throughout the year to support traditional aquatic life. As a result, some fish habitats evaporate on a seasonal cycle. Many Rivuline lineages have adapted to this cycle and developed a unique annual lifestyle that overcomes this environment. Imagine; these genera have become capable of surviving dry periods by producing eggs that can survive in the bottom layer of their environments' semi-moist soil.



If the water evaporates, the eggs remain viable, and the population will re-inhabit these temporary waters through the hatching of their offspring once the rains appear. Obviously, these species must grow extremely fast to become adults, often within several weeks or months, and start reproducing rapidly in order to survive as a species when the waters recede again. Each dry season can last several months, and in some locations, occasionally more than a year.

This adaptation is also seen in some African genera, such as Nothobranchius. Scientists do not agree where this type of survival mechanism first evolved, but DNA analyses indicate that annualism developed out of non-annual behavior. However, annualism has become the rule in the South American Rivulid world, and the number of annual genera is now much larger than the number of non-annual genera, which include Rivulus, Prorivulus, Kryptolebias, and most Middle American species. (You may see the abbreviation SAA occasionally - it stands for the loose term South American Annuals.)

In the last decade, numerous species included in a single genus have been split into several genera by scientists. This resulted from the need to provide a clearer view of these fishes' different lineages and their evolutionary paths. A significant number of the newer genera were erected by the Brazilian scientist, Dr. Wilson Costa.

The genera:

The oldest known are Adinia, Austrofundulus, Cualac, Cubanichthys, Cynolebias, Cynopoecilus, Fluviphylax, Garmanella, Hubbsichthys, Jordanella, Leptolebias, Leptolucania, Lucania, Moema, Orestias, Pterolebias, Rachovia, Rivulus, Simpsonichthys, Terranatos, and Trigonectes. Many of them are now divided into several other genera.
More recent erected genera are Aphyolebias Costa 1998, Austrolebias Costa 1998, Campellolebias Costa et al. 1989, Gnatholebias Costa 1998, Kryptolebias Costa 2004, Llanolebias Hrbek & Taphorn, Maratecoara Costa 1995, Megalebias Costa 1998, Micromoema Costa 1998, Millerichthys Costa 1995, Nematolebias Costa 2002, Neofundulus Costa 1998, Papiliolebias Costa 1998, Pituna Costa 1989, Plesiolebias Costa 1989, Renova Thomerson & Taphorn 1995, Simpsonichthys Costa 1996, Spectrolebias Costa & Nielson 1997 and Stenolebias Costa 1995. Some relative new annual genera are Hypsolebias, Ophthalmolebias by Costa in 2011, and Yssolebias in 2012 by Huber.

In 2011 Costa proposed re-ordering of the genus Rivulus. He divided the genus into 6 new genera, most of them former sub-genera, and left the genus Rivulus with only 3 taxa remaining. The 6 genus names then were Anablepsoides, Atlantirivulus, Cynodonichthys, Laimosemion Melanorivulus and Rivulus. Huber (2012) published a paper based on a broader array of meristic evidence only. In his paper, Huber explained that Costa's move was premature and not well supported by the mitochondrial, meristic, and osteological data Costa combined.

In this site, we are approaching the issue conservatively and following Huber's latest evidence (2012).  That means that we still see the genus Rivulus as a monophyletic assemblage with several subgenera or species groups. You can search for all subgenera under the Rivulus SS menu tag and find the taxa assigned to each subgenus.

In 2014 Costa introduced the new genus name Xenurolebias for two species known as Simpsonichthys myersi and S. izecksohni and added 2 new species to that genus. In 2014 Costa erected then the monotypic genus Mucurilebias for the taxon known so far as Leptolebias leitaoi.

Surprisingly, Costa (2014) considered the genus Aphyolebias, a genus erected by himself earlier, to be synonymous with Moema.

Most remarkable, however, is the synonymization of Rachovia to the older Austrofundulus. Costa (2014) lumped these genera into one genus, now Austrofundulus. This move is strange, and discussed as so often his moves were discussed in the past. Time will tell if this is a move that will stand.

A recent DNA study revealed the need to "re-shuffle" the grouping of the subgenera within the genus Austrolebias conducted by a group of young scientists from Brazil. This outcome is not congruent with the former classification, and this research is a still ongoing.