Rapidly Reproducing Killifish Defy Evolution

by on


Killifish are common in the pet trade, and come in varying sizes and colors. They have increasingly become common as lab animals as well. Researchers use them to study aging in humans since they mature rapidly. Yet killifish have only rarely been addressed in major creationist literature and generally only in response to evolutionists claiming they had evolved1 some new ability. Killifish deserve a deeper look as their life and reproductive cycles strongly point to a designer.

Killifish deserve a deeper look as their life and reproductive cycles strongly point to a designer.

Killifish are unique creatures with a vast array of designs and habitats. There are over twelve hundred species with unique color patterns and life cycles. They are popular aquarium fish, with several websites devoted to their care and sale. This is likely due to their brilliant color schemes and relative hardiness. Killifish reproduce sexually and lay eggs. Some species are annual, meaning they live a year or less; others, like the larger Golden Wonder Killifish (Aplochelius linneatus) can live for several years. Despite the fearsome name, killifish are largely benign creatures. They are non-aggressive in general and only obtained their name as a derivative of the Dutch word for the small ditches and ponds that many species inhabit.2


Annual Killifish are of interest to science for a number of reasons. Part of the interest comes from their incredible habitats. Many of these annual killifish live in tiny rainwater pools that only exist during the rainy season and dry up for large sections of the year. The adults mature rapidly and lay a multitude of eggs before dying. This is a strange lifestyle which has led researchers working on aging to investigate them.

Researchers tend to use the turquoise killifish (Nothobranchius furzeri) for aging research. The reasoning behind this is the turquoise killifish has an incredibly short lifespan and maturity rate. A recent study found that Turquoise killifish reach sexual maturity in a mere two weeks.3 This is the fastest known maturation time of any vertebrate. The researchers pointed out how important this was since some of the seasonal pools they collected the turquoise killifish from dried up in as little as three weeks. Previous studies had shown these fish had a maximum lifespan of six months4 in captivity, so maturing quickly and producing offspring is critical to the survival of the species.

The most remarkable feature of the turquoise killifish and other annual killifish has nothing to do with aging. It has to do with their ability to reproduce.

The most remarkable feature of the turquoise killifish and other annual killifish has nothing to do with aging. It has to do with their ability to reproduce. They produce eggs that must survive without moisture in the hot summer sun of Africa for up to ten months.5 The adults must mature and reproduce very rapidly, else the species would die out. This means their aging cycle has to be accelerated, leading to the abbreviated lifespan. As the ponds and puddles dry up, the adults die off or are picked off by predators, but the eggs settle into the mud and develop for two to three weeks. Once the heart forms and most of the body has completed development,6 the killifish embryo enters a phase called diapause. “Newly laid embryos quickly enter a dormant state called ‘diapause,’ which suspends all developmental processes and provides higher tolerance to various stresses, including the long drought.”7 Killifish eggs have a yet-unknown mechanism in their plasma membranes that causes them, to dehydrate very slowly.8 Some turquoise killifish eggs have survived three years of diapause and been successfully hatched.9

Hatching is triggered by a number of environmental cues. One of them is an elevated temperature. Laboratory eggs have been hatched simply by elevating temperature above twenty-eight degrees Celsius10 if left in water. However, this is unrealistic when compared to the drought conditions the eggs experience in the wild. It is believed the onset of rain combined with gas pressure changes spark the eggs to hatch, though how the diapause-suspended eggs sense this is a mystery. These eggs hatch within three days of the first rainfall.11 This allows the juveniles to begin maturing nearly immediately, shortening the time needed to reach sexual maturity.

The genome of the turquoise killifish has been completely sequenced. This sequencing resulted in a surprising discovery. When discussing the genes linked to the abbreviated lifespan of these killifish, researchers noted: “Remarkably, these genes are clustered on the sex chromosome, suggesting that short lifespan might have co-evolved with sex determination.”12 The researchers are essentially claiming that the abbreviated life cycle of the killifish came into existence with its reproductive capabilities. However, claiming evolution as the cause is unlikely at best. It makes far more sense to point to an all knowing Creator God. From that perspective, this find should not have been surprising. It makes sense that the sex chromosomes would be linked to aging genes in organisms that must reach sexual maturity and reproduce rapidly.


The implications of this study are significant. Based on the above information, there are a couple of requirements that must be in place for the turquoise killifish to survive in its environment. It must have a very accelerated life cycle because its habitats exist for very brief periods of time. Thus, it must be able to mate and produce eggs quickly. It cannot bear live young because the ponds would dry up and strand the next generation. The eggs it produces must be incredibly hardy to survive up to ten months of African sun. The eggs must be able to hatch almost immediately to ensure that the juveniles have as much time as possible to mature. However, there must also be a mechanism to prevent false starts, else one isolated rainstorm could wipe out the species. The turquoise killifish meets all of those requirements, as the scientific literature cited above proves.

The Problem

This presents a problem for evolutionists. All the features listed above must have been present in the original population of turquoise killifish or it would have died out in one generation as the stagnant pools dried up. To make matters worse, turquoise killifish are not the only annual killifish species. Dozens of species undergo similar life cycles across Africa and South America.13 Yet evolutionists believe these evolved independently from one another,14 effectively multiplying the difficulty. “The molecular phylogeny presented here suggests two independent derivations of annualism in the Rivulidae (killifish).”15 The same article also points out that a few other families of killifish have annual members, assuming such a process could evolve independently in them as well. It is difficult to overstate just how big a problem this is for evolution that it’s loudest proponent, Richard Dawkins, claims “has no purpose in mind. It has no mind and no mind’s eye. It does not plan for the future. It has no vision, no foresight, no sight at all.”16 Yet, for evolution to be true and the annual killifish to survive and reproduce, a multitude of interconnected molecules, proteins and organs must be in place simultaneously and this evolved independently in different species of killifish. Without the specialized protein-enveloped eggs, all such fish would die from dehydration before hatching. Without the rapid sexual maturation, the fish would die before spawning. If it bore live young as guppies do, the young would die as the pools dry up. Thus, evolutionists are presented with the unenviable position of explaining how the multi-faceted, interdependent annual lifestyle evolved independently multiple times.

Annual killifish like the turquoise killifish are fitted very well to their habitats, and evolutionists have no reasonable explanation.

Annual killifish like the turquoise killifish are fitted very well to their habitats, and evolutionists have no reasonable explanation. The creation model, however, can explain them quite well. In the beginning, God made the various kind(s) of annual killifish along with the other water creatures. (Genesis 1:21). After the fall, they existed in ponds and streams that they could undergo their annual life cycle until the flood. The flood temporarily expanded their habitats, leading to annual killifish spreading to two continents. When the flood waters began to recede, they would have eroded the landscape, creating ponds, lakes, and inland seas.17 Some of these would have washed out later, leaving small annual pools in their wake. Killifish, and thousands of other fish, were trapped in these ponds, streams, and puddles. The annual killifish were equipped with all the genes they needed to survive and reproduce in the tiny seasonal pools that were left behind as the waters receded. Thus natural selection and other mechanisms eliminated the other fish species in a short period of time. However, the killifish survived and thrived because of their rapid life cycles, which may in part be due to created heterozygosity (created genetic diversity) in their genome which was present from creation.18 The environment would have favored those killifish that had more rapid life cycles, particularly in drier years. This would have gradually reduced the variation in the turquoise killifish population until its lifespan and time to maturity reached what is observed today. Rapid developmental and reproductive cycles in annual killifish point to God as their Creator and Sustainer. There is no other plausible explanation for how well they are fitted to their environment.


  1. Thomas, Brian. “Fast-Changing Killifish Swim Past Evolution.” Institute for Creation Research. January 31, 2017. Accessed: August 14, 2018. http://www.icr.org/article/9804
  2. (No author listed) “Killifish: Species, Tank Conditions, Diet and Breeding.” Fishkeeping World. November 10, 2017. Accessed: August 14, 2018. https://www.fishkeepingworld.com/killifish/
  3. Vrtilek, Milan. Jakub Zak, Martin Psenicka and Martin Reichard. “Extremely rapid maturation of a wild African annual fish.” Current Biology Volume 28, Issue 15 (2018). pg822-824. https://www.cell.com/current-biology/fulltext/S0960-9822(18)30822-4
  4. Valenzano, Dario Riccard. Berenice A. Benayoun, Param Priya Singh, Elisa Zhang, Paul D. Etter, Chi-Kuo Hu, Mathieu Clement-Ziza, David Willemsen, Rongfeng Cui, Itamar Harel, Ben E. Machado, Muh-Ching Yee, Sabrina C. Sharp, Carlos D. Bustamante, Andreas Beyer, Eric A. Johnson and Anne Brunet. “The African turquoise killifish genome provides insights into evolution and genetic architecture of lifespan.” Cell Volume 163, Issue 6 (2015) pg1539-1554. https://www.cell.com/cell/fulltext/S0092-8674(15)01488-9
  5. Cellerino, Alessandro. Dario R. Valenzano and Martin Reichard. “From the bush to the bench: the annual Nothobranchius fishes as a new model system in biology.” Biological Reviews Volume 91, Issue 2 (2016) pg 511-533. https://onlinelibrary.wiley.com/doi/pdf/10.1111/brv.12183
  6. Ibid.
  7. Hu, Chi-Kuo and Anne Brunet. “The African turquoise killifish: A research organism to study vertebrate aging and diapause.” Aging Cell Volume 17, Issue 3 (2018) https://onlinelibrary.wiley.com/doi/abs/10.1111/acel.12757
  8. Podrabsky, Jason E. John F. Carpenter and Steven C. Hand. “Survival of water stress in annual fish embryos: dehydration avoidance and egg envelope amyloid fibers”. American Journal of Physiology Volume 280, Issue 1 (2001) https://www.physiology.org/doi/10.1152/ajpregu.2001.280.1.R123
  9. Cellerino et al 2016.
  10. Ibid.
  11. Vrtilek, et al 2018.
  12. Valenzano et al 2015.
  13. Nunziata, Charles. “Annual Killifish: A Story of Survival.” Tropical Fish Hobbyist. June 2011. Accessed August 15, 2018. http://www.tfhmagazine.com/details/articles/annual-killifish-a-story-of-survival-full-article.htm
  14. Furness, Andrew Ian. “The Evolution of an Annual Life Cycle in Killifish: Adaption to Seasonally Ephemeral Aquatic Habitat Across Two Continents.” Biological Reviews. May 2015. Accessed August 15, 2018. https://www.researchgate.net/publication/276268352/download
  15. Hrbek, Tomas. and Allan Larson. “The Evolution of Diapause in the Killifish family Rivulidae (Atherinomorpha, Cyprinodontiformes): A Molecular Phylogenetic and Biogeographic Perspective.” Evolution Volume 53, No 4.(1999). https://www.jstor.org/stable/2640823?newaccount=true&read-now=1&seq=13#page_scan_tab_contents
  16. Dawkins, Richard. The Blind Watchmaker New York: W.W. Norton & Company, Inc. 1996.
  17. Whitmore, John. “The Potential for and Implications of Widespread Post-Flood Erosion and Mass Wasting Processes.” Proceedings of the Seventh International Conference on Creationism. (2013) Accessed October 8, 2018. http://creationicc.org/2013_papers/2013_ICC_Whitmore.pdf
  18. Jeanson, Nathaniel. “Did Natural Selection Play a Role in Speciation?” Answers in Genesis. July 30, 2016. Accessed October 8, 2018. https://answersingenesis.org/natural-selection/speciation/did-natural-selection-play-a-role-in-speciation/


Get the latest answers emailed to you.

I agree to the current Privacy Policy.

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.

Answers in Genesis is an apologetics ministry, dedicated to helping Christians defend their faith and proclaim the gospel of Jesus Christ.

Learn more

  • Customer Service 800.778.3390