THREE-SPINED STICKLEBACK FISH

By Vithusha Thirumavalavan
external image threespine_stickleback.jpg
A Marine Three-Spined Stickleback Fish



1. Classification/Diagnostic Characteristics


The Gasterosteus Aculeatus, otherwise known as the stickleback fish, falls under the kingdom Animalia. It is a triblastic animal, meaning that its embryos have an endoderm, ectoderm, and mesoderm, similar to humans. Triblastic organisms can be distinguished into two categories, protostomes or deuterostomes, based on if the mouth or anus develops from the blastopore during gastrulation. The stickleback fish, as well as humans, both are deuterostomes, meaning that the anus develops from the blastopore (opposed to the mouth as with the protostomes) and the mouth forms later during development. Deuterostomes can be further broken down into three different clades, echinoderms, hemichordates, and chordates, the last of which is the category both humans and stickleback fish fall under because chordates are either sea squirts, lancelets, or vertebrates. Key defining characteristics of chordata present early in development are the presence of a dorsal hollow nerve cord, a tail extension beyond the anus, and a notocord, which is the flexible rod of cells that supports the embryo. Eventually, as development progresses, the notocord gets replaced with a vertebral column. Among the clade of Vertebrate Chordates, defining characteristics are of course the vertebral column, a ventral heart with a developed circulatory system, an anterior skull, and a large brain.[1]


The stickleback fish specifically is usually found to be 4-6 centimeters, although some reach up to 10 centimeters. They are migratory fish and usually live in schools, as many types of fish do.[2]
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2. Relationship to Humans


Genetic Relationship:
Both humans and stickleback fish are in the phylum, Chordata, meaning they both are vertebrates.[3]


General Interaction:
Humans use the stickleback fish for oil, animal feed, and agricultural fertilizer.[4] They are also common subjects for various laboratory experiments focused on molecular genetics of evolutionary change in wild populations. Evolutionary biologists particularly like the stickleback fish because of it's ability to quickly evolve in a new environment, sometimes within a time span as short as 10 years.[5] Outside of the laboratory, stickleback fish are not considered pests, except in the Black Sea region, as they compete for food against certain types of fish which humans consume. The stickleback fish itself is not consumed by humans.[6] [7]



3. Habitat and Niche


Marine sticklebacks can be found in salt water environments, specifically either the Atlantic or Pacific Oceans.[8] These marine sticklebacks often reside in different types of marine vegetation for cover, such as floating eelgrass or rockweed.[9] On the other hand, freshwater sticklebacks can be found in various freshwater lakes.[10]



4. Predator Avoidance


Both marine and freshwater stickleback fish use their bone structure as a protective mechanism. Because the greater number of predators in the marine environmental, marine sticklebacks have developed more complex bone structures over time, and thus, it's skeleton has much more prominent and lengthier pelvic bones as well as body plates.[11] These characteristic spines of the backs of stickleback fish make them potentially difficult and even painful for predators to swallow. Predators that often prey upon the stickleback fish include larger fish, kingfishers, herons, water shrews, and otters.[12] The freshwater fish on the other hand, has a much more minimized bone structure, for the dorsal and pelvic spines are much smaller[13] . (Look to Growth and Development for more molecular information). Freshwater stickleback fish characteristically have much fewer armored plates that are congregated near the head of the fish. This is because they are preyed upon by smaller, quicker predators so it is beneficial to have less armor for better agility. Less armor also allows them to grow to a larger size, which deters predators and allows for more energy storage for winter survival.[14]



5.Nutrient Acquisition


The stickleback fish obtains oxygen and nutrients through diffusion from the surrounding water. In the same manner, carbon dioxide diffuses out of the body cavity through gas exchange.[15]

Sticklebacks are both predator and prey, and omnivorous.[16] They generally eat small water invertebrates, small young fish, and fish eggs.[17]



6. Reproduction and Life Cycle


Marine Sticklebacks: Marine populations spend much of the early years of their lives in a salt-water environment, but migrate to a fresh-water environment for breeding.

Freshwater Sticklebacks: Freshwater populations spend their entire lives in freshwater, from initial growth and development, to reproduction, to ultimately, death.\


Stickleback fish normally breed from late March to early August, when there is the optimum amount of food to feed young fish. The coloration of the fish has a substantial impact on its ability to mate and reproduce successfully, but coloration also confers disadvantages, such as being more visible to predators.[18] During this mating season, male sticklebacks undergo a transformation that causes their throats and bellies to become a bright orange or red hue while their eyes become bright blue. These colors tend to attract females, as they indicate the fitness of the male, and also double as a warning for other males to stay out of their territories.[19] The reproductive success of the three-spined stickleback fish is largely dependent on the male's ability to secure a safe territory, which it defends while waiting for a female. In reproduction, a female fish enters a nest, where it will lay eggs. Meanwhile, a companion male fish waits nearby. After the female leaves the nest, the male fertilizes the eggs.[20]



7. Growth and Development

Stickleback.png








Because the separation of environments, marine and freshwater populations have slightly diverged, a great example being in the skeletal system. The Pituary homeobox transcription factor 1 (Pitx1) is a gene that induces the creation of plates and spines in the stickleback fish. In marine sticklebacks, this gene is expressed, while in freshwater sticklebacks the gene is inactive. As one can see in the image on the left (Figure 14.21), the lack of Pitx 1 expression in the bottom fish results in minimalistic bone structure opposed to the top fish, the marine stickleback which due to the expression of the Pitx 1 gene, has prominent and elongated dorsal and and pelvic spines among other bone structures.










8. Integument

The scaleless skin is generally protected by a variable number of hard, thin, bony plates on the sides of the body.[21] Stickleback fish skin can vary in colors, but it usually has silvery colored reflections on the side and belly of the body. Skin color is subject to change when the fish are mating, for both males and females develop a red tint on parts of their bodies and a brown color on their backsides.[22]



9. Movement

The fish swims by using the muscles on the sides of their bodies to push against the water. When the muscles on the right side of the fish contract, the tail is pulled to that side of the body, which pushes water backwards, propelling the fish forward through the water. Then, the muscles on the right side relax, and the left side contracts, pulling the tail the other way. This cycle is repeated over and over to produce thrust. While the muscular tails help with direction and push, their bladder assists with maintaining buoyancy by helping them adjust whether the fish sinks, floats to the top, or keeps going straight.[23] Internal body temperature also plays a role, for generally, the greater the overall internal temperature, the greater the internal muscle temperature, and the faster the fish can swim because it is more capable of generating and maintaining power.[24]



10. Sensing the Environment

Fish can feel, hear, and see. As a matter of fact, their eyesight is better than that of humans. Interestingly, almost all fish have a type of "special sense" organ called the lateral line system which allows them to detect and get a sense objects ahead of them. It is somewhat similar to the peripheral vision of humans.[25] (evan)



11. Gas Exchange

Gas Exchange.png





Oxygen is able to enter the fish and carbon dioxide is able to leave through diffusion with the water. Efficiency of gas exchange increases due to the counter-current flow of blood, as shown in the image to the right (Figure 37.3).








12. Waste Removal

Waste product is released through the anus.



13. Environmental Physiology (Temperature, water, and salt regulation)

Sticklebacks maintain homeostasis through their cells, tissues and organs. They use negative feedback which keeps physiological systems stable by returning it back to a set point. When receptor cells sense that the incoming stimulus is different from the set point, the fish will work to return the body condition back to that set point.[26]



14. Internal Circulation

The stickleback fish has a two-chamber heart. The blood travels in throughout the circulatory system in a single circuit, going from the heart to the gills and then looping through the rest of the body to get back to the heart. Blood is able to move because of the pressure system, initially created by the high pressure induced by the contraction of the ventricle (when blood leaves it to travel to the gills).
The two chamber heart
The two chamber heart

Thermoregulation: The stickleback fish maintains it's body temperature through the countercurrent heat exchanger, where blood vessels carrying blood in opposite directions allow for heat transfer, and thus, a internal body temperature higher than that of the surrounding water.


external image Countercurrent.jpg

15. Chemical Control (i.e. endocrine system)


16. Review Questions


1. Explain thermoregulation of the stickleback fish. How is the countercurrent heat exchange a beneficial adaptation for internal circulation?
2. How is the coloration of the stickleback fish important in reproductive success? What might the coloration represent? (Alexander Soloviev)
3. What is one way that humans and stickleback fish are related?
4. What is the connection between internal body temperature and the stickleback fish's movement speed? How do these fish use their muscles to swim through the water? (BHu)
5. Explain the importance of the Stickleback Fish's skeleton in relation to it's predator's ability to consume it.
6. What physical trait enables males to attract more females?



17. Citations


  1. ^ Hillis, David M., David Sadava, H. C. Heller, and Mary V. Price. Principles of Life High School Edition. Sunderland, MA: Sinauer Associates, 2012. Print.
  2. ^ http://www.arkive.org/three-spined-stickleback/gasterosteus-aculeatus-aculeatus/image-A9850.html
  3. ^ Hillis, David M., David Sadava, H. C. Heller, and Mary V. Price. Principles of Life High School Edition. Sunderland, MA: Sinauer Associates, 2012. Print.
  4. ^ http://www.ypte.org.uk/animal/stickleback-three-spined-/178
  5. ^ http://www.wisegeek.com/what-is-a-stickleback.htm
  6. ^ http://www.ypte.org.uk/animal/stickleback-three-spined-/178
  7. ^ http://www.gma.org/fogm/Gasterosteus_aculeatus.htm
  8. ^ Hillis, David M., David Sadava, H. C. Heller, and Mary V. Price. Principles of Life High School Edition. Sunderland, MA: Sinauer Associates, 2012. Print.
  9. ^ http://www.gma.org/fogm/Gasterosteus_aculeatus.htm
  10. ^ Hillis, David M., David Sadava, H. C. Heller, and Mary V. Price. Principles of Life High School Edition. Sunderland, MA: Sinauer Associates, 2012. Print.
  11. ^ Hillis, David M., David Sadava, H. C. Heller, and Mary V. Price. Principles of Life High School Edition. Sunderland, MA: Sinauer Associates, 2012. Print.
  12. ^ http://www.ypte.org.uk/animal/stickleback-three-spined-/178
  13. ^ Hillis, David M., David Sadava, H. C. Heller, and Mary V. Price. Principles of Life High School Edition. Sunderland, MA: Sinauer Associates, 2012. Print.
  14. ^ http://learn.genetics.utah.edu/content/variation/stickleback/
  15. ^ Hillis, David M., David Sadava, H. C. Heller, and Mary V. Price. Principles of Life High School Edition. Sunderland, MA: Sinauer Associates, 2012. Print.
  16. ^ http://www.gma.org/fogm/Gasterosteus_aculeatus.htm
  17. ^ http://www.ypte.org.uk/animal/stickleback-three-spined-/178
  18. ^
    http://www.uaa.alaska.edu/enri/people/Fellows/vonHippel/upload/von-Hippel-Black-male-bellies.pdf
  19. ^ http://learn.genetics.utah.edu/content/variation/stickleback/
  20. ^ Campbell, N.A., J.B. Reece. Biology. San Franciso: Benjamin Cummings. 2002.
  21. ^
    http://www.britannica.com/EBchecked/topic/566145/stickleback
  22. ^
    http://www.gma.org/fogm/Gasterosteus_aculeatus.htm
  23. ^
    http://wiki.answers.com/Q/How_do_fish_swim
  24. ^ Hillis, David M., David Sadava, H. C. Heller, and Mary V. Price. Principles of Life High School Edition. Sunderland, MA: Sinauer Associates, 2012. Print.
  25. ^
    http://library.thinkquest.org/C0124402/data/html/2/2sensesoffish.htm
  26. ^
    Hillis, David M., David Sadava, H. C. Heller, and Mary V. Price. Principles of Life High School Edition. Sunderland, MA: Sinauer Associates, 2012. Print.