Adaptive evolution of the lower jaw dentition in Mexican tetra (Astyanax mexicanus)

EvoDevo

Tamara Anne Franz-Odendaal²  Megan Dufton¹  Christine Hammer²  Atukorallaya Devi Sewvandini Atukorala² 

[1] Department of Biology, Dalhousie University, 1355 Oxford Street, Halifax, Nova Scotia B3H4R2, Canada;Department of Biology, Mount Saint Vincent University, 166 Bedford Highway, Halifax, Nova Scotia B3M3J8, Canada

关键词: Cusps;    Tooth;    Maxilla;    Premaxilla;    Mandible;    Oral jaws;    Cavefish;   

Others  :  806040
DOI  :  10.1186/2041-9139-4-28

 received in 2013-03-20, accepted in 2013-08-06,  发布年份 2013

【 摘 要 】

Background

The Mexican tetra (Astyanax mexicanus) has emerged as a good animal model to study the constructive and regressive changes associated with living in cave environments, as both the ancestral sighted morph and the cave dwelling morph are extant. The cave dwelling morphs lack eyes and body pigmentation, but have well developed oral and sensory systems that are essential for survival in dark environments. The cave forms and surface forms are interfertile and give rise to F1 hybrids progeny known as intermediates. In cavefish, degeneration of the lens is one of the key events leading to eye regression. We have previously shown that surgical lens removal in surface fish embryos has an effect on the craniofacial skeleton. Surprisingly, lens removal was also found to have an effect on the caudal teeth in the lower jaw. In order to understand this result, we analyzed the lower jaw and upper jaw dentitions of surface, cavefish and F1 hybrids of surface and cavefish and compared our findings with surface fish that underwent lens removal. We also investigated the upper jaw (premaxillae and maxillae) dentition in these fish.

Results

Our tooth analyses shows that cavefish have the highest numbers of teeth in the mandible and maxillae, surface forms have the lowest numbers and F1 hybrids are between these groups. These differences are not observed in the premaxillae. A wide diversity of cuspal morphology can also be found in these fish. Jaw size also differs amongst the groups, with the mandible exhibiting the greatest differences. Interestingly, tooth number in surgery fish is different only in the caudal region of the mandible; this is the region that is constrained in size in all morphs.

Conclusion

Our data provides the first detailed description of the jaw dentitions of two morphs of Astyanax mexicanus, as well as in F1 hybrids. Tooth number, patterning and cuspal morphology are enhanced in cavefish in all jaws. This is in contrast to the increase in tooth number previously observed on the lens ablated side of the surgery fish. These findings indicate that the mechanisms which govern the constructive traits in cavefish are different to the mechanisms causing an increase tooth number in surgery fish.

【 授权许可】

   
2013 Atukorala et al.; licensee BioMed Central Ltd.

【 图 表 】

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