Triops cancriformis

Triops cancriformis

Triops cancriformis
Tadpole shrimp
Taxonomic classification
Class:	Branchiopoda
Order:	Notostraca
Family:	Triopsidae
Genus:	Triops
NCBI taxid:	194544
Resources
Information
Research interest:	rice pest or beneficial, reproductive mode, living fossil, evo-devo, phylogenomics
WorkingGroup:	Plant pests and beneficials, Evo-Devo, EcoGen-PopGen
Nomination:	i5K initiative
Date:	2011/08/15

i5K Arthropod Sequencing Initiative  Supported by: 1 (List of supporters)

Triops or tadpole shrimps are Branchiopod crustaceans belonging to the order Notostraca. This is an ancient, but small, order, with less than 20 described species. Fossils with virtually identical morphology to living Triops have been dated to the Carboniferous, 350 million years ago (Fryer, 1988), and they are thus regarded as some of the oldest “living fossils”. Triops cancriformis has one of the widest diversities of reproductive modes in animals. These include gonochorism (males and females in equal proportions in populations), self-fertile hermaphrodites, and androdioecy, an extremely rare reproductive mode, in which populations are made of self-fertile hermaphrodites and a low proportion of males. Therefore Triops populations can reproduce through exclusive outbreeding to exclusive selfing. Triops cancriformis can be easily reared in the lab and its cysts can be stored for long periods of time until needed. This is an excellent system to investigate the genetic basis of variation in reproductive mode and the genomic impact of different levels of outcrossing.

Triops cancriformis lives in ephemeral ponds, playa lakes, fishery ponds and rice fields and survives through dry periods by producing long-lived resistant cysts, which hatch when suitable environmental conditions resume. Due mainly to environmental degradation and habitat destruction, many European populations have disappeared, and in several European countries Triops is considered extinct or as an endangered species. Only two populations are known in the U.K. As an ancient branchiopod group, a tadpole shrimp genome would help unravel the phylogeny of the arthropoda and, in particular, the relationships between insects and crustaceans.

References

Eder, E., & Hödl, W. (2002). Large freshwater branchiopods in Austria: diversity, threats, and conservational status. Modern approaches to the study of Crustacea, 281–289.

Feber, R., Hilton, G. M., Hutchins, E., Griffin, L., Ewald, N., Pain, D., Biggs, J., et al. (2011). Ecology and conservation of the Tadpole Shrimp Triops cancriformis in Britain. British Wildlife, (June), 334-341.

Fryer, G. 1988. Studies on the functional morphology and biology of the Notostraca (Crustacea: Branchiopoda). Phil. Trans. Roy. Soc. London B 321:27-124.

Gómez, A. and T. Zierold (2008) Extreme survivor: The 300-million year old living fossil. [1]Planet Earth, Winter 2008, 10-11.

Zierold T., Haenfling B. & Gomez A. (2007) [Recent evolution of alternative reproductive modes in the ‘living fossil’ Triops cancriformis [2]. BMC Evolutionary Biology, 7, 161.

Zierold T, Montero-Pau J, Hanfling B, Gómez A (2009) Sex ratio, reproductive mode and genetic diversity in Triops cancriformis. Freshwater Biology 54: 1392–1405.