Friday Fellow: Common Peanut Worm

by Piter Kehoma Boll

Leia em português

Today our fellow is a peculiar marine animal that is also a common food in China and Vietnam. Named Sipunculus nudus, or the common peanut worm, it is a member of the clade Sipuncula, usually called peanut worms.

As other peanut worms, the common peanut worm has considerably simple anatomy. Its body is consistent of basically two parts, a sac-like trunk and a proboscis, also called the introvert. The introvert is a retractile structure and, when the animal is not feeding, is pulled inside the trunk by a group of muscles. At the end of the introvert, when everted, there is a series of tentacles that takes the food, composed of detritus, into the gut.

The common peanut worm is commonly found burrowed into the substrate in intertidal waters all around the world, with its mouth directed upward. They may reach about 20 cm in length when the introvert is everted, with about 1/4 of this length being composed by the trunk.

As mentioned above, the common peanut worm is used as a food in China, especially in southern regions, and Vietnam. Although the species seems easy to be raised in captivity, currently most, if not all, harvest happens in the wild, which may lead to overexploitation and eventually a serious decrease in the populations.

Molecular analyses have revealed that, contrary to what is currently considered, Sipunculus nudus is not actually a cosmopolitan species. There are at least four clearly distinct lineages that certainly correspond to four distinct species. Of those, only one is found in waters around Europe, from which the species was originally described. The other three lineages correspond to those found in China and Vietnam (and the one used as food), the Atlantic Coast of the Americas (from Brazil to the USA) and the Pacific Coast of the Americas (around Panama). Let’s hope that soon this taxonomic problem will be solved.

– – –

Like us on Facebook!

Follow us on Twitter!

– – –

References:

Du, X., Chen, Z., Deng, Y., Wang, Q. (2009) Comparative analysis of genetic diversity and population structure of Sipunculus nudus as revealed by mitochondrial COI sequences. Biochemical Genetics 47: 884. doi: 10.1007/s10528-009-9291-x

Kawauchi, G. Y., Giribet, G. (2013) Sipunculus nudus Linnaeus, 1766 (Sipuncula): cosmopolitan or a group of pseudo-cryptic species? An integrated molecular and morphological approach. Marine Ecology 35(4): 478–491. doi: 10.1111/maec.12104

Trueman, E. R., & Foster-Smith, R. L. (2009). The mechanism of burrowing of Sipunculus nudus. Journal of Zoology, 179(3), 373–386. doi:10.1111/j.1469-7998.1976.tb02301.x

– – –

* This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

** This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.