Tag Archives: Annelida

Friday Fellow: Tiger Worm

by Piter Kehoma Boll

European in origin, but currently cosmopolitan, today’s Friday Fellow is a very useful earthworm for humans. Scientifically known as Eisenia fetida, this species has many different popular names, including tiger worm, red californian earthworm, red wiggler worm, etc.

Eisenia_fetida

Two specimens of Eisenia fetida. Photo by iNaturalist.org user nzwormdoctor.*

The tiger worm rarely lives underground, prefering to live among decaying vegetable matter, such as in the leaf litter, therefore being considered an epigean species. Due to its adaptability to live among and feed on decaying organic material, it is widely used by humans for vermicomposting, i.e., producing humus to be used as a nutrient rich soil in cultivation of vegetables. As a result, it has been introduced worlwide.

When molested, the tiger worm secrets a yellow and pungent liquid from its celomic cavity that has been shown to be toxic to some vertebrates, thus probably being a defense mechanism against predators.

Due to its agriculatural importance, the tiger worms has been used in many studies regarding its response to different soil contaminants, including pesticides, and its presence on the amount of inorganic nutrients, such as carbon and nitrogen, in the soil.

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References:

Albanell, E.; Plaixats, J.; Cabrero, T. (1988) Chemical changes during vermicomposting (Eisenia fetida) of sheep manure mixed with cotton industrial wastes. Biology and Fertility of Soils, 6(3): 266–269.

Spurgeon, D. J.; Hopkin, S. P. (1999) Comparisons of metal accumulation and excretion kinetics in earthworms (Eisenia fetida) exposed to contaminated field and laboratory soils. Applied Soil Ecology, 11(2–3): 227–243.

Zhang, B.-G.; Li, G.-T.; Shen, T.-S.; Wang, J.-K.; Sun, Z. (2000) Changes in microbial biomass C, N, and P and enzyme activities in soil incubated with the earthworms Metaphire guillelmi or Eisenia fetidaSoil Biology and Biochemistry, 32(14): 2055–2062.

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

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Friday Fellow: Giant Tube Worm

by Piter Kehoma Boll

Giant tube worms Riftia pachyptila. Photo extrected from planeterde.de

Giant tube worms Riftia pachyptila. Photo extracted from planeterde.de

ResearchBlogging.org Let’s dive deep into the ocean and talk about this awesome animal, the giant tube worm Riftia pachyptila. Initially classified in a separate phylum, Vestimentifera, today it is included in a family of Annelids called Sibloginidae. Its common name comes from the fact that it can reach a length of 2.4 meters, quite big for a worm.

Endemic to deep-sea hydrothermal areas in the Pacific ocean, these worms are adapted to tolerate the high temperatures, pressure and levels of hydrogen sulfide in their environments. With their body protected by a chitin tube which can reach 3 meters in length, the only part exposed is a red structure, the branchial plume, highly vascularized ad rich in a hemoglobin complex of high molecular mass.

Below the plume lies the vestimentum, a muscular region which hosts the brain and the heart and is responsible for the extension and withdrawal of the plume. The name of the old phylum comprising this species, Vestimentifera, refers to this structure.

Follwing the vestimentum is the trunk and after it the opisthosome, which anchors the animal to the tube.

The plume is used to carry oxygen, carbon dioxide and sulfides into the animal’s body, which, however, lacks a mouth and gut.

A worm out of its tube. Photo extracted from spineless.ucsd.edu

A worm out of its tube. Photo extracted from spineless.ucsd.edu

To achieve nutrients, the giant tube worms host an endosymbiotic chemolithoautotrophic γ-Proteobacterium inside the trophosome, a richly vascularized organ in the trunk that constitutes a specific morphological adaptation to house the symbiotic bacteria. The sulfides are transported by the worm from the environment to the symbionts, which possess a sulfur oxidizing respiratory system and so can produce metabolic energy for themselves and for the worm.

The association between the giant tube worm and its chemoautrophic bacteria was the first of this kind to be described more than 30 years ago by Cavanaugh et al. and is currently the best studied one, but many questions about the details of this relationship, including the achievement of the bacteria by young worms, are yet to be fully answered.

Since the worm lacks a digestive system, its nutrition is entirely dependent on its symbiotic bacteria and all the anatomic adaptations designed to allow this association makes this a very good example of coevolution and make us think that there are no limits for life to adapt itself.

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References:

Lopez-Garcia, P., Gaill, F., & Moreira, D. (2002). Wide bacterial diversity associated with tubes of the vent worm Riftia pachyptila. Environmental Microbiology, 4 (4), 204-215 DOI: 10.1046/j.1462-2920.2002.00286.x

Minic, Z., & Hervé, G. 2004. Biochemical and enzymological aspects of the symbiosis between the deep-sea tubeworm Riftia pachyptila and its bacterial endosymbiont. European Journal of Biochemistry, 271 (15), 3093-3102 DOI: 10.1111/j.1432-1033.2004.04248.x

Stewart FJ, & Cavanaugh CM 2006. Symbiosis of thioautotrophic bacteria with Riftia pachyptila. Progress in molecular and subcellular biology, 41, 197-225 PMID: 16623395

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