Riftia pachyptila (Jones 1981)
Geography and Distribution
Riftia pachyptila, commonly known as the giant tubeworm, is a type of vestimentiferan worm that is found at hydrothermal sites situated along the East Pacific Rise and the Galapagos Rift (Fig. 1) (Micheli et al., 2002; Minic and Herve, 2004). Preferring medium levels of venting with temperatures less than 30oC, R. pachyptila dominates the vestimentiferan zone (Mills et al., 2007).
They are considered ecosystem engineers – an organism that significantly modifies the ecosystem – and their recruitment at early succession stages soon allows for dense aggregations to form (Fig. 2), which then supports high species diversity as well as high species richness (Govenar et al., 2005). It increases diversity by providing a habitat to a number of species; for example, gastropod species attach to the R. pachyptila tubes (Fretter, 1988) whilst crabs and fish hide amongst the tubes of this species (Micheli et al., 2002; Desbruyéres et al., 2006). Similarly, it is can be a food resource for some predators, such as Bythograea thermydron (Dittel et al., 2005).
Appearance and Identification
Lacking a gut, mouth and anus (Jones, 1981; Minic and Herve, 2004), R. pachyptila is most identifiable by the blood red plume that is easily seen. This fused plumed region has an obvious non-ciliated groove running along its length, showing that the plume is also paired (Jones, 1981). Jones (1981) also describes the plume as looking almost feather-like (Fig. 3) with the vast number of red tentacular lamellae directed perpendicular to axis of the plume. The total length of this plume ranges is typically ranged between 11.6 – 36.0 % of the individual, though there is variability (Fisher et al., 1988).
This plume is normally seen coming out of the large, cylindrical tubes that R. pachyptila construct. They are white in colour, and the worm lives within it (Jones, 1981). The tube will normally indicate the length of the worm which can reach sizes of 1.5m in length (Fig. 4) and 4 cm in diameter.
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