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You are here:   animal list > Gastrolepidia clavigera



Gastrolepidia clavigera Schmarda, 1861

scale worm

Hei Wa Ho (2011)



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Commensalism adaptations

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Names & Taxonomy

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External Morphology

The dorsal side of the polychaete is covered with elytra. They have hooked ventral chaetae and special semicircular lobes that are developed laterally on the ventral side of each setiger (Britayev, 1996).

They have a large variety of colours, the coloration of the worms conforms exactly to that of the host. Commensals from the dark brown sea cucumber S. chloronotus are also dark brown; those from light brown A. echinites are brown or yellowish brown; and those from greenish gray S. variegatus are greenish gray with brown spots. However, exception were observed on a Stichopus variegatus, where a blackish scale worm were found. This is mostly likely to be the result of changing host (Gibbs, 1969).
 The dorsal view of gastrolepidia clavigera

 The ventral view of gastrolepidia clavigera

G. clavigera has overlapping dorsal scales which cover the entire body. When the worm is threatened or being dislodged, the scales fall off easily. There are also tiny white dots on the surface of the scale. The reason for having the spots are still unknown, it might be another strategy for morphology adaptations for communalism.
 the elytra (black arrows) of the scaleworm

 A close up shot of the elytron, showing all the white spots on the surface

G. clavigera also developed special semicircular lobes that are found laterally on the ventral side of each setiger. It is believed that those lobes are involved in attachment to the host.
 semicircular lobes (white arrows) on the ventral side of each setiger

Some drumsticks like structure are also found under the elytra. They are believed to mimic the tube feet of the host (holothurians). On the tip of the drumsticks, spikes are also found. One spike was found in each drumstick like structure. They might involve in attachment to the host.
 Circular lobes developed under the elytra

 A close up shot of the drumstick like structure, the spike (black arrow) found on the tip of the structure

The parapodia of the polychaete is hidden under the elytra.
 the hooked ventral parapodium (black arrows)

a close up shot of the parapodia (white arrows)

Gastrolepidia clavigera belongs to the clade Phyllodocida, which means it has an axial proboscis with a muscular pharynx. The species have a pair of chitin jaws, a strong muscular throat (Wolf, 1976).
 a close up shot of the mouth of the polychaete

 a close view at the head of the polychaete

 a dorsal view of the head of the scaleworm