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You are here:   OldClasses > 2012 > Myzostoma sp. | Samantha Eady




Myzostoma sp.

(Samantha Eady 2012)



Fact Sheet



Physical Description


Life History & Behaviour

Anatomy & Physiology

Evolution & Systematics

Biogeographic Distribution

Conservation & Threats

References & Links

Physical Description

Size, Shape and Colour

Myzostomids are tiny, soft-bodied worms that have a body size generally ranging from a few millimetres up to thirty millimetres in length (Eeckhaut and Lantebecq 2005). A large variety of body shapes and colours are exhibited within the Myzostomids. Dorso-ventrally flattened oval body shapes are most common, however many species have shown elongate or irregular body forms (Lanterbecq et al. 2009b). This great diversity in Myzostomid body shapes is thought to be due to their varied symbiotic lifestyles and hosts (Lanterbecq et al. 2009b). Myzostomid colour patterns are unique in that they mimic the colours and colour patterns of their hosts (Lanterbecq et al. 2009a). The colouring of the dorsal surface of Myzostoma sp. is a dark brown/maroon, which is very similar to  that of its host, especially the oral disc.     
                      Image showing dorsal surface of
Myzostoma sp. (photo by Sam Eady)
             Image of Crinoid (from family: Comasteridae) illustrating
     oral disc and colouring similar to
Myzostoma sp. (Photo by Sam Eady)

Identifying Characteristics         


The body plan of Myzostomids typically consists of a trunk and an anterior proboscis. The trunk can have a variety of shapes, thicknesses and curvature (Lanterbecq et al. 2006). In Myzostoma sp. the trunk is of a dorso-ventrally flattened orientation.



The proboscis (P) of Myzosotma sp.  consists of a muscular pharynx which can be extended and retracted through the proboscis. The everted tip of the proboscis represents the mouth (M) which is surrounded by buccal papillae (BP).


Five pairs of parapodia (PA) (the main influences on the symmetry of the body) can be found on the ventral surface of most Myzostomids, including Myzostoma sp. The location of these parapodia is a characteristic that can be used to help in identification (Graff 1883). They can be located along the very edge of the trunk margin, close to the centre (Graff 1883) or in between these two extremes as seen in Myzostoma sp. These parapodia are used as locomotory organs, and are moved through a complex system of musculature (Lanterbeqc et al. 2008). At the end of each parapodia are hook-like chaete (C) which assist in movement (Lanterbeqc et al. 2008).


Lateral Organs

Four pairs of lateral sensory organs (LO) or "suckers" are arranged radially around the ventral surface of Myzostoma sp., located alternately between parapodia.



Cirri are usually a characteristic feature of many myzosotmid worms, however in Myzostoma sp. they are absent. In other species, generally ten pairs of cirri are located around the margin of the trunk and are thought to act as chemosensory organs that can be used to determine certain substrata, or as organs for attchment (Graff 1883).



Image of the external morphology of Myzostoma sp.
showing the proboscis (P), parapodia (PA), lateral organs (LO)
and the trunk margin (T). (Photo by Sam Eady)

For a more in depth identification of Myzostomida species see Polychaetes and Allies: The Southern Synthesis by Grygier (2000).



(2 objects, created 5/6/2011)

Album: This is a private album that is not visible to anonymous users Great Barrier Reef Invertebrates



Album: 2012

Album: 2011