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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

Life History & Behaviour


The majority of Myzostoma species are sequential hermaphrodites, by which they pass through a functional male stage when younger/smaller and later become simultaneous hermaphrodites when older (Rouse 2005). The female organs consist of many dorsally located ovarian caeca while the male testes are usually located on the ventral surface on either side of the stomach (near the third parapodia) (Rouse 2005). Fertilization of Myzostomids occurs internally within the uterus (Rouse 2005). Tiny, fertilized eggs are then spawned into the surrounding water. This results in non-feeding, planktonic, trochophore-like larvae that have a life time of around ten days (though generally settle within five to eight days). This limited larval stage time has limited their ability to disperse (Rouse2005).


 In Myzostomids, a protrusible proboscis is used for sensing and capturing food particles (Eeckhaut et al.  1995). When feeding, this organ will protrude and when not feeding, it will retract by the use of longitudinal muscles (Eeckhaut et al.  1995). Myzostomid worms divert and consume food particles which are typically carried along the ambulacral grooves of their echinoderm host. The muscularised pharynx, which is located within the proboscis, uses a sucking motion to obtain food particles (Eeckhaut et al.  1995). Click on the below link for a video illustrating movement of the proboscis.


The body of many Myzostomida species, such as Myzostoma sp. are entirely adapted to its host in that they are unable to move to surrounding substrata (Lanterbecq et al. 2008). This means that the locomotion of Myzosotma sp. is merely for movement across its Crinoid host. Myzostoma sp. was found on the oral disc of its host, where it is thought to move around to meet others of the same species during mating or for feeding. Locomotion in Myzostomids is predominantly due to the five pairs of parapodia (PA) that are located on the ventral surface of their body (Lanterbecq et al. 2008). Each conical shaped parapodia encompasses a hook-shaped chaeate (C), replacement chaete and an internal aciculum (Lanterbecq et al. 2008). There are three pairs of chaete muscles that are involved in the movement of the parapodia chaete including the parapodium flexor and extensor, aciculum protractor and retractor and the hook protractor with conjunctor (Lanterbecq et al. 2008). The contraction of other muscle fibers within and surrounding the parapodia that don't come into contact with the chaete result in the shortening and lengthening of the parapodia (Lanterbecq et al. 2008). The movement of the parapodia in these worms can be seen in the below video links. For a more in depth recount of the locomotion in Myzostomid worms see Lanterbecq et al. 2008.


Myzostomids lack respiratory systems and in turn use diffusion across their whole body surface to exchange gases (Grygier 2000).



(2 objects, created 5/6/2011)

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Album: 2012

Album: 2011