|Life cycle and mode of infestation of Myzostoma cirriferum (Annelida), a symbiotic myzostomid of the comatulid crinoid Antedon bifida (Echinodermata)|
Eeckhaut, I.; Jangoux, M. (1993). Life cycle and mode of infestation of Myzostoma cirriferum (Annelida), a symbiotic myzostomid of the comatulid crinoid Antedon bifida (Echinodermata). Dis. Aquat. Org. 15(3): 207-217
In: Diseases of Aquatic Organisms. Inter Research: Oldendorf/Luhe. ISSN 0177-5103, more
Behaviour; Hosts; Infestation; Larvae; Life cycle; Marine molluscs; Metamorphosis; Population density; Antedon bifida (Pennant, 1777) [WoRMS]; Echinodermata [WoRMS]; Myzostoma cirriferum Leuckart, 1836 [WoRMS]; ANE, France, Brittany [Marine Regions]
Eight different stages succeed one another in the life cycle of the myzostomid Myzostoma cirriferum, viz. the embryonic stage, 4 larval stages, and 3 postmetamorphic stages. Fertilization is internal. Embryogenesis starts after egg laying and takes place in the water column. Ciliated protrochophores and trochophores are free-swimming. Ciliated metatrochophores (i.e., 3 d old larvae) bear 8 long denticulate setae and form the infesting stage. They infest the host Antedon bifida through the feeding system of the latter: they are treated by hosts as food particles and are caught by the host's podia. By means of their setae, metatrochophores attach on the host's podia and are driven by the latter in the pinnule groove where they eventually attach and undergo metamorphosis. Juveniles and early males remain in the pinnules. They attach to the ambulacral groove through parapodial hooks and produce localized pinnular deformations. Late male and hermaphroditic individuals move freely on their host. They occur outside the ambulacral grooves and are located respectively on the pinnules, the arms or the upper part of the calyx of the host, depending on their stage and size. The success of the Myzostoma cirriferum-Antedon bifida symbiosis is ensured by the usually high density of the hosts' populations, the way the myzostomids reproduce (reproduction occurs year-round) and their effective mode of infestation.