page_title: Monstrilloida
section_title: Biology
hierarchical_section_title: Monstrilloida / Biology
caption_attribution_description: Cymbasoma danae syn. Haemocera danae English: Stages in the life-history of Haemocera danae, one of the Monstrillidae A, Free-swimming nauplius larva; B, embryo after penetrating into the body of the worm Salmacina; C, D, E, successive stages in the body of the host; F, free-swimming adult female; a', Antennule; br, brain; e, nauplius eye; f, swimming feet; g.s., hairs on which the eggs are carried; m, position of mouth; md, hooked mandible of nauplius; n, nerve cord; ov, mass of eggs carried by female; ovy, ovary; pr, absorptive processes Subject: Monstrillidae, Haemocera, Parasites Tag: Invertebrates
context_page_description: Monstrilloida is an order of copepods with a cosmopolitan distribution in the world's oceans. The order contains a single family, Monstrillidae. The name of the first ever described genus Monstrilla is derived from latin, meaning "tiny monster", because the lack of usual diagnostic features of copepods puzzled early taxonomists.
context_section_description: Biologically and ecologically, our knowledge of the order is limited, although the life cycle differs from that of all other copepods: Members of the Monstilloida are  protelean parasites, meaning that their larval stages are parasitoids that kill their host to emerge as free-living subadults. Apparently, some hosts recover after the final subadult monstrilloid exits their body. It is hypothesized, that the host's relative body size and the number and location of copepods parasitizing the same host determine whether it survives an infection. The detailed life cycle may vary between different species, but generally follows a certain sequence: after a free-swimming, infective nauplius stage, the larvae develop inside benthic polychaetes, gastropods, sponges and bivalve mussels (They may be a pest in commercially important bivalve aquaculure), from where the planktonic adults emerge. They do not possess functioning mouth-parts, their sole purpose is to reproduce. In Contrast to holoplanktonic calanoid and cyclopoid copepods, Monstrilloids do not use their largest cephalic appendages, the antennulae, for locomotion, but to create a stream-line shaped corridor, rather using their four pairs of swimming legs to move in the water column. Sex determination depends on conspecifics infecting the same host individual. In case of 2-3 coexisting monstrilloids they become males, when there is only one parasite in a host, it develops into a female.
caption: different life cycle stages of Cymbasoma danae
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