page_title: Ceratothoa oestroides
section_title: Life cycle
hierarchical_section_title: Ceratothoa oestroides / Life cycle
caption_attribution_description: English: Fig 2: Infective stages (pulli) extracted from the marsupium of the adult female of Ceratothoa oestroides.
context_page_description: C. oestroides is a crustacean isopod, obligate ectoparasite of marine fish that dwells in the buccal cavity. It is the causative agent of various pathologies including tissue damage at the parasitisation site, growth defects, decrease in mean host weight and size and increases mortalities in farmed and wild fish populations. It has been recorded in six different fish families: Sparidae, Carangidae, Clupeidae, Maenidae, Scorpenidae, and Mugilidae.
  Adult male and female mate in the host buccal cavity. Embryos develop in the female marsupium, where offspring pass through different pullus stages until they are released from the marsupium as free swimming manca, ready for infecting fish hosts. C. oestroides is one of the most devastating ectoparasites in Mediterranean aquaculture, with an unequal distribution along different geographical areas
context_section_description: The life cycle of Cymothoidae, which are proteandric hermaphrodites, encompasses mating of adult male and female in the host buccal cavity, development of embryos in the female marsupium followed by moulting through pullus stages (I – IV stages). The first pullus (I stage) can be found only in the marsupium where it moults into second pullus (II stage). Although most Cymothoidae have pullus stages I-IV, only pullus stages I and II seem to exist in Ceratothoa oestroides (Fig. 2).
  Sexual differentiation occurs only after young leave the brood pouch . As free swimming manca (infective stage), the parasite will seek and attach to an appropriate host, and will then moult, losing the swimming setae and becoming immotile. The parasite attaches on the host body (flanks, fins), and then crawls towards the operculum, where it enters the buccal cavity and settles on the base of the tongue. After permanent attachment is completed, another moult follows. A seventh segment and pair of pereopods appears, typical for the isopod pre-adult form. An isopod in this pre-adult form will function as male until conditions require it to transform in to female. Sexual transformation is a complex process and depends on many factors. After transformation into female (Figs. 3 and 4), the isopod is known as an adult. Alternatively, individuals that are first to reach the buccal cavity may undergo sexual differentiation (male puberty, mature male, transitory male stage, female puberty, mature female). Females block sexual differentiation of a second individual parasite within a host. This second individual remains in the mature male stage as long as the female is alive. All the life stages of C. oestroides are found on the fish host, if we also include the pulli that are situated in the female pouch.
caption: Fig 2: Infective stages (pulli) extracted from the marsupium of the adult female Ceratothoa oestroides.
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