Post-larval development of the microcotylid monogenean Sparicotyle chrysophrii (Van Beneden and Hesse, 1863): Comparison with species of Microcotylidae and Heteraxinidae

The chronology of post-larval development in S. chrysophrii, a polyopisthocotylean monogenean parasite of the gilthead seabream (Sparus aurata L.), was experimentally studied. It is compared with other species within the Microcotylidae and the Heteraxinidae, including an analysis of the changes in attachment and the growth rate. Gilthead seabreams infected by larvae of S. chrysophrii were killed periodically in order to collect the different developmental stages. Parasite total body length, haptor length, largest clamp width, and total number of clamps were recorded. Specimens of S. chrysophrii in culture conditions at 20 °C became gravid after 26–30 days, with 37 pairs of clamps. The S. chrysophrii growth curve appears to be sigmoid with 3 growth periods (slow–fast–slow). The haptor of S. chrysophrii grows linearly with total body length, but the main contribution to total body length growth is that of the non-haptoral body. The relationship between number of clamps and total body length during development can be fitted to an exponential curve for all the reviewed species, i.e.: Microcotyle spinicirrus, Microcotyle donavini, Microcotyle gotoi, Microcotyle sebastis, Microcotyle hiatulae, Polylabroides multispinosus, Bivagina tai, Heteraxinoides xanthophilis, Heteraxine heterocerca, and Zeuxapta seriolae. The sequence of events was common for all of the species compared: terminal lappet is lost when about 15% of clamps were developed; primordia of testes at approximately 30% of clamps developed, and maturity (as first egg appearance) at about 65% of clamps developed.

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► Sparicotyle chrysophrii life-cycle lasts 26–36 days from hatching to maturation.
► Three growth rates were found during ontogenetic development, slow–fast–slow.
► These rates were associated with settlement, maturation and reproduction.
► Common timing of hook loss and maturation exist in microcotylids and heteraxinids.
► During development, effects on gills change as attachment mechanisms change.