Characterization of eversion syndrome in captive Scyphomedusa jellyfish.

Objective: To determine whether Scyphomedusa jellyfish with eversion syndrome had alterations in husbandry conditions, elemental content, or histologic appearance, compared with unaffected jellyfish.

Animals: 123 jellyfish (44 with eversion syndrome and 79 without) at 6 institutions.

Procedures: Elemental analyses were performed on 24 jellyfish with eversion syndrome and 49 without, and histologic examinations were performed on 20 jellyfish with eversion syndrome and 30 without. A questionnaire distributed to 39 institutions with Scyphomedusa jellyfish was used to gather information about husbandry, environmental conditions, and prevalence of eversion syndrome.

Results: For the 39 institutions that responded to the questionnaire, prevalence of eversion syndrome ranged from 0% to 30%. For Aurelia aurita, eversion was more common at institutions with only captive-raised and no wild-caught jellyfish. Eversion was most common among young (approx 1- to 2-month-old) growing jellyfish and older (> 6-month-old) jellyfish. Elemental analysis revealed only minor differences between affected and unaffected jellyfish, with great variation among jellyfish from the same institution and among jellyfish from different institutions. Striated muscle degeneration and necrosis and extracellular matrix (mesoglea) degeneration were evident on histologic examination of affected jellyfish.

Conclusions And Clinical Relevance: Results suggested that eversion syndrome is a complex phenomenon associated with degenerative changes of the bell matrix.