The sea cucumber Parathyone braziliensis (Verrill, 1868) is a tropical, infaunal, holothuroid inhabiting intertidal shores along the Brazilian coast, up to Santa Catarina State. Other than morphologic and taxonomic information, there is a complete gap of knowledge about its life cycle and reproduction. The commercial interest, high prices and the recent threats of unregulated fisheries of sea cucumbers throughout the world increased the interest for aquaculture development. The production of juveniles in the hatchery is a fundamental step towards the development of aquaculture technology for marine invertebrates. Aiming to gain knowledge about reproduction and early life development of P. braziliensis, as well as to assess the potential for hatchery production of juveniles, it was attempted to carry out induction to spawning, larval culture and settlement on artificial collectors.
Adults were collected at Armação do Itapocoroy, Penha, Santa Catarina, (26°47’ S; 48°36’ W) during low tide in November 2023 (License to collect native fauna Brasil/MMA/SISBIO No. 68215) and transferred to the laboratory (Centro Experimental de Maricultura, Univali, Penha). After 72 hours a in sea water-recirculating system, four individuals were transferred to a 200-L tank for elimination of the digestive content for 1-hour, after which they were transferred to the induction tank. Temperature was increased from 24 to 28oC (1 µm; UV-treated seawater). After initiation of gamete release, the sea cucumbers were transferred to individual 10-L buckets, where spawning behavior was observed and recorded with video camera. After fertilization, the embryos were transferred to 150-L tank and samples were taken to examine the embryonic and larval development. Larval cultures were carried out in static system with water renewal every 72-hours. Diet consisted of 50% Chaetoceros muelleri e 50% Nannochloropsis oculata, in concentrations ranging from 2x104 to 4x104 cells/mL.
Three individuals started to release sperm approximately 1 hour after the temperature increase. Half an hour later a female started to release large (458,1±27,9µm), lecithotrophic, negatively buoyant oocytes, which were stuck in a mucous string. Parental tentacle movements acted as to disperse the strings. The embryonic development was encapsulated, leading to the release of a pentactula larva sixty hours after fertilization. Pentactula larvae tended to settle in the walls and bottom of the culture containers, as well as in fiberglass sheets immersed in the culture containers. Larval to juvenile development was followed for one month and results will be presented.
The direct development of P. braziliensis without the stages of auricularia and doliolaria is a great advantage for sea cucumber aquaculture, since it eliminates the period of planktonic larval culture, which is time consuming and often prone to large mortalities. The results of the present study highlighted the potential of P. braziliensis as a new candidate for aquaculture in Brazil.
Project funded by Fundação de Amparo à Pesquisa e Inovação do Estado de Santa Catarina (FAPESC), edital 12/2020.