Inducción al desove de la almeja estuarina amenazada, Polymesoda arctata (DESHAYES, 1854)

Abstract

In order to promote knowledge in conservation and sustainable use of globally threatened mollusks, juveniles are being obtained in the laboratory for restocking and aquaculture production. P. arctata has a high potential for aquaculture because they feed on primary productivity, have early maturity, external fertilization, hermaphroditism and the possibility of finding mature organisms all year round. Despite these characteristics, in 2002 this species was included in the list of endangered species in Colombia in the vulnerable category (Ardila et al., 2002). This research seeks to expand the knowledge of P. arctata in terms of its reproductive biology and induced reproduction, evaluating the efficiency of different stimuli to induce spawning of the estuarine clam Polymesoda arctata in laboratory conditions, sexually mature. For this purpose, between December 2020 and March 2021, monthly collections of 100 adult specimens (greater than 35 mm in length) were made in the Ciénaga Grande de Santa Marta (10°43'-11°00' N and 74°16'- 74°38' W) and transported to the laboratory of Molluscs and Microalgae of the Universidad del Magdalena, Taganga, Santa Marta (11°16' N, 74°11' W), where they were acclimatized to laboratory conditions. A representation of fully mature or stage IV females was found between 7 and 57%, except in the month of February, when no females were found (Figure 1). In contrast, only fully mature males (between 33 and 80%) were found for the months of March and May. In spite of this, spawning specimens were obtained in all months of the study, except for females in February. Males had an average shell length of 35.5 ± 0.8 mm, while females had an average shell length of 39.0 ± 0.8 mm, and females were larger than males (gl = 1, F = 8.09, p = 0.0057). The effectiveness of all the methods applied was tested, finding spawning in P. arctata, demonstrating that serotonin at a concentration of 20 µM and KCL (only spawning in males), were the methods with positive results. As for spawning, the average percentage of clams spawned ranged from 0 to 16%. With the injection of serotonin placed in the foot at a low concentration of 20 µM, spawning was obtained in both sexes. In contrast, with KCl injection, only males spawned, while no spawning was obtained with the stimuli supplied to the water (UV-irradiated water flow, temperature and salinity changes). Higher percentages of spawned animals were found in those treated with serotonin at low concentration compared to the other 12 treatments (gl =9, F = 5.71, p < 0.0001). Among the methods, the time of onset of the spawning response after serotonin stimulation was between 22 and 37 minutes, with males responding faster than females in serotonin-stimulated organisms (gl =1, F = 18.43, p = 0.0002). Post-stimulation mortality of spawning-induced specimens ranged from 4 to 51%, being higher when a high serotonin concentration was used, either by piercing the shell or without piercing, compared to that obtained for the remaining treatments (gl = 4, F = 3.83, p = 0.0388). the best spawning percentage, response time and survival was obtained with 20 µM serotonin.