Uma abordagem taxonômica, ecológica e ontogenética de Holothuroidea (Echinodermata) do Atlántico Sudoeste Tropical, Brasil

Abstract

The class Holothuroidea, popularly known as sea cucumbers or sea cucumbers, has about 1,690 species distributed in 7 distinct orders. In Brazil there are records of 5 of these orders comprising about 50 species. The study aimed to know the fauna of Holothuroidea associated with different types of substrates from shallow waters of the Southwest Tropical Atlantic and was divided into three chapters: 1- Taxonomy and Morphometry of Holothuroidea (Echinodermata) from reef ecosystems of Paraíba; 2- Environmental Influence on the Spatio-Temporal Distribution of Sea cucumbers; 3- Ontogenetic variation of the Thyonidium Seguroensis species (Deichmann, 1930). The material was collected between 2019 and 2021, at 7 sampling points along the coast of Paraíba. All collected material was stored and registered in the Paulo Young Invertebrate Collection at UFPB. The systematic study of sea cucumbers was carried out from the analysis of the external, internal, and calcareous ossicles morphology. The ossicles were observed from slides made with tissue fragments from different regions of the animal's body. Tables with means and standard deviation were added to facilitate the visualization of ossicle variation. To assess diversity, diversity indices were observed. Data normality and homoscedasticity were tested using the Shapiro and Levene test. To see if there is statistical difference in diversity and location, the Kruskal-Wallis test was performed, and a posteriori the Dunn test for multiple comparisons and controlling the experimental error rate. A PERMANOVA was performed to statistically compare the effect of environmental variables in the dry and rainy periods, and to relate the abiotic matrix to the biotic one, an RDA was made. Analyzes were performed using the R software. A total of 118 specimens were collected and classified into 11 species, belonging to 3 orders, 6 families and 10 genera. The species found represent about 50% of the species already recorded for the coast of Paraíba. Among the listed species Trachythyone crassipeda is a new occurrence for Paraíba. The morphometry of the ossicles showed a relatively high variation in size in the same individual, but that differed little when compared to individuals of the same species with similar length. The greatest variations are observed between young and adult individuals. The Praia Formosa community in the reef area had the highest absolute richness with 7 species. Two species were more representative in relation to abundance, Stolus cognatus with 35.59% and Thyonidium seguroensis with 34.75%. There was a significant difference between the diversity of sea cucumbers and the locations (p=0.01), but there was no statistically significant difference between the diversity of sea cucumbers and the periods. It was noticed in the ontogenetic development of Thyonidium seguroensis, a variation in the ossicles, where in some stages its absence may occur. In the analyzed specimens, the dorsal body wall towers are larger than the ventral body wall towers. This work is a useful tool to support future studies on the Class Holothuroidea, to help the management and conservation of the species, as well as to broaden the understanding of the Phylum Echinodermata.