The purpose of this study was to examine the masking preferences of the spider crab, Notomithrax ursus. The algal composition of the mask in the natural habitat at Kaikoura was examined to determine the general rules the crab follows when decorating itself. The effects of size and sex on the mask composition were examined, as well as determining how the composition of the mask varies by body part. The preference of the crabs was further examined through the use of choice and background change experiments in the laboratory. It was determined that the preference of certain types of algae for mask material is not entirely dependent on their relative abundance in the environment. Possible explanations for this behaviour are given.

The purpose of this study was to examine the masking preferences of the spider crab, Notomithrax ursus. The algal composition of the mask in the natural habitat at Kaikoura was examined to determine the general rules the crab follows when decorating itself. The effects of size and sex on the mask composition were examined, as well as determining how the composition of the mask varies by body part. The preference of the crabs was further examined through the use of choice and background change experiments in the laboratory. It was determined that the preference of certain types of algae for mask material is not entirely dependent on their relative abundance in the environment. Possible explanations for this behaviour are given.

Orientador: William Ricardo Amancio Santana / Resumo: O gênero anfi-americano Macrocoeloma Miers, 1879 é composto por caranguejos decoradores de habitats tropicais e subtropicais. Esses caranguejos são encontrados em substratos distintos, incluindo principalmente recifes de corais e rochas. Esse gênero passou por várias alterações sistemáticas em seu status de família, desde sua descrição original até a sua recente exclusão de Mithracidae. No início deste estudo Macrocoeloma era considerado incertae sedis, devido ao pouco conhecimento das relações entre as espécies do gênero e outros gêneros relacionados, sendo sua revisão taxonômica sugerida diversas vezes na literatura. Assim, com o objetivo de suprir essas lacunas taxonômicas e filogenéticas, este estudo empregou abordagens morfológicas e moleculares para reconstruir as relações filogenéticas de Macrocoeloma. Para isso, utilizamos um conjunto de dados moleculares combinados de um gene nuclear (18S) e três mitocondriais (12S, 16S, COI), usando máxima verossimilhança e inferência bayesiana. Além disso, uma inferência de delimitação de espécies foi realizada com o modelo de Poisson tree processes (PTP), usando a filogenia de máxima verossimilhança do gene mitocondrial COI. Foi realizada a revisão taxonômica de Macrocoeloma, com diagnóstico elaborado, descrições detalhadas e mapas de distribuição geográfica com base no material examinado. A monofilia de Macrocoeloma foi demonstrada, após exclusão de Pericera heptacantha Bell, 1836 e P. septemspinosa Stimpson, 1871. O gênero monot... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The amphi-American genus, Macrocoeloma Miers, 1879, is composed of decorator crabs from tropical and subtropical regions. These crabs are found on distinct substrates, including mainly coral reefs and rock. Macrocoeloma has undergone several systematic changes in its family status, since the original description until its recent exclusion of Mithracidae. Prior to this study, Macrocoeloma was considered incertae sedis, due to little knowledge of the relationships between species of the genus and related genera, and its taxonomic revision has been suggested several times in the literature. Thus, in order to address these taxonomic and phylogenetics gaps, this study employed morphological and molecular approaches to reconstruct the phylogenetic relationships of Macrocoeloma. We used a combined molecular dataset of a nuclear (18S) and three mitochondrial genes (12S, 16S, COI) using Maximum Likelihood and Bayesian Inference. In addition, the inference of species delimitation was performed with the Poisson tree processes model (PTP), using Maximum Likelihood phylogeny of the mitochondrial COI gene. The taxonomic revision of Macrocoeloma was provided with elaborated diagnosis, detailed descriptions and maps of geographic distribution based on examined material. The monophyly of Macrocoeloma was demonstrated after exclusion of Pericera heptacantha and P. septemspinosa. The monotypic genus Thersandrus Rathbun, 1897 is a sister group of Macrocoeloma, followed by the new genus proposed ... (Complete abstract click electronic access below) / Doutor