Sur la communauté des animaux vagiles associés àSargassum cymosumC. Agardh, à Ubatuba, Etat de São Paulo, Brésil∗

Abstract

On the community of motile animals inhabiting the seaweed Sargassum cymosum C. Agardh, at Ubatuba, SP, Brazil.Twenty-nine samples of marine animals, mainly invertebrates, inhabiting the seaweed Sargassum cymosum were collected in 1967 and 1968, at Ubatuba, Enseada do Flamengo (23° 30' S and 45°' 4' 20" W). They have been studied qualitatively and quantitatively. The main conclusions are: (1) Out of 19,193 animals, 50.2% were Mollusca, 18.8% Polychaeta, 18.7% Crustacea, 10.6% Echinodermata, and 1.7% various other groups. As most of the Foraminifera, Copepoda, Ostracoda, Nematoda, and Acarina were less than 0.2 mm, none were counted in the total or percentages. This is especially important for the percentage given here for Crustacea.(2) The distribution of frequencies of animals as a function of the hour of sampling shows that there is a strong diurnal migration of the fauna as a whole. Between 6 and 10 h there is a migration down from the seaweed to the rocky substrate, and between 18 and 22 h, the seaweed is again invaded by animals which stay through the night. (3) It is suggested that the animals respond to changes in the concentration of free O 2 and CO 2 in the seawater, factors which vary according to the photosynthetic activity of the plants. The descent out of the seaweeds by day, which in certain animals occurs against a positive phototaxy, is considered as a search for food on the surface of the rocks on which S. cymosum grows, and this movement is only possible during the day when seaweeds are producing oxygen by photosynthesis. S. cymosum by itself is not used as food, except in a few cases by young Lytechinus variegatus, and never significantly. The invasion of seaweeds by night is necessary for reaching water with more oxygen and less carbon dioxide brought to the upper surfaces of the plant layer by waves. (4) Despite considerable variability, periods of high seasonal densities could be noted for some of the dominant animal species represented in the samples. Most of the populations increased in the spring and continued high during the summer, then began to diminish in autumn to reach their lowest densities in early winter. (5) Mollusca were studied in more detail: Prosobranchia represented 92.8% of the individuals, Opisthobranchia 6.0% and Pelecypoda 1.2% (6) The dominant species was Tricolia affinis (C. B. Adams, 1850), a prosobranch representing 18.1% of the whole community. The diurnal migrations of this species were peculiar in showing late ascent onto the seaweeds in the evening. Perhaps T. affinis is more resistant than other organisms to an increase of CO 2 or a decrease of O 2 , and thus can stay on the rocks longer and compete better for food with the rest of the community. * Contribution no. 23 du Programme d

Gastropoda (Mollusca) associated to Sargassum sp. beds in São Sebastião Channel - São Paulo, Brazil

“…Similar records had already been found for phytal assemblages of other algae species and from other localities (Montouchet 1979, Schézy & Paula 2000, Chemello & Milazzo 2002, Jacobucci & Leite 2002, Jacobucci et al 2006, Almeida 2007, Leite et al 2009, Veras 2011. Many families identified in this work, including the most abundant ones (Cerithiidae, Phasianellidae and Columbellidae) have recurrent records in general phytal studies already developed in Brazil (Montouchet 1979, Jacobucci et al 2006, Almeida 2007, Leite et al 2009, Veras 2011.…”

“…Studies highlighting and describing the diversity of phytal molluscan assemblages are scarce in Brazil, especially in the coast of Sã o Paulo state, some of which are Montouchet (1979), Jacobucci et al (2006) and Leite et al (2009). Furthermore, illustrated inventories are practically absent in the literature, this kind of work being an important tool to the development of future studies of the phytal gastropod assemblages, as it can facilitate the species identification.…”

“…In these communities, algae provide several advantages for invertebrate and vertebrate animals inhabiting their fronds, including protection against desiccation, wave action and predators, better temperature and salinity conditions, as well as food resources (Jacobucci & Leite 2002, Jacobucci et al 2006, Leite et al 2009). Among macroalgae groups composing the phytal, those of Sargassum can be considered one of the most representative in some localities of the Brazilian coast (Széchy & Paula 2000), with the malacofauna standing out both in abundance and diversity (Montouchet 1979, Schézy & Paula 2000, Chemello & Milazzo 2002, Jacobucci & Leite 2002, Leite et al 2009, Veras 2011.…”

Levantamento de Mollusca, Crustacea e Echinodermata associados a Sargassum spp. na Ilha da Queimada Pequena, Estação Ecológica dos Tupiniquins, litoral sul do Estado de São Paulo, Brasil

“…Já a fauna de moluscos apresenta poucas congruências entre os representantes do litoral norte e os da ilha do litoral sul. Dentre os 16 taxa de moluscos encontrados, apenas os gastrópodes dos gêneros Anachis e Odostomia e os bivalves dos gêneros Musculus e Modiolus são representantes da fauna associada à Sargassum comuns às duas regiões do estado de São Paulo (Montouchet 1979). No entanto, representantes do gênero Fissurela já foram relatados na região de Santos em associação à alga Amphiroa fragilissima (Masunari 1982).…”

“…O presente estudo foi parte de um levantamento mais amplo destes táxons nas regiões de meso e infralitoral nas unidades de conservação mencionadas (G. B. Jacobucci et al, dados não publicados). Devido à necessidade de restrição das coletas destrutivas, optou-se por priorizar o fital de Sargassum, visto que há vários relatos da literatura que confirmam a grande ocorrência de crustáceos, moluscos e equinodermos associados a algas desse gênero no país (Montouchet 1979, Tararam & Wakabara 1981, Wakabara et al 1983, Leite et al 2000, Tanaka & Leite 2003.…”