MUSEO ARGENTINO DE CIENCIAS NATURALES "BERNARDINO RIVADAVIA"
Unidad Ejecutora - UE
The distribution of colonies of the bryozoan Antarctothoa bougainvillei on the red alga Hymenena laciniata
LIUZZI, M.G.; LÓPEZ GAPPA, J.
Lugar: Dordrecht; Año: 2008 vol. 605 p. 65 - 65
The cheilostome bryozoan Antarctothoa bougainvillei (dOrbigny) is the most frequent epibiont on the ribbonlike red alga Hymenena laciniata (Hooker f. & Harvey) Kylin in San Sebastián Bay (Tierra del Fuego, Argentina). Twentyone thalli and 1484 colonies were examined in order to analyse the relationship between both species. In most cases, number and area of colonies did not differ significantly at both sides of the thallus. Ancestrulae (i.e., founder zooids originating colonies by asexual budding) were mostly oriented facing the algal growing edge. Colonies were more frequent on central than on marginal zones of the thalli. The population of A. bougainvillei was mainly composed of very small colonies (<10 mm2). Larger colonies predominated and intraspecific competition was more intense near the basal portions of the thalli. Fecundity (number of ovicells) increased at a significantly higher rate in colonies with margins obstructed by conspecific neighbours than in freegrowing colonies. Colonies were significantly larger on somatic than on reproductive algal tissues. As total and reproductive surfaces covered by colonies of A. bougainvillei were on average very low (4.43% and 0.53%, respectively), this epibiont is not supposed to produce a negative effect on H. laciniata.