ABSTRACT
Introduction: The locomotion behavior of an organism involves the integration of aspects like body symmetry, sensory and locomotor systems. Furthermore, various ecological factors seem to be related to locomotion characteristics, such as foraging strategy, migration trends, response to predators and competitors, and environmental stress. Objective: To analyze locomotion and the influence of body symmetry in the crawling and righting movements of the sea star Asterina stellifera. Methods: We carried out laboratory experiments in aquariums in the presence/absence of water current and on a horizontal and vertical surface. Results: The speed is similar to speed in other species of similar size. Both the speed and linearity of displacement were independent of individual body size. A water current leads to faster crawling and straight paths, but there is no rheotaxis: streams do not affect locomotion. Speed and linearity of displacement were independent of individual body size. The displacement pattern described here may be an adaptation of organisms that present dense populations in communities with high prey abundance, as is the case of A. stellifera. Conclusions: Like other asteroids, this species did not show an Anterior/Posterior plane of symmetry during locomotion, or righting movement: it does not tend to bilaterality.
Introducción: El comportamiento de locomoción de un organismo implica la integración de aspectos como la simetría corporal, los sistemas sensorial y locomotor. Además, varios factores ecológicos parecen estar relacionados con las características de la locomoción, como la estrategia de alimentación, las tendencias migratorias, la respuesta a los depredadores y competidores y el estrés ambiental. Objetivo: Analizar el patrón general de locomoción y la influencia de la simetría corporal en la locomoción y enderezamiento de la estrella de mar Asterina stellifera. Métodos: Realizamos experimentos de laboratorio en acuarios en presencia / ausencia de corriente de agua y en superficie horizontal y vertical. Resultados: La velocidad es similar a la velocidad en otras especies de tamaño similar. Tanto la velocidad como la linealidad del desplazamiento fueron independientes del tamaño corporal individual. Una corriente de agua conduce a una velocidad de desplazamiento mayor y a trayectorias más rectas, pero no hay reotaxis: una corriente de agua no afecta el patrón de locomoción. La velocidad y la linealidad del desplazamiento fueron independientes del tamaño corporal individual. El patrón de desplazamiento aquí descrito puede ser una adaptación de organismos que presentan densas poblaciones en comunidades con alta abundancia de presas, como es el caso de A. stellifera. Conclusiones: Al igual que otros asteroides, esta especie no mostró un plano de simetría Anterior / Posterior durante la locomoción o el movimiento de enderezamiento: no tiende a la bilateralidad.
Subject(s)
Animals , Starfish/growth & development , Locomotion , Asterias/growth & developmentABSTRACT
Guppies (Poecilia reticulata Peters 1859) in lakes and from captive-bred populations are predicted to show little rheotaxis compared to conspecifics in a stream environment that are regularly exposed to flash floods associated with involuntary downstream migration. Here we test this hypothesis using an artificial stream, examining guppies of two wild riverine populations, one lake population, and one ornamental strain. Guppies from the most upstream riverine habitat show the most pronounced rheotaxis and are less likely to be swept downstream during flooding events. However, there is no significant difference between guppies from the lowland riverine habitat, the Pitch Lake and ornamental strain. We propose that station-keeping behaviours are most strongly selected in the upstream population because large spatial differences exist in ecology and environment between up- and downstream habitats. Given that these sites are separated by barrier waterfalls that prevent compensatory upstream migration, natural selection operates particularly strong against upstream guppies that have been displaced downstream during flooding events.
Populações de guppies (Poecilia reticulata Peters) que vivem em lagos e em cativeiro podem demonstrar menos reotaxia em comparação com populações que habitam rios e que estão frequentemente expostas a enchentes e que provocam a migração involuntária para jusante. Neste trabalho, vamos testar esta hipótese num rio artificial utilizando guppies de duas populações selvagens que habitam em rios, uma população que habita em lagos, e uma linhagem ornamental. Os resultados demonstram que os guppies de rios que provêm de localidades a montante demonstram maior reotaxia, diminuindo assim probabilidade de serem arrastados para jusante em períodos de enchentes. No entanto, não foram encontradas diferenças significativas entre guppies de localidades a jusante, do lago Pitch ou ornamentais. Este resultado pode dever-se ao facto de existirem grandes diferenças ecológicas entre os habitats localizados a jusante e a montante dos rios. Devido ao facto de estas localidades estarem separadas por cachoeiras, impossibilitando a migração rio-acima, a seleção natural poderá estar a actuar contra guppies que sejam arrastados rio abaixo durantes os períodos de cheias.