Food capture and escape behavior of Leposternon microcephalum Wagler, 1824 (Squamata: Amphisbaenia)

Amphisbaenians are fossorial reptiles that have a cylindrical and elongated body covered with scales arranged in rings, and are all apodal, except for the three species of the genus Bipes. The amphisbaenian diet consists of a variety of invertebrates and small vertebrates. As these animals live underground, many aspects of their natural history are difficult to study. Most feeding studies of amphisbaenians have focused on the composition of the diet and feeding ecology, and the data available on feeding behavior are based on precursory observations. The present study describes the food capture behavior of Leposternon microcephalum Wagler, 1824 in captivity. In this experiment we used non-live bait (moist cat food), which was placed near a burrow opening, on the surface of the substrate. Three animals were monitored visually and filmed using cellphone cameras deployed at fixed points, to capture images from the dorsal and lateral perspectives of the study subjects. Two principal types of behavior were observed: the capture of food and defense mechanisms. The strategies used to capture the food were similar to those observed in other fossorial species. Although the backward movement has already been observed and described, we were able to record this movement being used as an escape strategy. These findings enrich our knowledge on different aspects of the natural history of the amphisbaenians.

Distribution and Sediment Selection by the Mud Shrimp Upogebia noronhensis (Crustacea: Thalassinidea) and the Potential Effects on the Associated Macroinfaunal Community

Burrowers such as thalassinideans remobilize sediment in benthic ecosystems, altering granulometry, enhancing organic matter cycling and oxygenation. We characterized the distribution of the mud shrimp Upogebia noronhensis and the associated macroinfauna along a depth and granulometric gradient in a shallow subtidal area in the southern Brazilian coast. Mud shrimp densities were estimated by burrow opening count using 0.25 m2 quadrats in three sediment zones: sand, sand-mud transition and mud. Macroinfaunal community descriptors and sediment granulometric characteristics were assessed. U. noronhensis average density varied from 0.6 to 145 individuals m−2 and was highest in the transition zone and lowest in the sand zone. Macrofauna in the sand zone was at least three times more abundant and 1.2 times richer, averaging 436.3 organisms and 39 species, while the transition and mud zones were more even in species distribution (species evenness > 0.7). The shrimp presence seems to be linked to a coarse sand content <80% and clay and silt <40% in the sediment, a compromise between gallery construction ability and filter-feeding suitability. High densities and aggregated distribution of mud shrimp, combined with alteration of sediment grain composition and organic matter, are likely to affect macroinfaunal abundance nearby the burrows.

Space Occupation by the Polychaetous Annelid Perinereis Cultrifera: Influence of Substratum Heterogeneity and Intraspecific Interactions on Burrow Structure

Spatial analysis, laboratory experiments and field observations in the intertidal zone of La Ranee Estuary (northern coast of Brittany, France) of the infaunal polychaete Perinereis cultrifera indicate that the distribution and the abundance of this species appear to be related to the availability of cobbles. Individuals build U-shaped galleries with a surface gutter network protected by a cobble which acts as a roof. The study of spatio-temporal evolution of P. cultrifera burrows showed experimentally that density is important in space-sharing modalities within the sediment. Effects of increased density lead to modifications in the shape and size of the burrows. The absence of connections between burrows, as observed in ‘sandwich aquaria’ and in resin casts, suggest that the gallery is defended against intruders. The study of the distance between individuals in the laboratory did not reveal a regular distribution pattern. These results probably mean that the area around the burrow opening is not defended and, therefore, does not constitute a territory. Perinereis cultrifera is probably competing for burrow space while food may be shared. Territoriality is certainly the main factor involved in the organization and the spatial arrangements of individuals within a population.