Probability Of Prey Capture Research Articles

Experimental analysis of lizard pause-travel movement: pauses increase probability of prey capture

AbstractThe probability that common lizards (Lacerta vivipara), which have a pause-travel locomotor pattern, would detect and capture living crickets (Acheta domestica) dropped into their immediate environment was determined for five conditions. These were when a lizard was basking (stationary for >30 s), pausing during locomotion (stationary for <0.8 s), or moving at one of three speed ranges defined as searching, standard or fleeing, at the moment when the cricket reached the substrate. The probability that prey would be captured was greatest in basking lizards, and decreased progressively through pausing, searching movement and standard movement to fleeing movement during which no prey were ever captured.

The Tentacle Cilia of Aglantha digitale (Hydrozoa: Trachylina) and their Control

AbstractThe tentacles of Aglantha have ciliary bands along the sides. Metachronal waves pass along these bands. The strong ciliary currents produced propel water past the tentacles, increasing the probability of prey capture. The ciliated cells are unusual in having many (up to about 500) cilia per cell, where most cnidarian ciliated cells have only one. The cells are also peculiar in containing numerous axonemes without membrane coverings, lying loose in the cytoplasm.Tentacles show independent, rhythmic, slow flexions in the oral direction and groups of tentacles show coordinated, slow flexions as part of a regularly repeated fishing cycle. In both cases, these slow, graded movements are mediated by a slowly conducting system, probably the network of small neurons present in the ectoderm, and are accompanied by ciliary arrests. Much faster, more powerful, coordinated contractions of the tentacles occur in the context of escape behaviour; these are mediated by giant axons which run down the tentacles and are also accompanied by ciliary arrest. Ciliary and muscle effectors evidently share a common motor innervation. Electron microscopy shows that the giant and non‐giant nerves both synapse with muscle cells. The latter are joined to the ciliated cells by gap junctions, and it is suggested that whenever the muscles are excited depolarizations spread to the ciliated cells through the gap junctions and cause ciliary arrests. Neuronal control of ciliary activity has not previously been reported in the Hydrozoa.

Optimum Diet and Body Size in Backswimmers (Heteroptera: Notonectidae, Pleidae)

Relations between predator and prey sizes and profitability of the prey to the predator were analyzed for cost-benefit in the backswimmers Notonecta lunata Hungerford, N. undulata Say, N. irrorata Uhler, N. insulata Kirby (Notonectidae) and the pigmy backswimmer Neoplea striola (Fieber) (Pleidae). As costs of pursuing prey are often great (i.e., subjecting predator to predation), the probability of prey capture (p) was incorporated multiplicatively in a cost-benefit function. Attack distances of Notonecta spp. increased with prey size and decreased with predator size; attacks by Neoplea were the same length on all prey sizes. In both genera, handling time and the amount of a prey item eaten depended on both predator and prey size. Pursuit costs of time and energy appear too low to affect the profitability of prey. Generally, larger predators obtained less profit from prey. The profitability of prey appeared normally distributed with reference to prey size in N. lunata, N. undulata, and N. irrorata, but generally remained constant in N. insulata and Neoplea striola. Prey density did not affect the sizes in the diet of Neoplea but starvation increased the proportion of large prey eaten. This tendency poorly fits an hypothesis of diet optimization. Prey-sizes selected by Notonecta spp. reveal little or no diet optimization. Alternatives to diet optimization are examined.