The Importance of Vision in Agonistic Communication of the Crayfish Orconectes Rusticus. I: an Analysis of Bout Dynamics

Abstract

Abstract1. The importance of vision for efficient agonistic communication was investigated in the rusty crayfish, Orconectes rusticus, a species active both day and night. Agonistic bout dynamics were analyzed from isosexual pairs of males and females interacting under moderate (350 lux) and dim (11 lux) light levels, and in complete darkness (using infra-red video recording). Under dim light we determined the effect of visual light and dark adaptation on communication. 2. As light diminished, bouts became less frequent, but longer, and the crayfish invested more time and performed more acts when resolving bouts. Thus, communication efficiency was clearly lower in the dark than under moderate light, for both sexes. Males performed more acts than females overall, and were generally more aggressive than females. 3. The frequency of visually-mediated behaviours (e.g. Lunge, Follow) decreased in the absence oflight, while tactile behaviours (e.g. Antenna Tap, Chela Strike, Push) were performed more frequently. Males especially performed more highly aggressive tactile behaviours in the dark. It was shown that some behaviours previously considered to be visually mediated (e.g. Meral Spread) are also tactually or proprioceptively mediated, and some behaviours assumed to be tactually mediated (e.g. antennal movements) are probably also visually mediated. 4. Under dim light, crayfish with light-adapted eyes resolve bouts more efficiently in terms of time and energy investment than do dark-adapted animals. This is consistent with the effects of pigment migrations during dark adaptation in the crayfish superposition compound eye, which enhance visual sensitivity, but decrease acuity. We suggest that dark adaptation diminishes a crayfishes ability to deal with the subtleties of visual communication, but may well enhance its ability to detect predators.

Biogenic amines influence aggressiveness in crayfish but not their force or hierarchical rank

“…Simultaneously, an experienced observer (ET) recorded the winner of each fight so that at the end of this phase, we could determine the dominant crayfish, alpha (and consequently the subordinate crayfish, beta) for each pair, that is, the winner (and the loser) of more than 50% of the total fights. The 'winner' was defined as the crayfish that did not retreat or that retreated after the opponent showed a motionless posture, which is typical for a subordinate (Bruski & Dunham 1987). Before this phase started, we measured the chelar force (see below) exercised by the members of 30 pairs, designated at random.…”

“…According to Bruski & Dunham (1987), the body of dominant individuals is usually raised with their abdomen extended and their chelipeds are most often raised with the chelae open to easily grasp any offered object. The opposite was found for subordinate crayfish.…”

“…(4) Behavioural patterns (as described by Bruski & Dunham 1987) performed by alphas and betas: in particular, we recorded the strong contacts (chelae strikes and interlocked) that allowed us to estimate the aggressiveness of each animal.…”

Visual recognition of conspecifics in the American lobster, Homarus americanus

“…Vision can also be important for the resolution of fights (e.g. Vannini & Gherardi 1981;Bruski & Dunham 1987); aggressive interactions, for example, escalate under decreased light intensity (Bruski & Dunham 1987) and are modulated by visual displays (Heckenlively 1970;Rubenstein & Hazlett 1974). In C. dispar, when the claws of the original winners were disabled, the winners kept on winning against the same opponents; this effect disappeared when the previous winners encountered unfamiliar individuals (Seebacher & Wilson 2007).…”

Evaluation of body appendage injuries to juvenile signal crayfish (Pacifastacus leniusculus): relationships and consequences

“…Aggressive interactions are reduced in an environment with high habitat complexity (Corkum and Cronin, 2004;Baird et al, 2006), which should result in lower frequency of injured crayfish. Antennae are important in mediating social interactions (Rutherford et al, 1996;Horner et al, 2008) during which hierarchies of dominance are established (Bruski and Dunham, 1987;Cook and Moore, 2009). Antennae are essential for gaining tactile information for sensing the local topography (Basil and Sandeman, 2000;Koch et al, 2006), and for localizing food and conspecifics Dunham, 1999, 2000).…”