Aegla longirostri Bond-Buckup and Buckup 1994
Creators: name: Ayres-Peres, Luciane
name: Araujo, Paula B.
name: Santos, Sandro
Publisher: name: Zenodo
Year: 2011
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Aeglidae
Aegla
Aegla longirostri

description: Aegla longirostri
showed an agonistic behavior that was strongly marked by the use of antennae and chelipeds. The combats were initiated by an approach, progressing from brief contacts with repeated movements of antennae during all recorded time to touching the carapace or the opponent’s antennae, to the use of chelipeds to touch or hold the opponent. After these initial acts, on many occasions the individuals invested in a fight, going to the extreme of an intense combat in which they used all the structures of their bodies (antennae, pleon, chelipeds, and pereiopods) and in attempting to attack the other animal (Table 1), or, in some situations, the animal walks away from the opponent. Besides the acts that are well known for other species of crustaceans, such as the use of chelipeds to hit and hold, the aeglids showed some acts in low frequency which are not usually reported as being a dominant attitude, such as: push, climb and/or turn the opponent (Fig. 1).
In all trials, the agonistic encounters occurred each time that one animal approached, made physical contact, and this contact provoked a response in the opponent. The aeglids took about 198 seconds (minimum = 25 and maximum = 475, mean ± standard error = 192.5 ± 46.3 s) to start the combats. In five of ten contests, the winner was the individual that started the combat.
Of the 26 kinds of behavioral acts described (Table 1) and quantified (Table 2), 16 are classified as aggressive acts, and the remainder are related to activities such as: remaining still (WD1 and WD2), walking and climbing the arena; receiving stimuli from the opponent: being touched, pulled, or held (caught) with the chelipeds; being pushed/ moved by the opponent’s body; and being turned and climbed on by the opponent.
For winners and losers, the most frequently observed acts were: keeping still, but with activity (31.75% of the time), keeping still and without activity (14.73%), walking (12.83%), fighting (9.52%), holding (5.63%), and hitting with chelipeds (4.23%) (Table 2). The intensity values (Table 3) in eight of ten trials showed significant differences (P, 0.05) among the values for the sum of intensities obtained from combats between winners and losers (Fig. 2). Acts with a negative score were those in which the animal avoided fighting, walked away (-1) or fleeing (-2), or when it was ‘‘attacked’’ by the opponent. Scores 0 and 1 were reserved for encounters in which there was no physical contact, with or without movement of an individual. A score of 2 refers to opponents approaching to initiate combat. Scores 3 to 5 indicate interaction with physical contact between opponents (Table 3). The most aggressive individuals were those of the smallest pair (Fig. 2).
There was a statistically significant difference between the time spent by winners and losers with negative (-1 and -2) and null (0) scores (Fig. 3), where the losing animals performed these acts with more frequency than the winners. On the other hand, the winners spent significantly more time in activities such as walking and climbing the arena (score 1), approaching (2), and chasing, and/or use antennae, and/or hitting with chelipeds (3) than did the losers, with no significant difference in the highest levels of intensity (4 and 5) (Fig. 3).
The most aggressive acts were performed by the winning individuals, even considering that at the beginning of fights, both animals showed a low intensity level of aggressiveness, which increased during the course of an experiment. At the end of the observation period (between 1020 and 1200 s), there was a clear separation between the level of aggressiveness of the winners and losers (Fig. 4).
The mean time (± standard deviation) of the first encounter was 28 ± 32.59 s (minimum =10 and maximum = 110). Individuals that won combats used their antennae more frequently than did the losers (x 2 = 97.53; P, 0.0001). The mean number (± standard deviation) of contacts with antennae by winners was 37.8 ± 26.2 (minimum = 11 and maximum = 95); whereas the mean number of contacts by losers was 25.6 ± 20 (minimum = 0 and maximum = 56). Whipping with the antennae did not differ significantly between the groups, with a mean (± SD) of 1.7 ± 2.7 (minimum = 0 and maximum = 7) in winners and 4.1 ± 7.6 (minimum = 0 and maximum = 24) in losers.
Significant differences in the frequency of aggressiveness of both winners and losers were observed in the following acts: walking away, approaching, hitting with chelipeds, walking, fleeing, chasing, with no movement from place to place (and no activity), and being touched by the opponent (Fig. 5).
description: Published as part of Ayres-Peres, Luciane, Araujo, Paula B. & Santos, Sandro, 2011, Description Of The Agonistic Behavior Of Aegla Longirostri (Decapoda: Aeglidae), pp. 379-388 in Journal Of Crustacean Biology 31 (3) on pages 380-381, DOI: 10.1651/10-3422.1, http://zenodo.org/record/7806409