Lateralisation of aggressive displays in a tephritid fly

Abstract

Lateralisation (i.e. different functional and/or structural specialisations of the left and right sides of the brain) of aggression has been examined in several vertebrate species, while evidence for invertebrates is scarce. In this study, we investigated lateralisation of aggressive displays (boxing with forelegs and wing strikes) in the Mediterranean fruit fly, Ceratitis capitata. We attempted to answer the following questions: (1) do medflies show lateralisation of aggressive displays at the population-level; (2) are there sex differences in lateralisation of aggressive displays; and (3) does lateralisation of aggression enhance fighting success? Results showed left-biased population-level lateralisation of aggressive displays, with no consistent differences among sexes. In both male-male and female-female conflicts, aggressive behaviours performed with left body parts led to greater fighting success than those performed with right body parts. As we found left-biased preferential use of body parts for both wing strikes and boxing, we predicted that the left foreleg/wing is quicker in exploring/striking than the right one. We characterised wing strike and boxing using high-speed videos, calculating mean velocity of aggressive displays. For both sexes, aggressive displays that led to success were faster than unsuccessful ones. However, left wing/legs were not faster than right ones while performing aggressive acts. Further research is needed on proximate causes allowing enhanced fighting success of lateralised aggressive behaviour. This is the first report supporting the adaptive role of lateralisation of aggressive displays in insects.

First report of behavioural lateralisation in mosquitoes: right-biased kicking behaviour against males in females of the Asian tiger mosquito, Aedes albopictus

“…Differences in the number of mosquito females using left or right legs over repeated testing phases were analysed by JMP (SAS) using a Generalised Linear Mixed Model (GLMM) with a binomial error structure (to model left/right asymmetries) and one fixed factor (Ariyomo and Watt 2013; Benelli et al 2015a): y jw =μ+RT j +ID w +e jw in which y jw is the observation, μ is the overall mean, RT j is the fixed effect of repeated testing (j=1−4), ID w is the w th random effect of individuals (due to repeated measures, W=1−120) and e jw the residual error. Averages were separated by Tukey's HSD test (P<0.05).…”

“…Averages were separated by Tukey's HSD test (P<0.05). Within each testing phase, difference in the number of mosquitoes that used left or right aggressive displays was analysed using a χ 2 test (P<0.05) (Benelli et al 2015a).…”

“…To evaluate the constancy of body parts use, repeated testing (T2-T4, as suggested in Frasnelli et al 2012;Benelli et al 2015a) of T1 females was carried out under the conditions described above. The time interval between testing phases was 5 min.…”

“…Recently, evidence has also documented the phenomenon in invertebrates, highlighting that lateralisation of the nervous system may be a feature of simpler brains as well (Frasnelli et al 2012). Behavioural asymmetries during aggression have been studied in many vertebrates such as cichlids (Arnott et al 2011), Siamese fighting fishes (Takeuchi et al 2010), zebra fishes (Ariyomo and Watt 2013), lizards (Hews et al 2004), deer (Jennings 2014) and horses (Austin and Rogers 2014); however, very little information is available for invertebrates (Ades and Ramires 2002;Backwell et al 2007;Rogers et al 2013b;Benelli et al 2015a).…”

“…albopictus females, since this may be connected to the prolonged Balmost-social^interactions (sensu Benelli et al 2015a) occurring in mosquito mating swarms. On this basis, in this study, we investigated lateralisation and success of kicking behaviour in Ae.…”