Donato Romano

Lateralisation of aggressive displays in a tephritid fly

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.

Nanoparticles as effective acaricides against ticks—A review

Ticks serve as vectors of a wide range of infectious agents deleterious to humans and animals. Tick bite prevention is based to a large extent on the use of chemical repellents and acaricides. However, development of resistance in targeted ticks, environmental pollution, and contamination of livestock meat and milk are major concerns. Recently, metal, metal oxide and carbon nanoparticles, particularly those obtained through green fabrication routes, were found to be highly effective against a wide array of arthropod pests and vectors. We summarize current knowledge on the toxicity of nanoparticles against tick vectors of medical and veterinary importance. We also discuss the toxicity of products from botanical- and bacterial-based as well as classic chemical nanosynthesis routes, showing differences in bioactivity against ticks based on the products used for the fabrication of nanoparticles. Further research is needed, to validate the efficacy of nanoparticle-based acaricides in the field and clarify mechanisms of action of nanoparticles against ticks. From a technical point of view, the literature analyzed here showed little standardization of size and weight of tested ticks, a lack of uniform methods to assess toxicity and concerns related to data analysis. Finally, an important challenge for future research is the need for ecotoxicology studies to evaluate potential negative effects on non-target organisms and site contamination arising from nanoparticle-based treatments in close proximity of livestock and farmers.

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

Lateralisation (i.e. functional and/or structural specialisations of left and right sides of the brain) of aggressive traits has been studied in a number of vertebrates, while evidence for invertebrates is scarce. Mosquito females display aggressive responses against undesired males, performing rejection kicks with the hind legs. In this research, we examined lateralisation of kicking behaviour in females of the Asian tiger mosquito, Aedes albopictus. We found a right-biased population-level lateralisation of kicking behaviour. Four repeated testing phases on mosquito females confirmed the preferential use of right legs. However, when left legs were used, the mean number of kicks per rejection event was not different to that performed with right legs. Both left and right kicking behaviour lead to successful displacement of undesired partners. This is the first report about behavioural lateralisation in mosquitoes.

Contest experience enhances aggressive behaviour in a fly: when losers learn to win

In several animal species, aggressive experience influences the characteristics and outcomes of subsequent conflicts, such that winners are more likely to win again (the winner effect) and losers more likely to lose again (the loser effect). We tested the olive fruit fly, Bactrocera oleae (Diptera: Tephritidae), as a model system to evaluate the role of the winner and loser effects in male-male territorial contests. Further, we conducted experiments to test if winning and losing probabilities are affected only by the outcome of the previous contests, or whether the fighting experience itself is sufficient to induce an effect. Both winners and losers of two consecutive encounters displayed higher intensity of aggression and fought longer in subsequent contests. In both cases, they achieved higher fighting success than naïve males. The enhanced fighting performance of both winners and losers was stimulated by merely experiencing a contest, not necessarily by the relative outcome of previous fights. Overall, this study highlights the fact that previous victories and defeats both enhance aggressive behaviour in olive fruit flies, allowing them to achieve higher fighting success in subsequent contests against inexperienced males.

Population-level lateralized aggressive and courtship displays make better fighters not lovers: evidence from a fly

Lateralization (i.e., left-right asymmetries in the brain and behavior) of aggressive and courtship displays has been examined in many vertebrate species, while evidence for invertebrates is limited. We investigated lateralization of aggressive and courtship displays in a lekking tephritid species, the olive fruit fly, Bactrocera oleae. Results showed a left-biased population-level lateralization of aggressive displays, with no differences between the sexes. In both male-male and female-female contests, aggressive behaviors performed with left body parts led to greater fighting success than those performed with right body parts, while no differences in fighting duration were found. Olive fruit fly males also showed a side bias during courtship and mating behavior, courting females more frequently from the left than the right, front, or back sides. No differences were detected between courtship duration and copulation duration following the different male directional approaches. Male mating success was comparable whether females were approached from the left, right, front, or back side. Lateralized aggressive and courtship displays at the population-level may be connected to the prolonged social interactions occurring among lekking flies. Further research is needed on possible benefits arising from lateralization of courtship traits in insects.

Do right-biased boxers do it better? Population-level asymmetry of aggressive displays enhances fighting success in blowflies

Lateralisation (i.e. left-right asymmetries in brain and behaviour) of aggressive traits has been deeply studied in a number of vertebrates, while evidence for invertebrates is scarce. We investigated lateralisation of boxing behaviour in the blowfly Calliphora vomitoria (Diptera: Calliphoridae), where males fight for non-resource based spaces. We found a population-level lateralisation of aggressive displays: three repeated testing phases confirmed the preferential use of right legs over left ones. Duration of contests and number of boxing acts per fighting event were not different between males using left and right legs. The use of right legs for boxing acts lead to higher fighting success over males using left legs. Lateralised aggressive displays at population-level may be connected to the prolonged social interactions occurring among males searching for food and mates.

Lateralized courtship in a parasitic wasp.

ABSTRACT Lateralization (i.e. left-right asymmetries in the brain and behaviour) of courtship displays has been examined in a growing number vertebrate species, while evidence for invertebrates is limited. In this study, we investigated lateralization of courtship and mating displays in the parasitic wasp Leptomastidea abnormis. Results showed a population-level lateralization of male courtship displays. Male antennal tapping on the females head was right-biased. However, right-biased male courtship acts were not characterized by higher male antennal tapping frequencies, nor success in mating although antennal tapping frequency was higher in males with mating success with respect to unsuccessful males. Overall, our results add basic knowledge to the behavioural ecology of insect parasitoids. To the best of our knowledge, this is the first report of behavioural lateralization in parasitic Hymenoptera.

Multiple cues produced by a robotic fish modulate aggressive behaviour in Siamese fighting fishes

The use of robotics to establish social interactions between animals and robots, represents an elegant and innovative method to investigate animal behaviour. However, robots are still underused to investigate high complex and flexible behaviours, such as aggression. Here, Betta splendens was tested as model system to shed light on the effect of a robotic fish eliciting aggression. We evaluated how multiple signal systems, including a light stimulus, affect aggressive responses in B. splendens. Furthermore, we conducted experiments to estimate if aggressive responses were triggered by the biomimetic shape of fish replica, or whether any intruder object was effective as well. Male fishes showed longer and higher aggressive displays as puzzled stimuli from the fish replica increased. When the fish replica emitted its full sequence of cues, the intensity of aggression exceeded even that produced by real fish opponents. Fish replica shape was necessary for conspecific opponent perception, evoking significant aggressive responses. Overall, this study highlights that the efficacy of an artificial opponent eliciting aggressive behaviour in fish can be boosted by exposure to multiple signals. Optimizing the cue combination delivered by the robotic fish replica may be helpful to predict escalating levels of aggression.

Sex differences in fighting-induced hyperaggression in a fly

In many animals, after experiencing an intraspecific aggressive interaction, winners are more likely to win again (the winner effect) and losers more likely to lose again (the loser effect). However, the winner and loser effect has been studied in few arthropod models, and comparative approaches between the sexes are hard to find. In this study, we evaluated the role of previous experience in male–male and female–female contests of Mediterranean fruit flies, Ceratitis capitata (Diptera: Tephritidae). In this species, lekking males fight for courtship territories, while females fight to maintain single oviposition sites, as well as for mates. We addressed the following questions. (1) Are winners more likely to win again and losers more likely to lose again? (2) Are different interfight intervals critical to detect experience-induced effects on aggression? (3) Are winning and losing probabilities affected solely by the outcome of the previous contests, or is fighting experience itself sufficient to induce the effect? (4) Does experience affect differently aggression displayed by males and females? Results showed reduced fighting success in males and females that experienced a single defeat, while individuals that experienced two previous victories or defeats had higher aggression rates and more wins in subsequent contests (i.e. hyperaggression). This was achieved merely by experiencing a contest, while the actual outcomes of previous fights did not affect the aggressiveness level. Some differences were documented between male–male and female–female contests (e.g. females fought longer than males), showing the value of a comparative approach between the sexes when studying experience-induced hyperaggression. This study highlights that both consecutive victories and defeats enhance fighting performances of fruit fly males and females defending courtship territories and oviposition sites, respectively. To the best of our knowledge, this is the first evidence about how repeated defeat experiences reverse the loser effect in animals, leading to higher fighting success.

Behavioral asymmetries in ticks - Lateralized questing of Ixodes ricinus to a mechatronic apparatus delivering host-borne cues

Ticks are considered among the most dangerous arthropod vectors of disease agents to both humans and animals worldwide. Lateralization contributes to biological fitness in many animals, conferring important functional advantages, therefore studying its role in tick perception would critically improve our knowledge about their host-seeking behavior. In this research, we evaluated if Ixodes ricinus (L.) (Ixodiidae) ticks have a preference in using the right or the left foreleg to climb on a host. We developed a mechatronic device moving a tuft of fox skin with fur as host-mimicking combination of cues. This engineered approach allows to display a realistic combination of both visual and olfactory host-borne stimuli, which is prolonged over the time and standardized for each replicate. In the first experiment, the mechatronic apparatus delivered host-borne cues frontally, to evaluate the leg preference during questing as response to a symmetrical stimulus. In the second experiment, host-borne cues were provided laterally, in an equal proportion to the left and to the right of the tick, to investigate if the host direction affected the questing behavior. In both experiments, the large majority of the tested ticks showed individual-level left-biased questing acts, if compared to the ticks showing right-biased ones. Furthermore, population-level left-biased questing responses were observed post-exposure to host-mimicking cues provided frontally or laterally to the tick. Overall, this is the first report on behavioral asymmetries in ticks of medical and veterinary importance. Moreover, the mechatronic apparatus developed in this research can be exploited to evaluate the impact of repellents on tick questing in highly reproducible standardized conditions.