Morphology, Function And Mating Behavior Of Male External Genitalia Of Cricket

Sexual reproduction is general in most of insects.Courtship and mating behavior are important components of the reproductive activities of amphoteric reproductive insects.Genitalia and related structures play an important role in courtship and mating behavior.These structures tend to evolve faster than other features of the insect body,especially the male genitalia,which are often regarded as important species classification features.However,the understanding of the evolution and surface microstructure of male genitalia is still lacking.Grylloidea belongs to the order Orthoptera within the class Insecta,widely distributed all over the world.In this paper,the phylogenetic tree was constructed to study the phylogenetic structure of the morphological traits of male genitalia of crickets,and the ancestral status of four traits were reconstructed.Secondly,the types and morphology of receptors on the surface of male genitalia were studied by scanning electron microscopy.Finally,the mating behaviors of some groups of crickets were observed,analyzed and compared.At the same time,the function of the structure of the male external genitalia of crickets was discussed by taking the morphological basis and mating behavior as the entry point.The main findings are as follows:1.The ancestral state of these four traits was reconstructed,and the results showed that:the male genitalia of primitive groups of crickets mainly showed the state of bone;the male genitalia of primitive groups may have no acantha;in addition,ectoparameron base outside a flat may be primitive ancestors status;and the antecedents of the shape of the epiphallus was not clear,the unfused form,"T" shape and inwards concave in the epiphallus may be the original ancestor state.2.Scanning electron microscopy showed that there were 10 receptor types on the surface of the male genitalia of 27 genera crickets:sensilla trichodea,sensilla chaetica I,sensilla chaetica II,Bohm's bristle,sensilla basiconica,sensilla coeloclnica,sensilla cavity,sensilla styloconica,sensilla campaniformia,sensilla auricillica.The receptor types of different groups were different,the type of receptor of Gryllotalpinae was the least,and the type of receptor of Podoscirtinae was the most.On the number of receptors,sensilla chaetica I was the largest number,sensilla cavity and sensilla coeloclnica were second,B(?)hm's bristle,sensilla styloconica,sensilla campaniformia were the least number.3.Through the observation of mating behaviors of 15 species of crickets,it was found that most of the male crickets would make courtship calls before mating.The mating position is that the female is superior and the male is inferior and parallel,but the female body has angular torsion,such as Parasongella ornaticeps(Chopard,1969),Gryllus bimaculatus(De Geer,1773),Velarifictorus dianxiensis(He,2018).Before mating,some females will gnaw the metanotal gland on the posterior dorsal plate of the males,such as Itara vienamensis(Gorochov,1985),Oecanthus sinensis(Walker,F.1869)and Xenogryllus ululiu(Gorochov,1990).And the mating time of most species remained at 1-3 minutes,but the mating time of Svistella bifasciata(Shiraki,1911)was only about 10 seconds.In addition,it was found that the female and male external genitals of Zvenella acutangulata(Hsia,Liu&Yin,1991)were closely connected in the mating behavior,suggesting that there might be some correspondence between the male and female external genitals of crickets.4.Epiphallus and the ectoparameron are the most ossified part of the male genitalia.The epiphallus was related to the sensation of female sexual pheromone and chemical stimulation.The ectoparameron has a retractable function,which can be extended to detect the female and perceive external information,and stimulate the female.The ectoparameron of some crickets is laterally curved,forms a certain cavity space with epiphallus,and they join in holding the female genitals.In addition,the male genitalia of some crickets with hook or spiny structure,the male and female genitals of the connection mainly through the spiny structure fixed female genitals to complete the mating.