Diversity of the Bacterial Community Associated with Hindgut, Malpighian Tubules, and Foam of Nymphs of Two Spittlebug Species (Hemiptera: Aphrophoridae)

Abstract

Spittlebugs are xylem-sap feeding insects that can exploit a nutrient-poor diet, thanks to mutualistic endosymbionts residing in various organs of their body. Although obligate symbioses in some spittlebug species have been quite well studied, little is known about their facultative endosymbionts, especially those inhabiting the gut. Recently, the role played by spittlebugs as vectors of the phytopathogenetic bacterium Xylella fastidiosa aroused attention to this insect group, boosting investigations aimed at developing effective yet sustainable control strategies. Since spittlebug nymphs are currently the main target of applied control, the composition of gut bacterial community of the juveniles of Philaenus spumarius and Lepyronia coleoptrata was investigated using molecular techniques. Moreover, bacteria associated with their froth, sampled from different host plants, were studied. Results revealed that Sodalis and Rickettsia bacteria are the predominant taxa in the gut of P. spumarius and L. coleoptrata nymphs, respectively, while Rhodococcus was found in both species. Our investigations also highlighted the presence of recurring bacteria in the froth. Furthermore, the foam hosted several bacterial species depending on the host plant, the insect species, or on soil contaminant. Overall, first findings showed that nymphs harbor a large and diverse bacterial community in their gut and froth, providing new accounts to the knowledge on facultative symbionts of spittlebugs.

Chemical composition of the foam enfolding juveniles of Aphrophora alni (Hemiptera: Aphrophoridae)

“…The sap taken by spittlebugs contain only a few essential amino acids, while they contain large amounts of polysaccharides. In order to provide the organism with the dietary components missing from the food, spittlebugs have a number of symbiotic organisms located in different areas of the digestive tract or specially adapted tissues -bacteriomes [6,22,23]. These organisms produce a whole range of biologically active compounds that pass into the foam produced [11].…”

Adhesive properties of Aphrophoridae spittlebug foam

“…Proteins and mucopolysaccharides act as surfactants, stabilizing the foam bubbles [34,[37][38][39][40][41][42][43][44]. Interestingly, the foam is inhabited by various tiny creatures, such as amoebae, infusoria, rotifers [31], bacteria [33,35,50] and dipteran larvae [51], which metabolites may also influence the foam properties.…”