Fine structure of mouthparts and feeding performance of Pyrrhocoris sibiricus Kuschakevich with remarks on the specialization of sensilla and stylets for seed feeding

Abstract

Mouthpart structure and feeding behavior in the temperate firebug, Pyrrhocoris sibiricus Kuschakevich, an important pest that feeds on seeds of leguminous and gramineous plants, are described for the first time. Mouthparts were observed using scanning electron microscopy to examine the external morphology, distribution and abundance of sensilla on mouthparts. Feeding performance by adults on both seeds and shoots were observed using a binocular microscope. The four-segmented labium contains 3 types of sensilla trichodea, 3 types of sensilla basiconica, 1 type of sensilla placodea and 1 type of sensilla campaniformia. Among them, sensilla trichodea are most abundant. The tripartite apex of the labium consists of two lateral lobes and an apical plate. Each lateral lobe possesses a field of 12 thick-walled uniporous peg sensilla and long non-porous hair sensilla. The mandibular stylet tips have three central teeth and two pairs of lateral teeth, which may help in penetrating hard seed coats. A series of scale-like projections are present on the inner surface of the mandibular stylets. The externally smooth maxillary stylets interlock to form a larger food canal and a smaller salivary canal, and there are five tubercles near the tip of the right stylet. Cross-sections of the stylet fascicle show that each mandibular stylet has a dendritic canal. The adult feeding process involves several steps, including exploring and puncturing of the host epidermis, a probing phase, an engorgement phase, and removal of the mouthparts from the host tissue. The structure and function of the mouthparts are adapted for the seed feeding habits.

Morphological Disparity of the Mouthparts in Polyphagous Species of Largidae (Heteroptera: Pentatomomorpha: Pyrrhocoroidea) Reveals Feeding Specialization

“…There were distinct differences in total length of the labium among the four largid bug species observed (longest in Macrocheraia grandis (Lohitini: 19,204 µm), being shorter in Physopeltini (7053 µm; 6713 µm; 5415 µm, Table 2)). In Pyrrhocoris sibiricus, the labium was much shorter (3487 µm) [17]. The mentioned species belong to two closely related families of seed-feeding bugs, so the differences in length of the labium may be regarded as taxonomic characteristics for these families.…”

“…The latter are formed by the mandibles and the maxillae, which are entirely or partly covered by the sheath. Previous studies of hemipteran mouthparts have shown that these structures differ among taxa [8,[12][13][14][15][16][17], reflecting adaptations to different diets and the fact that the specialized digestive system has contributed to their success in feeding on a broad range of foods [18]. Previous studies have focused on Pentatomomorpha species of economic importance [19,20].…”

“…Several species of Dysdercus are major pests of seeds (bolls) of cotton and other Malvaceae. The mouthpart structures were described previously for Dysdercus fasciatus by Signoret [23], and for Pyrrhocoris sibiricus Kuschakevich by Wang and Dai [17].…”

“…Because the few published studies of Pyrrhocoroidea mouthparts have focused on the family Pyrrhocoridae [8,17,29], and no such studies so far have focused on Largidae, we compared the mouthparts of these two families. We expected that the mouthpart structures and feeding behavior observed in individual species would be different due to the use of different host plants and plant tissues.…”

Functional morphology of the mouthparts of lady beetle Coccinella transversoguttata (Coccinellidae, Coleoptera), with reference to their feeding mechanism

“…More importantly, it is the way of feeding, rather than the specific diet or prey, that determines the shape of mandibles as well as other units of a mouthpart (Samways et al, ). Although detailed investigations of the mouthparts allow conclusions about feeding preference (Jiang & Hua, ; Krenn, Fournel, Bauder, & Hugel, ; Wang & Dai, ), it is only of limited value, and further behavioral investigations, as well as detailed analysis on gut content are necessary to study the specific feeding behavior of lady beetles.…”