Morphology and distribution of the external labial sensilla in Fulgoromorpha (Insecta: Hemiptera)

Abstract

The present paper describes the sensory structures on the apical segment of the labium in fifteen fulgoromorphan families (Hemiptera: Fulgoromorpha), using the scanning electron microscope. Thirteen morphologically distinct types of sensilla are identified: five types of multiporous sensilla, four types of uniporous sensilla and four types of nonporous sensilla. Three subapical sensory organ types are also recognized, formed from one to several sensilla, each characteristic of a family group. Sensilla chaetica (mechanoreceptive sensilla) fall into three categories dependent on length and are numerous and evenly distributed on the surface of the labium except where they occur on specialized sensory fields. The planthopper morphological ground plan is represented by two apical pair of sensory fields (dorsal and ventral) on which 11 dorsal pairs of sensilla (10 peg-like pairs + 1 specialized pair dome or cupola-like) and 2 ventral pairs of sensilla basiconica occur. Two main patterns (cixiid and issid) together with more specialized ones (derbid, lophopid, flatid and fulgorid) are reported. Disparity and diversity of the sensory structures are analyzed from a taxonomic and functional perspective. A gustatory function is provided for several chemoreceptive labial sensilla, as in the antennal flagellum sensilla in some other Hemiptera. This represents a more recently evolved function for the planthopper labium. Finally, further lines of study are suggested for future work on the phylogeny of the group based on the studied characters.

A comparison of the external morphology and functions of labial tip sensilla in semiaquatic bugs (Hemiptera: Heteroptera: Gerromorpha)

“…Papillate sensilla: PAS1 (short peg with a flattened tip) in Nepidae and Belostomatidae and PAS2 (short peg with a tappered tip) in remaining Nepomorpha (Brożek, 2013). Tall peg sensilla (PGUS1), short peg sensilla (PGUS2) and clavate sensilla (CLUS) in Fulgoromorpha (Brożek & Bourgoin, 2013). Subapical: Dome-shaped (PDS) and elongated dome-shaped (UDeS) in Peiratinae (Brożek & Chłond, 2010).…”

“…Both types of sensilla with inflexible sockets. Apical, olfactory: Placoid (OPSM) in Nogodinidae, peg, complex peg, cupola-or dome-shaped in other Fulgoromorpha (Brożek & Bourgoin, 2013). Subapical, olfactory and thermosensitive: Sa-eCLT sensilla (elevated, cone-like to tubular) in Cixiidae, Meenoplidae and Lophopidae; Sa-TeBM sensilla (branched or multilobed tubular) in Delphacidae; however, the placoid sensilla (Sa-PFPL) in Ricaniidae, Dictyopharidae, Tropiduchidae, and Nogodinidae might respond only to odors (Brożek & Bourgoin, 2013), and sensilla placodea (PPLS) in Peiratinae (four species) presumably also have olfactory function (Brożek & Chłond, 2010).…”

“…The first type (PAS1) characteristically has a flattened tip and resembles plate sensilla (Nepidae and Belostomatidae), while the second type (PAS2) in the remaining 11 families of Nepomorpha is similar to peg sensilla (Brożek, 2013). In several species of fulgoromorphan families there are four morphological types of uniporous gustatory peg sensilla on the labial tip [pit peg sensilla (PPSU), peg sensilla tall (PGSU1), peg sensilla short (PGSU2), clavate sensilla (CLSU)] (Brożek & Bourgoin, 2013). Peg and basiconic gustatory sensilla are present also in some other hemipterans.…”

“…The five different multiporous sensilla on the labial tip of fulgoromorphans [placoid (OPSM), peg, peg-complex, cupola, dome-shaped] probably function as olfactory receptors (Brożek & Bourgoin, 2013). In many fulgoromorphan families there are several different sub-apical sensilla (multiporous, multilobed and branched or placoid, placed subapically on the labium in a cavity: Foster et al, 1983;Backus, 1985;Liang, 2005;Brożek & Bourgoin, 2013); possible olfactory and thermosensitive functions have been suggested (Table 1D).…”

“…In many fulgoromorphan families there are several different sub-apical sensilla (multiporous, multilobed and branched or placoid, placed subapically on the labium in a cavity: Foster et al, 1983;Backus, 1985;Liang, 2005;Brożek & Bourgoin, 2013); possible olfactory and thermosensitive functions have been suggested (Table 1D). They have different structure and distribution of dendrites in comparison with the multiporous sensillum on the tip of labium, but their exact function has not been identified (Foster et al, 1983;Backus, 1985).…”