Ultrastructure of the larval antenna of Tenebrio molitor L. (Coleoptera: Tenebrionidae): structure of the blunt-tipped peg and papillate sensilla

Abstract

Each antenna of a final instar Tenebrio molitor larva has two blunt-tipped pegs and two papillate sensilla. The former are short pegs with fluted cuticle and a terminal moulting pore and are set in deep sockets. Two large microtubule-filled dendrites fill a dense dendritic sheath within the peg; below the base of the peg they are joined by a lamellate dendrite and a dendrite resembling a scolopidial cilium. There are four accessory cells, the innermost resembling a scolopale cell. This sensillum may be thermo- and hygro-receptive.Superficially the papillate sensillum is radially symmetrical with a central zone of small cuticular papillae surrounded by one or two rings of smooth cuticle. Three or four dendrites (of five) end under a turret of longer papillae at the center of the papillate cuticle. Fine pores from the dendritic canal extend to the surface between the papillae. One or two dendrites, one of which may be lamellate, end well below the end organ. There are five accessory cells. The sensillar and ciliary sinuses are large and the bounding membranes of the sheath cells highly elaborated. The function of this sensillum is uncertain.

Morphological and Micromorphological Description of the Larvae of Two Endemic Species of Duvalius (Coleoptera, Carabidae, Trechini)

“…Sensilla basiconica have the role of contact chemoreceptors [26]. Trichoid sensilla present on galea and maxillary palps have an olfactory role [51]. Bland et al [52] suggested that these sensilla are involved in the chemoreception of pheromones.…”

Transformation of external sensilla to chordotonal sensilla in thecut mutant ofDrosophila assessed by single-cell marking in the embryo and larva

“…Ch-like features include the presence of the well-developed ciliary rootlet and welldeveloped zonula adherens junctions with the scolopale cell. Although this particular type was not recorded in the only ultrastructural investigation of this organ in (Bloom et al, 1982). C: A range of crustacean mechanoreceptive sense organs.…”

“…A further form of sense organ with mixed neuronal types is the es organ with a single ch-like neuron (Altner and Thies, 1984;Altner et al, 1978;Bloom et al, 1982;Crouau et al, 1987). These multiinnervated sensilla are es-like in most ways except that one ch-like neuron terminates beneath the cuticular peg of a thermo-hygroreceptive sense organ or a chemoreceptive hair (Fig.…”

Electrophysiological and behavioural responses to lactic acid stimuli in larvae of Tenebrio molitor L. (Coleoptera: Tenebrionidae) and permeability of antennal sensilla

“…With this technique, we have identified probable gustatory sensilla on the antennae and the maxillary and labial palps of Tenebrio molitor larvae. Bloom et al (1982a) suggested that the aporous long trichoid and the multiporous U-shaped placoid sensilla on the antennae of T.molitor larvae were chemosensilla based on the morphology of their sensory cuticles and their innervation. Neither type is permeable to aqueous CO++, and therefore both probably respond to lipophilic rather than hydrophilic compounds.…”

“…They described the fine structure of four types of the antennal exterosensilla and, based on this morphology, proposed the following functions. The long aporous hairs on the flagellar tip were presumed to be chemosensory with perhaps some degree of chemospecificity, and the long uniporous pointed pegs on the flagellum and pedicel which are structurally similar to gustatory pegs wcrc considered to have chemosensory and mechanosensory neurones (Bloom et al, 1982a). The unique papillate plates with a central pore were presumed to be gustatory sensilla also, and the aporous short blunt-tipped pegs were assigned a putative thermo-hygrosensing func-tion (Bloom et al, 1982b).…”