A new species of Chiridurothrips Okajima from Miocene amber of the Dominican Republic (Thysanoptera: Phlaeothripidae)

The thysanopteran genus Chiridurothrips Okajima is known from a single extant species, C. hisakoae Okajima, collected in Japan (ThripsWiki 2019). Occurring on dead leaves and branches of evergreen trees in the subtropical Ryukyu Islands, this species remains known from only five females (Okajima 1981, 2006; also pers. comm. 2018). Within Phlaeothripidae, Chiridurothrips is associated with the tribe Plectrothripini. Species of this sub-group feed on fungal hyphae or the break-down products of fungal attack on decaying plant material (Mound & Ng 2018). They are found mainly under the bark of trees or on dead branches, and they do not seem to inhabit leaf-litter (Okajima 1981). At present, Plectrothripini comprises 60 extant species in 13 genera, with no fossils recorded. Of these species 32 are placed in the genus Plectrothrips Hood, ten in Streptothrips Priesner, and six in Chirothripoides Bagnall, whereas both Menothrips Hood and Mastigothrips Priesner each include only two species. The remaining eight species are all placed in separate monobasic genera (ThripsWiki 2019). Concerning this strongly asymmetric classification, Mound and Ng (2018) suggest that Plectrothripini might be particularly old, with the large number of monobasic genera each representing a relict lineage. An alternative possibility, however, might be an unusual instability in the genes controlling morphogenetic processes, and thus resulting in striking autapomorphies on which each one of these genera is diagnosed (Mound & Ng 2018). Species associated with Plectrothripini share the following character states (Okajima 1981; Mound & Tree 2017): antennae 8-segmented, segment II with the campaniform sensillum situated in the basal half, III–IV with stout sense cones, VIII slender with narrow base; head with posterior ocelli close to compound eyes; pronotum commonly with sclerotized plate eroded or reduced, prosternal basantra week or absent; legs with fore tarsal tooth large; mid and hind tibiae commonly with apical spur-like setae; macropterae with fore wings parallel-sided, usually with duplicated cilia; pelta broad at base, abdominal tergite II eroded laterally; abdominal sternites often with reticulate glandular areas. Regarding the fore wings, it seems worth mentioning that in some members of Plectrothripini the subbasal wing vein is reduced and thus the three subbasal wing setae are lacking (see Plectrothrips tenuis Okajima, Chiridurothrips [c.f. fig. 2], Chirothripoides, Lonchothrips Hood; Bhatti 1998; Okajima 1981). This short vein that is present in (almost all) other macropterous Phlaeothripidae has been interpreted as a plesiomorphic feature that resulted from the reduction of a former well-developed longitudinal first vein of ancestral Tubulifera, the Rohrthripidae (Ulitzka 2018, 2019).

Ultrastructural organization of NompC in the mechanoreceptive organelle of Drosophila campaniform mechanoreceptors

Mechanoreceptive organelles (MOs) are specialized subcellular entities in mechanoreceptors that transform extracellular mechanical stimuli into intracellular signals. Their ultrastructures are key to understanding the molecular nature and mechanics of mechanotransduction. Campaniform sensilla detect cuticular strain caused by muscular activities or external stimuli in Drosophila. Each campaniform sensillum has an MO located at the distal tip of its dendrite. Here we analyzed the molecular architecture of the MOs in fly campaniform mechanoreceptors using electron microscopic tomography. We focused on the ultrastructural organization of NompC (a force-sensitive channel) that is linked to the array of microtubules in these MOs via membrane-microtubule connectors (MMCs). We found that NompC channels are arranged in a regular pattern, with their number increasing from the distal to the proximal end of the MO. Double-length MMCs in nompC29+29ARs confirm the ankyrin-repeat domain of NompC (NompC-AR) as a structural component of MMCs. The unexpected finding of regularly spaced NompC-independent linkers in nompC3 suggests that MMCs may contain non-NompC components. Localized laser ablation experiments on mechanoreceptor arrays in halteres suggest that MMCs bear tension, providing a possible mechanism for why the MMCs are longer when NompC-AR is duplicated or absent in mutants. Finally, mechanical modeling shows that upon cuticular deformation, sensillar architecture imposes a rotational activating force, with the proximal end of the MO, where more NOMPC channels are located, being subject to larger forces than the distal end. Our analysis reveals an ultrastructural pattern of NompC that is structurally and mechanically optimized for the sensory functions of campaniform mechanoreceptors.

Morphology of the first instar nymph of Leucaspis loewi Colvée (Hemiptera: Coccinea: Diaspididae)

Morphology of the first instar nymph of Leucaspis loewi Colvée (Hemiptera: Coccinea: Diaspididae) The first instar nymph of Leucaspis loewi Colvée is redescribed and illustrated. The sex has not been determined. It has 5-segmented antennae, one trilocular disc pore associated with the anterior spiracle, one pair of well-developed lobes, and fimbriate plates on all abdominal segments. Tibia and tarsus are not fused - they are separated from each other by a septum. A campaniform sensillum is always present at the bases of the tarsi. Dorsal submedian setae are present on each abdominal segment 1-7.

Scanning Electron Microscopy of Antennal Sense Organs in Prosapia bicincta (Say) (Hemiptera: Cercopidae)

The external morphology of the sensilla on the antennae of the adult spittlebug, Prosapia bicincta (Say) (Hemiptera: Cercopidae), is described for the first time, using scanning electron microscope observations. The sensilla include one peg-like basiconic sensillum (about 65.05 to 65.90 μ in length and 13.33 to 14.08 μ in width at base), 18 to 23 porous coeloconic sensilla (mostly 7.38 to 8.94 μ in diam), one campaniform sensillum and a cluster of trichoid sensilla (about 45 to 55 (μ long). The first two types of sensilla are located on the expanded flagellar base, while the latter two sensilla are on the pedicel.

Cholinergic synaptic transmission between proprioceptive afferents and a hind leg motor neuron in the locust

1. The physiology and pharmacology of the connections made by stress-sensitive campaniform sensilla on the proximal dorsal tibia of a locust hind leg with a fast extensor tibiae motor neuron (FETi) have been examined. 2. Mechanical stimulation of a campaniform sensillum on the anterior surface of the tibia elicited bursts of spikes in its afferent and a depolarization in FETi. Each afferent spike was followed at short and constant latency by an excitatory postsynaptic potential (EPSP) in FETi, even at high-frequency stimulation. Electrical stimulation of the extensor tibiae muscle with the tibia fixed elicited an antidromic spike in FETi followed by a compound potential which resulted from the activation of the campaniform sensillum afferent. The connections between the campaniform sensillum and FETi was monosynaptic and chemically mediated. 3. Ionophoresis of ACh into the neuropil depolarized FETi, as did the application of the cholinesterase inhibitor physostigmine. Bath application of the cholinergic agonists, nicotine and muscarine, also depolarized FETi, with nicotine causing a reduction in input resistance, while muscarine caused no detectable change in input resistance. Muscarine and the muscarinic agonist oxotremorine also caused rhythmic depolarizations and bursts of spikes in FETi. These effects were seen in low calcium/high magnesium saline to block synaptic transmission and are therefore due to direct effects on FETi. FETi therefore appears to have both nicotinic and muscarinic receptors. 4. The compound potential in FETi, caused by activation of the campaniform sensillum, was reduced by bath application of nicotinic cholinergic antagonists. However, the muscarinic antagonist scopolamine increased the amplitude of the compound potential.(ABSTRACT TRUNCATED AT 250 WORDS)

Ultrastructure of the aporous sensilla on the galea of larval Mamestra configurata (Walker) (Lepidoptera: Noctuidae)

The galea of fifth-instar Bertha armyworms, Mamestra configurata, has three types of aporous sensilla: one spire-shaped basiconic peg, two short basiconic pegs, and one campaniform sensillum. The spire-shaped peg is set in an inflexible socket, innervated by three bipolar neurons, and enveloped by three sheath cells. One microtubule-laden dendrite completely fills the distal portion of the dendritic sheath and ends within the peg. It is joined by a lamellate and a scolopidium-like dendrite that end near and below the base of the peg, respectively. The ciliary sinus is large and the membrane of the enveloping inner sheath cell is highly elaborate. This sensillum exhibits features characteristic of thermo-hygrosensilla. The short basiconic pegs and campaniform sensillum are each innervated by a single bipolar neuron and each is associated with three sheath cells. In both sensilla, the dendrite ends in a tubular body, typical of mechanosensilla.