Between extreme simplification and ideal optimization: antennal sensilla morphology of miniaturized<i>Megaphragma</i>wasps (Hymenoptera: Trichogrammatidae)

Diakova, Anna V.; Makarova, Anastasia A.; Polilov, Alexey A.

doi:10.7717/peerj.6005

Cited by 15 publications

(13 citation statements)

References 56 publications

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“…Ultrastructural complexity may be a further limit on size, but this may vary depending on the specific phenotype. The observations of Diakova, Makarova & Polilov (2018) on the antennal sensilla arrays of Megaphragma , for example, are in line with these expectations. Diakova et al .…”

Section: Discussionsupporting

confidence: 71%

Functional diversity of attachment and grooming leg structures is retained in all but the smallest insects

et al. 2020

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Miniaturization strongly affects functional morphology. Whereas some anatomical structures are barely affected by scaling, others can fundamentally change as the body becomes ever smaller. No prior study has focused on the effect of miniaturization on grooming and attachment structures in Hymenoptera, which can be highly diverse and complex. Through comparative description of the legs of the extremely small wasps of the families Mymaridae and Trichogrammatidae, we evaluate the functional and phylogenetic patterns concerning possible functional effects of miniaturization. On the one hand, the studied species retain some features characteristic of other Chalcidoidea, while on the other, they display some parallelisms associated with miniaturization in leg structure. These observations support a two‐stage morphocline of miniaturization, wherein the first stage is characterized by the preservation of structural complexity and retention of all basic functions, as for instance in examined Megaphragma and the females of Dicopomorpha. The second stage is characterized by a significant simplification, with the loss of redundant non‐essential functions, as observed for the males of Dicopomorpha, which have grossly reduced leg structures, including total loss cleaning devices. Whether these stages are ordered or unordered should be evaluated in future study. Functional optimization of attachment in male Dicopomorpha is indicated by the highly derived mushroom‐shaped tarsi, complemented by novel grappling spurs on the hindfeet, possibly for copulation. Our observations underline adaptive trade‐offs in the expression of complex and multifunctional leg structures at extreme scales.

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Section: Discussionsupporting

confidence: 71%

Functional diversity of attachment and grooming leg structures is retained in all but the smallest insects

et al. 2020

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“…The earlier examination (Diakova et al 2018) and our re-examination of the external microsculpture of the PS after sputtering with gold 20-25 nm thick using a Giko IB-3 system did not reveal any pores, and irregularities of sputtering were found on the cuticle surface (Fig. 1B, C).…”

Section: Resultsmentioning

confidence: 50%

“…The study of the external morphology and microsculpture of the placoid sensilla (PS) was performed by Focused Ion Beam Scanning Electron Microscopy (FIB-SEM) and Scanning Electron Microscopy (SEM). The SEM used was a Jeol JSM-6380 (accelerating voltage (AV) 20-30 kV, working distance (WD) 10-20 mm) and FEI Inspect F50 (AV 10 kV, WD 5-10 mm), following fixation, dehydration, critical-point drying, and gold sputtering of the specimens (Giko IB-3, sputtering thickness 20-25 nm; for more details see Diakova et al (2018)). Additionally, we studied samples prepared according to the same protocol but with chromium sputtering (Cressington 208HR, sputtering thickness 15 nm, orbital rotation with an inclination of up to 45°) using an FEI Quattro S microscope in the environmental SEM mode (ESEM, AV 5-10 kV, WD 10 mm, Pressure 200 Pa, water vapor) or gold sputtered under the same conditions and using the same microscope, but in the high vacuum mode (HV, AV 8-15 kV, WD 5-10 mm).…”

Section: Methodsmentioning

confidence: 99%

“…The third flagellomere of the female antenna of the parasitic wasp Megaphragma (Hymenoptera: Trichogrammatidae) bears two peculiar placoid sensilla (PS), described as having no pores (Diakova et al 2018), which would fundamentally distinguish them from other hymenopteran placoid sensilla and raise doubts about their possible sensory function. Since Megaphragma wasps are extremely miniaturized insects, the presence of non-functional sensory organs in them is unlikely.…”

Section: Introductionmentioning

confidence: 99%

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Porous or non-porous? The challenge of studying unusual placoid sensilla of Megaphragma wasps (Hymenoptera, Trichogrammatidae) with electron microscopy

Diakova¹,

Polilov²

2021

JHR

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Extreme miniaturization implies a high degree of optimization, rendering the retention of non-functional organs almost impossible. Two unique non-porous placoid sensilla on the antennae of females of Megaphragma were described in the literature. Placoid sensilla in Hymenoptera have an olfactory function and always bear pores; the apparent absence of pores therefore raises the questions whether such sensilla are functional in Megaphragma and whether their surface sculpture had been sufficiently well examined. We examined in detail the external microsculpture and internal ultrastructure of the placoid sensilla using Focused Ion Beam Scanning Electron Microscopy and Scanning Electron Microscopy with various types of sputtering and show that these sensilla actually have a porous cuticle and are innervated by 11 or 12 neurons with branched cilia, which is typical of olfactory sensilla. Comparison of various methods of electron microscopy allows us to conclude that for an accurate determination of the morphofunctional types of sensilla, especially in miniature insects, it is necessary to study both the internal ultrastructure of the sensilla and their external morphology using carefully selected scanning electron microscopy methods.

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“…It is generally believed that the antennae and/or sensilla of insects are the result of long‐term adaptation to specific environment (Baaren, Boivin, Bourdais, & Roux, 2007; Meng, Pu, Xiao, & Huang, 2015). The close evolutionary relationships among the insects have the similar sensilla types (Amornsak, Cribb, & Gordh, 1998; Diakova, Makarova, & Polilov, 2018; Gomez‐Dominguez et al, 2018; Heraty et al, 2013; Huang et al, 2017). It's helpful to understand the type and function of antennal sensilla in X. quadripes by consulting the same family and genus in other longhorn beetle sensilla.…”

Section: Discussionmentioning

confidence: 99%

Morphology and distribution of antennal sensilla in adults of Xylotrechus quadripes

Yang

Shan²,

Liu

et al. 2021

Microscopy Res & Technique

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Xylotrechus quadripes (Chevrolat) is the serious woodborer pest of arabica coffee (Coffea arabica L.). To further elucidate the behavior mechanism of the insect based on chemical odorant and to advance effective trapping methods, the typology, distribution, and abundance of antennal sensilla were investigated meticulously in both sexes of X. quadripes by scanning electron microscopy. The filiform antennae of both sexes are composed of 11 segments, namely the scape, pedicel, and nine flagellomeres (f1-9). Ten types (14 subtypes) of sensilla were identified morphologically: sensilla chaetica (three subtypes, Ch.1-3), sensilla basiconica (three subtypes, Ba.1-3), Böhm bristles (Bb), sensilla dentiform (De), sensilla trichodea (Tr), sensilla auricillica (Au), sensilla campaniformia (Ca), grooved peg sensilla (Gp), cuticular pores (Cp), and a newly observed sensillum, named sensilla cone (Cone). The sensilla were mainly distributed in flagellomeres, and the types and amounts increased in frequency from scape to the ninth flagellomere. The numbers of sensilla were the highest on the antennal dorsal side, while the lowest on the ventral side. The types of sensilla were the most abundant on the lateral side, and two sensilla basiconica (Ba.1-2) were found exclusively. The average number of Tr, Ba, and Au on the antenna of the males was significantly greater than females, while the Gp and Cp on the antenna of the females were significantly greater than males. Ca was exclusively occurred on the male antennae but was absent in females. This study discusses the putative functions of the antennal sensilla in adults of X. quadripes based on their characteristics in related species' sensilla, and these results provide an important foundation to clarify the ecological adaption, olfactory recognition mechanism, and to develop the chemical ecology control of X. quadripes.

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Between extreme simplification and ideal optimization: antennal sensilla morphology of miniaturizedMegaphragmawasps (Hymenoptera: Trichogrammatidae)

Cited by 15 publications

References 56 publications

Functional diversity of attachment and grooming leg structures is retained in all but the smallest insects

Functional diversity of attachment and grooming leg structures is retained in all but the smallest insects

Porous or non-porous? The challenge of studying unusual placoid sensilla of Megaphragma wasps (Hymenoptera, Trichogrammatidae) with electron microscopy

Morphology and distribution of antennal sensilla in adults of Xylotrechus quadripes

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