Foreleg Tibia Research Articles

A New Genus of Crickets (Orthoptera: Gryllidae) in Mid-Cretaceous Myanmar Amber

Crickets (Orthoptera: Grylloidea) are a highly diverse and successful group that due to their chirping are often heard more often than they are seen. Their omnivorous diet allows them to exist in a variety of terrestrial habitats around the world. In some environments, cricket populations can build up and become plagues, resulting in significant damage to seedling crops. A new genus and species of cricket, Pherodactylus micromorphus gen. et sp. nov. (Orthoptera: Gryllidae) is described from mid-Cretaceous Myanmar amber. The new genus is characterized by the following features: head without prominent bristles, pronotum longer than wide, middle of pronotal disk with two distinct large dark “eyespots”, fore leg robust and 3 apical spurs arranged on inner side of fore leg tibia. Shed portions of a lizard skin adjacent to the specimen reveal possible evidence of attempted predation.

A New Genus of Crickets (Orthoptera: Gryllidae) in Mid-Cretaceous Myanmar Amber

Crickets (Orthoptera: Grylloidea) are a highly diverse and successful group that due to their chirping are often heard more often than they are seen. Their omnivorous diet allows them to exist in a variety of terrestrial habitats around the world. In some environments, cricket populations can build up and become plagues, resulting in significant damage to seedling crops. A new genus and species of cricket, Pherodactylus micromorphus gen. et sp. nov. (Orthoptera: Gryllidae) is described from mid-Cretaceous Myanmar amber. The new genus is characterized by the following features: head without prominent bristles, pronotum longer than wide, middle of pronotal disk with two distinct large dark “eyespots”, fore leg robust and 3 apical spurs arranged on inner side of fore leg tibia. Shed portions of a lizard skin adjacent to the specimen reveal possible evidence of attempted predation.

The complex tibial organ of the New Zealand ground weta: sensory adaptations for vibrational signal detection

In orthopteran insects, a complex tibial organ has evolved to detect substrate vibrations and/or airborne sound. Species of New Zealand weta (Anostostomatidae) with tympanal ears on the foreleg tibia use this organ to communicate by sound, while in atympanate species (which communicate by substrate drumming) the organ is unstudied. We investigated the complex tibial organ of the atympanate ground weta, Hemiandrus pallitarsis, for vibration detection adaptations. This system contains four sensory components (subgenual organ, intermediate organ, crista acustica homolog, accessory organ) in all legs, together with up to 90 scolopidial sensilla. Microcomputed tomography shows that the subgenual organ spans the hemolymph channel, with attachments suggesting that hemolymph oscillations displace the organ in a hinged-plate fashion. Subgenual sensilla are likely excited by substrate oscillations transmitted within the leg. Instead of the usual suspension within the middle of the tibial cavity, we show that the intermediate organ and crista acustica homolog comprise a cellular mass broadly attached to the anterior tibial wall. They likely detect cuticular vibrations, and not airborne sound. This atympanate complex tibial organ shows elaborate structural changes suggesting detection of vibrational stimuli by parallel input pathways, thus correlating well with the burrowing lifestyle and communication by substrate-transmitted vibration.

Spatial organization of tettigoniid auditory receptors: Insights from neuronal tracing

The auditory sense organ of Tettigoniidae (Insecta, Orthoptera) is located in the foreleg tibia and consists of scolopidial sensilla which form a row termed crista acustica. The crista acustica is associated with the tympana and the auditory trachea. This ear is a highly ordered, tonotopic sensory system. As the neuroanatomy of the crista acustica has been documented for several species, the most distal somata and dendrites of receptor neurons have occasionally been described as forming an alternating or double row. We investigate the spatial arrangement of receptor cell bodies and dendrites by retrograde tracing with cobalt chloride solution. In six tettigoniid species studied, distal receptor neurons are consistently arranged in double-rows of somata rather than a linear sequence. This arrangement of neurons is shown to affect 30-50% of the overall auditory receptors. No strict correlation of somata positions between the anterio-posterior and dorso-ventral axis was evident within the distal crista acustica. Dendrites of distal receptors occasionally also occur in a double row or are even massed without clear order. Thus, a substantial part of auditory receptors can deviate from a strictly straight organization into a more complex morphology. The linear organization of dendrites is not a morphological criterion that allows hearing organs to be distinguished from nonhearing sense organs serially homologous to ears in all species. Both the crowded arrangement of receptor somata and dendrites may result from functional constraints relating to frequency discrimination, or from developmental constraints of auditory morphogenesis in postembryonic development.

Visual stimuli that elicit visual tracking, approaching and striking behavior from an unusual praying mantis, Euchomenella macrops (Insecta: Mantodea)

In comparison to other similarly sized mantis species examined in previous studies, Euchomenella macrops has a significantly smaller head, shorter foreleg tibia, but longer prothorax which have been interpreted as specializations for the capture of smaller, slower prey. We tested this conjecture by assessing the rates at which computer generated stimuli elicit visual tracking, approaching, and striking behaviors by adult females. When presented with black disks moving erratically against a white background, strike rate rose progressively as disks enlarged up to 44deg (visual angle) if the disks moved rapidly (e.g., 143deg/s); at slower speeds (113, 127deg/s), smaller disks (<27deg) were preferred. When black moved linearly from the visual periphery to visual field center (at 73 or 143deg/s) and then stopped, E. macrops struck consistently at disks as small as 5deg after movement ceased. E. macrops also struck at higher rates in response to 23deg erratically moving (subjective) red (versus subjective blue or green) disks that were luminance matched to a grey background although they tracked all colors at equally high rates. Unlike some other species, E. macrops did not strike at higher rates in response to elongated rectangular stimuli moving parallel (versus perpendicular) to their long axis, although the former elicited higher rates of approaching. An analysis of tracking behavior revealed that virtually all tracking movements were a result of head (versus) prothorax rotation.

Effects of morphological traits, age and copulation experience on mate choice in Ophraella communa

Ophraella communa is a biological control agent of invasive common ragweed, Ambrosia artemisiifolia. To understand the mate choice tactic of the beetle and improve mass-rearing of high-quality populations, the effects of morphological traits, age and copulation experience on mate choice in this beetle were studied in the laboratory. The results showed thatmate choice of male or female was related to certain adult morphological traits. Wing length, black streak width of frons and metaleg femur length of males were central to female mate choice. Females with longer wing length, black streak width of frons, pronotum width and foreleg tibia length were more attractive to males than those with the smaller ones. The chosen rate of older males was significantly higher than those of younger ones, and the chosen rate of females reached a maximum value on the 8th day after eclosion. The newly copulated females were less attractive to males than virgins, but females that have copulated in the distant past were more attractive than or were similar to virgins. The chosen rates of virgin males were significantly higher than those of newly copulated and 8 days past copulated ones, but no difference between virgin males and 3, 5 or 12 days past copulated ones in O. communa. The results of our study have added much needed empirical data regarding the significance of morphological traits, age and copulation experience as a source of variation in insect copulation signals. In addition, the results provide valuable information for mass-rearing of high-quality populations of O. communa.

The evolutionary origin of auditory receptors in Tettigonioidea: the complex tibial organ of Schizodactylidae

Audition in insects is of polyphyletic origin. Tympanal ears derived from proprioceptive or vibratory receptor organs, but many questions of the evolution of insect auditory systems are still open. Despite the rather typical bauplan of the insect body, e.g., with a fixed number of segments, tympanal ears evolved at very different places, but only ensiferans have ears at the foreleg tibia, located in the tibial organ. The homology and monophyly of ensiferan ears is controversial, and no precursor organ was unambiguously identified for auditory receptors. The latter can only be identified by comparative study of recent atympanate taxa. These atympanate taxa are poorly investigated. In this paper, we report the neuroanatomy of the tibial organ of Comicus calcaris (Irish 1986), an atympanate Schizodactylid (splay-footed cricket). This representative of a Gondwana relict group has a tripartite sensory organ, homologous to tettigoniid ears. A comparison with morphology-based cladistic phylogeny indicates that the tripartite neuronal organization present in the majority of Tettigonioidea presumably preceded evolution of a hearing sense in the Tettigonioidea. Furthermore, the absence of a tripartite organ in Grylloidea argues against a monophyletic origin and homology of the cricket and katydid ears. The tracheal attachment of sensory neurons typical for ears of Tettigonioidea is present in C. calcaris and may have facilitated cooption for auditory function. The functional auditory organ was presumably formed in evolution by successive non-neural modifications of trachea and tympana. This first investigation of the neuroanatomy of Schizodactylidae suggests a non-auditory chordotonal organ as the precursor for auditory receptors of related tympanate taxa and adds evidence for the phylogenetic position of the group.

Developmental stability and predation success in an insect predator-prey system

I investigated the relationships among developmental stability (as measured by individual bilateral asymmetry values), two measures of locomotory performance and predation success in an insect predator-prey system. In this system yellow dungflies Scathophaga sttrcoraria preyed upon houseflies Musco domtstica in laboratory-controlled conditions. There was no relationship between locomotion and absolute asymmetry or mean size of two morphological traits (fourth longitudinal wing vein, foreleg tibia) in either species. Analysis of single predation trials indicated that locomotion performance and trait size are not associated with the probability of predation. However, Musca that were captured had tibia that were more asymmetric than Musca that survived. Similarly, Scathophaga that were successful predators had more symmetric forelegs than unsuccessful predators. There was no relationship between predation and wing vein asymmetry, which may indicate the importance of terrestrial-based predatory avoidance tactics in this system. There were no relationships between morphology or locomotion with predation latency, prey handling times, or the number of times a prey escaped from a predator. The mechanisms behind the relationship between tibia asymmetry and predation success are discussed. This is the first experiment to reveal direct evidence for selection for symmetric, devdopmentally stable individuals through differential predation.

Artificial selection for a secondary sexual character in males of Drosophila silvestris from Hawaii

Drosophila silvestris is endemic to the rain forests of Hawaii Island. In populations from the northeast side, the male foreleg tibia bears about 100 long cilia; these are used as a brush to stimulate the female during courtship. Cyclical family selection for high and low cilia number was carried out on progeny of lines started from single wild isofemales collected at a single site. Significant response in both directions was obtained; in the third generation the lines differed by a mean of 25 cilia. Despite much effort to save them, both lines died out without further advance; the low cilia number line died after five and the high cilia number line died after nine generations. The data are compatible with the view that the cilia character is polygenic and is maintained in nature by a stabilizing sexual selection that also favors a polygenic heterozygous state. Although selection in these experiments resulted in dysgenesis, such a result is not inevitable. Disorganization and reorganization of such a genetic system following a population bottleneck might be important as a predisposing condition for the emergence of a specifically novel and possibly isolating mode of courtship.

Change in a secondary sexual character as evidence of incipient speciation in Drosophila silvestris

Search for genetic changes that are pivotal in species formation has led to intraspecific studies of Drosophila silvestris, a giant species found only on the geologically new island of Hawaii. Males bear large, curved, modified bristles or cilia on the dorsal surface of the foreleg tibia and tarsus. In males from the south and west parts of the island there are two rows of cilia separated by a naked area, but in males from the north and east there is a mean of between 20 and 30 additional cilia between the two major rows on the tibia. These extra cilia are absent in closely related species of this subgroup, including the sympatric species D. heteroneura and three species from adjacent islands. Males use the foreleg tibiae in vibratory movements against the female's abdomen during courtship, so this character difference is likely to be important in the reproductive biology of the species. Inversion polymorphisms are similar in both northeast and southwest populations; they show large and strikingly parallel altitudinal shifts in frequency distributions involving the same inversions. Populations from various parts of the island cannot be distinguished by routine electrophoresis of soluble proteins encoded by 25 loci. Thus the "extra cilia" character is superimposed on a more ancient genetic background of similarity involving both chromosomal and electrophoretic polymorphisms. We interpret the extra cilia as a specific new embellishment of a secondary sexual character brought about by altered sexual selection occurring very recently in one part of the species range. This suggests incipient speciation.

A light and electron microscopic study of sensory organs and associated structures in the foreleg tibia of the cricket, Gryllus assimilis.

AbstractEarly descriptions of insect sensory organs included three presumed mechanotransducers in the tibia of Orthoptera, namely the subgenual organ, the intermediate organ, and the tympanal organ. This investigation re‐evaluates the light microscopic appearances of these organs in the foreleg tibia of the cricket, Gryllus assimilis, initially described by Herbig in 1902.The study also examines the fine structure of the subgenual and intermediate organs and provides the first fine structure analysis of these structures.The subgenual and intermediate organs are typical scolopophorus organs suspended perpendicular to each other within the dorsal hemolymph canal. Each is innervated by dendrites from the anterior ganglion. Neither the subgenual, intermediate, nor tympanal organ is structurally related to the larger posterior tympanic membrane.The study shows that the tibial tympanal organ in the cricket is not a scolopophorus organ, but consists of highly modified epithelium, associated with the anterior tympanic membrane, and receiving innervation from the anterior ganglion.

An electron microscopic study of the tympanal organ and associated structures in the foreleg tibia of the cricket, Gryllus assimilis.

AbstractEarly descriptions of insect sensory organs included three presumed mechanotransducers in the tibia of Orthoptera, namely the subgenual organ, the intermediate organ, and the tympanal organ. The following study examines the fine structure of the tympanal organ in the foreleg tibia of the cricket, Gryllus assimilis. This investigation provides the first fine structure analysis of this structure and shows that the tibial tympanal organ is not a scolopophorus organ. It consists of highly modified epithelium, associated with the anterior tympanic membrane, and receives innervation from the anterior ganglion.