Tactile hairs and leg reflexes in wandering spiders: physiological and anatomical correlates of reflex activity in the leg ganglia

Intracellular recordings and Lucifer-yellow fillings were used in a wandering spider,Cupiennius salei Keys., to identify central neuronal correlates of local reflex activity in muscle c2, which inserts on the leg coxa. Here we describe related neuronal elements in the hindleg neuromere of the fused, subesophageal-ganglion complex:

Splitting hairs

A dual-transgenic mouse with localized expression of two different fluorescent markers is the foundation for an inventive strategy for dissecting hair follicles and isolating their component cell populations.     

Tumoral pathology in spiders

The basis of tumoral pathology in spiders is shown through histologic pictures of three different morbid cases, each affecting a particular species. The first two are merely tumors in terms of new growth visualized by gross examination: parietal reaction granuloma of opisthosoma in Peucetia lucasi (Oxyopidae) and hypodermocuticular cyst by ventral tegumentary inclusion in Psechrus alticeps (Psechridae). More original, the third case is a genuine neoplasm in the female genital tract of Pachygnatha clercki (Tetragnathidae). Its heavy invading proliferation exhibits several malignancy criteria but excludes metastasis.     

Vibratory communication in spiders

We analyzed the response of the vibration sensitive lyriform organ on the metatarsus of female spiders (Cupiennius salei) to dummies of male courtship vibrations. One of the two representative slits studied is sharply tuned to 500 Hz. Only the other slit is sensitive enough at lower frequencies to represent the parameters contained in the behaviourally effective dummies:

1. Amplitude. The physiological threshold is similar to the behavioural threshold. The stimulus acceleration amplitudes leading to a good synchronization between response and temporal stimulus pattern coincide with those effectively eliciting a behavioural response. The most frequent spike intervals remain nearly constant in this range. At acceleration amplitudes above the natural range, syllable and pause durations are misrepresented by the receptor response.
2. Frequency. Varying the carrier frequency between 35–500 Hz changes the most frequent spike intervals. Interval histograms resulting from behaviourally effective stimuli (50–200 Hz), however, are similr for carrier frequencies differing by a factor of 2.
3. Temporal pattern. Response duration reflects the temporal parameters of the stimulus. The most frequent spike interval only changes with temporal stimulus characteristics far off the natural range. The number of spikes during a syllable decreases in ongoing stimulus series. The quality of copying the temporal stimulus pattern remains unchanged, however.

     

Chemosensitive conductance and inositol 1,4,5-trisphosphate-induced conductance in snake vomeronasal receptor neurons

Snake vomeronasal receptor neurons in slice preparations were studied using the patch-clamp technique in the conventional and nystatin-perforated whole-cell configurations. The mean resting potential was approximately -70 mV; the average input resistance was 3 GOmega. Neurons required current injection of only 1-10 pA to display a variety of spiking patterns. Intracellular dialysis of 100 microM inositol 1,4,5-trisphosphate (IP(3)) evoked an inward current in 38% of neurons, with an average peak amplitude of 16.4 +/- 2.8 pA at a holding potential of -70mV. Application of 100 microM 3-deoxy-3-fluoro-D-myo-inositol 1,4,5-trisphosphate (F-IP(3)), a derivative of IP(3), also evoked an inward current in 4/8 (50%) neurons (32.6 +/- 58 pA at -70 mV, n = 4). The reversal potentials of the induced components were estimated to be -14 +/- 5 mV for IP(3) and -17 +/- 3 mV for F-IP(3). Bathing the neurons in 10 microM ruthenium red solution greatly reduced the IP(3)-evoked inward current to 1.6 +/- 1.1 pA at -70 mV (n = 6). With Cs(+)-containing internal solution, neither the Ca(2+)-ATPase inhibitor thapsigargin (1-50 microM) nor the Ca(2+)-ionophore ionomycin (10 microM) evoked a significant current response, suggesting that IP(3) can elicit current response in the neurons without mediation by intracellular Ca(2+) stores. Intracellular application of 1 mM cAMP evoked no detectable current response. Extracellular application of chemoattractant for snakes evoked a very large inward current. The reversal potential of the chemoattractant-induced current was similar to that of the IP(3)-induced current. The present results suggest that IP(3) may act as a second messenger in the transduction of chemoattractants in the garter snake vomeronasal organ.     

Arboreal spiders in eastern hemlock

Eastern hemlock [Tsuga canadensis (L.) Carrière] is a foundation species in forests of eastern North America that plays a key role in ecosystem function. It is highly susceptible to the exotic invasive hemlock woolly adelgid (Adelges tsugae Annand), which is causing widespread hemlock mortality. We surveyed the spider communities of eastern hemlock and deciduous canopies over 2 yr, collecting over 4,000 spiders from 21 families. We found that eastern hemlock canopies harbored a more abundant, rich, and diverse spider community than did deciduous canopies. Five spider families were present in our hemlock collections that were absent from the deciduous collections, including Mysmenidae, Theridiosomatidae, Mimetidae, Lycosidae, and Agelenidae. In hemlock canopies there were 4× the number of web builders, consisting primarily of the Tetragnathidae and Araneidae, than active hunters, consisting primarily of the Anyphaenidae and the Salticidae. Ours is the first in depth study of the spider community in eastern hemlock. Spider abundance in hemlock canopies suggest that they may play a role regulating herbivore populations, and could possibly affect the invasive hemlock woolly adelgid, either through direct consumption of the adelgids themselves or through interactions with classical biological control agents.     

The hypochilomorph spiders

A group of five genera of spiders has in the past been placed in a special sub-order the Hypo-chilomorpha, lying between the Mygalomorpha and the Araneomorpha. In general they resemble the araneomorphs, but they share some primitive characters, notably the presence of two pairs of lungs. Four of them, Hypochilus, Ectatosticta, Hickmania and Austrochilus have a cribellum, while Gradungula does not. In attempting to determine their relationships, their internal anatomy is here compared with that of the members of the three main suborders, Liphis-tiomorpha, Mygalomorpha and Araneomorpha. The conclusion arrived at is that these genera belong to the Araneomorpha, and that there should not be a suborder Hypochilomorpha. Hypochilus and Ectatosticta are very similar and are placed in the family Hypochilidae, while the other three are placed in individual families. Within the Araneomorpha there seem to be two evolutionary lines. In one, the Cribellata, the anterior median spinnerets of the ancestor remained functional and became the cribellum. In the other, the Ecribellata, the anterior median spinnerets lost their function and became vestigial or absent. The most primitive cribel-late family is the Hypochilidae, while the Gradungulidae is the most primitive ecribellate one, at least with respect to its lungs and heart.     

How plants split hairs

The unicellular three-branched trichomes, or 'hairs', of Arabidopsis provide a model system for studying cell morphogenesis in plants. Recent results, including the characterization of a newly identified mutant with multicellular trichomes, have led to a new view of how trichome morphogenesis might be controlled.