The hair plate proprioceptors at the thoraco-coxal joint of insect limbs provide information about the movements of the most basal joint of the legs. The ventral coxal hair plate of a middle leg consists of group of 10-15 long hairs (70 microns) and 20-30 short hairs (30 microns). The long hairs are deflected by the trochantin as the leg is swung forward during the swing phase of walking, and their sensory neurones respond phasically during an imposed deflection and tonically if the deflection is maintained. Selective stimulation of the long hairs elicits a resistance reflex that rotates the coxa posteriorly and is similar to that occurring at the transition from the swing to the stance phase of walking. The motor neurones innervating the posterior rotator and adductor coxae muscles are excited, and those to the antagonistic anterior rotator muscle are inhibited. By contrast, selective stimulation of the short hairs leads only to a weak inhibition of the anterior rotator. The excitatory effects of the long hairs are mediated, in part, by direct connections between their sensory neurones and particular motor neurones. A spike in a sensory neurone elicits a short-latency depolarising postsynaptic potential (PSP) in posterior rotator and adductor motor neurones whose amplitude is enhanced by hyperpolarising current injected into the motor neurone. When the calcium in the saline is replaced with magnesium, the amplitude of the PSP is reduced gradually, and not abruptly as would be expected if an interneurone were interposed in the pathway. Several sensory neurones from long hairs converge to excite an individual motor neurone, evoking spikes in some motor neurones. The projections of the sensory neurones overlap with some of the branches of the motor neurones in the lateral association centre of the neuropile. It is suggested that these pathways would limit the extent of the swing phase of walking and contribute to the switch to the stance phase in a negative feedback loop that relieves the excitation of the hairs by rotating the coxa backwards.
In the field: an interview with Harald Wolf
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In our new Conversation, Harald Wolf talks about his fieldwork experiences working with desert ants in Tunisia to understand their navigation.
Propose a new Workshop
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Our Workshops bring together leading experts and early-career researchers from a range of scientific backgrounds. Applications are now open to propose Workshops for 2024, one of which will be held in a Global South country.
Julian Dow steps down and John Terblanche joins the JEB team
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After 15 years with the journal, Julian Dow from University of Glasgow, UK, is stepping down as a Monitoring Editor. We wish Julian all the best for the future and welcome John Terblanche, Stellenbosch University, South Africa, who is joining the team. Julian talks about his long association with The Company of Biologists and the journal and John tells us about his life and career in this News article.
The capture of crude oil droplets by filter feeders at high and low Reynolds numbers
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Researchers from the University of Montreal, Canada, reveal how tiny filter feeding barnacles and Daphnia entrap and consume minute droplets of crude oil, introducing the pollutant at the bottom of the food chain.
Patterns and processes in amphibious fish
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In their Review, Keegan Lutek, Cassandra Donatelli and Emily Standen discuss the biomechanics and neural control of terrestrial locomotion in amphibious fish. They explore how locomotor mode depends on body shape, physical constraints and phylogeny.
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