6533b833fe1ef96bd129b672

RESEARCH PRODUCT

Ultrastructure of a muscle spindle-analogous receptor organ in the mandible of Oncopeltus fasciatus (Insecta, Heteroptera) with remarks on the homology of the mandibular muscles

subject

description

A non-ciliary muscle receptor organ in the first mandibular retractor muscle of Oncopeltus fasciatus is described. The organ consists of two specialized muscle fibres of the first retractor, which are embedded in a thickened layer of connective tissue. The sensory innervation is supplied by three multiterminal sense cells sending several dendrites to the receptor muscle fibres. ‘Naked’ dendritic terminals are attached to the muscle surface or connective tissue fibrils. The far-reaching analogy of the receptor to the intrafusal chain-fibres of vertebrate muscle spindles is remarkable. The existence of a muscle receptor organ in the first mandibular retractor may serve as an argument in favor of the homology of this muscle with the musculus tentorio-mandibularis of orthopteroid insects.