Morphology of chemosensory organs required for feeding in the leechhirudo medicinalis

Abstract

Sensilla that line the upper edge of the lip in the leech Hirudo medicinalis and that contain chemoreceptors required for feeding were examined in the scanning and transmission electron microscopes. The sensilla include two size-classes of ciliated button-like mounds--one about 35 microns in diameter and another about 10 microns in diameter. The larger sensilla are at the center of unpigmented patches of skin which are visible in the light microscope, while the smaller sensilla have not been previously described as distinct structures. Electron microscopy, though not light microscopy, shows that the lip sensilla differ markedly from the segmental sensilla of the leech, which have been shown to mediate mechanoreception and photoreception. In particular, the chemosensory lip sensilla contain multiciliated cells with cilia of a uniform length, whereas the segmental sensilla contain uniciliated cells with long, whip-like cilia, as well as multiciliated cells with short, stiff cilia. Thus, the two types of sensilla differ morphologically as well as functionally. In addition to the ciliated sensilla along the upper lip, structures consisting of a short, club-like process surrounded by granular material were observed inside the mouth. These structures may also be chemosensory organs.

Copper-Impaired Chemosensory Function and Behavior in Aquatic Animals

“…In either case, leeches rely on chemosensation to locate potential food sources. This is evidenced by the development of specialized chemoreceptors, which are found in three different areas of the leech body: (i) spread diffusely over the body; (ii) surrounding the dorsal lip; and (iii) in a specialized chemosensory epithelium lining the gut to facilitate post-ingestive food sampling (Elliot 1987;Kornreich and Kleinhaus 1999).…”

Leech photoreceptors project their galectin-containing processes into the optic neuropils where they contact AP cells

“…In all embryos, the axons of these photoreceptors were significantly more strongly stained than the cell bodies. Immunostained axons were observed to emanate from the eyes, but not from any other sensory organs in the head such as the lip sensilla which contain chemoreceptors (Elliott, 1987). To demonstrate that antibody was able to penetrate into all head nerves under these conditions, sibling embryos were treated with mAb Lazl-1 (not shown here) which readily stained the axons of chemoreceptors emanating from the lip sensilla (Zipser et al, 1994).…”

Sanguessugas parasitas da ordem Rhyncobdellida (Clitellata: Hirudinida) do território brasileiro

“…Esta confusão pode estar associada ao uso da expressão "papilas segmentares", usada por Pinto (1923). Apesar de não deixar claro a natureza da estrutura estudada, Pinto (1923) Elliott (1987), as sensilas localizadas próximas aos lábios da ventosa oral diferem em tamanho, distribuição e comprimento dos cílios.…”

“…Elliott (1987) apresentou resultados semelhantes ao estudar o tegumento de Hirudo medicinalis, onde dois principais tipos de estruturas foram identificados, as sensilas labiais pequenas e grandes.…”

“…Desta forma, optou-se pela utilização apenas do termo "tubérculo", já que não foi verificada qualquer diferença externa entre as estruturas apontadas na literatura. Este termo foi escolhido, pois se diferencia das estruturas descritas por Elliott (1987), as sensilas, tradicionalmente consideradas como órgãos sensoriais e sempre localizadas nos anéis a2, correspondendo à localização dos gânglios nervosos ventrais nos segmentos. Os tubérculos observados neste estudo, apesar de apresentarem padrão metamérico, normalmente não estão restritos ao anel a2.…”