Ultrastructure of the water‐movement‐sensitive sensilla in the medicinal leech

Phillips, C. E.; Friesen, W. Otto

doi:10.1002/neu.480130603

Cited by 50 publications

(35 citation statements)

References 15 publications

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“…Leeches possess constellations of peripheral sensory neurons that extend axons into the CNS (Laverack, 1969;Kretz et al, 1976;Gascoigne and McVean, 1993), many of which are clustered in discrete sensilla along the central annulus of each midbody segment (Derosa and Friesen, 1981;Philips and Friesen, 1982;McVean et al, 1990). The axons of the sensillar neurons have been examined using monoclonal antibodies and have been shown to project in tightly fasciculated bundles (McKay et al, 1983;Peinado et al, 1987bPeinado et al, , 1990Johansen et al, 1992) into the CNS whereupon they segregate into a limited number (initially 3, later 4) of stereotyped fascicles in each of the central interganglionic connectives.…”

Section: Jellies Et Almentioning

confidence: 97%

Specific pathway selection by the early projections of individual peripheral sensory neurons in the embryonic medicinal leech

Jellies

Johansen²,

Johansen³

1994

J. Neurobiol.

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In leech, the central annulus of each midbody segment possesses seven pairs of sensilla, which are mixed clusters of primary peripheral sensory neurons that extend their axons into the CNS where they segregate into distinct fascicles. Pathway selection by individual afferent growth cones of sensillar neurons was examined by double labeling using intracellular dye-filling with antibody labeling in early Hirudo medicinalis embryos. The monoclonal antibody Lan3-2 was used because sensillar neuronal tracts are specifically labeled by this antibody. Examining 68 individually filled neurons we found that sensillar neuron growth cones bifurcate within the CNS, that they project long filopodia capable of sampling the local environment, and that all of them appeared to choose a single particular CNS fascicle without apparent retraction or realignment of growth cones. Furthermore, each side of the bifurcating afferent growth cones always chose the same fascicle, implying a specific choice of a distinct labeled pathway. By dye-filling individual central neurons (P-cells), we show that there are centrally projecting axons present at the time sensillar afferents enter the ganglionic primordia and select a particular fascicle, and we confirm that at least the dorsal peripheral nerve is likely to be pioneered by central neurons, not by the peripheral afferents. In the sensillum studied here, we found examples of sensory neurons extending axons into one of all the available fascicles. Thus, an individual embryonic sensillum possesses a heterogeneous population of afferents with respect to the central fascicle chosen. This is consistent with the idea that segregation into distinct axon fascicles may be based upon functional differences between individual afferent neurons. Our findings argue strongly in favor of specific pathway selection by afferents in this system and are consistent with previous suggestions that there exists a hierarchy of cues, including surface glycoconjugates that mediate navigation of the sensillar growth cones and the fasciculation of their axons.

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Section: Jellies Et Almentioning

confidence: 97%

Specific pathway selection by the early projections of individual peripheral sensory neurons in the embryonic medicinal leech

Jellies

Johansen²,

Johansen³

1994

J. Neurobiol.

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“…The reason for this is discussed in the Results. The reason for placing the electrodes between ganglia was to avoid activating the sensory receptors associated with the sensilla (Kretz et al 1976;Phillips and Friesen 1982).…”

Section: Preparation and Proceduresmentioning

confidence: 99%

The whole-body shortening reflex of the medicinal leech: motor pattern, sensory basis, and interneuronal pathways

Kristan

1995

J Comp Physiol A

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The leech whole-body shortening reflex consist of a rapid contraction of the body elicited by a mechanical stimulus to the anterior of the animal. We used a variety of reduced preparations - semi-intact, body wall, and isolated nerve cord - to begin to elucidate the neural basis of this reflex in the medicinal leech Hirudo medicinalis. The motor pattern of the reflex involved an activation of excitatory motor neurons innervating dorsal and ventral longitudinal muscles (dorsal excitors and ventral excitors respectively), as well as the L cell, a motor neuron innervating both dorsal and ventral longitudinal muscles. The sensory input for the reflex was provided primarily by the T (touch) and P (pressure) types of identified mechanosensory neuron. The S cell network, a set of electrically-coupled interneurons which makes up a 'fast conducting pathway' in the leech nerve cord, was active during shortening and accounted for the shortest-latency excitation of the L cells. Other, parallel, interneuronal pathways contributed to shortening as well. The whole-body shortening reflex was shown to be distinct from the previously described local shortening behavior of the leech in its sensory threshold, motor pattern, and (at least partially) in its interneuronal basis.

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“…Leeches have two sensory systems capable of sensing water movement: mechanosensory hairs along their body; and simple eyes that sense changes in light level that occur as surface waves cast shadows on their body (Carlton and McVean, 1993;Derosa and Friesen, 1981;Dickinson and Lent, 1984;Friesen, 1981;Kretz et al, 1976;Phillips and Friesen, 1982;Young et al, 1981). Both of these sensor types have an extensive distribution over the body of the leech (Blinn et al, 1986;Friesen, 1981).…”

Section: Introductionmentioning

confidence: 99%

Developmentally regulated multisensory integration for prey localization in the medicinal leech

Harley

Cienfuegos

Wagenaar

2011

Journal of Experimental Biology

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SUMMARYMedicinal leeches, like many aquatic animals, use water disturbances to localize their prey, so they need to be able to determine if a wave disturbance is created by prey or by another source. Many aquatic predators perform this separation by responding only to those wave frequencies representing their prey. As leechesʼ prey preference changes over the course of their development, we examined their responses at three different life stages. We found that juveniles more readily localize wave sources of lower frequencies (2Hz) than their adult counterparts (8-12Hz), and that adolescents exhibited elements of both juvenile and adult behavior, readily localizing sources of both frequencies. Leeches are known to be able to localize the source of waves through the use of either mechanical or visual information. We separately characterized their ability to localize various frequencies of stimuli using unimodal cues. Within a single modality, the frequency-response curves of adults and juveniles were virtually indistinguishable. However, the differences between the responses for each modality (visual and mechanosensory) were striking. The optimal visual stimulus had a much lower frequency (2Hz) than the optimal mechanical stimulus (12Hz). These frequencies matched, respectively, the juvenile and the adult preferred frequency for multimodally sensed waves. This suggests that, in the multimodal condition, adult behavior is driven more by mechanosensory information and juvenile behavior more by visual. Indeed, when stimuli of the two modalities were placed in conflict with one another, adult leeches, unlike juveniles, were attracted to the mechanical stimulus much more strongly than to the visual stimulus. Supplementary material available online at

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Ultrastructure of the water‐movement‐sensitive sensilla in the medicinal leech

Cited by 50 publications

References 15 publications

Specific pathway selection by the early projections of individual peripheral sensory neurons in the embryonic medicinal leech

Specific pathway selection by the early projections of individual peripheral sensory neurons in the embryonic medicinal leech

The whole-body shortening reflex of the medicinal leech: motor pattern, sensory basis, and interneuronal pathways

Developmentally regulated multisensory integration for prey localization in the medicinal leech

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