The structure and distribution of external sense organs in newly hatched and mature earthworms

Abstract

Fully mature adult Eisenia foetida sensory buds are abundant on the prostomium and the first segment. In subsequent segments they are restricted to the anterior half where they form a single row aligned with the setae and encircling the worm. In the more posterior regions of the worm the buds are widely separated and fewer. The surface of each bud is a raised circular or oval area from which 15 to 100 so-called sensory hairs arise, being cylindrical and apparently flexible. The number of these projections decreases toward the posterior end of the worm. In worms newly emerged from egg cocoons, the general pattern of distribution and external form of sensory buds resembles that of adults, but the buds are much fewer and smaller than in adults. Although these worms emerge with their definitive adult number of segments, new buds and additional sensory projections are formed during post hatching development.

Identification and Pattern of Primary Sensory Cells in the Body Wall Epithelium of the Tubificid Worm, Limnodrilus hoffmeisteri

“…Later on, SEM observations supported her data (Aros et al, 1978;Moment & Johnson, 1979), suggesting that the distribution pattern of sensillas is identical in lumbricid worms.…”

“…SEM is widely used to identify sensillas in oligochaete species (Aros et al, 1978;Moment & Johnson, 1979), but this is mainly suitable for observation of ciliated primary sensory cells. Those structures having no penetrating cilia across the cuticle (phaosomal photoreceptors, non-penetrative multiciliate sensory cells and basal ciliated sensory cells) could not be, or hardly be, observed.…”

External sense organs in freshwater oligochaetes (Annelida, Clitellata) revealed by scanning electron microscopy

“…The present data on 16 species of freshwater oligochaetes, together with the literature data on about 20 other freshwater, marine, and terrestrial species (Vejdovsky, 1884;Hesse, 1894;Langdon, 1895;Brode, 1898;Atheston, 1899;Michaelsen, 1903;Stephenson, 1930;Sperber, 1948;Aros et al, 1978;Moment and Johnson, 1979;Jamieson, 1981;Farnesi et al, 1982b;Smith, 1983;Römbke and Schmidt, 1999;Kuperman et al, 2002) strongly support a general pattern of distribution for the ciliate sense organs in the Oligochaeta as follows: ciliate sense organs are scattered on the prostomium, peristomium, and pigidium, and arranged in, at least, a transversal row (transverse chaetal row) in the remaining segments. Moreover, the presence of ciliate sense organs scattered on the entire surface of the chaetal segments or arranged into a few other discrete transversal rows per segment is probably another general characteristic for the entire group, although overlooked in some of the previous studies.…”

“…There are very few published data concerning the length of the cilia in aquatic oligochaetes (Atheston, 1899;Smith, 1983) as well as in earthworms (Langdon, 1895;Moment and Johnson, 1979;Römbke and Schmidt, 1999). The range of these values (0.2-9 m) is similar to that of the multiciliate organs of short cilia.…”

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

“…Second, the cilia in the earthworm are arranged in a row parallel to the long axis of the cell rather than being grouped close together. Consequently, it is not easy to distinguish uniciliate from multiciliate hair projections in SEM micrographs of earthworm sensory buds (Moment and Johnson, 1979). Third, the multiciliate cells in earthworms have ciliary rootlets, whereas we found no ciliary rootlets in any of the leech sensory cells, Fourth, the earthworm has four to 18 cilia per cell while the leech has two to four cilia per cell.…”