H. Wiederhoft et H. Greven, THE CEREBRAL GANGLIA OF MILNESIUM-TARDIGRADUM DOYERE (APOCHELA, TARDIGRADA) - 3-DIMENSIONAL RECONSTRUCTION AND NOTES ON THEIR ULTRASTRUCTURE, Zoological journal of the Linnean Society, 116(1-2), 1996, pp. 71-84
Differential interference contrast micrographs from stretched animals,
serially sectioned semi-thin and ultrathin sections revealed that the
cerebral ganglia (supraoesophageal mass) of the eutardigrade Milnesiu
m tardigradum lie above the buccal tube and adjacent tissue like a sad
dle. It has an anterior indentation which is penetrated by two muscles
that arise from the cuticle of the forehead. The cerebral ganglia con
sist of lateral outer lobes bearing an eye on each side, and two inner
lobes which extend caudally. Between the inner lobes a cone-like proj
ection tapers into a nerve bundle. Each outer lobe is joined with the
first ventral ganglion. From the outer lobe near the eye the ganglion
for a posterolateral sensory field extends to the epidermis. Anterior
to the supraoesophageal mass are three dorsal ganglia for the upper th
ree peribuccal papillae. Two additional ganglia attached to the cerebr
al mass supply the lateral cephalic papillae. The cerebral ganglia are
covered by a thin neural lamella. The pericarya which surround the ne
uropil have large nuclei. Near the axons in the centre of the supraoes
ophageal mass the cytoplasm is crowded with vesicles of different size
and appearance. Some of them resemble synaptic vesicles while others
resemble dense sore bodies. Structurally different types of synapses a
nd axons can be distinguished within the neuropil. (C) 1996 The Linnea
n Society of London