Dasydytes ornatus Voigt, 1909
Most likely ID: n.a.
Synonym: n.a.
Sampling location: Simmelried
Phylogenetic tree: Dasydytes ornatus
Diagnosis:
- body elongate, trunk spindle-shaped with constrictions
- length 150–200 µm (without spines)
- head broad, transversely elliptical, cephalion distinct
- dorsally 2 distant setolae on neck and 2 terminal setolae
- dorsolateral long spines arranged in 2 X 8 bundles
- largest spines 84–86 µm long
- each spine with one secondary spine and and distally with double tip
- on dorsal side of head 3 pairs of spines, the foremost is a simple spine
Dasydytes ornatus is one of the most common and conspicuous gastrotrichs in the Simmelried. The specimens are usually found in the uppermost mud layer.
The specimens are conspicuous even at small magnifications due to their unusually long spines, which can be spread out in case of danger. They are considerably longer than the body and lie against the body like a coat when swimming (s. figs. 1 a-d).
The spines of Dasydytes ornatus arise not only from the trunk, but also on the dorsal side of the head (s. fig. 3). There are located 3 pairs of spines which originate laterally on the head. The foremost spine has no secondary tip and is simple (s. fig. 3). The other spines have a secondary spine and distally a double tip (s. fig. 4). This (among other characteristics) distinguishes the genus Dasydytes from the genus Stylochaeta, which also has more than body-length spines. However, the distal ends of the spines of Stylochaeta are always single and do not form a double tip.
The spines of Dasydytes ornatus are angled where the secondary spine is located (s. fig. 4). The degree of this angle was used to serve to distinguish the similar species Dasydytes goniathrix from Dasydytes ornatus. In the meantime, however, there is increasing evidence that the two species are synonymous.
Fig. 1 a-d: Dasydytes ornatus. L = 177 µm (without spines). A freely swimming specimen from dorsal (a-c) and from left (d). Obj. 40 X.
Fig. 2 a-b: Dasydytes ornatus. L = 177 µm (without spines). Two focal planes of the slightly squashed specimen as shown in fig 1 a-d. Obj. 60 X.
Fig. 3: Dasydytes ornatus. The head with each 3 dorsal spine in lateral position (1-3). The foremost spine (arrow) is a simple spine spine without secondary spine. Obj. 100 X.
Fig. 4: Dasydytes ornatus. The dorsolateral spines of the trunk have one secondary spine (SSp). The distal ends have a double tip (arrows). Obj. 100 X.