WHAT YOU ARE LIKELY TO FIND

Members of the genus Echiniscus are cosmopolitan, armored Herteotardigrades of moderate size (0.10-0.35 mm in length). They are identified by the number, shape, and placement of their dorsal armored plates and spines or cirrus (Figure 6). A dentate collar on the fourth pair of legs has teeth and the internal claws may have spurs, the external claws are smooth (Figure 8B). The eggs are oval and deposited in the exuvium (Figure 5).

Two general types of Echiniscus are recognized, the first has only one spine, the most anterior cirri "A." The granulation on the plates is dense and uniform. The internal claws have large curved spurs and the dentate collar on fourth pair of legs has many sharp teeth (Figures 6, 8B). The other type is distinguished by having several spines present on the edges of the dorsal plates (Figures 6, 14). They generally have red eyes, a double granulation composed of a very fine, uniform sculpture, and a courser set of depressions or pores of irregular size and arrangement. The dentate collar has small irregular teeth.

Pseudechiniscus are small (0.10-0.20 mm) red, armored Heterotardigrades with a pseudo-segmental plate inserted between median plate three and the terminal plate (Figure 6). They have large, black eyes and very fine granulation. The only appendages are a cirrus and clavae arising between the head and first plate, other appendages are absent (Figures 1, 6). Medial plates I and II are divides; median plate III is single. The internal claws on all legs have a spur just above base. A dentate collar is not present on the fourth pair of legs.

Milnesium is a genus of large (up to 1.0 mm in length), very common, cosmopolitan tardigrades. Milnesium is distinguished by its anteriorly sloping body, the very wide buccal tube, the muscular pharynx without placoids. Six oral papillae and triangular lamellae surround the mouth opening (Figure 7C). The claws are distinctive with a long, thin primary branch and a short, multi hooked secondary branch (Figure 8C). It is a carnivorous species and is occasionally observed eating nematodes. The mouth parts of rotifers and the buccal apparatus of other tardigrades may occasionally be observed in its gut.

Diphascon is a genus of medium-sized (0.20-0.40 mm), smooth, eyed tardigrades with long, thin bodies. The buccal tube is also very thin. The esophageal tube is very long, thin and leads to an elongated pharynx. Long, thin macroplacoids are present. A microplacoid and a septulum may be present (Figure 7D). Macroplacoids usually increase in size from the first to the last. Cuticular bars are often present at the base of hypsibius-type claws.

The Ramazzottius genus contains common cosmopolitan mid-sized (0.20-0.35 mm in length) tardigrades with a granular cuticle that has a pigmented (red or brown) pattern often appearing in longitudinal rows and transverse bands. The buccal tube is narrow, the pharynx oval to round (Figure 7E). An apophysis is preset as are two roundish, smooth macroplacoids, nearly equal in size. The claws are oberhaeuseri-type (Figure 8E) with the primary branch of the external claws very thin, long, and whip-like.

Hypsibius is a common genus of smooth tardigrade with or without eyes and up to 0.35 mm in length. They have a short, broad buccal tube and a round pharynx. In the pharynx is a large apophysis, two elongated, globular macroplacoids, and no microplacoid (Figure 7F). The claws are typical hypsibius-type in the 1-2-1-2 pattern (Figure 8F). The eggs are generally smooth and left in the cuticle, but some species do leave free eggs with small projections (Figure 6C).

Dactylobiotus is a large (0.30-0.50 mm), smooth, aquatic genus of tardigrade. A broad buccal tube leads to an oval pharynx with two slender macroplacoids, the first twice the length of the second (Figure 7G). No microplacoids are present. The large, thin claws are connected at their base with a chitinous bar (Figure 8G). The eggs have small, cone shaped projections and are laid free (Figure 6D).

The Macrobiotus cf. harmsworthi group contains medium to large (0.20-0.50 mm), cosmopolitan tardigrades with a smooth cuticle and eye spots. The supported buccal tube is wide. The oval pharynx has three macroplacoids and a large microplacoid (Figure 7H). The claws are Y shaped with small lunules. Eggs have prominent projections that look like cones rising from the surface (Figure 6A). Eggs are required for identification.

Members of theMacrobiotus cf. hufelandi group are large (0.30-0.50 mm), white tardigrades with a smooth cuticle and eye spots. The supported buccal tube is moderate in width. Two macroplacoids and a microplacoid are found in the elongated pharyngeal bulb. The first macroplacoid is longer than the second and often constricted to appear as two (Figure 71). They have Y-shaped claws with prominent lunules and accessory points (Figure 8I). The eggs are deposited free, with ornamentation that resembles inverted egg-cups or goblets (Figure 6B). Many species in this group are very difficult to separate even for experts. Eggs are required.

The Minibiotus genus is composed of small (0.10-0.25 mm), smooth tardigrades with large eye spots. They have three round equal sized macroplacoids in a round pharyngeal bulb and a tiny microplacoid (Figure 7J). The stylet supports are joined to the buccal tube at the midpoint of its length. The claws are small of the hufelandi type with large accessory spines and large lunules (Figure 8J). The eggs have smooth dome-like projections (Figure 6E).