An outer cuticle and ventral cilia A body cavity
Bilaterally symmetrical and worm-like Circulatory or gaseous exchange systems
A body covered in spines, hooks and adhesive tubes  
A through gut and anus  
A nervous system and two longitudinal cords  
Hermaphrodite or parthenogenic  
Aquatic, freshwater and marine  
Chaetonotus maximus, Gastrotrich

Greek: gaster = stomach, thrix = hair

Gastrotrichs (hairy-backs) are small (less than 4 mm), dorsoventrally flattened, transparent worms. At the anterior end they have sensory bristles, cilia, sensory pits, and some species have eye spots. The body ends in a tail or fork. Over 400 species are known.

They inhabit interstitial spaces in sand and compacted surfaces, and move using epidermal cilia to glide along, or loop in a leech-like fashion using adhesive tubes, see Chaetonotus sp. on the right and below which has two adhesive tubes.

Males tend to be rare and poorly developed.The marine species tend to be less well known, but their food is the same as Chaetonotus sp. below.

On the left is Chaetonotus maximus, a freshwater gastrotrich, and below another in the same genus. Chaetonotus sp. feeds on detritus, bacteria, diatoms and protozoa.

Chaetonotus, Gastrotricha

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