Hirudinea

Leeches are the most recognized organisms under Hirudinea by presence of anterior and posterior suckers. In Hong Kong freshwaters, there are two families Glossiphoniidae and Erpobdellidae could be found.

Glossiphoniidae (Order Rhynchobdellida)

Body is strongly dorsoventrally flattened and leaf-like, usually <50mm long. Eyes (one, two, three or four pairs) always present. Mouth is a small pore with a protrusile muscular proboscis that can be everted for feeding.

Individuals

 

 

Erpobdellidae (Order Arynchobdellida)

Body ribbon-like, to 50mm or more in length. Elongate or cylindrical body shape, with red 'blood', but decolorized in preservative. Three or four pairs of eyes arranged in transverse rows.

Individuals

 

 

Oligochaeta

Oligochaetes are segmented worms with bundles of chaetae (or setae) on every segments except the first. Unlike the polychaetes, the anterior portion of the body has no other projections or appendages, and most oligochaetes lack eyes. Compared to the familiar earthworm, most freshwater oligochaetes are rather small (< 30mm long) and delicate with thin, almost transparent, body walls. Identification requires detailed microscopic examination of the form of the tips of the setae. Generally not found in sample from stony streams, but they can be present in large numbers in muddy substrates where the water has high levels of organic pollutions.