Mention leeches and immediately images of large, swamp dwelling beasts, stuck to the bodies of fever racked unfortunates, to be removed with a lighted cigarette, are conjured up. Yet Ireland has its fair share of the animals, some thirty two species from two orders and five families (1). Eighteen of these are marine. And they are not all out for your blood either. Many feed exclusively on other invertebrates. Take the fresh water Glossiphonia complanata, a snail leech. As its common name implies, it feeds on aquatic gastropods that it encounters in fast flowing, rock streams, although it will also feed on Oligochaeta, Chironomidae, and Amphipoda in decreasing magnitude (2). It achieves this by inserting its probiscus into the soft parts of its prey and sucking out their body fluids. G. complanata is a relatively short leech, with a broad body that is flattened dorso-ventrally. It is often encountered attached to the underside of stones, waiting for prey (3).
G. complanata shows a degree of parental care that is surprising for an invertebrate. As hermaphrodites, each individual produces a cocoon with a soft transparent covering containing the developing embryos. This is attached a stone and brooded over by the parent for about 20 days. Upon hatching, the young cling to the ventral surface of the parent (4).
- Ferriss et al., 2009. Irish Biodiversity: a Taxonomic Inventory of Fauna pp. 74-75
- Wrona et al., 1979. Canadian Journal of Zoology 57 pp. 2136-2142
- Mann, 1956. Journal of Animal Ecology 26
- Kutschera, 1986. Animal Behaviour 34 pp. 941-942