Placobdella costata

Placobdella costata is a large, elliptical, flattened leech,^[10] with somewhat variable colour. At rest, the adults are between 2 and 7 centimetres (0.79 and 2.76 in) long, and between 0.6 and 2.5 centimetres (0.24 and 0.98 in) wide.^[11] In colour the leeches can be greenish-brown,^[10] dark brown, blue-green, or, more often, yellowish-brown. They have an interrupted dark brown band down the middle of their backs.^[11]

Placobdella costata is somewhat unusual among Glossiphoniid leeches in that its mouth is located towards the front of its anterior sucker, while in many other species the mouth is in the centre of the sucker.^[12] This forwards mouth is shared by other species which parasitize mammals and reptiles, including Haementeria ghilianii.^[13]

Leeches have exhibit a variety of eye types, numbers, and arrangements, and are therefore "taxonomically invaluable".^[14] Within the family Glossiphoniidae alone there is considerable diversity. Placobdella costata at first appears to have two very close, often touching, eyes on its third segment, but more detailed observation with the use of histological techniques has shown that the leeches additionally have a pair of small, "rudimentary" eyes, anterior to and below its primary pair.^[15]

• Blanchard, Raphaël (1893). "Courtes notices sur les Hirudinées" [Short notes on the Hirudinea]. Bulletin de la Société zoologique de France (in French). 18.
• Elliott, J. M.; Mugridge, R. E. R.; Stallybrass, H. G. (Oct 1979). "Haementeria costata (Hirudinea: Glossiphoniidae), a leech new to Britain". Freshwater Biology. 9 (5): 461–465. doi:10.1111/j.1365-2427.1979.tb01530.x. eISSN 1365-2427. ISSN 0046-5070.
• Elliott, J.M.; Tullett, P.A. (1982). Provisional Atlas of the Freshwater Leeches of the British Isles (PDF). Occasional Publication No. 14. Freshwater Biological Association. ISSN 0308-6739.
• d'Hondt, Jean-Loup; Ben Ahmed, Raja (2009). "Catalogue et Clés Tabulaires de Détermination des Hirudinées d'eau douce de la Faune Française" [Catalogue and identification key for freshwater Hirudinea of French fauna]. Bulletin de la Société zoologique de France (in French). 134: 272.
• Richardson, Dennis J.; Hammond, Charlotte I.; Moser, William E.; Phillips, Anna J.; Lazo-Wasem, Eric A.; Barger, Michael A. (2020-10-27). "Molecular Variation and Biogeography of the Common North American Turtle Leech, Placobdella parasitica". Bulletin of the Peabody Museum of Natural History. 61 (2). doi:10.3374/014.061.0201. ISSN 0079-032X.
• Romero, David; Duarte, Jesús; Narváez-Ledesma, Lucía; Farfán, Miguel; Real, Raimundo (2014). "Presence of the leech Placobdella costata in the south of the Iberian Peninsula". Acta Parasitologica. 59 (2). doi:10.2478/s11686-014-0232-4. ISSN 1896-1851.
• Sawyer, Roy T. (1986). Leech Biology and Behaviour Volume I: Anatomy, Physiology, and Behaviour. Oxford Science Publishing. ISBN 0-19-857377-4.
• Siddall, Mark E.; Bely, Alexandra E.; Borda, Elizabeth (2006). "Chapter 9: Hirudinida". In Rouse, Greg; Pleijel, Frederick (eds.). Reproductive Biology and Phylogeny of Annelida. Taylor & Francis.