The Piscicolidae are a family of jawless leeches in the order Rhynchobdellida that are parasitic on fish. They occur in both freshwater and seawater, have cylindrical bodies, and typically have a large, bell-shaped, anterior sucker with which they cling to their host. Some of the leeches in this family have external gills, outgrowths of the body wall projecting laterally, the only group of leeches to exchange gases in this way.
Worldwide, around 60 genera and 100 species of leeches are in this family, all parasitic on the blood of marine, estuarine, and freshwater fishes. These leeches are less common in the tropics, and more abundant in temperate and polar waters.
Taxonomy Historically, the Piscicolidae have been divided into three subfamilies: the Pontobdellinae, characterised by two pairs of pulsatile vesicles on each urosome segment; the Piscicolinae, characterised by a single pair of pulsatile vesicles on each urosome segment; and the Platybdellinae, with no pulsatile vesicles. However, molecular phylogenetic analyses performed by Williams and Burreson in 2006, do not support these subdivisions. The Piscicolidae were confirmed as being monophyletic, but the Platybdellinae were shown to be polyphyletic with four distinct clades, and the Piscicolinae were similarly polyphyletic, again with four distinct clades, and the Pontobdellinae were paraphyletic with respect to the genus Oxytonostoma.
Ecology The Piscicolidae are parasitic on the blood of fishes. They produce a variety of anticoagulants to help them drink blood freely. Some species are host-specific, while others can accept a larger range of hosts. Some, such as the European Piscicola geometra, take a blood meal and then drop off the host and hide somewhere while they digest the blood; some, mostly in marine or estuarine habitats with soft substrates, attach themselves temporarily to a crustacean after leaving their fish host; others remain attached to a fish semipermanently. Leeches are hermaphrodites, and mating may take place on or off the fish host, but in either case, the cocoon, usually containing a single egg, is deposited elsewhere, usually stuck to a stone or piece of vegetation, or even to the carapace of a crustacean. When the egg hatches, the juvenile leech has about a week to find a suitable fish host for itself.
Genera The World Register of Piscicolidae Species lists the following 71 genera:
Acipenserobdella Epshtein, 1969
Aestabdella Burreson, 1976
Alexandrobdella Bolotov, Klass, Konopleva, Bespalaya, Gofarov, Kondakov et Vikhrev, 2020
Ambulobdella Utevsky et Utevsky, 2018
Antarcticobdella Dollfus, 1965
Austrobdella Badham, 1916
Austroplatybdellina A. Utevsky, S. Utevsky, Cichocka, Bielecki et Trontelj, 2023
Baicalobdella Dogiel et Bogolepova, 1957
Bathybdella Burreson, 1981
Bdellamaris Richardson, 1953
Beringobdella Caballero, 1974
Branchellion Savigny, 1822
Brumptiana Llewellyn et Knight-Jones, 1984
Calliobdella van Beneden et Hesse, 1863
Caspiobdella Epshtein, 1966
Ceratobdella Utevsky et Gordeev, 2015
Codonobdella Grube, 1873
Cottobdella Utevsky, 1997
Crangonobdella Selensky, 1914
Cryobdella Harding, 1922
Cryobdellina Brinkmann, 1948
Cyrillobdella Leigh-Sharpe, 1933
Cystobranchus Diesing, 1859
Dolichobdella Utevsky et Chernyshev, 2012
Dollfusobdella Burreson et Williams, 2008
Galatheabdella Richardson et Meyer, 1973
Ganymedebdella Leigh-Sharpe, 1915
Glyptonotobdella Sawyer et White, 1969
Gonimosobdella Williams & Burreson, 2005
Hemibdella van Beneden et Hesse, 1863
Heptacyclus Vasileyev, 1939
Ichthyobdella Blainville, 1827
Italobdella Bielecki, 1993
Janusion Leigh-Sharpe, 1933
Johanssonia Selensky, 1914
Leporinabdella Burreson et Williams, 2008
Limnotrachelobdella Epshtein, 1968
Lizabdella A. Utevsky, 2007
Makarabdella Richardson, 1959
Malmiana Strand, 1942
Marsipobdella Moore, 1952
Megaliobdella Meyer et Burreson, 1990
Mooreobdellina Epshtein, 1972
Mysidobdella Selensky, 1927
Myzobdella Leidy, 1851
Notobdella Benham, 1909
Notostomum Levinsen, 1882
Nototheniobdella A. Utevsky, 1993
Oceanobdella Caballero, 1956
Orientobdella Epstein, 1962
Ostreobdella Oka, 1927
Oxytonostoma Malm, 1863
Pawlowskiella Bielecki, 1997
Phyllobdella Moore, 1939
Phyllobdellina Epstein et Utevsky, 1993
Phyllobranchus Girard, 1851
Piscicola Blainville, 1818
Piscicolaria Whitman, 1889
Platybdella Malm, 1863
Pleurobdella Utevsky, 1995
Pontobdella Leach, 1815
Pontobdellina Harding, 1927
Pterobdella Kaburaki, 1921
Pterobdellina Boisen Bennike et Bruun, 1939
Richardsonobdella Burreson et Dybdahl, 1989
Stibarobdella Leigh-Sharpe, 1925
Taimenobdella Epshtein, 1969
Trachelobdella Diesing, 1850
Trachelobdellina Moore, 1957
Trulliobdella Brinkman, 1947
Zeylanicobdella Silva, 1963
References