Biologia 66/2: 294—298, 2011 Section Zoology DOI: 10.2478/s11756-011-0019-0
TheinvasionoftheleechPiscicola respirans (Hirudinea: Piscicolidae) on the fins of European grayling Thymallus thymallus
Aleksander Bielecki1, Joanna M. Cichocka1,JanuszTerlecki2 & Andrzej Witkowski3
1Department of Zoology, University of Warmia and Mazury, Oczapowskiego St. 5, 10-718 Olsztyn, Poland; e-mail: [email protected] 2Department of Applied Ecology, University of Warmia and Mazury, Oczapowskiego St. 5, 10-718 Olsztyn, Poland 3Museum of Natural History, Wroc law University, Sienkiewicza St. 21, 50-335 Wroc law, Poland
Abstract: This study presents the parasitical relationships between the leech Piscicola respirans and European grayling Thymallus thymallus. It determines leech invasion intensity and extensity as well as describes the preferences of fin selection by the parasite as a place to attach and feed. It also shows the significance of fin selection by the leech in the initial phase of life cycle. Finally, the study defines P. respirans as a predominantly fin-parasite of fishes. Most probably the host-searching mechanism is based on positive phototaxis. Key words: leech; Hirudinea; Piscicolidae; European grayling
Introduction fore using statistical analysis was not easy (Lestage 1936; Sitowski 1937; Epure 1945; Hoffman 1955a, b; Freshwater species of fish leeches (piscicolids), with Wojtas 1959; Bielecki 1977). a few exceptions, live in Holarctic continental waters Piscicola respirans always occurs on fishes in huge (Utevsky & Trontelj 2004; Utevsky 2007). Piscicolid amounts, resulting in economic losses. Moreover, par- leeches are parasites of many fish species (Sket & Tron- asite infestation discourages fishermen from catching telj 2008) although a few species also feed on crus- such infected fish (Bielecki 1977, fishermen’s oral in- taceans and octopus blood (Epshtein 1959; Burreson formation). & Allen 1978; Janssen 1993). Fish leeches feeding on Classification of the species P. respirans is a con- blood, for example Piscicola geometra (L., 1761), stay troversial matter. Epshtein (1968) and Bielecki (1997) on their hosts for a comparatively short time – up to 24 suggested that this species should be classified in hours. Since leeches drop off quickly after attaching to a the genus Piscicola. However, traditional research by host, parasitologists have shown little interest in study- Sawyer (1986) as well as molecular studies by Utevsky ing them (Polyanski 1955; Utevsky & Trontelj 2004). & Trontelj (2004) and Utevsky et al. (2007) have shown However, Piscicola respirans Troschel, 1850, stays on the possibility of transferring P. respirans to the genus its host throughout its life cycle (about 3–4 months) Cystobranchus. and leaves the host only after laying cocoons. The aim of the study is to analyze the relationship Some parasitic leeches can occur in huge amounts. between the parasite P. respirans and one of its hosts A good example is Johanssonia kolaensis Selensky, – the European grayling. The authors put forward two 1914, which parasitizes Anarhichas L. fishes, and in hypotheses: 1. It is most probable that P. respirans is extreme cases destroy their fins (Epshtein 1968). More- an obligatory fin-parasite; 2. there is a high probability over, piscicolids are vectors of fish haematozoans (Khan of parasitic invasion, mainly on paired fins. & Paul 1995). Piscicola respirans is a fish ectoparasite. Its main hosts are salmonid fishes (Salmonidae): salmon Salmo Material and methods salar L., 1758, brown trout Salmo trutta morpha trutta L., 1758, brook trout Salmo trutta morpha fario L., European graylings were caught using electrofishing in the 1758, thymallid fish (Thymallidae) European grayling Dunajec River on the segment between Ostrowsko – Sro- mowce Wy˙zne and in the estuary parts of two tributaries: Thymallus thymallus (L., 1758), as well as cyprinid the Niedziczanka and the Le´snicabrooks,from7to11April, fishes (Cyprinidae): barbel Barbus barbus (L., 1758) 1986. A random sample of 100 mature European graylings and dace Leuciscus leuciscus (L., 1758). Most studies were caught for examinations. The fish body lengths were concerning leech occurrence on fish were based on very measured with an accuracy of 0.5 cm. The numbers of little material (this also applies to P. respirans), there- leeches were assessed on all fins and on the trunk.