Biologia 66/2: 294—298, 2011 Section Zoology DOI: 10.2478/s11756-011-0019-0

TheinvasionoftheleechPiscicola respirans (Hirudinea: ) 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, Wroclaw University, Sienkiewicza St. 21, 50-335 Wroclaw, Poland

Abstract: This study presents the parasitical relationships between the 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 of fish (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): Salmo Material and methods salar L., 1758, 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.

c 2011 Institute of Zoology, Slovak Academy of Sciences Invasion of Piscicola respirans on European grayling 295

Fig. 1. Frequency of European graylings (in %) with fins para- Fig. 3. Frequency of European graylings with certain number of sitized by Piscicola respirans; n – number of European graylings leeches on all fins; n – the number of European graylings with with leeches; P – probability of null hypothesis (H0). leeches; P – probability of null hypothesis (H0).

quency of infection of the other fins by the leeches was statistically the same (χ2,df=1,P < 0.05); a signif- icant difference was only recorded between caudal and anal fins (χ2,df=1,P < 0.0105). The leeches were recorded both on one fin and on several fins simultane- ously (Fig. 2). Majority (57.7%) of fishes (χ2,df=1,P < 0.001) had only one fin infected, and 30.9% of fishes had two fins with leeches. The percentage of European graylings with leeches on three and four fins was low (6.4% and 5.1%, respectively). The number of leeches recorded on a single fin ranged from 1 to 31 (Fig. 3). Statistically, most often one or two leeches were found; Fig. 2. Frequency of European graylings with certain number of in 42.3% and 24.4% of fishes, respectively (χ2,df=1, fins infected by Piscicola respirans (independently on a fin type); P < 0.05); three leeches were found on 10.3% of fishes, n – the number of European graylings with leeches; P – proba- bility of null hypothesis (H0). and four leeches were found on 6.4% of fishes. A statistically significant increase in the number of leeches on the fins correlated with the increase in Using χ2 2 × 2 tables of frequencies, the following the European grayling body lengths was recorded (rs = null hypotheses were verified: (1) the frequency of European 0.2576, n = 78, P < 0.05). The number of leeches on the graylings with pectoral, pelvic, anal, caudal and dorsal fins caudal fin increased along with the body lengths (rs = parasitized by leeches was the same (there were as many 0.4184, n = 27, P < 0.05; Table 1), but no statistically fishes with leeches on the pectoral fin as on the pelvic fin, significant increases in the numbers of leeches on the anal fin, etc.); (2) the frequency of European graylings with pectoral and pelvic fins were recorded (rs = 0.2796, n one infected fin as well as two, three or four fins infected = 19, P > 0.05) and (rs = 0.2386, n = 48, P > 0.05), in one time was the same; (3) the frequency of European respectively. graylings with varying number of leeches on the fins was the same (there were as many fishes with one leech as there A statistically significant positive correlation be- were with two, three, four, etc.). Spearman’s rank correla- tween the number of leeches on paired fins (rs = 0.8094, tion coefficients were calculated for relations: (i) between n =8,P < 0.05) as well as a correlation between the the body length of parasitized European graylings and the number of leeches and the number of infected fins (rs number of leeches that were located on fins; (ii) between the = 0.4687, n = 45, P < 0.05; Table 1) were recorded. number of leeches and the number of infected fins. Discussion Results It is difficult to compare the obtained results with the The leech P. respirans was recorded on the fins of 78% results of other studies on the relationships between of European graylings. The leech species occurred on all hosts and parasitic leeches (Bielecki 1988b). Hoffman fins, except the adipose fin. On the trunk of fishes, only (1955a, b, 1956) collected extensive data on the wide two leeches were found. Of the 78 European graylings on scaleoccurrenceofP. respirans on fish in the Rhine which leeches were recorded, 61.5% had infected pelvic River basin as well as on the death of many fish caused fins, 34.6% had infected caudal fins and 24.4% had in- by this leech. In the Rhine River basin, P. respirans par- fected pectoral fins (Fig. 1). Statistically, most often asitized mainly brown trout with an average intensity the leeches occurred on the pelvic fins (χ2,df=1,P of 10–20 leeches per fish, and in single cases the inten- < 0.001) and most rarely on the caudal fins. The fre- sity reached up to 47 leeches at the end of April. In the 296 A. Bielecki et al.

Table 1. Spearman’s rank correlation coefficients (rs) between the total length of European grayling (in cm) and the number of leeches Piscicola respirans (n) on infected fins. Bold numbers represent statistical significance (P < 0.05).

Characteristics Total length Dorsal fin Caudal fin Anal fin Pelvic fins Pectoral fins Together fins

Spearman’s rank correlation coefficients

Total length XXX –0.2021 0.4184 0.2480 0.2386 0.2796 0.2576 Dorsal fin 17 XXX 0.4700 0.8660 –0.1240 0.5000 0.4368 Caudal fin 27 6 XXX – 0.4417 0.2343 0.7293 Anal fin 13 3 – XXX 0.1964 – 0.7193 Pelvic fins 48 7 18 8 XXX 0.8094 0.7965 0.8159 Pectoral fins Number of 19 3 6 – 8 XXX Together fins observations 78 17 27 13 48 19 XXX

Cerna River in Romania, which flows into the Danube The observation that the number of European River, P. respirans were recorded on barbel in substan- graylings with pelvic fins infected by P. respirans was tial numbers. On each examined fish, 10–15 leeches were the highest (39%) and that most leeches were attached found in April (Epure 1945). In the rivers of Belgium, to the fins (48%) can be explained by positive pho- according to fishermen’s estimates, the infection inten- totaxis. Till now the mechanism of host-searching by sity of brown trout by this leech ranged from 50 to 100 leeches has been explained only based on chemotaxis (Lestage 1936). Even if recent data are slightly inaccu- (Friesen 1981; Khan & Emerson 1981). However, most rate, there is definitely an intensive infection of brown likely the chemotaxis mechanism dominates in stagnant trout as well as other rheophilic fish species by these water (e.g., lakes, ponds), because it is more possible to leeches in the drainage basin of the Rhine River and send and receive chemical signals in such conditions. In also in other rivers (San, Nysa Klodzka – Bielecki 1977, lotic waters (e.g., rivers, and especially brooks) such 1978 and unpubl. data). In the current study, the extent possibility is less or non-existent. In fast flowing waters of infection of European grayling by P. respirans was which are overexposed to the bottom, the mechanism of high and statistically significant with an intensity of up positive phototaxis dominates. In this case the chemo- to 31 leeches. The whole-scale occurrence of P. respi- taxis is a secondary phenomenon. Only after reach- rans on fish was also recorded in Poland in the Dunajec ing a fish, the leeches discover, using the mechanism River and its tributaries (Sitowski 1937; Wojtas 1959, of chemotaxis, whether it found an appropriate host. 1960, 1961; Bielecki & Witkowski 1988). The invasion of Sawyer (1986) and many other authors studying Pisci- brown trout and European grayling by this leech species cola geometra L., 1761 have mentioned the importance with quite big intensity (up to nine leeches) was re- of mechanic stimuli (’responsive to water disturbance ported by Bielecki (1977, 1988a) in the Nysa Klodzka etc.). We have mentioned these suppositions because River and in its tributaries. Due to this data it is rea- they have not been falsified. Piscicola geometra, unlike sonable to be alarmed that P. respirans may lead to P. respirans, predominantly occurs in fishponds, lakes a wide-scale diminishing of the brown trout and other andinslow-flowingrivers,where the detection of water fish species (Johansson 1929; Sch¨aperclaus 1954). disturbance is more possible than in brooks. Andersson (1965) studied the infection of Euro- The leeches do not swim to their host but are at- pean grayling by another clitellate, Acanthobdella pele- tached to the substrate by a posterior sucker. They dina Grube, 1851, in rivers of Scandinavia. Usually up penetrate a specific space in which they seek for a po- to a third of the fish population was infected, however, tential host and this area of penetration depends, to the infection intensity was either very low (4–5 leeches) a high degree, on the leech body length. The pelvic or very high (1–100 leeches). The leech prefers central fins of fish afford the easiest access for these parasites fins, especially their bases, followed by the caudal fin. as they are the closest to the river bottom. Moreover, Other fins were infected with a similar intensity. the pelvic and pectoral fins, which are outstretched lat- Leeches choose specific microhabitats: trunk, fins, erally, offer a relatively large space. In addition, the mouth and gills. The current location of P. respirans on pelvic and pectoral fins are located in the middle of a fish was unknown. In the European grayling, leeches the body, which is also significant. The leeches choose occurred on all fins (except the adipose fin); thus P. the most illuminated locations in order to be able to respirans should be considered as a fin parasite. perceive the shadow of a host (a decrease in light inten- In the Nysa Klodzka River, Bielecki (1997 and un- sity). Leeches recognize decreased light intensity using publ. data) also recorded single occurrences of the leech eye-like spots that are situated on the posterior sucker on body sides, eyes and in the mouth cavity and gill cav- (Bielecki 1988c, 1997, 1998, 1999; Fig. 4). In order to ity. In these studies only two specimens were recorded detect the lowest decrease in light intensity (the small- out of fins. However, they were at the beginning of the est shadow), leeches must migrate to the lightest places life cycle, thus they could be caught during their mi- (positive phototaxis). The greatest decrease in light in- gration to the fins. tensity arises when the middle of a fish body (ventral Invasion of Piscicola respirans on European grayling 297

1850 et Piscicola geometra (L.) (Hirudinea, Piscicolidae), p. 32. In: Le 2–eme Congres des Spécialistes des Sangsues, Ot- tawa, Canada. Bielecki A. 1997. Fish leeches (Hirudinea: Piscicolidae: Piscicoli- nae) of Poland in relation to the Palearctic piscicolines. Genus 20: 223–375. Bielecki A. 1998. Significance of positive phototactism in host- searching by fish leeches (Hirudinea, Piscicolidae): Pisci- cola respirans (Troschel), Piscicola geometra (L.) and Cas- piobdella fadejewi (Epshtein), p. 331. In: Zjazd PTP, 9–12 September 1988, Olsztyn, Poland. Bielecki A. 1999. Rola plamek oczoksztaltnych u pijawek paso- zytniczych˙ (Hirudinea: Piscicolidae) w odszukiwaniu ryb- zywicieli˙ [Role of eye-like spots in parasite leeches (Hirudinea: Piscicolidae) in fish-hosts searching]. Wiad. Parazyt. 45 (3): 339–345. Bielecki A. & Witkowski A. 1988. Zara˙zenie lipieni Thymal- lus thymallus (L.) pijawk˛a Cystobranchus respirans Troschel, 1850 (Hirudinea, Piscicolidae), w dorzeczu Dunajca [Infection of graylings Thymallus thymallus (L.) by the leech Cysto- branchus respirans Troschel, 1850 (Hirudinea, Piscicolidae) in Dunajec basin], pp. 15–16. In: XIV Zjazd PTZool., Szczecin, Poland. Fig. 4. Piscicola respirans: A – Two pairs of eyes on an anterior Burreson E.M. & Allen M.D. 1978. Morphology and biology of sucker, B – 10 eye-like spots on a posteriori sucker (photo: A. Mysidobdella borealis (Johansson) comb. N. (Hirudinea: Pis- Bielecki, retouched). cicolidae), from mysids in the Eastern-North Atlantic. J. Par- asit. 64: 1082–1091. Epshtein V.M. 1959. O sistematicheskom polozhenii, obraze zhizni i proiskhozhdenii endemichno˘ı bajkal’sko˘ı piyavki Tra- fins) is located above the leeches. Thus, the result of chelobdella torquata (Grube) [On the systematic position, life the leech reaction to the shadow and movement of a history, and origin of the endemic Baikal leech Trachelobdella torquata (Grube)]. Dokl. Akad. Nauk SSSR 125: 935–937. fish converges in the half of the body length next to the Epshtein V.M. 1968. Zoogieograficheski˘ı analiz ribikh piyavok ventral fins. It is interesting that the numbers of leeches Antarktiki i reviziya roda Trachelobdella Diesing, 1850 [Zoo- on the pectoral and ventral fins are significantly corre- geografical analysis of fish leeches of Antarctica and revi- sion of genus Trachelobdella Diesing, 1850], pp. 137–138. In: lated (rs = 0,8094, n =8,P < 0.05; Table 1). An attack Vsiesojuz. Sowies po Bolezniyam i Parazitam Rib i Vodn. of the leech on the pectoral fins is much more difficult Biezpozvonochnykh, Leningrad. than an attack on the ventral fins because the pectoral Epure E. 1945. Cystobranchus respirans (Troschel). Un rare fins are situated farther from waiting leeches than the Ichthyobdelide trouve en Roumanie. Bull. Soc. Cluj 9: 557– ventral fins. Furthermore, the shadow of a swimming 563. Friesen W.O. 1981. Physiology of water motion detection in the fish is not prominent yet, thus it does not produce a medicinal leech. J. Exp. Biol. 92: 255–275. great decrease in light intensity (Bielecki 1998). These Hoffmann J. 1955a. Faune hirudinéenne du Grand-Duché de are probably the reasons why fewer leeches can be found Luxembourg. Arch. Inst. Gr.-Ducal Luxembourg. Sec. Sci. on pectoral than on ventral fins. Natur., Phys. Math. 22: 175–221. Hoffmann J. 1955b. Quelques caracteres éthologiques de la Pis- In conclusion, the two hypotheses in this study cicolidée: Cystobranchus respirans Troschel. Arch. Inst. Gr.- have been supported: (1) Piscicola respirans is mainly a Ducal Luxembourg. Sec. Sci. Natur., Phys. Math. 22: 223– fin parasite; (2) the invasion of the parasite P. respirans 225. is directed mainly to the paired fins. Hoffmann J. 1956. Contributions a l’étude des spécificités mor- phologiques et éthologiques de la Piscicolidée: Cystobranchus respirans (Troschel 1850). Arch. Inst. Gr. – Ducal Luxem- 23: References bourgSec.Sci.Natur.Phys.Math. 209–239. Janssen H.H. 1993. Morphology, egg cocoons, and transmis- sion paths of the Antarctic leech Glyptonotobdella antarctica Andersson E. 1965. Ecological notes Acanthobdella peledina Sawyer and White, 1969 (Hirudinea: Rhynchobdelliformes: Grube found on grayling and brown trout. Rep. Inst. Fresh- Piscicolidae). Polar Biol. 13: 347–354. DOI: 10.1007/BF0023 water Res. Drottningholm 46: 185–199. 8361 Bielecki A. 1977. Pijawki (Hirudinea) rybzyj˛acych ˙ w rzekach Johansson L. 1929. Hirudinea (Egel.), pp. 133–155. In: Dahl F. i potokach Kotliny Klodzkiej [Leeches (Hirudinea) of fishes (ed.), Die Tierwelt Deutschlands und der angrenzenden Meer- living in rivers and Brooks of Kotlina Klodzka]. Przegl. Zool. esteile, Verlag Gustav Fischer, Jena, 168 pp. 21 (2): 141–145. Khan R.A. & Emerson C.J. 1981. Surface topography of marine Bielecki A. 1978. Nowe stanowisko pijawki Cystobranchus fas- leeches as revealed by scanning electron, microscopy. Trans. ciatus (Kollar, 1882) (Hirudinea, Piscicolidae) [A new stand Am. Microsc. Soc. 100 (1): 51–55. of leech Cystobranchus fasciatus (Kollar, 1882) (Hirudinea, Khan R.A. & Paul A.J. 1995. Life cycle studies on arctoboreal Piscicolidae)]. Przegl. Zool. 22 (3): 249–251. leeches (Hirudinea). J. Helminthol. Soc. Wash. 62: 105–110. Bielecki A. 1988a. Cystobranchus respirans Troschel, 1850 (Hi- Lestage J.A. 1936. La presence dans les eaux belges de I’ichtyo- rudinea, Piscicolidae) w rzece M˛akolnicy [Cystobranchus parasites Cystobranchus respirans (Troschel) (Hirudinea). respirans Troschel, 1850 (Hirudinea, Piscicolidae) in the Ann. Soc. Zool. Belg. 66: 127–132. M˛akolnica River]. Przegl. Zool. 32 (1): 53–57. Polyanski Y.I. 1955. Materialy po parazitologii ryb severnykh Bielecki A. 1988b. Pijawki (Hirudinea) paso˙zyty ryb [Leeches (Hi- morey SSSR. Parazity ryb Barentsova Morya [Parasitology rudinea) the fish parasites]. Wiad. Parazyt. 41: 2–7. of fishes of the northern seas of the USSR. Parasites of the Bielecki A. 1988c. L’emportance de la phototaxie positive pour fishes of the Barents Sea]. Tr. Zool. Inst. Akad. Nauk SSSR retrouver des hôtes par Cystobranchus respirans Troschel, 19: 5–170. 298 A. Bielecki et al.

Sch¨aperclaus W. 1954. Fischkrankheiten. Akademie Verlag, Wojtas F. 1959. Pijawki (Hirudinea) Tatr, Podhala i Pienin Berlin, 708 pp. [Leeches (Hirudinea) of Tatry, Podhale and Pieniny]. Zeszyty Sitowski L. 1937. O masowym wyst˛epowaniu pijawki Cysto- Naukowe UniwersytetuLódzkiego,  Nauki Matematyczno- branchus respirans (Troschel) w Dunajcu i jego doplywach Przyrodnicze 2(5):133–146. [On mass occurrence of leech Cystobranchus respirans (Tro- Wojtas F. 1960. Uwagi o rozrodzie pijawki Cystobranchus respi- schel) in Dunajec River and its tributaries]. Przegl. Ryb. 10: rans (Troschel) [Comments about reproduction of leech Cys- 185–187. tobranchus respirans (Troschel)]. Zeszyty Naukowe Uniwer- Sket B. & Trontelj P. 2008. Global diversity of leeches (Hirudinea) sytetuLódzkiego,  Nauki Matematyczno- Przyrodnicze 2(7): in freshwater. Hydrobiologia 595: 129–137. DOI: 10.1007/ 153–159. s10750-007-9010-8. Wojtas F. 1961. Pijawka Cystobranchus respirans (Troschel) Sawyer R. T. 1986. Leech Biology and Behaviour. Vol. I, II, III, –malo znany paso˙zyt ryb [Leech Cystobranchus respirans Clarendon Press, Oxford, 1065 pp. (Troschel) – polory known fish parasite]. Przegl. Zool. 5: 361– Utevsky A. 2007. Antarctic Piscicolid Leeches. Zoologisches 362. Forschungsmuseum Alexander Koenig (ZFMK), Bonn, 80 pp. Utevsky S.Yu. & Trontelj P. 2004. Phylogenetic relationships of Received July 8, 2010 fish leeches (Hirudinea: Piscicolidae) based on mitochondrial Accepted December 10, 2010 DNA sequences and morphological data. Zool. Scr. 33: 375– 385.