Written by Andrew Smart, Head of Science & Research
Lawson, B. et al , 2024. Predation of anurans in southern England by Batracobdella algira, a leech previously unknown in the UK. Herpetological Journal. 34 221-227
Leeches are often identified as potential predators of the various life stages of amphibians and in the case of frogs and toads, four native species of leech have been identified as feeding on blood and one leech, Haempois sanguisuga, (the horse leech) are know to be predatory on froglets and toadlets.
Reports of leech infestation on a common toad in 2020 led the authors of this recently published paper to explore the occurrence of leech predation on anurans more widely. A call for Citizen Scientists to report sightings led to 41 new records between 2020 and 2023. The authors undertook a detailed review of the species involved, either through morphological or genetic identification, and found that in 2 of the 9 cases identified, the species was Placobdella costata, while in the remaining 7 of the 9 records where leeches were identified to species, the species was Batracobdella algira, a species previously unrecorded in the UK.
The genotype of the animals collected corresponds with that of individuals from Tunisia and, along with a localised distribution in the south and south west, this suggests the possibility that it is a non-native invasive species. The authors suggest that possible routes of ‘invasion’ include release through animal or plant trade or natural long distance dispersal by birds.
Two other publications from 2016[1] and 2018[2] highlight the link between this leech species and cave salamanders in Sardinia, which suggest that the leech could parasitise newt species. The leech has been recorded on painted frog (Discoglossus pictus) and marsh frog ( Pelopphylax ridibundus) [3] in Morocco and has also be found to parasitize Bufo spiniosus in Tunisia[4] and Algeria[5], a possible pre-adaptation for parasitism of Bufo bufo in the UK.
There is no evidence of the leech being a problem for amphibians within its natural range but it will certainly be worth toad patrols and amphibian surveyors looking out for any new records of leech predation this coming breeding season and notifying the Garden Wildlife Health Project at ZSL of any new records.
References
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[1] Manenti, R., Lunghi, E., Canedoli, C., Bonaccorsi, M. and Ficetola, G., 2016. Parasitism of the leech, Batracobdella algira (Moquin-Tandon, 1846), on Sardinian cave salamanders (genus Hydromantes)(Caudata: plethodontidae). Herpetozoa, 29(1-2), pp.27-35.
[2] Lunghi, E., Ficetola, G.F., Mulargia, M., Cogoni, R., Veith, M., Corti, C. and Manenti, R., 2018. Batracobdella leeches, environmental features and Hydromantes salamanders. International Journal for Parasitology: Parasites and Wildlife, 7(1), pp.48-53.
[3] Mabrouki, Y., Ahmed, R.B., Taybi, A.F. and Rueda, J., 2019. An annotated checklist of the leech (Annelida: Hirudinida) species of the Moulouya River basin, Morocco, with several new distribution records and a historical overview. African Zoology, 54(4), pp.199-214.
[4] Hassine, J.B. and Escoriza, D.., 2014. Bufo spinosus in Tunisia: new data on occurrence, parasitism and tadpole morphology. Herpetol. Bull, 127, p.22.
[5] Merabet, K.. and Karar, M., 2021. First cases of predation of Bufo spinosus by two leech species in Algeria. The Herpetological Bulletin, 156(156), pp.38-39.