# Turtle leech
Turtle leeches are freshwater leeches, chiefly in the glossiphoniid genera *Placobdella* and *Placobdelloides*, that attach to turtles and feed on their blood. They are jawless leeches of the order [Rhynchobdellida](https://www.edgepedia.org/rhynchobdellida) that use a proboscis to obtain a blood meal by penetrating epidermal tissues under the scales or bony tissues of the turtle shell[1](https://www.sciencedirect.com/org/science/article/pii/S131428362000007X). The best-known North American species is the smooth turtle leech, *Placobdella parasitica* (Say, 1824)[2](https://scholars.uky.edu/en/publications/an-assessment-of-leech-parasitism-on-semi-aquatic-turtles-in-the-/).
| Key fact | Detail |
|---|---|
| Group | Glossiphoniid leeches (Rhynchobdellida), mainly *Placobdella* in the Americas and *Placobdelloides* in Africa, Asia, and Australasia[1](https://www.sciencedirect.com/org/science/article/pii/S131428362000007X) • [3](https://pmc.ncbi.nlm.nih.gov/articles/PMC6254108/) |
| Feeding | Jawless; a proboscis penetrates epidermal tissue under scales or bony shell tissue to take blood[1](https://www.sciencedirect.com/org/science/article/pii/S131428362000007X) |
| Attachment sites | Mostly the underside of marginal scutes and the region between the plastron and inguinal area[2](https://scholars.uky.edu/en/publications/an-assessment-of-leech-parasitism-on-semi-aquatic-turtles-in-the-/) |
| Prevalence example | In nine North Carolina ponds, *P. parasitica* was the only leech found on turtles and occurred in every pond[2](https://scholars.uky.edu/en/publications/an-assessment-of-leech-parasitism-on-semi-aquatic-turtles-in-the-/) |
| Disease vector | *Placobdella costata* is the unique vector of the blood parasite *Haemogregarina stepanowi*[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC10302864/) |
| Parental care | *Placobdelloides siamensis* both carries its cocoons and attaches them to the substrate[3](https://pmc.ncbi.nlm.nih.gov/articles/PMC6254108/) |
| Winter persistence | Leeches of several size classes remain attached to hibernating adult map turtles throughout the winter[5](https://pubmed.ncbi.nlm.nih.gov/9406801/) |
## Feeding and attachment
Turtle leeches are hematophagous ectoparasites. *Placobdelloides siamensis*, the Siamese shield leech, feeds by penetrating the epidermis under scales or the bony tissue of the shell with a proboscis[1](https://www.sciencedirect.com/org/science/article/pii/S131428362000007X). Surveys record most leeches attached to the underside of the marginal scutes or between the plastron and the inguinal region, positions where the shell edges meet the body[2](https://scholars.uky.edu/en/publications/an-assessment-of-leech-parasitism-on-semi-aquatic-turtles-in-the-/). When turtles are removed from water, leeches concentrate on the head, axillary, groin, and caudal regions, the moistest parts of the body; leeches left on a dry shell overnight shrink and die[1](https://www.sciencedirect.com/org/science/article/pii/S131428362000007X).
Attachment is persistent. In a winter study of map turtles (*[Graptemys](https://www.edgepedia.org/graptemys)*), leeches of various size classes remained attached to hibernating adults throughout the winter, and in a March sample all seven turtles recovered carried leeches, four of them with broods of 9 to 52 young[5](https://pubmed.ncbi.nlm.nih.gov/9406801/).
## Host range and specificity
Host use varies by species. *Placobdella parasitica* is common on North American turtles and was the only parasitic leech found in a 2005 survey of nine ponds in the North Carolina Piedmont[2](https://scholars.uky.edu/en/publications/an-assessment-of-leech-parasitism-on-semi-aquatic-turtles-in-the-/). At the other extreme, *Placobdella multilineata* is a generalist reported from 18 species and subspecies of alligators, amphibians, crocodiles, snakes, and turtles across the southeastern United States and northward through the [Mississippi River](https://www.edgepedia.org/mississippi-river) valley[6](https://scholarworks.uark.edu/cgi/viewcontent.cgi?article=3264&context=jaas). Other *Placobdella* species span the range: *P. montifera* and *P. phalera* infest many host species, while *P. ornata* infests turtles as well as fish, amphibians, birds, and humans[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC10302864/).
In Southeast Asia, *Placobdelloides siamensis* parasitizes geoemydid turtles including the Southeast Asian box turtle (*Cuora amboinensis*), the yellow-headed temple turtle (*Heosemys annandalii*), and three snail-eating turtles of the genus *Malayemys*[3](https://pmc.ncbi.nlm.nih.gov/articles/PMC6254108/). Later work added *Cyclemys oldhamii* and *Heosemys grandis* as hosts and reported the leech across northern, northeastern, western, central, and southern Thailand[1](https://www.sciencedirect.com/org/science/article/pii/S131428362000007X).
## Effects on hosts
**Prevalence and intensity vary widely.** In the North Carolina Piedmont survey, female [painted turtles](https://www.edgepedia.org/painted-turtle) were parasitized more often than males (54.7% versus 40.9%), possibly because they are larger and offer more attachment surface, and snapping turtles carried the highest load of any species at a mean of 32.3 leeches per turtle[2](https://scholars.uky.edu/en/publications/an-assessment-of-leech-parasitism-on-semi-aquatic-turtles-in-the-/). On map turtles, 72.6% of 208 females but only 28.6% of 35 males carried at least one *P. parasitica*, a significant difference[5](https://pubmed.ncbi.nlm.nih.gov/9406801/).
Heavy infestations can be severe. In Thailand, every *Malayemys* turtle examined carried *P. siamensis* throughout the year, with an average of 474.80 ± 331.38 leeches per infected host, or 76.53 ± 20.27 leeches per 100 g of body weight; infection was higher in larger and heavier turtles and was not affected by season or aquatic environmental factors[1](https://www.sciencedirect.com/org/science/article/pii/S131428362000007X). Concentrated leech colonies caused rot wounds and shell holes that killed hosts, and heavy parasitism harms turtles through anemia, malnutrition, and haemoparasite transmission[1](https://www.sciencedirect.com/org/science/article/pii/S131428362000007X).
**Native versus invasive hosts.** In an Atlantic Forest assemblage in southern Brazil after more than 10 years of co-occurrence, 19 of 62 captured turtles carried the hematophagous leech *Placobdella* sp., a prevalence of 30% for the assemblage. Native turtles showed 56% prevalence against 3% for invasive taxa, and 89% of parasitized individuals were the native side-necked turtle *Phrynops geoffroanus*, with infestation intensities of 1 to 96 leeches per turtle; one *Hydromedusa tectifera* carried more than 300 ectoparasites. The authors attributed the native-invasive gap to parasite-host coevolution and specificity[7](https://pmc.ncbi.nlm.nih.gov/articles/PMC12673372/).
## Role as disease vectors
Turtle leeches transmit blood parasites of the genus *Haemogregarina*, apicomplexans whose life cycle requires a vertebrate intermediate host and an invertebrate definitive host and vector[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC10302864/). *Placobdella costata* is known as the unique vector of *Haemogregarina stepanowi*, which infects many European and North African freshwater turtles including *Emys orbicularis* and several *[Mauremys](https://www.edgepedia.org/mauremys)* species[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC10302864/). In an experimental demonstration, six *Placobdella ornata* fed on a painted turtle infected with *Haemogregarina balli* and, after a period of diapause, transmitted the parasite to two laboratory-reared snapping turtles[8](https://pubmed.ncbi.nlm.nih.gov/11695407/).
## Life history and taxonomy
Glossiphoniid turtle leeches show parental care. Study of live *Placobdelloides siamensis* provided the first data on its coloration and on the combination of carrying cocoons and attaching cocoons to the substrate[3](https://pmc.ncbi.nlm.nih.gov/articles/PMC6254108/). Brooding is also visible in field data: in the map turtle winter study, one 64.4 mm leech carried 153 brood-sized young (mean 4.5 mm) on its venter, and broods were found on 16.3% of females and 5.7% of males[5](https://pubmed.ncbi.nlm.nih.gov/9406801/).
Taxonomy within the group is active. Molecular work on *P. costata* has shown independent lineages suggesting at least five unique leech species across [Western Europe](https://www.edgepedia.org/western-europe), and seven lineages across [Central and Eastern Europe](https://www.edgepedia.org/central-and-eastern-europe) and Algeria based on COI and ITS1 variation[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC10302864/). New species continue to be described, including *Placobdella ringueleti* from turtles in Chiapas, Mexico in 2009[9](https://pubmed.ncbi.nlm.nih.gov/19566347/) and *Placobdelloides sirikanchanae* from southern Thailand, the second member of its genus found on geoemydid turtles[10](https://www.sciencedirect.com/org/science/article/pii/S1313298919001642). In eastern North America, the two common turtle-feeding species *P. parasitica* and *P. rugosa* overlap geographically and coexist on the same hosts, and a 2021 study of a tuberculated [Albemarle](https://www.edgepedia.org/albemarle) leech from northeastern North Carolina provisionally identified it as *P. multilineata* while noting that radical morphological transformations across its life cycle complicate diagnosis[11](https://www.mapress.com/zt/article/view/42838).
## References
1. [Trivalairat et al. Parasitism of *Placobdelloides siamensis* in snail-eating turtles, *Malayemys* spp.](https://www.sciencedirect.com/org/science/article/pii/S131428362000007X)
2. [McCoy, Failey, Price & Dorcas. An assessment of leech parasitism on semi-aquatic turtles in the Western Piedmont of North Carolina](https://scholars.uky.edu/en/publications/an-assessment-of-leech-parasitism-on-semi-aquatic-turtles-in-the-/)
3. [Redescription of the Siamese shield leech *Placobdelloides siamensis* with new host species and geographic range](https://pmc.ncbi.nlm.nih.gov/articles/PMC6254108/)
4. [Molecular phylogenies of leeches and haemoparasites infecting freshwater turtles in aquatic ecosystems of Northern Africa](https://pmc.ncbi.nlm.nih.gov/articles/PMC10302864/)
5. [Map turtle winter leech loads (PubMed)](https://pubmed.ncbi.nlm.nih.gov/9406801/)
6. [Leech parasitism of the Gulf Coast box turtle, *Terrapene carolina major*, in Mississippi, USA](https://scholarworks.uark.edu/cgi/viewcontent.cgi?article=3264&context=jaas)
7. [Leech infestation patterns between native and invasive freshwater turtles](https://pmc.ncbi.nlm.nih.gov/articles/PMC12673372/)
8. [Transmission of *Haemogregarina balli* from painted turtles to snapping turtles through the leech *Placobdella ornata*](https://pubmed.ncbi.nlm.nih.gov/11695407/)
9. [New species of rhynchobdellid leech, a parasite of turtles from Chiapas, Mexico](https://pubmed.ncbi.nlm.nih.gov/19566347/)
10. [*Placobdelloides sirikanchanae* sp. nov., a new glossiphoniid leech and turtle parasite from lower southern Thailand](https://www.sciencedirect.com/org/science/article/pii/S1313298919001642)
11. [Sawyer, R.T. (2021). Description and taxonomic analysis of a tuberculated turtle leech from the Outer Banks, North Carolina. Zootaxa 4991(1)](https://www.mapress.com/zt/article/view/42838)
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*Topic: Encyclopedia › Life and health › Animals › Invertebrates › Other invertebrate lineages › Annelids › Clitellata › Leeches (Hirudinea) › Leech reproduction and ecology*
*Initially written Sep 17, 2026 · Reviewed: Oct 21, 2026 · Edited: Oct 15, 2026; Oct 21, 2026 · Last review: Oct 21, 2026*
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