- Scientific name: Macrobdella sestertia
- Species of Greatest Conservation Need (MA State Wildlife Action Plan)
- Special Concern (MA Endangered Species Act)
Description
The New England medicinal leech is one of the largest leeches found in New England, reaching a length of 150 mm (6 in). The dorsal surface is bright to olive green in color with 20 or more reddish orange spots along its median and 20 or more rectangular pots along its margins (Sawyer 1986). The ventral surface is orange to red with occasional black patches. This species is a sanguivorous (bloodsucking) leech, having a medium to large mouth with 38 to 48 teeth on each of its toothed jaws. Five pairs of eyes form a distinctive arch along the front end of the animal. Identification of this species is difficult because it requires knowledge of specific anatomical features of leeches.
The New England medicinal leech is closely related to the American medicinal leech (Macrobdella decora), a common and widespread species. These two species are quite similar in color and size but can be differentiated by the number of copulatory gland pores and the number of annuli between male and female gonopores. The New England medicinal leech has 24 copulatory glands with gonopores separated by 2.5 annuli on its ventral surface, while the American medicinal leechhas only four gland pores with gonopores separated by 4.5 annuli (Smith 1977). See Smith and Hanlon (1997) to separate these species and images from Phillips et al. (2016) for copulatory gland and gonopore examples of M. sestertia.
Life cycle and behavior
Little is known of the life history and behavior of the New England medicinal leech. The species is presumed to be similar to the American medicinal leech (M. decora), a closely related, more common, and widespread sanguivorous (blood-feeding) leech. Peak activity periods of this similar leech are during the spring and early summer. It is found in warm, protected shallow areas of ponds with little wave action. It stays concealed during the day in dark places provided by vegetation, stones, and debris, and is most active at night (Moore 1923). The species moves along the substrate like that of inchworms, and swims through the water column in an undulating motion. As a sanguivorous leech, it parasitizes vertebrates presumably amphibians and may also consume fish and amphibian eggs and embryos (Poly 2018).
Distribution and abundance
The New England medicinal leech is one of the rarest species of leech in North America. Until the early 1990s it was thought that the New England medicinal leech was endemic to the coastal freshwaters of Massachusetts. Since then, the distribution of the species has expanded to Maine (Smith and Hanlon 1997), New Hampshire (Phillips et al. 2016), and more recently South Carolina (Poly 2018), where its native status is unclear. The species has not been observed since 2008 across its entire range, but not enough evidence supports the species’ extinction (Carlson and Phillips 2020).
Little is known regarding the status of the New England medicinal leech in Massachusetts. Only three individuals have been collected from the state since Whitman described the species in 1886, bringing the total number of discoveries in the state to four. Two specimens were collected from a lake in Essex County and one from a river in the town of Harwich. The only information available regarding those specimens described by Whitman is that they were collected from the Massachusetts coastal plain. Only one of those specimens was saved and it can be found in Harvard University’s Museum of Natural History (Smith 1977). Several attempts were made to find the species again in Essex County but were unsuccessful (M. Siddall, personal communication 2003). This rarely encountered leech is listed under the Massachusetts Endangered Species Act as a species of Special Concern. All listed species are protected from killing, collecting, possessing, or sale and from activities that would destroy habitat and thus directly or indirectly cause mortality or disrupt critical behaviors. In addition, listed animals are specifically protected from activities that disrupt nesting, breeding, feeding, or migration.
Habitat
The New England medicinal leech inhabits shallow waters along the Atlantic coastal plain. In Massachusetts, early specimens were found in the detritus of a vegetated area along the shores of a coastal kettlehole pond that was characterized by dark, naturally tea-colored waters. Elsewhere it has been recorded from a pristine, clear, low-nutrient lake in inland Maine (Smith and Hanlon 1997) and in clear streams with rocky substrates in South Carolina (Poly 2018).
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Threats
Habitat degradation of potential wetlands including shoreline development, water quality degradation from pollution, and potential water level alterations pose potential threats to this species. Further, threats to local populations of amphibians including frogs may indirectly affect the persistence of this species.
Conservation
Survey and monitoring
The New England medicinal leech has not been observed in Massachusetts since the late 1970s. Limited survey effort and lack of identification skills may have contributed to its current known status in Massachusetts. Surveys are needed to redocument this species at its historical sites and in new waterbodies that may support the species. Monitoring is recommended every five years or to the extent practical at its historical locations. New documentation of the species is plausible along the coastal regions of Massachusetts and New England.
Management
If the species is still extant in Massachusetts, protection of wetlands from habitat degradation (e.g., water quality, water level alteration, riparian development) is critical for species persistence.
Research needs
The species needs standardized surveys at historical and new potentially suitable waterbodies to better understand its distribution, abundance, host preferences, phenology, and habitat requirements in Massachusetts. Discovery of new populations is critical for its status in Massachusetts but also for the species rangewide.
References
Phillips, A.J., R. Salas-Montiel, and A. Oceguera-Figueroa. 2016. Distribution of the New England Medicinal Leech, Macrobdella sestertia Whitman, 1886 and redeterminations of specimens of Macrobdella (Annelida: Clitellata: Macrobdellidae) at the National Museum of Natural History, Smithsonian Institution. Proceedings of the Biological Society of Washington 129:103-113.
Carlson, C.J. and A.J. Phillips. 2020. Is the New England medicinal leech (Macrobdella sestertia) extinct? Biological Conservation 243:108495.
Moore, J.P. 1923. The control of bloodsucking leeches, with an account of the leeches of Palisades Interstate Park. Roosevelt Wild Life Bulletin 2: 1-53.
Poly, W.J. 2018. Range extension for the elusive New England medicinal leech, Macrobdella sestertia Whitman, 1886 (Hirudinida: Macrobdellidae), in South Carolina, U.S.A., with notes on morphology, coloration, and biology. Proceedings of the California Academy of Sciences 4, 64(12):347-359.
Sawyer, R.T. 1986. Leech biology and behavior Volume II. Feeding biology, ecology, and systematics. Oxford University Press, Oxford, England. pp 419-793.
Smith, D.G. 1977. The rediscovery of Macrobdella sestertia Whitman (Hirudinea: Hirudinidae). J. Parasitol. 63: 759-760.
Smith, D.G. 1981. Selected freshwater invertebrates proposed for special concern status in Massachusetts. Massachusetts Department of Environmental Quality Engineering. Division of Water Pollution Control. Westborough, MA.
Smith, D.G., and S. Hanlon. 1997. Macrobdella sestertia (Hirudinea: Hirudinidae) in Maine and a key to the Hirudiniform leeches of Maine. Northeastern Naturalist 4 (4): 231:236.
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| Date published: | April 11, 2025 |
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