Macrobdella decora

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Macrobdella decora
Macrobdella decora white background.png
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Annelida
Clade: Pleistoannelida
Clade: Sedentaria
Class: Clitellata
Subclass: Hirudinea
Order: Arhynchobdellida
Family: Macrobdellidae
Genus: Macrobdella
Species:
M. decora
Binomial name
Macrobdella decora
(Say, 1824)
M. decora range.png
  Observed
Synonyms [1]
  • Hirudo decora Say, 1824

Macrobdella decora, also known as the North American medicinal leech, is a species of freshwater leech found in much of eastern North America in freshwater habitats, although there is one disjunct population in northern Mexico. M. decora is both a parasite of vertebrates, including humans, and an aquatic predator of eggs, larvae, and other invertebrates. Macrobdella decora is a medium-sized leech with a spotted greenish-brown back and a reddish underbelly. It has ten ocelli, or simple eyes, arranged in a horseshoe shape, as well as three long jaws. Internally, a pharynx takes up a tenth of its digestive tract; a stomach, the majority of its body length. The stomach connects to an intestine, followed by a colon, a rectum, and finally an anus located on the leech's back. M. decora, like all leeches, is hermaphroditic, and has ten testisacs and two ovisacs, in addition to male and female genital pores. First described by Thomas Say in 1824, the species is now placed in the genus Macrobdella. Its sister taxon is believed to be the species Macrobdella diplotertia.

Contents

Taxonomy

Macrobdella decora was originally placed in the genus Hirudo by Thomas Say, who described it in 1824 in an appendix to a book about an expedition up the Minnesota River. [2] When Addison Emery Verrill erected the genus Macrobdella in 1872, he transferred Say's species into his new genus Macrobdella. [3] : 138  A common name for the species is the North American medicinal leech. [4]

Macrobdella decora is the sister taxon to Macrobdella diplotertia ; the genus Macrobdella is believed to be a monophyletic grouping. Macrobdella ditreta was previously believed to be sister to the decora / diplotertia clade, but a new species, Macrobdella mimicus was discovered in 2023 and placed as the sister taxon to said clade. [5] : 587  [6] : 563 

Cladogram illustrating species closely related to M. decora

M. decora

M. diplotertia

M. mimicus

Description

Back of Macrobdella decora - note the row of orange dots down the middle and the two sets of black ones on the sides. Macrobdella decora (I1994) 0420 (42233396575).jpg
Back of Macrobdella decora – note the row of orange dots down the middle and the two sets of black ones on the sides.

Macrobdella decora is a medium-sized leech, growing between 5 and 8.5 cm (2.0 and 3.3 in) long, and weighing from 1.48 to 3.69 grams (0.052 to 0.130 oz). [7] : 67  [8] : 155  It has a dark green, brown or olive-green back with a line of 20 or so small orange or red dots down the middle, and two corresponding sets of black dots on its sides. Its underbelly is reddish with black spots dispersed irregularly across it. [7] : 67  [2] [9] [10] : 160  Its back is rounded but its belly is flattened. [10] : 160  [11] : 230  All leeches have 32 segments, but they are all also covered with external rings called annuli; the body of M. decora has between 90 and 94 annuli total. [12]

Anatomy

The head of M. decora is rounded and has ten ocelli on the front of its body: one pair between segments two and three; a second pair on segment three; a third on four; a fourth on six; and a fifth and final pair on segment nine. [3] : 138  They are arranged in the shape of a horseshoe. [10] : 160  [11] There are twenty-one ganglia in the leech's body. [10] : 166  A jawed leech, Macrobdella decora has three long jaws which are semicircular and laterally compressed, each with one row of about sixty-five teeth. [11] [13]

M. decora has a large muscular pharynx which accounts for the first tenth or so of the leech's digestive tract. The stomach, a large pouch composed of smaller sacs, is not nearly as muscular as the pharynx, but it occupies about five sixths of the leech's whole body and is subdivided into eleven chambers. The intestine extends from behind the stomach and narrows towards the anus. The last part of the intestine is the colon, followed finally by a small rectum. [10] : 163–5  The anus is located on the leech's back, above of its circular acetabulum. [11]

Leech saliva is known to contain several compounds, including hirudin, an anti-coagulant. [14] [15] The saliva of M. decora is known to contain several substances not previously all identified from the same leech, as well as an anticoagulant dubbed decorsin which might be unique to M. decora. [15]

Reproductive anatomy

All leeches are hermaphrodites whose male reproductive organs mature first and the female ones later. [16] M. decora has ten pairs of testisacs located from segments thirteen to twenty-three, with large, compact, and much-coiled epididymes, and crescent-shaped or globular ovisacs which are located in the thirteenth segment. A 2023 paper described the leech's oviducts as "thin" and "torturously folded". [8] : 155  [13] : 510  The male and female gonopores, which are external openings to the internal reproductive organs, are usually separated by five annuli, or external rings. [7] : 67  [17] [18] The male one, when withdrawn, appears as nothing more than a hole in between segments eleven and twelve; however, when the male gonopore and its surrounding parts are everted, they appear as a small cone, with the organ at the tip and having deeply furrowed sides. The leech's four copulatory glands are arrayed in a square in an area of rough skin on segments thirteen and fourteen. [13] : 509 

Ecology

Distribution and habitat

The most widely distributed Macrobdella species, M. decora, is found in North America east of the Rocky Mountains in southern Canada and the neighbouring United States. There is, however, one isolated population in Mexico, in the state of Nuevo León. [5] : 587  Leeches of the species have been found as far west as Alberta, North Dakota, Nebraska, Colorado, and New Mexico. [19] The leeches may be panmictic – that is to say, mixing and breeding randomly – across much their range. Some populations in Ontario and New England have refrained from panmixia, and, furthermore, a 2024 paper that studied the leeches' phylogeography concluded that it should not be assumed "that M. decora is truly panmictic" of the study's large range, and that more research into the topic was needed. [19] [20]

Macrobdella decora is a freshwater species that is found in still or slow-moving water bodies such as streams, temporary ponds, ditches, and wetlands. [7] [21] [22]

An individual from Buckingham, Quebec. North American Medicinal Leech imported from iNaturalist photo 56392667 on 4 December 2022.jpg
An individual from Buckingham, Quebec.

Parasitism and diet

Macrobdella decora is both parasitic and predaceous. It sucks the blood of many vertebrates, using its teeth to pierce the host's skin, including humans but also amphibians, fish, turtles, wading birds, and cattle. It also hunts voraciously, and eats oligochaete worms, snails, amphibian eggs, the larvae of insects, and even other individuals of its own species. In the spring, the leech's aggressive predation of American toad eggs may lead to up to 80% mortality. [7] : 67–8 

The leeches engorge themselves with blood before mating. One or two months after feeding, the leeches produce spongy cocoons, which are pale yellow and elliptical in shape. About another month later, the young, only 20 to 22 millimetres (0.79 to 0.87 in) long, emerge. [7] : 68  They take several years to become fully mature. [23]

Gut microbiome

The gut microbiome of the North American Macrobdella decora is quite similar to that of Europe's Hirudo verbana. Bacteria of the genera Aeromonas , Bacteroides , Butyricicoccus , and Proteocatella dominate M. decora's gut microbiota. [4] : 1  The intraluminal fluid – that is, fluids found in the gut [24] – was found to be most abundant with bacteria like Aeromonas and Bacteroidales ; combined, on median they represented 60% of microbiota living in the fluids, while much of the rest was Clostridiales , which on median accounted for 30% of the microbiota. [4] : 5 

Interactions with humans

Macrobdella decora does parasitize humans and is often found by people swimming in Canada and the northern United States. Sometimes swimming areas have had to be restricted or even closed due to the leech's presence. [7] : 67  Historically, M. decora was in fact not used very much in bloodletting, despite its common name as a "medicinal leech". [4] : 2  However, there is some evidence of their medicinal use as a replacement to the European medicinal leeches, specifically in Philadelphia during the 19th century. [19] Indeed, Addison Emery Verrill, writing in 1872, noted M. decora's use by doctors as a stand-in for "imported leeches", and he noted the North American species was "equally efficacious". [3] : 132  It is possible that human leech-trading helped move leeches between water bodies; today, they are sometimes used as and transported for fishing bait, but they are not a very favoured choice. [19]

Conservation

In Ontario, NatureServe lists the species as "Secure", but no assessment has been completed for other regions. [25] M. decora was described as unendangered in 2021 paper proposing its use as a model for digestive tract symbioses. [4] : 1 

Related Research Articles

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<span class="mw-page-title-main">Gastrointestinal tract</span> Organ system within humans and other animals

The gastrointestinal tract is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organs of the digestive system, in humans and other animals, including the esophagus, stomach, and intestines. Food taken in through the mouth is digested to extract nutrients and absorb energy, and the waste expelled at the anus as feces. Gastrointestinal is an adjective meaning of or pertaining to the stomach and intestines.

<span class="mw-page-title-main">Entoprocta</span> Phylum of aquatic invertebrates

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References

  1. ↑ "Macrobdella decora". WoRMS. World Register of Marine Species . Retrieved 5 January 2025.
  2. 1 2 Keating, William Hypolitus; Keating, William Hypolitus; Long, Stephen H.; Schweinitz, Lewis David von (1824). Narrative of an expedition to the source of St. Peter's river, Lake Winnepeek, Lake of the Woods, &c., performed in the year 1823, ... under the command of Stephen H. Long. Vol. 2. Philadelphia: H. C. Carey & I. Lea. p. 268.
  3. 1 2 3 Verrill, A. E.; Silliman, Benjamin (1872). Dana, James D.; Silliman, Benjamin (eds.). "Brief Contributions to Zoölogy from the Museum of Yale College. No. XVII.—Descriptions of North American fresh-water Leeches". The American Journal of Science and Arts. ser.3:v.3=no.13-18 (1872). New-Haven: S. Converse. Archived from the original on 2023-11-08. Retrieved 2024-11-29.
  4. 1 2 3 4 5 McClure, Emily Ann; Nelson, Michael C.; Lin, Amy; Graf, Joerg (2021-04-27). Johnson, Karyn N. (ed.). "Macrobdella decora: Old World Leech Gut Microbial Community Structure Conserved in a New World Leech". Applied and Environmental Microbiology. 87 (10). Bibcode:2021ApEnM..87E2082M. doi:10.1128/AEM.02082-20. ISSN   0099-2240. PMC   8117757 . PMID   33674439.
  5. 1 2 Phillips, Anna J.; Salas-Montiel, Ricardo; Kvist, Sebastian; Oceguera-Figueroa, Alejandro (2019-08-15). "Phylogenetic Position and Description of a New Species of Medicinal Leech from the Eastern United States". Journal of Parasitology. 105 (4): 587–597. doi:10.1645/18-119. ISSN   0022-3395. PMID   31414949.
  6. ↑ Phillips, Anna J.; Siddall, Mark E. (2005). "Phylogeny of the New World medicinal leech family Macrobdellidae (Oligochaeta: Hirudinida: Arhynchobdellida)". Zoologica Scripta. 34 (6): 559–564. doi:10.1111/j.1463-6409.2005.00210.x. ISSN   0300-3256.
  7. 1 2 3 4 5 6 7 Sawyer, Roy T. (1972). "North American freshwater leeches, exclusive of the Piscicolidae, with a key to all species". Illinois Biological Monographs. 46. Urbana: University of Illinois Press. doi:10.5962/bhl.title.53881. hdl: 2142/27340 . ISBN   0-252-00214-8. OCLC   304005. Archived from the original on 2017-03-19. Retrieved 2024-11-29.
  8. 1 2 Phillips, Anna J.; Goetz, Freya E. (2023). "Comparative reproductive morphology of two species of Macrobdella (Hirudinea: Arhynchobdellida: Macrobdellidae)". Zoomorphology. 142 (2): 153–168. doi:10.1007/s00435-023-00596-6. ISSN   0720-213X.
  9. ↑ Govedich, Fredric R.; Bain, Bonnie A.; et al. (2001). "Annelida (Clitellata): Oligochaeta, Branchiobdellida, Hirudinida, and Acanthobdellida". Ecology and Classification of North American Freshwater Invertebrates. Elsevier. ISBN   978-0-12-690647-9.
  10. 1 2 3 4 5 Brooks, William Keith (1882). Handbook of invertebrate zoology. For laboratories and seaside work. Boston: S. E. Cassino.
  11. 1 2 3 4 Leidy, Joseph (1868). "Notice of some American Leeches". Proceedings of the Academy of Natural Sciences of Philadelphia. Vol. 20. Philadelphia: Academy of Natural Sciences of Philadelphia. p. 230. Archived from the original on 2022-01-20. Retrieved 2024-11-30.
  12. ↑ Kuo, Dian-Han; Lai, Yi-Te (4 November 2018). "On the origin of leeches by evolution of development". Development, Growth & Differentiation. 61 (1): 43–57. doi: 10.1111/dgd.12573 . PMID   30393850. S2CID   53218704. and a fixed number (32) of segments
  13. 1 2 3 Moore, J. Percy (Feb 1901). "The Hirudinea of Illinois". Bulletin of the Illinois State Laboratory of Natural History. 5. Archived from the original on 2024-12-02. Retrieved 2024-11-30.
  14. ↑ "IV. On the action of a secretion obtained from the medicinal leech on the coagulation of the blood". Proceedings of the Royal Society of London. 36 (228–231): 478–487. 1883. doi: 10.1098/rspl.1883.0135 .
  15. 1 2 Min, Gi-Sik; Sarkar, Indra Neil; Siddall, Mark E. (2010). "Salivary Transcriptome of the North American Medicinal Leech, Macrobdella decora". Journal of Parasitology. 96 (6): 1211. doi:10.1645/GE-2496.1. ISSN   0022-3395.
  16. ↑ Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate Zoology, 7th Edition. Cengage Learning. pp. 477–8. ISBN   978-81-315-0104-7.
  17. ↑ "Crustacea Glossary::Definitions". research.nhm.org. Retrieved 2025-01-04.
  18. ↑ "gonopore". Oxford Reference. Retrieved 2025-01-04.
  19. 1 2 3 4 Kennedy, Nat; Kvist, Sebastian; Oceguera-Figueroa, Alejandro; Phillips, Anna J.; Stacey, Donald F.; de Carle, Danielle (2024-09-03). "A phylogeographic analysis of the North American medicinal leech, Macrobdella decora (Say, 1824)". Zoologica Scripta. 54: 103–118. doi: 10.1111/zsc.12692 . ISSN   0300-3256.
  20. ↑ "Definition of PANMIXIA". www.merriam-webster.com. Retrieved 2025-01-04.
  21. ↑ Garcia de Jesus, Erin I. "This Smithsonian Scientist is on a Mission to Make Leeches Less Scary". www.smithsonianmag.com. Archived from the original on 2024-11-30. Retrieved 2024-11-29.
  22. ↑ "Freshwater leech (Macrobdella decora) – Lloyd Center for the Environment, Dartmouth MA" . Retrieved 2024-11-29.
  23. ↑ Beckerdite, Fred Willie. The Description and Life History of a New Species of Alloglossidium (Trematoda: Macroderoididae).Alloglossidium (Trematoda: Macroderoididae) (PhD thesis). Louisiana State University and Agricultural and Mechanical College. Archived from the original on 2024-07-19. Retrieved 2024-12-20.
  24. ↑ Skolnick, M. Leon (1981), Skolnick, M. Leon (ed.), "Intra- and Extraluminal Fluid", Real-time Ultrasound Imaging in the Abdomen, New York, NY: Springer, pp. 191–212, doi:10.1007/978-1-4612-5919-0_9, ISBN   978-1-4612-5919-0, archived from the original on 2025-01-01, retrieved 2025-01-01
  25. ↑ NatureServe. "Macrobdella decora". NatureServe Explorer. Arlington, Virginia.
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