Branchellion torpedinis

Branchellion torpedinis
Branchellion torpedinis photographed in Granada in 2019.
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Annelida
Clade:	Pleistoannelida
Clade:	Sedentaria
Class:	Clitellata
Subclass:	Hirudinea
Order:	Rhynchobdellida
Family:	Piscicolidae
Genus:	Branchellion
Species:	B. torpedinis
Binomial name
Branchellion torpedinis Savigny, 1822

Branchellion torpedinis is a species of marine leech found in the North Atlantic Ocean and the Mediterranean Sea. A permanent and exclusive parasite of elasmobranchs, B. torpedinis was first described in 1822 from the eastern Mediterranean.

Classification

Branchellion torpedinis was first described in 1822 by Jules-César Savigny from the eastern Mediterranean. Its specific epithet, torpedinis, refers to its hosts, which include the electric rays, or Torpedo . ^[1] The genus Branchellion, which B. torpedinis is the type species, was erected in the same work. ^{[1] [2]} The leeches are classified in the family Piscicolidae, jawless parasites of saltwater fish. ^[3] In 2023, a new species of Branchellion, dubbed B. brevicaudatae, was discovered from Japan, parasitizing the short-tail stingray. ^[4] A maximum-likelihood phylogenetic analysis based on genetic information found that the new species was the sister taxon to B. torpedinis. ^[5]

Cladogram of species related to Branchellion torpedinis

B. lobata B. parkeri Branchellion sp. B. torpedinis B. brevicaudatae

After a phylogenetic tree by Jimi et al., 2023.

Distribution

Underside of Branchellion torpedinis, 5 centimetres (2 in) long.

Branchellion torpedinis is found in the Atlantic Ocean along the coasts of the United States Europe, and Senegal. In 1994 the leech was discovered in Venezuela; it had been found along with another Branchellion species feeding on a spotted eagle ray which was caught by a fisherman near Ocumare de la Costa. ^[6] It was also collected the same year on the same species in the Caribbean. ^[7]

Description

All members of the genus Branchellion sport distinctive leaf-shaped gills. B. torpedinis has 33 pairs of gills on each annulus located between its fourteenth and twenty-fifth segments. The gills do not move endogenously. In young leeches, the gills are reduced by "outfoldings of loose skin" similar to structures found on Trachelobdella lubrica . ^[2]

Reproductive and genetic biology

The morphology of Branchellion torpedinis spermatozoa is "basically the same" as that of Piscicola geometra , a freshwater leech. ^[8] In the leeches' post-embryonic development, their genital areas are "very conspicuous" unlike some other Rhynchobdellid species, such as Haementeria ghiliani . ^[9] The leeches have 12 sets of chromosomes; this number varies among all leeches and even within the family Piscicolidae: for example, the Arhynchobdellid species Erpobdella octoculata has 8 sets of chromosomes, while the Piscicolid species Piscicola geometra has 16. ^[10] There is a phylogenetic trend among leeches "for chromosomes to become smaller and more numerous". ^[11] Humans, by contrast, have only two sets of chromosomes. ^[12]

Behaviour

Branchellion torpedinis is an exclusive parasite of elasmobranch fish. Their parasitism is known to cause death, and, more mildly, a variety of symptoms such as anorexia and anemia. Accidental introductions of B. torpedinis to aquariums are hard to manage. ^[13] Many piscicolid leeches drop off from their fishy hosts after feeding to go plant their cocoons, but B. torpedinis is believed to a permanent parasite, sticking to its hosts all its life. ^[3]

References

1. Savigny 1822, p. 109.
2. Sawyer 1986, p. 101.
3. Marancik, Dove & Camus 2012, p. 52.
4. Jimi et al. 2023, p. 308.
5. Jimi et al. 2023, pp. 311–2.
6. Pauls & Provenanzo 1999, p. 73.
7. Williams, Bunkley-Williams & Burreson 1994, p. 133.
8. Sawyer 1986, p. 22.
9. Sawyer 1986, p. 53.
10. Sawyer 1986, p. 19.
11. Sawyer 1986, p. 17.
12. "Diploid". www.genome.gov. Retrieved 2025-03-31.
13. Marancik 2012, p. 1.

Bibliography

• Jimi, Naoto; Shinji, Junpei; Hookabe, Natsumi; Okanishi, Masanori; Woo, Sau Pinn; Nakano, Takafumi (2023). "A New Species of Branchellion (Hirudinea: Piscicolidae) Parasitizing the Gills of Short-tail Stingrays (Batoidea: Dasyatidae) From the West Pacific". Zoological Science . 40 (4). doi:10.2108/zs220057. hdl: 2433/284559 .
• Marancik, David Paul (2012). Understanding the Pathologic and Immunologic Relationship Between Elasmobranchs and the Marine Leech Branchellion torpedinis (PDF) (PhD thesis). University of Georgia.
• Marancik, David P.; Dove, Alistair P.; Camus, Alvin C. (10 Oct 2012). "Experimental Infection of Yellow Stingrays Urobatis jamaicensis with the Marine Leech Branchellion torpedinis" (PDF). Diseases of Aquatic Organisms . 101. doi:10.3354/dao02508.
• Pauls, Sheila M.; Provenanzo, Fransisco (March 1999). "Branchellion torpedinis Savigny, 1822 (Hirudinea, Piscicolidae): primera cita de una sanguijuela marina para Venezuela" [Branchellion torpedinis Savigny, 1822 (Hirudinea, Piscicolidae): first record of a marine leech from Venezuela.](PDF). Acta Biologica Venezuelica  [ es ] (in Spanish). 19 (1).
• Savigny, Jules-César (1822). "Système des Annelides, principalement de celles des côtes de l'Égypte et de la Syrie" [Systematics of Annelids, mainly those of the Egyptian and Syrian coasts]. Description de l'Égypte (in French). Vol. 1.
• Sawyer, Roy T. (1986). Leech Biology and Behaviour Volume I: Anatomy, Physiology, and Behaviour. Oxford Science Publishing. ISBN   0-19-857377-4.
• Williams, Ernest H.; Bunkley-Williams, Lucy; Burreson, Eugene (1994). "Some New Records of Marine and Freshwater Leeches from Caribbean, Southeastern U.S.A., Eastern Pacific, and Okinawan Animals" (PDF). Journal of the Helminthological Society of Washington . 61 (1).