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Kodiak Blackjack/sandbox2
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Platyhelminthes
Class: Cestoda
Order: Tetraphyllidea
Family: Phyllobothriidae
Genus: Clistobothrium
Dailey & Vogelbein, 1990
Type species
Clistobothrium carcharodoni
Species

5 recognized, 11 known; see text

Clistobothrium is a genus of phyllobothriidean[1] tapeworms from the family Phyllobothriidae.[2] Members of this genus parasitize the spiral intestine of mackerel sharks (order Lamniformes), which serve as their definitive hosts.

Adult Clistobothrium specimens have been collected from all five extant members of the family Lamnidae—the great white shark, the shortfin mako, the longfin mako, the porbeagle, and the salmon shark—as well as the only living representative of the family Pseudocarchariidae, the crocodile shark (Pseudocarcharias kamoharai). Clistobothrium larvae, or plerocerci, are transmitted to the intestines of their intended host through the consumption of infected prey: known secondary and/or paraptenic hosts of these tapeworms include marine mammals (esp. dolphins and pinnipeds), squaliform sharks, squid, oarfish, and sockeye salmon. This makes the presence of larval or adult Clistobothrium infection in an organism an invaluable long-term biomarker for those researching their host's predator-prey interactions with other organisms in the marine food web.[3]

The systematics of this genus are an ongoing matter of debate among parasitologists, and are complicated by the difficulty of correctly identifying their larval forms,[4] obtaining host cadavers for necropsies,[5] and the inherent ethical concerns of doing so.[6] As of 2024, five species are currently recognized as valid by the World Register of Marine Species (WoRMS), but recent molecular phylogenetics support the existence of up to eleven.

Taxonomy[edit]

As of May 2024, five species of Clistobothrium have been formally described and recognized by the World Register of Marine Species:[2]

Another two species were transferred to Clistobothrium following a phylogenetic review of the genus conducted in 2020,[9] but are not yet recognized by the World Register of Marine Species:[2]

Four undescribed species are also known from this genus.[9]

Etymology and nomenclatural history[edit]

The genus Clistobothrium was first erected in 1990 following the discovery and subsequent description of the type species, Clistobothrium carcharodoni.[7] The genus derives its name from the Greek words clisto (κλειστός), meaning "closed," and bothrios (βόθρος), meaning "pit."[16] Although this was the first Clistobothrium species described as such,

Phylogeny[edit]

Anatomy and description[edit]

Life cycle[edit]

Host records[edit]

C. amyae, C. gabywalterorum[edit]

The definitive host of both Clistobothrium amyae and Clistobothrium gabywalterorum is the crocodile shark (Pseudocarcharias kamoharai).

C. carcharodoni, C. tumidum[edit]

The definitive host of both Clistobothrium carcharodoni and Clistobothrium tumidum is the great white shark (Carcharodon carcharias).

C. montaukense[edit]

The definitive host of Clistobothrium montaukense is the shortfin mako shark (Isurus oxyrinchus).

The plerocercoid stage has been recorded in giant oarfish (Regalecus glesne), indicating the possibility of a predator-prey relationship between the two species.

Clistobothrium n. sp. 1[edit]

The definitive host of Clistobothrium n. sp. 1 (formerly Clistobothrium cf. montaukensis) is the porbeagle shark (Lamna nasus).

The pleocercoid stage is known from three species: the western highfin spurdog (Squalus altipinnis), the longnose velvet dogfish (Centroselachus crepidater), and Russel's oarfish (Regalecus russelii).

Clistobothrium n. sp. 2[edit]

The definitive host of Clistobothrium n. sp. 2 is the longfin mako shark (Isurus paucus).

Clistobothrium n. sp. 3[edit]

The definitive host of Clistobothrium n. sp. 3 is the salmon shark (Lamna ditropis).

C. delphini, C. grimaldii, and Clistobothrium n. sp. 4[edit]

As of 2024, the definitive hosts of Clistobothrium delphini, Clistobothrium grimaldii, and Clistobothrium n. sp. 4 remain unknown — all three species are known only from their pleocercoid stage.

The possibility of the megalodon having survived to the present-day and being the definitive host of these species has been jokingly posited as an explanation for their lack of adult records.[17]

References[edit]

Citations[edit]

  1. ^ Caira et. al 2014.
  2. ^ a b c Bray & Gibson 2021.
  3. ^ Caira et. al 2020, p. 1043: "Cestodes are considered ideal subjects for providing valuable insights into the predator–prey relationships between their definitive and intermediate hosts because they are trophically transmitted between the series of hosts required to complete their complex life-cycles (Caira and Reyda, 2005; Jensen and Bullard, 2010)."
  4. ^ Caira et. al 2020, p. 1043: "This is, however, only the case if individual cestode larvae can be accurately associated with their corresponding adult form. This task is often challenging because the undifferentiated morphology of the larvae of many cestode species looks little like that of the adult form on which their taxonomy is based (e.g., Joyeux and Baer, 1961; Chambers et al., 2000; Jensen and Bullard, 2010)."
  5. ^ Caira et. al 2020, p. 1052: "Alternatively, it may simply be an artefact of poor sampling—in both regions the number of [great white] shark individuals examined was extremely small."
  6. ^ Caira et. al 2020, p. 1052: "[G]reat white sharks in the western Mediterranean Sea would be especially interesting to investigate. Unfortunately, the fact that sharks must be sacrificed in order for cestodes to be collected from their spiral intestines is complicated by concern for the dwindling numbers of this iconic animal."
  7. ^ a b Dailey & Vogelbein 1990.
  8. ^ a b Ruhnke 1993.
  9. ^ a b Caira et. al 2020.
  10. ^ Caira et. al 2020, p. 1050: "Phyllobothrium delphini (Bosc, 1802) van Beneden, 1868 is hereby transferred to Clistobothrium as Clistobothrium delphini (Bosc, 1802)"
  11. ^ Caira et. al 2020, p. 1050: "Monorygma grimaldii (Moniez, 1889) Baylis, 1919 is hereby transferred to Clistobothrium as Clistobothrium grimaldii (Moniez, 1889)"
  12. ^ Caira et. al 2020, p. 1044: "Randhawa and Brickle (2011) [...] referred to this species as Clistobothrium cf. montaukensis; in recognition of its distinct taxonomic status, it is referred to here as Clistobothrium n. sp. 1."
  13. ^ Caira et. al 2020, p. 1049: "Our collections from lamniform sharks appear to have yielded adults of two undescribed species of Clistobothrium [...] The first, which we have referred to as Clistobothrium n. sp. 2, was discovered in the longfin mako shark in Taiwan.
  14. ^ Caira et. al 2020, p. 1050: "In recognition of their novel molecular signature, these larvae are provisionally referred to here as Clistobothrium n. sp. 3—the name assigned to the adults of Clistobothrium found in the salmon shark off Alaska."
  15. ^ Caira et. al 2020, p. 1050: "The large plerocercoid form of Aznar et al. (2007), which has not yet been assigned a formal name, is herein referred to as Clistobothrium n. sp. 4."
  16. ^ Dailey & Vogelbein 1990, p. 108: "ETYMOLOGY: Clisto (Gr.) = closed; bothrios (Gr.) = pit."
  17. ^ Caira et. al 2020, p. 1053: "As a farfetched alternative hypothesis, we are left wondering if the giant Carcharocles megalodon (Agassiz) is perhaps not in fact extinct after all, but instead roams the oceans of the world today, devouring marine mammals with abandon, and thereby maintaining the life-cycles of these three elusive species of Clistobothrium!"

Bibliography[edit]

  • Bray, Rod (9 June 2021) [10 September 2010]. Gibson, David (ed.). "Clistobothrium Dailey & Vogelbein, 1990". WoRMS. World Register of Marine Species. Retrieved 23 May 2024.

Category:Cestoda Category:Cestoda genera Category:Parasitic helminths of fish Category:Taxa described in 1990

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