Smalltooth sawfish

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Smalltooth sawfish
Pristis pectinata in
Aquarium of the Americas

Critically Endangered  (IUCN 3.1)[1]
CITES Appendix I (CITES)[2]
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Superorder: Batoidea
Order: Rhinopristiformes
Family: Pristidae
Genus: Pristis
Species:
P. pectinata
Binomial name
Pristis pectinata
Latham, 1794
IUCN range
  Extant (resident)
  Possibly extinct
  Presence uncertain

The smalltooth sawfish (Pristis pectinata) is a species of

critically endangered species that has disappeared from much of its historical range.[1]

Distribution and habitat

The smalltooth sawfish is found in tropical and subtropical parts of the Atlantic, including the Caribbean and Gulf of Mexico. Its original range was the smallest of the sawfish species, covering about 2,100,000 km2 (810,000 sq mi).[5] In the west it once ranged from the United States to Uruguay and in the east from Senegal to Angola.[1] Today it has disappeared from much of its historical range.[5] There are old reports from the Mediterranean Sea, but this likely involved vagrants[5] and according to the FAO the species can be considered locally extinct in the Mediterranean Sea.[6]

Smalltooth sawfish are mostly found in coastal marine and

brackish waters. It prefers water less than 8 m (26 ft) deep, but adults are occasionally seen offshore at depths of up to 122 m (400 ft).[7] During periods with increased salinity, juveniles have been seen far up rivers.[7] This species is mostly found in places with soft bottoms such as mud or sand, but may also occur over hard rocky bottoms or at coral reefs.[8] They are often found in areas with mangrove or seagrass.[1] The lower water temperature limit is 16–18 °C (61–64 °F).[9]

Appearance

Aquarium of the Americas

The smalltooth sawfish reputedly reaches a total length of up to 7.6 m (25 ft),[10] but this is likely an exaggeration and the largest confirmed size is 5.54 m (18.2 ft).[4] It weighs up to 350 kg (770 lb).[10]

Its upperparts are brownish-gray, gray, bluish-gray or blackish, and the underparts are whitish.[4][11]

Unlike the

green sawfish (P. zijsron) by the distribution (both are only found in the Indo-Pacific) and the dorsal fin (its leading edge is placed slightly or clearly behind the leading edge of the pelvic fins in the dwarf and green sawfish).[4] The smalltooth sawfish has a relatively narrow rostrum ("saw") with 20–32 teeth on each side.[4][11][note 1]

Function of the saw

Pristis pectinata, X-ray image

For feeding

For many years, rarity of seeing a sawfish in the wild prevented scientists from collecting conclusive evidence about the use of their distinctive rostrum. This led them to falsely assume that the sawfish, like many other marine vertebrates with a "beak," or an elongated rostrum, follow the rule that the appendage is used to either sense prey or capture prey, but never both. There are no other highly studied marine animals with similar rostral characteristics that have shown that the rostrum is used for both of these feeding techniques. Recent studies have demonstrated, however, that the sawfish utilize their rostrum to both sense and manipulate prey.[14]

A sawfish's saw is made up of thousands of

bottom-dwelling behavior of sawfish. Utilizing their saw as an extended sensing device, sawfish are able to "view" their entire surroundings by maintaining a position low to the sea floor.[16]

Sawfish were thought to primarily prey upon sand dwelling

mollusks, similar to other ray species or the closely related group of guitarfishes,[17] by using their unique anatomical structure as a tool for digging and grubbing about in sand or mud,[18] However, molecular evidence from prey item identification of DNA in the feces of southwest Florida smalltooth sawfish using a broad 18S rRNA molecular marker indicated the majority of their diet (71% of animal DNA sequences) consists of fish.[19] The same study found mollusks and crustaceans were a minority (14% of animal DNA sequences) and nearly all were identified as Harpacticoida copepods,[19] making it an unlikely prey item due to its small size and may represent 'secondary predation', a phenomenon where the DNA of an organism consumed by a prey item is detected in molecular gut or fecal analyses of a predator.[20] A follow-up study using higher resolution mitochondrial 12S and 16S rRNA markers targeting fishes determined smalltooth sawfish to be a generalist piscivore, identifying the DNA of 24 fish species from 7 orders and 11 families across 15 fecal samples analyzed.[21]

It is believed that the elongated rostrum first evolved for its use in prey immobilization.[16] Smalltooth sawfish have been observed to approach large shoals of fish while striking their saw rapidly from side to side. Due to the high density of small fish in a shoal, there is a high probability that the sawfish will hit, stab, stun, or kill several prey during one shoal attack.[22]

Vertebrate biologist Barbara Wueringer, of the University of Queensland, demonstrated that sawfish use their extended rostrum to detect and manipulate prey. She observed the animals' reaction to food already at the bottom of the tank, food falling from the water's surface, and introduced electric dipoles.

dipoles throughout the tank to simulate the electrical signals that surround moving prey.[23] Just as the sawfish displayed different aggressive behaviors towards the "prey," they also responded differently based on the electrical signals they received by either avoiding or approaching the signal source. With this evidence, the sawfish is now regarded as the only jawed fish to use its rostrum for both prey detection and manipulation.[14]

For defense

The many teeth of a sawfish's saw are not actually teeth at all, but rather special types of scales known as

dermal denticles.[24] These protruding weapons, combined with the animal's ability to strike from side to side with great force, provide it with a powerful and efficient defense mechanism.[18] Although the saw is mainly used for feeding purposes, observations of sawfish in captivity show that they may also be used for self-defense.[22] When sharks or other marine creatures threaten them, they retaliate with three swift blows to the instigator's dorsum. Sawfish are not considered harmful to humans unless they are threatened.[22]

Reproductive behavior

A juvenile smalltooth sawfish being released

The reproductive behavior of smalltooth sawfish has not been well studied, despite their classification as a

claspers, which are paired intromittent organs, into the female's vagina. The claspers contain subdermal siphon sacs that provide the propulsive power for sperm transfer. It is also possible that the siphon sacs assist with sawfish sperm competition by washing away rival sperm from the female's vagina before copulations.[27]

Smalltooth sawfish have recently been observed, for the first time, to reproduce parthenogenetically in the wild. About 3 percent of the sawfish living in a Florida estuary are the result of parthenogenesis. The research team speculates that since smalltooth sawfish are so rare, females might sometimes fail to find a male during the mating season, inducing the parthenogenetic process.[29]

Elasmobranchs are

polygamous matings.[27]

Conservation status

Sign for the protection of smalltooth sawfish in Florida, USA
A smalltooth sawfish briefly captured for tagging as part of a conservation project

Smalltooth sawfish are extremely vulnerable to

Convention on International Trade in Endangered Species.[1]

Atlantis Paradise Island became the world's first aquarium to breed sawfish when four pups were born there in 2012.[32]

Small numbers are maintained in

studbooks listing 12 individuals (5 males, 7 females) in 2014.[33] The only kept elsewhere are at a public aquarium in Colombia.[34] It is the only species of sawfish that has been bred in captivity.[33]

In early 2024, state and federal wildlife agencies in Florida, USA, became aware of an "unusual mortality event" from an unknown cause.[35] Affected fish exhibited spinning or whirling behavior. An effort was being made to rescue and rehabilitate affected fish.[36]

See also

  • Threatened rays

Notes

  1. ^ Sawfish occasionally lose teeth during their life and these are not replaced.[12] Correct tooth count refers to actual teeth and alveoli ("tooth sockets") from lost teeth.[13]

References

  1. ^
    doi:10.2305/IUCN.UK.2022-2.RLTS.T18175A58298676.en
    . Retrieved 20 May 2023.
  2. ^ "Appendices | CITES". cites.org. Retrieved 2022-01-14.
  3. doi:10.7755/fb.114.4.8
    .
  4. ^
    ISBN 9780643109148
    .
  5. ^
    doi:10.1002/aqc.2525
    .
  6. ^ Mendez, L.; Bacquet, A.; Briand, F. (2022). "List of locally extinct species". Guide of Mediterranean Skates and Rays. The Mediterranean Science Commission (CIESM). Retrieved 16 July 2023.
  7. ^ a b c d Whitty, J.; Phillips, N. & Scharfer, R. "Pristis pectinata (Latham, 1794)". Sawfish Conservation Society. Retrieved 17 November 2017.
  8. JSTOR 24321140
    .
  9. ^ a b "Sawfish Myths". University of Florida. 2017-05-04. Retrieved 27 November 2017.
  10. ^ a b Froese, Rainer; Pauly, Daniel (eds.) (2006). "Pristis pectinata" in FishBase. April 2006 version.
  11. ^
    ISBN 978-0-8018-9838-9
    .
  12. JSTOR 1442018
    .
  13. ^
    S2CID 3352391
    .
  14. ^
    ISBN 9781440560262
    .
  15. S2CID 16357946
    .
  16. ^
    S2CID 3352391
    .
  17. ISSN 0025-3154
    .
  18. ^
    JSTOR 1438539
    .
  19. ^
    ISSN 1863-5407
    .
  20. PMID 16313606
    .
  21. PMID 31797939
    .
  22. ^
    ISBN 978-1577855385
    .
  23. PMID 22401891
    .
  24. JSTOR 1442018
    .
  25. ^ a b Alan D. Henningsen; Malcolm J. Smale; Ian Gordon (2001). "Captive Breeding and Sexual Conflict in Elasmobranchs" (PDF). Elasmobranch Husbandry Manual: Proceedings of the First International Elasmobranch Husbandry Symposium. Archived from the original (PDF) on 4 October 2013. Retrieved 4 October 2013.
  26. ISBN 978-0-86727-152-2
    .
  27. ^
    ISBN 978-90-481-5655-9. {{cite book}}: |journal= ignored (help
    )
  28. ^ Tonya R. Wiley; Colin A. Simpfendorfer; Vicente V. Faria & Matthew T. Mcdavitt (2008). "Range, sexual dimorphism and bilateral asymmetry of rostral tooth counts in the smalltooth sawfish Pristis pectinata Latham (Chondrichthyes: Pristidae) of the southeastern United States" (PDF). Zootaxa. Retrieved 4 October 2013.
  29. ^ "Critically Endangered Ocean Giant is Reproducing Without Sex in the Wild |". June 2015.
  30. doi:10.1111/j.1096-3642.2012.00872.x
  31. ^ NOAA Fisheries (2 January 2015). Smalltooth Sawfish (Pristis pectinata). Endangered Species Act. Retrieved 8 June 2015.
  32. ^ "The endangered Smalltooth Sawfish gives birth at Atlantis, Paradise Island". Bahamas Local. 31 May 2012. Retrieved 17 November 2017.
  33. ^
    ISBN 978-0-86727-166-9. {{cite book}}: |work= ignored (help
    )
  34. ^ "Sawfish in Aquariums and the Media". Sawfish Conservation Society. Retrieved 17 November 2017.
  35. ^ "Sawfish are spinning, and dying, in Florida waters as rescue effort begins". Yahoo News. 2024-03-28. Retrieved 2024-03-29.
  36. ^ Mazzei, Patricia (April 15, 2024). "What's Killing Endangered Sawfish in Florida?". The New York Times. Retrieved April 16, 2024.

External links

Retrieved from "https://en.wikipedia.org/w/index.php?title=Smalltooth_sawfish&oldid=1219581926"