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Actinopyga caerulea

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Actinopyga caerulea
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Echinodermata
Class: Holothuroidea
Order: Holothuriida
Family: Holothuriidae
Genus: Actinopyga
Species:
A. caerulea
Binomial name
Actinopyga caerulea
Actinopyga caerulea is located in Indian Ocean
Actinopyga caerulea
Actinopyga caerulea
Actinopyga caerulea
Actinopyga caerulea
Actinopyga caerulea
Actinopyga caerulea
Actinopyga caerulea
Actinopyga caerulea
Actinopyga caerulea
Actinopyga caerulea
Actinopyga caerulea
Actinopyga caerulea distribution map[4]

Actinopyga caerulea, the blue sea cucumber, is a species of sea cucumber in the family Holothuriidae. Named for its unique blue coloration, this species can be found along the continental shelf of the tropical Western Indo-Pacific region, at depths between 12 and 45 m (39 and 148 ft). It is a commercially important species, and is harvested for food along its range.

Etymology

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The specific epithet, caerulea, is derived from the Latin caeruleus, meaning "blue or greenish-blue; cerulean, azure." This is in reference to its distinctive blue coloration,[5] which is also the origin of its vernacular name, the blue sea cucumber.[6]

Taxonomy

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While Actinopyga caerulea was first discovered and photographed off the coast of New Caledonia in 1984, it was initially misidentified as Actinopyga crassa, and none were collected for further study.[7] The species was photographed at a number of Pacific localities throughout the next decade, including Sulawesi, Bali, and Thailand,[8] but it would not be accurately recognized as a undescribed species until 1998, when Australian zoologist F.W.E. Rowe identified a specimen photographed in the Philippines by Erhardt & Baensch as Actinopyga (?) bannwarthi.[9] In 2003, several specimens were collected in Comoros and Papua New Guinea by Yves Samyn, Didier VandenSpiegel, and Claude Massin, who formally described the new species as Actinopyga caerulea in 2006.[10]

The holotype specimen of this species (RMCA 1803) was collected by Samyn and VandenSpiegel on November 22, 2003, and is deposited in the zoology collections of the Royal Museum for Central Africa, Tervuren, Belgium.[11] The type locality is off the coast of Iconi (Ikoni), Grande Comore, Comoros, at a depth of 37 m (121 ft).[12] The four paratype specimens (CNDRS 2004.09, RBINS IG 30376, NMHN EcHo 8081, and NHM 2005.2405) were also collected off the coast of Grande Comore, at depths ranging from 21 to 28 m (69 to 92 ft).[13]

Phylogeny and evolutionary history

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Actinopyga caerulea was initially identified by Samyn et. al, 2006 to be a member of the echinites group, a paraphyletic group[14] within the genus Actinopyga which consisted of A. echinites, A. agassizii, A. bannwarthi, A. crassa, A. flammea, A. serratidens, and the now-obsolete A. plebeja (today considered to be synonymous with A. echinites).[15]

However, a DNA barcoding study published in 2010 revealed that the closest known relative of Actinopyga caerulea is actually Actinopyga lecanora, and that the two species comprise a sister group within the genus with a genetic distance of just 0.9%.[16] In fact, the two species are so closely related that their taxonomic validity has been called into question: there is a possibility that one of them could be a hybrid species between the other and their next-closest relative, Actinopyga obesa.[17]

Distribution and habitat

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Actinopyga caerulea is found off the coasts of Asia and Africa, in the tropical Indian Ocean and the western Pacific Ocean. Its range extends from Comoros to Indonesia, Papua New Guinea, the Philippines, Taiwan, and other island groups in the western Pacific. It is found on the seabed in deeper tropical water on sand and rubble, as well as coral patches on the edge of coral reefs, at depths between 12 and 45 m (40 and 150 ft).[18] It is also associated with garden eel plains.[19]

Anatomy and description

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A specimen found in the Maldives (Baa Atoll) Note the five distinctive anal teeth surrounding the anus.

Actinopyga caerulea is a large sea cucumber, growing to a length of up to 400 mm (16 in) and a width of up to 140 mm (6 in) across the midsection.[20] The body of this sea cucumber is white, with numerous dark blue tube feet and papillae discontinuously covering its surface.[21] The density of these tube feet and papillae, and therefore an individual's coloration, can vary from sea cucumber to sea cucumber, but density typically increases on the dorsal area.[3]

The body itself is stout and loaf-shaped,[22] with a smooth, firm body wall measuring up to 14 mm (1 in) thick.[23] The mouth is usually surrounded by 15-18 large shield-shaped feeding tentacles, which are bluish-grey in coloration.[24] The anus is surrounded by five prominent "anal teeth" (heavily-calcified tube feet, see picture), which are white in coloration. This species lacks Cuvierian tubules.[25] It has one club-shaped Polian vesicle, which is roughly one-seventh of its body length in preserved specimens.[26]

Body composition

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In 2010, thirty (30) individual Actinopyga caerulea were purchased from a seafood market in Guangzhou, China as part of a study on the chemical composition and nutritional quality of several commercially important species of sea cucumbers.[27] The percent composition of A. caerulea was approximately 0.81% (±0.03) moisture, 56.9% (±0.36) protein, 10.1 (±0.25) fat, and 28.4% (±0.32) "ash."[note 1] Compared to other sea cucumbers, A. caerulea had comparatively higher fat content[28] and levels of omega-3 fatty acids,[29] but less overall nutritional value than Thelenota ananas, Bohadschia argus, and its congener Actinopyga mauritiana.[30]

Ecology and behavior

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Actinopyga caerulea is a detrivore, and forages during the day for organic detritus along sandy plains and coral patches on the outer slopes of coral reefs.[31]

Reproduction and life cycle

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Like many other members of the class Holothuroidea, blue sea cucumbers are gonochoric, and only have a single gonad. During spawning season, eggs and sperm are externally released into the surrounding water by female and male individuals, respectively, and are fertilized when they meet.[32]

Commensal relationships

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The emperor shrimp (Zenopontonia rex) is known to inhabit the surface of Actinopyga caerulea in a commensal relationship, possibly feeding on ectoparasites or organic detritus on the surface of its skin.[33] There is also at least one recorded instance of Pleurosicya mossambica living on it off the coast of Bitung.[34]

Conservation status

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As of its latest assessment in 2010, the IUCN Red List considers Actinopyga caerulea to be a data deficient species.[1] It has a wide geographic distribution, but is considered a rare species across its range, which makes the collection of accurate population data difficult.[35] It is harvested commercially for food in some parts of its range, and is used in the production of bêche-de-mer in Papua New Guinea;[36] however, to what extent commercial activities impact its population is currently unknown.[37] Its distribution overlaps with at least one marine protected area (MPA).[38]

Notes

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1 All holothurian specimens in the study were incinerated after their moisture, protein, and fat percent compositions were recorded. "Ash" is a catch-all referring to anything not moisture, protein, and fat that was fully incinerated: e.g. ossicles, calcareous rings, gut contents.

References

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  1. ^ a b Conand, Purcell & Gamboa 2013: "ABSTRACT: Blue Sea Cucumber Actinopyga caerulea has most recently been assessed for The IUCN Red List of Threatened Species in 2010. Actinopyga caerulea is listed as Data Deficient."
  2. ^ Samyn, VandenSpiegel & Massin 2006.
  3. ^ a b ITIS 2015.
  4. ^ "Actinopyga caerulea Samyn, VandenSpiegel & Massin, 2006". Global Biodiversity Information Facility. Retrieved 8 October 2024.
  5. ^ Samyn, VandenSpiegel & Massin 2006, p. 61: "Etymology: The name caerulea, Latin, refers to the unique blue colour of the species."
  6. ^ Conand, Purcell & Gamboa 2013: "COMMON NAMES (English): Blue Sea Cucumber"
  7. ^ Samyn, VandenSpiegel & Massin 2006, p. 53: "Cherbonnier & Féral (1984) recorded, and later Féral and Cherbonnier (1986) published a photograph of a specimen from New Caledonia which they identified incorrectly as Actinopyga crassa Panning, 1944. Other specimens have been photographed and no voucher material collected, making definitive identification impossible."
  8. ^ Samyn, VandenSpiegel & Massin 2006, p. 64: "Geographic distribution: Tropical Indo-Pacific; confirmed sightings have been made in Thailand (see Erhardt & Moosleitner 1995, as A. crassa), the Philippines (see Erhardt & Baensch 1998, as A. (?) bannwarthi), Indonesia [Bali (Myers pers. comm.) and Sulawesi (Lane pers. comm.)"
  9. ^ Samyn, VandenSpiegel & Massin 2006, p. 53: "Erhardt & Baensch (1998) drew upon the expertise of F.W.E Rowe, who put the name Actinopyga (?) bannwarthi to their photographed specimen from the Philippines."
  10. ^ Samyn, VandenSpiegel & Massin 2006, p. 64–65: "The recently collected Comoros material, together with a specimen collected earlier in Papua New Guinea by one of us (C.M.), allows a definitive identification of the previously photographed specimens. All are here recognized as a species new to science."
  11. ^ Samyn, VandenSpiegel & Massin 2006, p. 57–58: "The holotype of the new species is deposited in the collections of the Royal Museum of Central Africa, Tervuren, Belgium (RMCA) [...] Union des Comores (Grande Comore, Ikoni), 22.XI.2003, 37 m depth, coll. Y. Samyn & D. VandenSpiegel, RMCA 1803 (holotype)"
  12. ^ Samyn, VandenSpiegel & Massin 2006, p. 58: "Union des Comores (Grande Comore, Ikoni), 22.XI.2003, 37 m depth, coll. Y. Samyn & D. VandenSpiegel, RMCA 1803 (holotype)"
  13. ^ Samyn, VandenSpiegel & Massin 2006, p. 58: "Union des Comores (Grande Comore, H.L.M Langouste), 11.X.2004, 28 m depth, coll. Y. Samyn, D. VandenSpiegel & C. Massin, CNDRS 2004.09 (paratype 1); Union des Comores (Grande Comore, Itsandra), 20.XI.2003, 23 m depth, coll. Y. Samyn & D. VandenSpiegel, RBINS IG 30376 (paratype 2); Union des Comores (Grande Comore, Aérodrome), 16.V.2005, 26 m depth, coll. Y. Samyn & D. VandenSpiegel, NMHN EcHo 8081 (paratype 3); Union des Comores (Grande Comore, Itsandra), 16.V.2005, 21 m depth, coll. Yves Samyn & D. VandenSpiegel, NHM 2005.2405 (paratype 4)"
  14. ^ Uthicke, Byrne & Conand 2010, p. 642: "Most Actinopyga species fell into one distinct cluster in the COI analysis (Fig. 1). One notable exception is Actinopyga agassizi, which fell outside this clade. The latter is the only Atlantic species investigated."
  15. ^ Samyn, VandenSpiegel & Massin 2006, p. 55, 64, 67: "TABLE 1. Species and groups as recognized by Panning (1944). [...] Group 2 — ‘Act. echinites’ A. echinites echinites A. echinites plebeja A. echinites crassa A. serratidens agassizii A. serratidens serratidens A. serratidens bannwarthi [...] Actinopyga caerulea sp.nov belongs to what Panning (1944) has termed the ‘echinites group. [...] The more recently described A. flammea also appears to belong to Panning’s (1944) ‘echinites group’, an observation we share with Cherbonnier (1979)."
  16. ^ Uthicke, Byrne & Conand 2010, p. 642: "Most other [Actinopyga] species were distinct, but the genetic distance between a specimen of Actinopyga caerulea and one of Actinopyga palauensis was small (0.9%)."
  17. ^ Uthicke, Byrne & Conand 2010, p. 643: "Although most Actinopyga species were well resolved with DNA barcodes, further taxonomic research is required to investigate the species status of Actinopyga caerulea and Actinopyga palauensis (and to some extent Actinopyga obesa) and explore the possibility that one of these might be a hybrid between the other species and third taxon."
  18. ^ Conand, Purcell & Gamboa 2013.
  19. ^ Hoeksema & van der Meij 2010, p. 48: "The most notable sea cucumber finds were the recently described (2006) Indo-Pacific Actinopyga caerulea, found on a garden eel plain off west Halmahera (Fig. 4)"
  20. ^ Samyn, VandenSpiegel & Massin 2006, p. 60: "Very large species; living specimens up to 400 mm long and 140 mm wide mid-body"
  21. ^ Samyn, VandenSpiegel & Massin 2006, p. 60: "Colour in life bluish with patches of white devoid of tube feet at anterior and posterior ends and, discontinuously, along sides (Plate 1)."
  22. ^ Samyn, VandenSpiegel & Massin 2006, p. 60: "Body loaf-shaped with slight ventral flattening (more or less cylindrical with some distal tapering)."
  23. ^ Samyn, VandenSpiegel & Massin 2006, p. 60: "Body wall smooth, up to 14 mm thick."
  24. ^ Samyn, VandenSpiegel & Massin 2006, p. 60: "Mouth ventral, surrounded by 15–18 large, peltate, uniformly bluish-grey tentacles, in turn surrounded by a stout collar of bluish papillae, fused at their base."
  25. ^ Samyn, VandenSpiegel & Massin 2006, p. 61: "Cuvierian organ absent."
  26. ^ Samyn, VandenSpiegel & Massin 2006, p. 61: "Single, club-shaped Polian vesicle, about one seventh of length of preserved animals."
  27. ^ Wen, Hu & Fan 2010, p. 2469–2470: "Samples of dried S[tichopus] herrmanni, Thelenota ananas, Thelenota anax, Holothuria fuscogilva, Holothuria fuscopunctata, Actinopyga mauritiana, Actinopyga caerulea and Bohadschia argus products were purchased from a local retail market in Guangzhou, China. There were 30 individuals per sample, with each sample divided into three groups (10 individuals to each group)."
  28. ^ Wen, Hu & Fan 2010, p. 2470: "All fat contents of sea cucumber species were less than 2.0%, except for T. anax (9.9%) and A. caerulea (10.1%)."
  29. ^ Wen, Hu & Fan 2010, p. 2469: "T. ananas, A. mauritiana and A. caerulea contained more n-3 PUFA."
  30. ^ Wen, Hu & Fan 2010, p. 2470: "The comparison showed that T. ananas, A. mauritiana and B. argus possessed higher nutritional values than other sea cucumber species."
  31. ^ Samyn, VandenSpiegel & Massin 2006, p. 61: "The species is predominantly a detritus/deposit feeder on coral patches on the outer slope of coral reefs; it forages actively during the day."
  32. ^ Palomares & Pauly 2024.
  33. ^ Barathieu 2019.
  34. ^ Greenfield 2014.
  35. ^ Conand, Purcell & Gamboa 2013: "This species appears to be widespread in the Indo-Pacific, and is considered rare."
  36. ^ Conand, Purcell & Gamboa 2013: "This species is harvested for the production of bêche-de-mer in Papua New Guinea (Kinch et al. 2008), and has been purchased from a local retail market in Guangzhou, China (Wen et al. 2010)."
  37. ^ Conand, Purcell & Gamboa 2013: "The extent that this species is currently fished or will be fished in the future is not known."
  38. ^ Conand, Purcell & Gamboa 2013: "Occurs in at least one protected area: Yes"

Sources

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