Skeleton panda sea squirt | |
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Colony of C. ossipandae near Kume Island | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Subphylum: | Tunicata |
Class: | Ascidiacea |
Order: | Aplousobranchia |
Family: | Clavelinidae |
Genus: | Clavelina |
Species: | C. ossipandae
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Binomial name | |
Clavelina ossipandae Hasegawa & Kajihara, 2024
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Clavelina ossipandae, the skeleton panda sea squirt (Japanese: ガイコツパンダホヤ, romanized: gaikotsu panda hoya), is a species of colonial sea squirt or ascidian, a group of sessile, marine filter-feeding invertebrates. Originally discovered near Kume Island in Japan by local divers, pictures of the animal attracted attention in the media for its appearance prior to its formal taxonomic description in 2024.
C. ossipandae lives at around 20 metres (66 ft) of depth, anchored to the substrate in coral reefs with strong currents, in colonies of one to four transparent individuals or zooids measuring up to 2 centimetres (0.79 in) each. Individuals in a colony are linked through connections called stolons, and originate from a single organism reproducing asexually, although they are also capable of sexual reproduction.
Among sea squirts, C. ossipandae is most recognizable for its white horizontal blood vessels, giving it a skeleton-like appearance, and black frontal dots of unknown function, that have been compared to a panda's eyes and nose. After it was featured on television programs and social media, a crowdfunded expedition sampled specimens of the animal in 2021, formally describing it three years later.
History
While lacking a formal description, images of the tunicate have been shared by Kume Island divers, notably Shunji Terai, introduced to the sea squirts by a friend in 2017, whose diving shop drew in tourists interested in seeing the creatures.[1] Popular on social media such as Twitter, the animal was also featured in television programs, by NHK as well as commercial broadcasters.[2]
The images attracted the attention of Hokkaido University tunicate expert Naohiro Hasegawa, who encountered them on Twitter in 2018 and recognized the animal as distinct from other ascidian species. Thanks to crowdfunding efforts, a team of Japanese researchers led by Hasegawa sampled the tunicate in 2021 from the rocky outcrop of Tonbara, off Kume Island, only accessible in winter because of tidal currents and wind. In a 2024 paper announcing the discovery, the team formally described it as the new species Clavelina ossipandae.[3][1] Four specimens were collected: the holotype and three paratypes, in colonies ranging from one to four individuals. They were later deposited in the Invertebrate Collection of the Hokkaido University Museum in Sapporo.[4]
Etymology
The generic name Clavelina, Latin for "little bottle", refers to the shape of zooids in the genus.[1]
The specific epithet ossipandae is derived from Latin os (bone) and panda. Like the common name, it refers to the white rib-like markings on the sides of the zooid, as well as to the black and white patterns on its front part, resembling the face of the giant panda.[4]
Description
Clavelina ossipandae is a small colonial tunicate, found in colonies of one to four zooids. Unlike in related genera Euclavella and Nephtheis, zooids are free, although they extend from a basal mass and are connected to each other through vascular stolons. Individual zooids have been reported to range from 7 to 14 millimetres (0.28 to 0.55 in) long, or possibly up to 2 centimetres (0.79 in) long.[1][4]
Each zooid possesses its own transparent tunic, divided into thoracic and abdominal segments. Both are almost equal in length, although the thoracic tunic is thinner and softer than its abdominal counterpart. The thorax bears 10–11 pairs of longitudinal muscle bands, with 2 running from the abdomen to the endostyle, 5–6 to the oral siphon and 2–4 to the dorsal side.[4]
The zooid's oral siphon, through which food particles are drawn into the pharynx, is surrounded by 10 oral tentacles. The pharynx itself bears a dorsal tubercle with a ciliated slit-like opening, above a series of dorsal languets. It is connected through the esophagus to the stomach in the middle of the abdomen, followed by a tube-like intestinal loop.[4]
Patterns
Specimens bear several white transverse blood vessels along their length, running through their gills, giving the appearance of a series of ribs.[5] The black endostyle is visible below the oral siphon, as well as a mid-dorsal black line below the atrial siphon.[4]
C. ossipandae is also recognizable by the black markings on its white anterior portion (a central dot between the oral and atrial siphons, surrounded by two lateral bands), uniquely distinctive in the genus Clavelina. Two other species in the genus are known to bear similar patterns, although they differ in color, being dark blue on light blue in C. moluccensis and blue on yellow in C. viola.[4] The role of these markings remains unknown.[6]
Life cycle
C. ossipandae specimens possess both ovaries and testicular follicles, attached to the left side of the intestine beyond the stomach. A brood pouch is present on the back of the thorax, housing eggs and larvae. Like in all tunicates, larvae are motile and tadpole-shaped. They measure around 1.25 millimetres (0.049 in) in length, of which the tail comprises 0.75 millimetres (0.030 in). The larval body is divided into a frontal plate, with three adhesive papillae, and a trunk bearing an ocellus and an otolith.[4] Like other colonial sea squirts, C. ossipandae can also reproduce asexually through budding, forming colonies of genetically identical, connected zooids.[2][3]
Taxonomy
Several morphological traits were used to identify the skeleton panda sea squirt as a member of genus Clavelina. Namely, the zooids are free rather than fully embedded, the larvae lack the tubular structures in their adhesive organs characteristic of the related genus Pycnoclavella, and the number of spiracles (10–14) is consistent with the range seen in Clavelina species (8–20).[4][7]
Through sequencing of the cytochrome c oxidase subunit I gene from the holotype and a paratype, Clavelina ossipandae was more precisely recovered as the sister species of C. australis inside the genus Clavelina (found by the authors to be paraphyletic to Nephtheis).[4]
Distribution and ecology
The species is known from waters off the coast of Kume Island, Japan, where both the original reports and the later samples were obtained. Colonies were observed at depths of 10–20 metres (33–66 ft), anchored to coral reefs, and are believed to live specifically in areas with fast currents. It is the first species of ascidian known from Kume Island, although other specimens have been collected from the locality and are awaiting description as of 2024.[3][4]
While its feeding habits are not known with certainty, C. ossipandae has been assumed to consume phytoplankton like related filter-feeding ascidians.[3]
References
- ^ a b c d "Skeleton panda sea squirt sprays Japanese researchers with questions". The News. Retrieved 27 March 2024.
- ^ a b "ついにガイコツパンダホヤの正体が判明!" [The true identity of the skeleton panda sea squirt has finally been revealed!] (PDF) (Press release) (in Japanese). Hokkaido University. 1 February 2024.
- ^ a b c d "実は新種だった!?「ガイコツパンダホヤ」で知られる生き物の正体が判明…生態と特徴的な"白黒模様"の意味を聞いた|FNNプライムオンライン". FNN (in Japanese). 12 February 2024. Retrieved 27 March 2024.
- ^ a b c d e f g h i j k Hasegawa, Naohiro; Kajihara, Hiroshi (2024). "Graveyards of Giant Pandas at the Bottom of the Sea? A Strange-Looking New Species of Colonial Ascidians in the Genus Clavelina (Tunicata: Ascidiacea)". Species Diversity: 53–64. doi:10.12782/specdiv.29.53. Retrieved 19 February 2024.
- ^ "Japan's newest species is a tiny, panda-like sea creature". CNN. 20 February 2024. Retrieved 26 February 2024.
- ^ "Meet Japan's skeleton panda sea squirt". Yahoo! News. 15 February 2024. Retrieved 26 February 2024.
- ^ Rocha, Rosana Moreira da; Zanata, Thais Bastos; Moreno, Tatiane Regina (March 2012). "Keys for the identification of families and genera of Atlantic shallow water ascidians". Biota Neotropica. 12: 269–303. doi:10.1590/S1676-06032012000100022. ISSN 1676-0611.