Plankton Benthos Res 15(4): 317–326, 2020 Plankton & Benthos Research © The Plankton Society of Japan A new species of box jellyfish, Carybdea wayamba sp. nov. (Cnidaria: Scyphozoa: Cubomedusae: Carybdeidae) from Sri Lanka Krishan D. Karunarathne & M.D.S.T. de Croos* Department of Aquaculture and Fisheries, Faculty of Livestock, Fisheries and Nutrition, Wayamba University of Sri Lanka, Makandura, Gonawila (NWP), 60170, Sri Lanka Received 27 March 2020; Accepted 8 September 2020 Responsible Editor: Dhugal Lindsay doi: 10.3800/pbr.15.317 Abstract: A new species of box jellyfish, Carybdea wayamba sp. nov. is described here based on forty specimens collected from the south and northeast coasts of Sri Lanka, with the type location being Bonavista Reef, Galle Bay. This species is classified in the genus Carybdea due to the possession of a typical heart-shaped rhopaliar niche ostia with only one upper scale and epaulette-shaped gastric phacellae in the four corners of the stomach. This new species can be distinguished from other valid members of the genus Carybdea by the combination of the structure of the two velarial canal roots per octant with one broadly bi-forked velarial canal with narrow, lateral lobations on each root, and other morphological characters such as having typical knee-shaped pedalial canal bends without any appendages, and epaulette-shaped gastric phacellae with single-rooted, brush-shaped, multiple (three to five) short-stemmed, dendritically branched (both short and long branches) gastric filaments. This is the first novel cubomedusa described from Sri Lankan waters; and the first Carybdea species described with material from the North Indian Ocean. Key words: Indian Ocean, morphology, nematocysts, taxonomy Introduction The cubomedusae included many doubtful taxa until the beginning of the 21st century. In several studies over the last two decades, biologists have revised the taxonomy of this group (Gershwin 2005a, b, 2006a, Bentlage et al. 2010, Bentlage & Lewis 2012, Lewis et al. 2013, Straehler-Pohl 2014, 2019a, b, 2020, Straehler-Pohl & Gul 2017, Acevedo et al. 2019), but there are still some uncertainties to be clarified. In the classification of box jellyfish, Carybdeidae is a monotypic family containing the genus Carybdea, which represents the oldest genus of box jellyfish established by Péron & Lesueur (1810), which was subsequently misspelled (e.g. Charybdea), by several authors between Milne-Edwards (1833) and Mayer (1910), before the original name, Carybdea was re-established by Kramp (1961). The genus Carybdea previously contained a number of species that are now contained in other carybdeid fam* Corresponding author: M.D.S.T. de Croos; E-mail, dileepa_dc@yahoo. com, dileepad@wyb.ac.lk ilies; for example, Carybdea sivickisi Stiasny, 1926 has been moved to the family Tripedaliidae while changing its genus name to Copula (Bentlage et al. 2010). Gershwin (2005a) recognized that Carybdea alata Reynaud, 1830 was in fact a whole species complex and transferred them to a separate family, Alatinidae, while changing the genus name to Alatina (Gershwin 2005b) based on morphological and phylogenic differences. Likewise, Carybdea stiasnyi Bigelow, 1938 was also transferred to the family Alatinidae, while changing the genus name to Manokia (Gershwin 2005b). Some species, such as Carybdea periphylla Péron & Lesueur, 1810, Carybdea pisifera Oken, 1815, and Carybdea bitentaculata Quoy & Gaimard, 1833 were not even box jellies and had to be transferred into other taxonomic groups. Thereafter, only a few valid species remained in the genus Carybdea, with Carybdea marsupialis (Linnaeus, 1758) being the type species (Acevedo et al. 2019, Straehler-Pohl 2019b). Maas (1903, 1910), Bigelow (1909, 1938), Mayer (1910), and Kramp (1961) considered most of these Carybdea species as varieties of C. marsupialis, and 318 K. D. Karunarathne & M.D.S.T. de Croos Carybdea rastonii Haacke, 1886 (Straehler-Pohl et al. 2017, Straehler-Pohl 2019a); however, Bentlage et al. (2010) and Bentlage & Lewis (2012) revealed that these were not subspecies or varieties; but different species that dwell in distinct geographical areas of the world (Acevedo et al. 2019). Of the few records on Carybdea in the Indian Ocean, a single specimen of cubomedusa found from the pearl banks of Sri Lanka was predicted to be an immature specimen of Charybdea grandis Agassiz & Mayer, 1902 by Browne (1905); however, he classified it to be uncertain. Stiasny (1931) re-inspected the museum specimen, and reidentified it as C. alata [currently Alatina alata (Reynaud, 1830)]. Charybdea madraspatana Menon, 1930 was originally described from Madras, India and was reassigned as Alatina madraspatana (Menon, 1930) in the family Alatinidae by Gershwin (2005b). Recently, C. marsupialis was identified by Kazmi & Sultana (2008) off the coast of Pakistan but this was doubted by Gul et al. (2015) and was reclassified by Straehler-Pohl & Gul (2017) as Alatina grandis (Agassiz & Mayer, 1902). Hence, there is only one reliable record of a valid species belonging to the genus Carybdea occurring in the Indian Ocean so far – the species described by Gershwin & Gibbons (2009) as Carybdea branchi Gershwin & Gibbons, 2009 from the South African coast (from Port Elizabeth to Cape Town), that was later reclassified by Straehler-Pohl (2020) as Carybdea murrayana Haeckel, 1880. Sri Lanka is a tropical island located close to the equator, between the Arabian Sea and the Bay of Bengal in the Indian Ocean. As a country, this geographical location has become crucial to ensure a highly diverse marine faunal resource exists within the region (Keesing & Irvine 2005, Karunarathne & de Croos 2020). Due to the lack of studies carried out so far, knowledge on the scyphozoans that dwell in Sri Lankan waters is poor (Karunarathne et al. 2020). When considering the diversity of Sri Lankan cubomedusae, only five species have been recorded; out of them, Chiropsoides buitendijki (Van der Horst, 1907) was reported by Fernando (2001, 2006) after the A. alata identification by Stiasny (1931). Recently, two additional cubomedusae belonging to the genera Chironex and Tripedalia have been found in Sri Lanka (unpublished data of authors). A commonly found Carybdea species in the coastal waters of Sri Lanka has also been reported (Karunarathne & de Croos 2018), and it is described herein as the novel species, Carybdea wayamba sp. nov., the ninth valid species in the genus Carybdea. This is the first Carybdea species ever described not only from Sri Lanka, but also from the entire North Indian Ocean. Materials and Methods A systematic, year-round jellyfish survey was carried out in the pelagic zone of the continental shelf of Sri Lanka from March 2017 to April 2018. Forty (38 mature + 2 immature) specimens belonging to the new box jellyfish Fig. 1. Localities of Carybdea wayamba sp. nov. sampled along the coast of Sri Lanka (open circles): 1. Galle Bay [6.0278°N, 80.2289°E] (n=16); 2. Ambalantota [6.0964°N, 80.9937°E] (n=3); 3. Irakkandi [8.7238°N, 81.1850°E] (n=20); 4. Alampil [9.1877°N, 80.8609°E] (n=1). species were collected by a towed net (diameter 1 m, mesh size 1 mm) and a scoop net (mesh size 5 mm) from four locations along the south and northeast coasts of the country (Fig. 1). Water quality parameters (temperature, dissolved oxygen, pH, salinity, total dissolved solids, and turbidity) of each sampling locality were measured by using a digital multiparameter instrument (HACH HQ 40 D), and a portable turbidity meter (HACH 2100P). Coordinates of the sampling locations were recorded with a GPS unit (GARMIN 72H). Seven different morphometric features of all medusae were measured while fresh according to Gershwin (2005a, b) and Straehler-Pohl (2014). Here, the distance between the apex and the turnover of the bell below the rhopalium was measured as the bell height (BH). The diagonal bell width (DBW) was measured as the distance between outer keels of pedalial base by laying specimens flat with two pedalia spread out to the left and right sides, and the other two facing up and down in the centre. The inter-rhopalial width (IRW) (from the rhopalium to another adjacent rhopalium) was measured after laying the specimens flat. Across the widest area of the pedalia, the ʻpedalial widthʼ (PW) was measured, while the distance between the base and the distal end of the pedalium was measured as the Carybdea wayamba n. sp. from the Indian Ocean pedalial length (PL). Two additional features were defined and measured; the distance from the apex to the rhopalium (DAR) and the distance between the rhopalium and the turnover of the bell (DRT). If there was more than one measurement on a single morphometric character per individual medusa, i.e., two DBW, four IRW, four DAR, four DRT, four PW (if the pedalia were unbroken), and four PL (if the pedalia were unbroken), average values of them were calculated. All measurements were performed using a digital caliper to the nearest 0.1 mm. After recording the morphometric characteristics, samples were preserved in 5% formalin-seawater solution for taxonomic examinations. Minute structures of specimens were observed under a microscope (OLYMPUS CX22), and a stereo zoom microscope (OLYMPUS SZ 61). Nematocysts were identified following Gershwin (2006b) and were measured (under 400× magnification) with an inverted phase-contrast microscope with an imaging system (CARL ZEISS 415510-1101-000 Primovert). All the specimens inspected were deposited in the Museum of the Department of Aquaculture and Fisheries, Wayamba University of Sri Lanka (MDAFWU) by giving accession numbers. Results Systematics (based on Straehler-Pohl 2017, Jarms & Morandini 2019) Phylum Cnidaria Verrill, 1865 Subphylum Medusozoa Petersen, 1979 Class Scyphozoa Götte, 1887 Order Cubomedusae Haeckel, 1880 Suborder Carybdeida Lesson, 1843 Family Carybdeidae Lesson, 1843 Genus Carybdea Péron & Lesueur, 1810 Carybdea wayamba sp. nov. (Figs. 2–3 and Supplementary fig. 1) Type specimens. Of the 40 type specimens recognized in the study, the holotype (MDAFWU 2018/3, Male, 26 January 2018, Bonavista Reef, Galle Bay, Sri Lanka [6.0264°N, 80.2367°E], coll. by K.D. Karunarathne, with scoop net from surface; 21.1 mm BH, 24.2 mm DBW, 13.9 mm IRW, 17.4 mm DAR, 3.1 mm DRT, 10.9 mm PL, 4.0 mm PW) and 37 paratypes are mature (Table 1). The remaining two paratype specimens (MDAFWU 2018/15, Galle Bay, Sri Lanka [6.0278°N, 80.2289°E], 22 March 2018; 8.3 mm BH, 10.1 mm DBW, 5.1 mm IRW, 5.1 mm DAR, 3.2 mm DRT, 6.1 mm PL, 2.0 mm PW., MDAFWU 2018/28, Irakkandi, Sri Lanka [8.7238°N, 81.1850°E], 23 April 2018; 9.0 mm BH, 14.4 mm DBW, 7.5 mm IRW, 7.3 mm DAR, 2.1 mm DRT, 5.0 mm PL, 1.5 mm PW) are immature. Diagnosis. Carybdea with a small, flimsy, slightly transparent body. Inner keel of scalpel-shaped pedalia without warts or freckles. Knee-shaped bend of pedalial 319 canal without appendage. Velarial canal roots 2 per octant, with a broad, rounded, bident canal with narrow, lateral lobations on each root, all canals are equal in shape and complexity. Manubrium short, about one-third of the bell height. Gastric phacellae, epaulette-shaped with singlerooted, multiple (typically three to five) short-stemmed, dendritically branched (both short and long branches), brush-shaped gastric filaments. Description (mature medusa). Bell: with thin, flimsy mesoglea; small to medium in size, up to 29.0 mm in life, nearly cuboidal, with dome-shaped apex, smooth appearance as both apex and bell lack prominent nematocyst warts in live specimens, however, there are microscopic gelatinous warts (Fig. 3E). Coronal indentation deep just below apex. Interradius thickened throughout BH, with moderately deep furrows reaching all the way to the pedalium. Adradial furrows pronounced, deeper in the lower half of bell. Sensory niches: 4, perradial, heart-shaped, with single, shallowly convex covering scale and lack of lower scales (Fig. 2B); located approximately one-fifth of BH from velarial turnover; lacking rhopalial horns (Fig. 2B). Eyes 6 per rhopalium, 2 median lensed eyes plus 4 lateral pigmented eyespots (Fig. 2D). Rhopalial warts lacking. Statolith shape unknown. Pedalia: simple, unbranched, flattened, scalpel-shaped (Fig. 2F), moderate in size, about half of BH and three times higher than the width (Fig. 2A); lacking nematocyst clusters on the inner keel; outer keel rarely lined with a single row of white nematocyst clusters (Fig. 3A, B); distally inner keel quite rounder than outer, without tentacular overhang (Fig. 2F). Pedalial canal cross-section somewhat quadrate proximally, flat distally, straight at tentacle insertion; outer portion of knee-shaped bend without any appendage (Fig. 2E). Tentacles: 4, with single tentacle per pedalium, round or flattened somewhat in cross-section, with segmented appearance in preserved specimens (Fig. 2F); base to about 1 mm thick. Velarium: narrow, lacking nematocyst warts or freckles. Velarial canals, 2 roots per octant, 1 canal per root, widely biforked, typically U-shaped with narrow, lateral lobations bearing round or globular ends, non-anastomosing, both canals are equally complex (Fig. 2G). Perradial lappets absent. Frenulum well developed, about the root of a velarial canal in width, comprising a single hollow gelatinous structure, mostly reaching the velarial margin (Fig. 2H). Manubrium: short, about one-third of the bell height; with four small, smooth-edged, broadly pointed lips about one-third of the manubrium length, without nematocyst warts (Fig. 2I). Poorly developed perradial mesenteries extending up to halfway to rhopalium (Fig. 2J) (only with some specimens in the collection). Stomach flat. Gastric saccules absent. Phacellae: 4, epaulette-shaped (Fig. 2K), typically arising from the single root with three to five short stems giv- 320 K. D. Karunarathne & M.D.S.T. de Croos Fig. 2. Morphological features of Carybdea wayamba sp. nov. (A–M): A. Lateral view of the holotype; B & C. Exumbrellar view and subumbrellar view of rhopaliar niche respectively (holotype), US̶upper scale; D. Rhopalium dissected out from niche (MDAFWU 2017/358), note six eyes (LPI̶lateral pit eye, LSI̶lateral slit eye, ULI̶upper lens eye, LLI̶lower lens eye) and statolith (S); E. Pedalial canal knee-shaped bend (arrow) without appendage (holotype); F. Pedalium (holotype), note the tentacle with segmented appearance; G. Biforked velarial canals with lateral lobations (holotype), P̶pedalium, VC̶velarial canals; H. Frenulum (MDAFWU 2017/358), F̶frenulum, VC̶velarial canals; I. Short manubrium with wide, pointed, four lips (MDAFWU 2017/358); J. Poorly-developed mesentery (MDAFWU 2017/359); K–M. Phacellum (MDAFWU 2017/359) as usual, distinguished four short stems with branches (arrows), and isolated short stem (arrow) respectively. Scales: D=0.5 mm; B, C, E, F, H, K–M=1 mm; G, I, J=2.5 mm; A=5 mm. 321 Carybdea wayamba n. sp. from the Indian Ocean Fig. 3. Nematocyst features of Carybdea wayamba sp. nov. (A–E): A & B. Nematocyst clusters on the outer keel (arrows) of pedalia (MDAFWU 2018/11); C & D. Discharged tentacular nematocysts (SmI̶small isorhiza, SpI̶spherical isorhiza, ELE̶elongate lemonshaped eurytele); E. Microscopic warts on apex (holotype). Scales: D=10 µm; E=50 µm; B=2 mm; A=5 mm. ing rise to several dendritical branches in different lengths that end in a brush-shaped cluster of filaments (Fig. 2L, M). Occasionally, one or two stems of phacellae can exist outside of the main root. Gonads: attached along entire length of interradial septa; broadly leaf-shaped, typically overlapping along the interradius (Figs. 2A, 3A), pleated or simple. Interradial septa lacking perforations. Nematocysts: tentacular nematocysts are of three types, namely small isorhizas, spherical isorhizas, and elongate lemon-shaped euryteles (Fig. 3C, D). The nematocysts of the exumbrella, phacellae and manubrium were not examined. Colour in life: Bell and pedalia slightly transparent; gonads whitish; tentacles whitish. Etymology. This is the first ever species which is originally described at the Wayamba University of Sri Lanka, due to it being a young institution; therefore, the species is named to honour the university. The Sri Lankan national reference-collection of jellyfish is maintained in the university. Distribution. Currently known only from Sri Lanka, from Galle (6.0094°N, 80.2477°E) along the south coast to Hambantota (6.2800°N, 81.4267°E), and from Trincomalee (8.5679°N, 81.2391°E) along the northeast coast to Mullaitivu (9.3616°N, 80.7299°E). Habitat. Frequently found in shallow waters (range 0–10 m in depth), around coral reefs and river or lagoon mouths. Physiochemical conditions measured: temperature 24.9–33.0°C, dissolved oxygen 5.9–9.0 ppm, pH 7.8–8.3, salinity 24.8–31.5, total dissolved solids 23.9–30.2 ppt, and turbidity 1.1–19.4 NTU. Hazardousness. Mild stinger. However, when large numbers are in the water they can cause an uncomfortable prickly sensation. Discussion The genus Carybdea is differentiated from all other carybdeid families by the possession of a heart-shaped rhopaliar niche ostium with a single, upper covering scale and the lack of lower scales (Gershwin 2005a, Bentlage et al. 2010, Bentlage & Lewis 2012, Acevedo et al. 2019, Straehler-Pohl 2019b). Basically, due to the presence of lower covering scales at the rhopaliar niche opening and crescentic gastric phacellae, the species nominally considered to be Carybdea alata (C. alata, C. grandis, C. madraspatana, Carybdea moseri Mayer, 1906, Carybdea obeliscus Haeckel, 1880, Carybdea philippina Haeckel, 1880, Carybdea pyramis Haeckel, 1880, Procharybdis tetrapetra Haeckel, 1880, Procharybdis turricula Haeckel, 1880) were moved to a newly erected family, the Alatinidae, and into a new genus, Alatina, by Gershwin (2005b); likewise, Carybdea morandinii Straehler-Pohl & Jarms, 2011 was also transferred to the family Alatinidae and the genus Alatina by Straehler-Pohl & Toshino (2015). In this context, the new species described herein in the waters of Sri Lanka was classified under the genus Carybdea, particularly due to the possession of heart-shaped rhopaliar niche ostia with an upper scale and lack of lower scales (Fig. 2B), and the epaulette-shaped gastric phacellae (Fig. 2K). Species of the genus Carybdea are distinguishable based K. D. Karunarathne & M.D.S.T. de Croos 322 Table 1. Morphometric characteristics of the 38 mature specimens (BH: bell height; DBW: diagonal bell width; IRW: inter-rhopalial width; DAR: distance from apex to rhopalium; DRT: distance from rhopalium to turnover of bell; PL: pedalial length; PW: pedalial width), which were found in the coastal localities of Sri Lanka (L1̶Alampil [9.1877°N, 80.8609°E]; L2̶Ambalantota [6.0964°N, 80.9937°E]; L3̶Galle Bay [6.0278°N, 80.2289°E]; L4̶Irakkandi [8.7238°N, 81.1850°E]). Abbreviations used: n (number of specimens), SD (standard deviation). Locality Sampling date L1 (n=01) L2 (n=03) 22 April 2018 26 October 2017 L3 (n=15) 27 October 2017 26 January 2018 Accession no. (MDAFWU) 2018/17 2017/534 2017/535 2017/536 2017/537 2017/538 2017/539 2018/3* 2018/4 2018/5 2018/6 2018/7 2018/8 2018/9 2018/10 22 March 2018 2018/11 2018/12 2018/13 2018/14 L4 (n=19) 21 November 2017 2017/540 2017/541 2017/542 2017/543 2017/544 2017/545 2017/546 2017/547 2017/548 23 April 2018 2018/18 2018/19 2018/20 2018/21 2018/22 2018/23 2018/24 2018/25 2018/26 2018/27 Mean±SD (mm) Range (mm) Morphometric characteristics (measurements in mm) BH DBW IRW DAR DRT PL PW 17.0 29.0 26.7 18.7 20.2 21.0 14.3 21.1 13.0 19.0 17.1 16.0 13.4 14.4 13.4 19.0 22.0 20.0 23.2 25.0 18.6 20.0 18.2 21.1 20.4 20.4 20.1 12.5 18.2 18.1 17.3 20.2 15.5 16.5 15.1 13.2 10.2 11.2 18.2±4.1 10.2–29.0 23.1 33.0 30.3 18.4 24.5 26.6 15.3 24.2 18.1 24.1 23.2 21.4 17.2 17.3 18.1 23.1 25.4 22.1 30.2 29.2 23.1 24.3 22.1 26.1 25.2 26.0 24.3 16.2 22.5 19.3 21.2 23.2 21.3 19.4 20.1 17.4 13.3 14.2 22.2±4.5 13.3–33.0 11.5 20.1 17.5 11.0 15.2 15.1 9.3 13.9 8.5 12.5 10.1 11.2 8.3 9.3 9.4 13.1 13.2 12.3 15.5 17.5 11.5 12.2 11.0 13.2 13.2 13.1 12.5 9.1 12.1 10.3 10.4 11.5 10.5 10.3 9.5 9.5 9.1 8.4 11.9±2.7 8.3–20.1 13.5 23.3 21.4 15.6 17.4 16.5 12.2 17.4 10.5 16.5 14.0 12.5 10.2 10.3 11.4 13.5 16.5 14.5 18.1 20.5 15.2 17.5 15.1 16.5 17.1 16.2 17.0 10.0 14.2 14.5 14.1 16.3 12.5 13.5 12.5 11.5 8.2 9.2 14.7±3.4 8.2–23.3 3.5 5.8 5.3 3.1 3.2 4.5 2.1 3.1 2.5 5.8 3.1 3.5 3.2 4.1 2.0 5.5 5.5 5.5 5.1 4.5 3.4 2.5 3.1 4.5 3.3 4.2 3.1 2.5 4.1 3.5 3.3 4.2 3.2 3.1 2.5 1.5 2.1 2.3 3.6±1.2 1.5–5.8 8.1 12.5 10.4 8.5 9.7 10.8 7.0 10.9 7.4 8.8 9.4 9.9 7.9 6.8 7.8 8.9 10.0 10.3 10.0 10.0 7.8 9.0 10.0 10.6 9.6 9.2 10.4 5.9 8.3 9.0 8.0 8.0 8.0 7.0 7.1 6.9 5.0 5.5 8.7±1.6 5.0–12.5 2.9 3.8 3.5 3.0 3.0 2.8 2.0 4.0 2.3 3.8 3.1 3.3 2.4 2.0 2.0 2.6 3.0 3.8 3.6 4.0 3.0 3.0 3.0 3.8 3.6 3.7 3.6 2.0 2.3 2.6 2.5 4.0 2.0 2.0 2.0 1.9 1.8 1.5 2.9±0.7 1.5–4.0 *The holotype. Others are paratypes. on a combination of 3 characters (velarial canal system, pedalial knee structure and pattern of gastric phacellae– horizontal row or epaulette-shape) according to StraehlerPohl et al. (2017), Acevedo et al. (2019) and Straehler-Pohl (2019a). Some other characters, such as the size of the bell, and more detailed characteristics like the formation and arrangement of gastric filaments in the phacellae are also important (Gershwin 2005a, Straehler-Pohl et al. 2017, 2019a, Table 2. Comparison of significant characters of species in the genus Carybdea Péron & Lesueur, 1810. Named species data from Kishinouye (1891), Maas (1897), Gershwin (2005a), Gershwin & Gibbons (2009), Chae et al. (2017), Acevedo et al. (2019), Straehler-Pohl (2020), and this study. Species Distribution Bell height; exumbrellar nematocyst warts in living specimens Gastric phacellae; filament structure Velarial canal roots; velarial canals Pedalial outer keel in living specimens with thorn-like appendage C. confusa StraehlerPohl, Matsumoto & Acevedo, 2017 California (cold) up to 32.0 mm; densely scattered with white nematocysts of irregular shapes epaulette; single rooted, single short-stemmed, brush-shaped C. cuboides (Haeckel, 1880) Hawaii (tropical) up to 30.0 mm; scattered with small, colourless, nematocyst warts from apex to bell margin epaulette; single rooted, multiple 2 roots per octant; 1 canal per root, lined with rows of white nematocyst warts biforked to multiple branched, short-stemmed, short branches, with wide lateral lobations brush-shaped rounded, without appendage C. irregularis French Polynesia (tropiStraehler-Pohl, 2019 cal) up to 20.0 mm; no nematocyst warts scattered over the apex and bell of preserved specimens (might be rubbed off) and no data on living specimens epaulette; single rooted, multiple 2 roots per octant; 1 canal per root, No data simple to branched, with slight long, flask-shaped, thick stems, lobations brush-shaped rounded, without appendage C. marsupialis (Linnaeus, 1758) Mediterranean Sea (temperate) up to 40.5 mm; sparsely scattered with few, whitish nematocyst warts from apex to bell margin epaulette; single rooted, multiple (8–10) stemmed 3 roots per octant; 1 canal per root, lined with nematocyst freckles, smaller warts scatter on simple to biforked or branched, outer half slightly lobed C. murrayana Haeckel, 1880 South Africa, West Africa (cold to tropical) up to 82.0 mm; densely scattered with white nematocyst warts of different sizes and shapes from apex to bell margin epaulette; single rooted, multiple (about 20) long-stemmed, tree-shaped 2 roots per octant; 2–4 canals per root, complexly branched, with complex lobes C. prototypus (Haeckel, 1880) Japan, South Korea, Chinese Seas (temperate to tropical) up to 35.0 mm; scattered with tiny, colourless, nematocyst warts from apex to bell margin horizontal linear; multiple rooted, multiple (10–15), longstemmed, brush-shaped 3 roots per octant; 1 canal per root, scattered with tiny, round warts, and irregularly shaped, white complexly branched, slightly nematocyst bands lobed C. rastonii Haacke, 1886 Australia (cold to temper- up to 35.0 mm; scattered with colourless, nemaate) tocyst warts from apex to bell margin horizontal linear; multiple rooted, 2 roots per octant; 1 canal per root, scattered with large, white to triforked light brown nematocyst warts multiple (12–15), shortor bands stemmed, brush-shaped rounded, without appendage C. xaymacanna Conant, 1897 Caribbean Sea (tropical) up to 24.0 mm; scattered with tiny colourless nematocyst warts from apex to bell margin epaulette; single rooted, single short-stemmed, brush-shaped volcano-shaped to triangular C. wayamba sp. nov. Sri Lanka (tropical) up to 29.0 mm; scattered with microscopic nematocyst warts from apex to bell margin (no prominent warts therefore, smooth appearance with the naked eye) epaulette; single rooted, multiple 2 roots per octant; 1 canal per root, seldom lined with single row of white nematocyst clusters broadly biforked, with narrow (3–5), short-stemmed, both lateral lobations short and long branches, brushshaped densely scattered with irregular, white nematocyst warts and brownish marks 2 roots per octant; 1 canal per root, lined with white, irregular, simple to biforked nematocyst bands, scatter tiny warts rounded, without appendage volcano-shaped, upwards turned volcano-shaped, appended sharp peak Carybdea wayamba n. sp. from the Indian Ocean 2 roots per octant; 1 canal per root, scattered with round to oval multiple branched warts and white nematocyst bands Pedalial canal knee bend rounded, without appendage 323 324 K. D. Karunarathne & M.D.S.T. de Croos Fig. 4. Inferred distribution of valid species of the genus Carybdea Péron & Lesueur, 1810. The respective areas were recognized based on Haeckel (1880), Acevedo et al. (2019), Straehler-Pohl (2019a, 2020), and this study. b, 2020, Acevedo et al. 2019). Hence, it is important to compare the combination of such characteristics between the valid species of Carybdea when determining their taxonomic identity (Table 2). Carybdea rastonii and Carybdea prototypus (Haeckel, 1880) [Procharagma prototypus Haeckel, 1880=Carybdea brevipedalia Kishinouye, 1891] can clearly be distinguished from the Sri Lankan specimens due to the possession of horizontal linear gastric phacellae (Gershwin & Gibbons 2009, Acevedo et al. 2019, Straehler-Pohl 2019b, 2020) while the Sri Lankan specimens possess the epaulette-shaped gastric phacellae (Fig. 2K). The nature of the velarial canal system (two velarial canal roots per octant; 2–4 canals per root, with lateral lobations) of Carybdea murrayana (Charybdea murrayana Haeckel, 1880=Carybdea branchi) is characteristic of the species and its bell is more than double the height of Sri Lankan Carybdea specimens (Gershwin & Gibbons 2009, Straehler-Pohl 2020). Also, the number of stems per bundle of gastric phacellae in C. murrayana is about four times higher than the present specimens and the long stems are arranged in dense bundles (Gershwin & Gibbons 2009: Table 1, Acevedo et al. 2019, Straehler-Pohl 2020). Therefore, the Sri Lankan specimens can easily be distinguished from this species. Both the species, Carybdea confusa Straehler-Pohl, Matsumoto & Acevedo, 2017, and Carybdea xaymacanna Conant, 1897 have two velarial canal roots per octant with one canal per root. Both canals differ in complexity, and they possesses appendages in the pedalial canal knee bend and single-rooted, single-stemmed, epaulette-shaped gastric phacellae (Straehler-Pohl et al. 2017: Figs. 1E, I, K, 2S–V, Acevedo et al. 2019: Fig. 1F–I, K–M, Straehler-Pohl 2019: Fig. 2J–L, V–X); thus, the Sri Lankan specimens can certainly be distinguished from them, since the Sri Lankan specimens have two velarial canal roots per octant with equally complex velarial canals (Fig. 2G–H), multiple filament stems per phacellum (Fig. 2L–M), and a lack of appendages in the pedalial bend (Fig. 2E). Moreover, C. marsupialis possesses three velarial canal roots per octant (Straehler-Pohl et al. 2017: Fig. 2O, Acevedo et al. 2019: Fig. 1D, Straehler-Pohl 2019a: Fig. 2Q), while the observed specimens from Sri Lanka possess two per octant (Fig. 2G). Carybdea marsupialis also has a larger number of filament stems (8–10) per gastric phacellum (Gershwin 2005a: Table 2.5, Gueroun et al. 2015: Fig. 1D), therefore it is also different from Sri Lankan specimens. Carybdea irregularis Straehler-Pohl, 2019 possesses irregularly shaped, simple or complexly branched velarial canals. No canal is the same length as any other over the whole velarium (Straehler-Pohl 2019: Figs. 1L, M, 2N, 3L– O). The Sri Lankan specimens can be differentiated by having nearly equally shaped velarial canals (Fig. 2G) in all octants. Additionally, C. irregularis has flask-shaped, thick-stemmed gastric phacellae (Straehler-Pohl 2019a: Figs. 1H, 2O), but these are slender (non-flask-shaped) in the present specimens from the North Indian Ocean (Fig. 2M). Carybdea cuboides (Haeckel, 1880) [Procharybdis cuboides Haeckel, 1880=C. arborifera Maas, 1897], described from the central North Pacific region, is morphologically by far the most similar species to the specimens from the North Indian Ocean due to the nature of the pedalial canal knee bend, the number of velarial canal roots per octant, and the shape of the gastric phacellae of both species being similar, with even their bells being almost the same in size. Although both species have two velarial canal roots per octant, the canals are typically bi-forked with narrow lateral lobations in the Sri Lankan specimens (Fig. 2G), but bi-forked to multiply-branched with wide lateral lobations in C. cuboides (Acevedo et al. 2019: Page 526). The information recorded concerning the number of stems per gastric phacellum of C. cuboides, in the description by Maas (1897: Page 86), and the recent revision of the genus Carybdea wayamba n. sp. from the Indian Ocean Carybdea done by Acevedo et al. (2019) was not sufficient; however, typical length of those stems is clearly shown in Straehler-Pohl et al. (2017: Fig. 2A, B), Acevedo et al. (2019: Fig. 2C, D), and Straehler-Pohl (2019a: Fig. 2C). Carybdea cuboides usually possesses several short stems per gastric phacellum (Acevedo et al. 2019: Page 526), while in the Sri Lankan specimens, although those stems are short, they are typically few (three to five) in each phacellum (Fig. 2L, M). Branches in the phacellae of C. cuboides are short (Acevedo et al. 2019: Fig. 2D, Straehler-Pohl 2019a: Fig. 2C), but the Sri Lankan specimens have long branches (Fig. 2L, M). It can therefore be concluded that the present cubomedusan material from Sri Lanka belongs to a new carybdeid species, herewith named Carybdea wayamba sp. nov.. The distribution of this new species also complies with Acevedo et al. (2019), because it does not overlap with the inferred distributions of the other eight Carybdea species (Fig. 4). 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