Lychnorhiza malayensis ( Stiasny, 1920 )

Syazwan, Wan Mohd, Low, Liang Boon & Rizman-Idid, Mohammed, 2020, First record in Peninsular Malaysia and morphological redescription of Lychnorhiza malayensis (Scyphozoa: Rhizostomeae: Lychnorhizidae), Raffles Bulletin of Zoology 68, pp. 32-49 : 34-38

Lychnorhiza malayensis ( Stiasny, 1920)

( Figs. 2–4 )

Lychnorhiza malayensis – Stiasny, 1920: 226 (type locality: Java Sea, Indonesia); Stiasny, 1921: 122, pl. 2, fig. 9 (redescription of the type specimen); Menon, 1930: 17, pl. 2, fig. 8a–c (Madras, India); Stiasny, 1932: 89–95, figs. 1–4 (Java Sea, Indonesia); Nair, 1951: 74 (Trivandrum, India).

Material examined. 6 mature males, 2 mature females (bell diameter 98–155 mm) (MZUMCS 0255–0262), Klang Strait (3°10′06.8″N 101°16′44.4″E), bag net, coll. W.M. Syazwan, 4 October 2010. 1 immature male, 2 immature females, 2 sex-unidentified (bell diameter 45–60 mm) (MZUMCS 0264–0268), Kuala Besar (6°14′18.4″N 102°14′46.4″E), dip net, coll. W.M. Syazwan, 20 February 2014.

Description. Bell hemispherical in live specimens, more flattened in preserved ones ( Fig. 2A ). Bell diameter ranges from 45 to 155 mm. Exumbrellar surface with fine granules. At the margin, generally eight (four pairs) of almost symmetrical, slightly tapered velar lappets in each octant ( Fig. 2C ). Velar lappets separated by clefts formed by furrows with thin membranous base; each pair are separated by shorter and shallower furrows. Eight tear-drop shaped rhopalia; four perradial and four interradial. Each rhopalium situated in a bell-shaped rhopaliar pit with radiating furrows at the marginal cleft; flanked laterally by two rhopaliar lappets, more pointed, shorter and narrower than velar lappets ( Fig. 2E ).

Oral disc almost quadratic in shape; perradial and interradial diameters are ⅓ and ½ as wide as the bell diameter, respectively ( Fig. 2C ). Oral disc without appendages; supported by four interradial, broad-based pillars ( Fig. 2C ). Four perradial ostia lead from the subgenital cavity; located between two pillars, crescent-shaped, about as wide as the oral pillar.Three to five subumbrellar papillae projected around each ostium: two or three papillae positioned at the medial part, while one or two at the periphery ( Fig. 2C , see also Fig. 3 ). Medial papillae resting on the rhopaliar canal at the centre of ostium, highly varied in shape (oblong, ovoid, trapezoid, hammer-shaped) and not uniform in size. The peripheral papillae (one on each ostium’s margin) lie mostly within the ostium, uniform, smaller and shorter than the medial papillae; absent in some juvenile specimens. Papillae surface generally smooth or finely granulated.

Gastrovascular cavity cruciform in shape; with rounded corners, more dilated peripherally; diameter at perradial axis always slightly less than half the diameter at interradial axis ( Fig. 2D ). Perradial diameter of gastrovascular cavity about ¼ as wide as bell diameter.Gonad four in number, perradial, crescentic with concavity facing outward toward bell margin, entirely closed ( Fig. 2D ). Each gonad comprised of heavily folded tissue sheets, lying in the floor of gastrovascular cavity, associated with the inner side of oral disc and pillars. Gastric cirri (i.e., filaments) line the inner side of the gonad folds. Gonad visible as a cruciform-shaped structure from exumbrellar side. Matured gonads plump, immature ones thinner. Maturity reached when bell diameter ~ 90 mm. All specimens from Klang Strait mature (two females, six males); all specimens from Kuala Besar immature (two females, one male, two sex-unidentifiable).

A circular canal at ⅓ of radial distance from the bell margin ( Fig. 2C ). 16 irregularly-sized, bottle-shaped radial canals present, comprising eight rhopaliar canals (also known as perradial canals) extending to the bell margin, and eight slightly broader inter-rhopaliar canals (inter-radial canals) terminating at the circular canal. Some inter-rhopaliar canals appear to extend beyond the circular canal (as shown by the rhopaliar canals), but on closer inspection are thinner, and seem to be more subdivided than those of the rhopaliar canals. Rhopaliar canals broader at intra-circular than those at extra-circular part. Intra-circular network between adjacent radial canals comprises centripetal canals which communicate with the circular canal, but not with the adjacent rhopaliar and inter-rhopaliar canals. Number of centripetal canals (adradial canals) in between adjacent radial canals ranges from two to five in adults ( Fig. 3 ), and from one to five in juvenile specimens. Centripetal canals generally proportional to bell diameter in terms of width; always narrower than radial canals; more or less parallel; not uniform in length, terminating abruptly, but occasionally showing tendency to anastomose. Extra-circular canal network finely meshed, uniformly anastomosed, and becoming denser and narrower towards the periphery of bell. The penetration of this anastomosis network reaches the marginal lappets, but not all the way to the tips.

A well-developed circular muscle area of ca. 42–72 muscle folds extends distally from the outer base of pillars till the marginal lappets, covering approximately ⅔ of the subumbrellar surface ( Fig. 2C ). The musculature not interrupted over the 16 radial canals.

Eight oral arms, adradial, not coalesced with each other; each slightly shorter than the radius of the bell. Proximal portion half of the arm’s total length, laterally flattened, outer margin without frills. The remaining portion divided into three broad wings (one inner and two outer), more flattened than the proximal part ( Fig. 4A ). The edges of the three wings much-folded with frills containing numerous mouthlets among them. Mouth frills of inner wings reaching upward to inner margin of proximal portion and centre of oral disc. Oral arms lacking appendages. Oral arms of all immature specimens (bell diameter <60 mm) not well-developed.

Live and preserved individuals display minimal differences in colouration. Bell whitish. Exumbrellar surface in some specimens ornamented with reddish-brown spots or markings along the interradial and perradial axes that radiate from apex towards bell margin ( Fig. 2A, B ). Rhopaliar canals either colourless ( Fig. 3B ) or reddish-brown, with intense markings when adjoining circular canals ( Fig. 3A, C, D ). Inter-rhopaliar canals only coloured in parts, specifically when adjoining the gastrovascular cavity ( Fig. 3 A–C); generally fainter than the rhopaliar canal, while colourless in some specimens ( Fig. 3D ). Oral arms whitish, mouth frills whitish to faintly brown. Gonads whitish to faintly brown.

Morphological variation. A remarkable variation among individuals was observed in some key characters: (1) number of velar lappet per octant; (2) number, length and formation of centripetal canals; (3) number and shape of subumbrellar papillae; (4) the extension of inter-rhopaliar canal beyond circular canal; and (5) colouration of live and preserved specimens. The intraspecific morphological variations were persistent in both localities (Klang Strait and Kuala Besar) but individuals did not differ between sites. Principal component analysis (PCA) of these key characters did not suggest a clear separation between L. malayensis individuals from Klang Strait and Kuala Besar ( Fig. 5 ).

Other remarks. During a subsequent monthly ecological survey in Klang Strait from January until December 2011, L.

malayensis occurred during May 2011 (Southwest Monsoon) and later during October–November 2011 (Northeast Monsoon). Abundance was significantly greater during the latter period. This species also forms part of the commercial fisheries by-catch along with other scyphozoan jellyfishes, such as Cyanea sp., Phyllorhiza punctata , Lobonemoides robustus , and Rhopilema esculentum . At the northwestern Peninsular Malaysia (i.e., Langkawi Island and Penang Island), this species is commonly encountered in swarms with Acromitus flagellatus .

Figures

Fig. 2. Photographs showing different views and morphological characters of Lychnorhiza malayensis (fixed with 5% formaldehyde). A, lateral view of the whole body; B, exumbrellar view of the smooth bell surface; C, subumbrellar view of the bell showing main visible characters; D, subumbrellar view of the bell showing the exposed gastrovascular cavity; E, close-up subumbrellar view of the rhopalium and lappets. b, bell; oa, oral arm; od, oral disc; op, oral pillar; os, ostium; ext, extra-circular canal; cir, circular canal; cen, centripetal canal; rho, rhopaliar canal; int, inter-rhopaliar canal; gc, gastrovascular cavity; g, gonad; r, rhopalium; lv, velar lappet; lr, rhopaliar lappet. Black arrow, medial papillae; white arrow, peripheral papillae. Scale bars = 20 mm.

Fig. 3. Morphological variation among individuals observed in medial papillae (white box), centripetal canals between radial canals (black circle) and radial canal (i.e., rhopaliar and inter-rhopaliar canal) as shown in the subumbrellar view of specimens MZUMCS 0255–0258. A, specimen MZUMCS 0255 showing the ovoid-shaped papillae, two centripetal canals that terminate abruptly, entirely coloured rhopaliar canals and partially coloured inter-rhopaliar canals (near the gastrovascular cavity). B, specimen MZUMCS 0256 showing the oblongshaped papillae, three centripetal canals that terminate abruptly, entirely colourless rhopaliar canals and partially coloured inter-rhopaliar canals (only coloured near the gastrovascular cavity). C, specimen MZUMCS 0257 showing the trapezoid-shaped papillae, three lightly anastomosed centripetal canals, faintly coloured rhopaliar and inter-rhopaliar canals. D, specimen MZUMCS 0258 showing the oblongshaped papillae, four highly anastomosed centripetal canals, partially coloured rhopaliar canals (near the circular canal) and entirely colourless inter-rhopaliar canals. rho, rhopaliar canal; int, inter-rhopaliar canal. Scale bars = 20 mm.

Fig. 4. Differences in oral arm morphology between Lychnorhiza malayensis from Klang Strait and the Java Sea. A, lateral view of specimen MZUMCS 0256 from Klang Strait showing four of eight oral arms. B, illustration of a single oral arm of L. malayensis from the Java Sea by Stiasny (1932) (scale not available). The length of the winged portion of L. malayensis from Klang Strait is shorter (half of total arm’s length) than those described from the Java Sea (3/4 of total arm’s length). pp, proximal portion of oral arm; wp, wingedportion of oral arm; mo, frills of mouthlet. Scale bars = 20 mm.

Fig. 5. Two-dimensional principal component analysis (PCA) of 10 meristic characters (f4, f27, f29–33, f44, f45, f90) and 11 categorical characters (f51, f52, f80, f81, f83, f84, f87–89, f91, f92) indicating morphological similarity among Lychnorhiza malayensis individuals from Klang Strait (n = 7) and Kuala Besar (n = 5). PC1 explains 31.2 % of observed variation. PC2 explains 16% of observed variation. The character states are listed in Appendix 1.