Scyllaea fulva Quoy & Gaimard, 1824

Yiu, Sam King Fung, Leung, Thomas Ka Tung, Lee, Gabriel Yeung & Yan, Meng, 2024, Positive association between PTN polymorphisms and schizophrenia in Northeast Chinese Han population., Zoological Studies 63 (4), pp. 141-149 : 3-6

Species Scyllaea fulva Quoy & Gaimard, 1824

Synonyms

Nerea punctata (Lesson 1830) , Scyllaea dracaena ( Kelaart 1858) , Scyllaea quoyi ( Gray 1850) , Scyllaea pelagica ( Pola et al. 2012) .

Materials examined: NMMB-M 011734: 0.9 cm in length; NMMB-M 011735: 0.85 cm in length; NMMB-M 011736: 1.4 cm in length; NMMB-M 011737: 0.95 cm in length; NMMB-M 011738: 0.5 cm in length; NMMB-M 011739: 1.3 cm in length; NMMB-M 011740: 2.9 cm in length.

Locality: Seven specimens were collected from Sargassum spp. at Tai She Wan (22°21'32.7"N, 114°20'15.1"E) at 2 m on the 28th March and the 11th April 2023.

Type locality: New Guinea. Geographic distribution ( Fig. 1 ): Hong Kong (this study), Indo-Pacific region including Japan ( Baba 1949), Papua New Guinea, Philippines ( Pola et al. 2012), Réunion ( Cadet 2012), Gump Station, Cook’s Bay, Moorea, French Polynesia ( Goodheart et al. 2017 2018); Mozambique ( Tibiriçá et al. 2017) and Thailand ( Mehrotra et al. 2021).

Habitat: Inhabit the seaweed Sargassum spp. ( Fig. 2A ).

External morphology ( Fig. 2B–D and Fig. 3A– B ): The body colour varies from transparent to semitransparent green or light yellow. The body is slender, soft, flaccid, and elevated, but laterally compressed. The body surface is smooth. There are some black or brown spots on the body. The foot is narrow. The posterior crest is moderately large with an entire margin. The edge of posterior crest is brown. The front of the head is expanded in a semicircular veil. The rhinophores are perfoliate with 3–4 lamellae. There are two pairs of equal sized dorsolateral lobes. The lobes are wing-like and denticulated. Each dorsolateral lobe bears four to five large and transparent dendritic ‘gills’ on their upper surface and two on the tail as well as four on each side of the tail.

Internal morphology ( Fig. 3C–F and Fig. 4 ): The buccal mass contained a pair of thin and triangular jaws. The masticatory edge of the jaws is expanded into a wing-like flap. Over the edge of this flap is a series of pineapple-like structures. These structures form a honeycomb pattern over the entire surface of the masticatory edge, and the number of rodlets on the pineapple-like structure ranged from two to five. Central radular teeth were present. Each primary denticle bore two to five secondary denticles. The radula formula was 11 × 15.1.15. The reproductive system contained a small bursa copulatrix, a large female gland mass, and a duct connecting the female gland mass to the prostate and the ampulla.

Remarks: Scyllaea fulva can be distinguished from Scyllaea pelagica based on the radular formula. The radular formula of Scyllaea pelagica is 16–24 × 24–54.1.24–54 ( Odhner 1936), which exhibits a higher number of denticles compared to Scyllaea fulva .

Molecular analysis

Three gene sequences were obtained from each of the two specimens ( NMMB-M 011734 to 735). Alignment and concatenation resulted in a dataset of 1455 bp (661 bp for COI, 466 bp for 16S rRNA and 328 bp for H3). Our phylogenetic analyses showed that the two specimens we collected from the field were Scyllaea fulva ( Fig. 5 ). Pair-wise sequence comparisons were conducted to determine the inter- and intra-specific p -distances ( Table 1; Table S1). Interspecific p -distances amongst Scyllaea fulva and Scyllaea pelagica were 6.90%–7.20% for COI, 2.20%–2.50% for 16S and 0.00% for H3. Intraspecific p -distances in Scyllaea fulva were generally very small, with 0.00%–0.60% for COI, 0.00%–0.20% for 16S, and 0.00% for H3.

Figures

Fig. 1. Map showing the current known global distribution of Scyllaea fulva and Scyllaea pelagica.

Fig. 2. Selected photographs showing the sargassum habitat and Scyllaea fulva. A, Sargassum bed at Tai She Wan; B, In situ swimming Scyllaea fulva; C, Dorsal view of Scyllaea fulva in a beaker; D, Lateral view of Scyllaea fulva in a beaker. Scale bar = 0.5 cm.

Fig. 3. Drawing showing the external and internal morphology of Scyllaea fulva. A, Dorsal view; B, Lateral view; C, Jaw; D, Radula; E, Teeth; F, Reproductive system. bc, bursa copulatrix; fmg, female gland mass; pr, prostate; amp, ampulla; hd, hermaphroditic duct. Scale bars: A and B = 0.5 cm; C = 0.5 mm; D = 250 µm; E = 20 µm; F = 0.2 mm.

Fig. 4. SEM photos showing the jaws and radula. A, Overview of a jaw; B, Jaw element; C, Central teeth presented on the radula; D, Close-up image of the denticles. Scale bars: A = 500 µm; B = 20 µm; C = 500 µm; D = 20 µm.

Fig. 5. Phylogenetic tree of the concatenated COI/16S/H3 sequence dataset constructed using the maximum likelihood method. Bootstrap values> 50 are shown in the nodes.