Marphysa tribranchiata, Liu, Yubin, Hutchings, Pat & Sun, Shichun, 2017

Liu, Yubin, Hutchings, Pat & Sun, Shichun, 2017, Three new species of Marphysa Quatrefages, 1865 (Polychaeta: Eunicida: Eunicidae) from the south coast of China and redescription of Marphysa sinensis Monro, 1934, Zootaxa 4263 (2), pp. 228-250 : 236-240

Marphysa tribranchiata n. sp.

Figures 1 , 4 , Tables 2, 3

Material examined. Holotype: ASIZW0000348-2, collected by Shi-Kuei Wu from Wanli, 22.04.1965, (Long. 121.67°E; Lat. 25.2°N). Paratypes: ASIZW0000348-3, width on chaetiger 10, 3.3 mm, length from anterior to posterior margin of chaetiger 10 is 10.0 mm, complete with 181 chaetigers, collected by Shi-Kuei Wu from Wanli, 22.04.1965, (121.67°E; 25.2°N); ASIZW0000346, width on chaetiger 10, 2.7 mm, length from anterior to posterior margin of chaetiger 10 is 7.4 mm, complete with 161 chaetigers, collected by Shi-Kuei Wu from Shimen, 0 8.08.1964, (121.67°E; 25.2°N); ASIZW0000347-1, width on chaetiger 10, 3.4 mm, length from anterior to posterior margin of chaetiger 10 is 7.4 mm, complete with 160 chaetigers, collected by Shi-Kuei Wu from Wanli, 0 6.08.1965, (121.67°E; 25.2°N).

Additional material examined ASIZW0000354-2, width on chaetiger 10, 2.05 mm, length from anterior to posterior margin of chaetiger 10, 5.1 mm, complete with 85 chaetigers, collected by Shi-Kuei Wu, (no locality data or date of collection given); ASIZW 0000354-4 , width on chaetiger 10, 3.65 mm, length from anterior to posterior margin of chaetiger 10, 9.5 mm, complete with 195 chaetigers, collected by Shi-Kuei Wu, (no locality data or date of collection given). All posteriorly incomplete , ASIZW0000345-4; ASIZW0000347-3, ASIZW0000347-4 collected by Shi-Kuei Wu from Wanli, 0 6.08.1965, (121.67°E; 25.2°N); ASIZW0000348-4; collected by Shi-Kuei Wu from Wanli, 22.04.1965, (121.67°E; 25.2°N); ASIZW0000354-1, ASIZW0000354-3, collected by Shi-Kuei Wu, (no locality data or date of collection given); ASIZW0000348-2, ASIZW0000348-3, ASIZW0000348-4 were collected by Shi-Kuei Wu from Wanli, 22.04.1965, (121.67°E; 25.2°N); ASIZW 0000345-4 collected by Shi-Kuei Wu from Shimen, 0 8.08.1964, (121.67°E; 25.2°N). All material collected from Taiwan of China.

Description. Holotype complete with 215 chaetigers. Body iridescent. Preserved specimen colour red or dark pink. Maximum width at chaetiger 10, 3.9 mm, excluding parapodia. Length from anterior to posterior margin of chaetiger 10, 8.7 mm.

Prostomium longer than length of peristomium, margins of prostomium dorsally flattened with shallow median sulcus. Eyes absent. Antennae arranged with median one inserted more posteriorly to lateral ones. Length of antennae varies, median longer and thicker than lateral ones, longest antennae reaching to chaetiger 3 ( Fig. 4 A). Ceratophores smooth, ceratostyles digitiform with faint articulations. Palps smooth, shorter than antennae. Ratio of length between antennae and palps is 1.5x. Peristomial rings well demarcated all around. Mandibles with calcareous plates longer than sclerotized matrix ( Fig. 4 D). Maxillae I more than twice length of carrier; maxilla III arched with anterior teeth in line with posterior ones. Maxillary formula: I=1+1, II=4+4, III=5+0, IV=4+8, V=1+1 ( Fig. 4 F).

Parapodia vary along the body, prechaetal lobe small throughout, anterior parapodia with short chaetal lobe, postchaetal lobe longer, median with postchaetal lobe decreasing in size and becoming same length as chaetal lobe, posterior with chaetal lobe same length as chaetal lobe ( Fig. 4 C). Dorsal cirri conical, shorter than chaetal lobes. Ventral cirri globular throughout body, the base of ventral cirri inconspicuous, length similar throughout body. Length of dorsal cirrus and ventral cirrus differs along body; in anterior and median chaetigers, dorsal cirri longer than ventral cirri, in posterior chaetigers equal in length. Branchiae begin with chaetiger 26, finish at chaetiger 181, pectinate throughout. Number of branchial filaments in anterior branchiae with 1–2 simple filaments, with maximum number of branchial filaments 3, in median parapodia ( Fig. 4 B). Length of branchial filaments where best developed is up to 2–2.5x length of dorsal cirrus. Parapodia 3, 20, 55, 90, 125, 160, 195, examined under the light microscope. Aciculae brown, with maximum number of 5 in anterior parapodia ( Fig. 4 C). Subacicular hooks brown, unidentate and bidentate, present from chaetiger 20 onwards. Maximum number of subacicular hooks 6 per parapodia. Compound spinigers present, throughout. Number of compound spinigers within a parapodium 10–31. Compound falcigers absent. Pectinate chaetae present throughout body. Number of pectinate chaetae within a parapodium 3–5 in anterior and nearly 20 in median and posterior ones. Pectinate chaetae 3 types present ( Table 2), with both asymmetrical and symmetrical teeth, outer teeth diverse, in some chaetigers outer teeth longer than inner teeth ( Fig. 4 G). In anterior parapodia only symmetrical isodont pectinate chaetae with about 12 teeth present ( Fig. 4 H-11). In posterior 2 types present: symmetrical anodont pectinate chaetae with about 14 teeth ( Fig. 4 G-(1), 4H-I) and isodont symmetrical pectinate chaetae with about 17 teeth ( Fig. 4 G-(II), 4H–VI).

Limbate capillaries present, throughout body, all similar. Number of limbate chaetae within a parapodium 11– 24.

Pygidium with 2 pairs of pygidial cirri ( Fig. 4 F), one pair longer than the other and inserted posteriorly laterally, shortest pair about 0.2x length of longer pair and inserted ventrally.

Variation. The paratypes exhibit the following variation, branchiae starting from chaetigers 16 to 26, and with 21–34 of the posterior-most chaetigers without any branchiae, the maximum number of filaments1–3. The ratio of the length between the antennae and the palps varies between 1.3 to 1.7.

Remarks. Marphysa tribranchiata n. sp. is described as a new species because of the poorly developed branchiae with only 2–3 filaments, two types of symmetrical isodont pectinate chaetae with either 12 or 17 teeth, as well as symmetrical anodont chaetae with 14 teeth and the large number of subacicular hooks present which begin from around chaetiger 20. Also the W10 ranges for the two species differs, with M. multipectinata n. sp. always being larger (4.05–5.7) than M. tribranchiata n. sp. (2.05-3.65). Using all these characters the new species can be distinguished from both M. multipectinata n. sp. and M. tripectinata n. sp. which occur in Taiwan and on mainland China (see Table 3). Marphysa tribranchiata n. sp. co-occurs with M. multipectina n. sp. at Shihmen , Taipei; however, unfortunately no habitat details are available. Zanol et al. (2016) also found two species of Marphysa cooccuring on the same mud flats at several locations along the New South Wales coast , Australia.

Marphysa tribranchiata n. sp. can be distinguished from the other recorded species of Marphysa from this region, including Marphysa orientalis which lacks pectinate chaetae until chaetiger 67 although details regarding their dentition are not known and M. tamurai Okuda, 1934 which has pectinate chaetae from about chaetiger 20 and anterior ones with about 18 teeth, although again the numbers present along the body or types of pectinate chaetae remain unknown.

Etymology. The specific name tribranchiata refers to the maximum number of branchial filaments which are present.

Habitat. Not recorded.

Type locality. Wanli, Taiwan of China, (121.67°E; 25.2°N), see Fig. 1 .

Distribution. Wanli and Shimen, Taiwan of China.

Figures

FIGURE 1. Type localities of Marphysa tripectinata n. sp., M. multipectinata n. sp., M. tribranchiata n. sp. and M. sinensis.

FIGURE 4. Marphysa tribranchiata n. sp. and pectinate chaetae variation present in the three new species. Light photographs A. Anterior end of holotype, dorsal view. B. Branchiae at median region of holotype. C. Right median parapodium of holotype, lateral view. D. Mandible, ventral view. E. Maxillary apparatus, dorsal view. F. Pygidium of holotype, lateral view. G. 2 types of pectinate chaetae of holotype, parapodium 195: (I) symmetrical anodont pectinate chaetae with about 14 teeth; (II) symmetrical isodont pectinate chaetae with about 17 teeth. H. Schematic drawings of pectinate chaetae present in posterior parapodia of three new species. I. symmetrical anodont with parallel 12 teeth; II. symmetrical isodont with 8 – 12 teeth; III. symmetrical isodont with about 14 – 16 teeth; IV. asymmetrical anodont with about 4 teeth; V. asymmetrical anodont with about 14 teeth; VI. asymmetrical anodont with about 17 teeth; VII. asymmetrical anodont with 14 – 18 teeth; VIII. asymmetrical anodont with 5 – 7 teeth; IX. asymmetrical isodont with more than 30 teeth. A, B, C, F, G. ASIZW 0000348 - 2. D, E. ASIZW 0000348 - 3. H. ASIZW 0000348 - 2, ASIZW 0000345 - 1, AM W. 49069. Scale bars: A, B. = 2 mm. C = 0.5 mm. D, E, F = 1 mm. G = 0.2 mm. H = is not to scale.