Marphysa merchangensis, Che Engku Abdullah & Idris & Fahmi & Flaxman & Hutchings, 2024

Che Engku Abdullah, Che Engku Siti Mariam, Idris, Izwandy, Fahmi, Afiq Durrani Mohd, Flaxman, Beth & Hutchings, Pat, 2024, Four new species of Marphysa (Annelida, Eunicida, Eunicidae) from the east coast of Peninsular Malaysia, ZooKeys 1204, pp. 65-103 : 65-103

Marphysa merchangensis sp. nov.

Figs 1 , 2 , 8 , 9 , 10

Material examined.

Holotype. UMTAnn 2149 , complete, antero-ventrally dissected, some parapodia mounted for SEM . Paratypes. AM W. 54044 , complete, some parapodia mounted for SEM. LACM-AHF 13494 to 13496, complete, some parapodia removed; ZRC. ANN. 1604 to 1606, complete, some parapodia removed; SAM-MB-A 096021, complete, some parapodia removed . All material was collected from the east coast of Peninsular Malaysia, Terengganu, Merchang mangrove estuary (05 ° 01.393 ' N, 103 ° 17.994 ' E), October 2021.

Diagnosis.

Prostomium completely bilobed, five prostomial appendages without articulations; eyes present. Peristomium without peristomial cirri. Maxillary apparatus with four pairs of maxillae, an unpaired on the left side, MI with falcal arch extended at sub-right angle, basal outer edge arched, basal inner edge lacking curvature. MII with triangular teeth and without attachment lamella. MIII slightly curved, with equal-sized triangular teeth, without attachment lamella. MIV with rectangular and curved attachment lamella. Branchiae distributed along entire body. Dorsal cirri without articulations; postchaetal lobe well developed in anterior regions. Ventral cirri with swollen, inflated base. Sub-aciculae black, blunt, and translucent at distal end, pale brown in posterior-most parapodia. Supra-acicular chaetae include limbate, pectinate thin, narrow isodont with short and slender inner teeth, pectinate thick, wide isodont with short or long and slender inner teeth, and pectinate thick, narrow and wide anodont with long and thick inner teeth. Subacicular chaetae include only compound spinigers. Subacicular hook unidentate throughout chaetigers. Pygidium with two pairs of anal cirri, without articulation.

Description

(based on holotype, with variation in parentheses for paratypes). Preserved specimen beige (Fig. 8 A ), 257 (165–294) chaetigers, 94 mm (37–144 mm) long, L 10 - 5.25 mm (3.45–5.85 mm), W 10 - 2.85 mm (1.95–3.15 mm), excluding parapodia. Anterior region of body with dorsum convex and flat ventrum, without groove (Fig. 8 A ); body depressed from chaetiger 25, elongated and tapering at distal end. Live specimens pink with red branchiae (Fig. 10 D ).

Prostomium bilobed, anteriorly rounded with two dorsoventrally flattened lobes with an anterior notch between them (Fig. 8 A, B ). Prostomial appendages in a semicircle, median antenna isolated by a gap (Fig. 8 B ). Palps reach middle of second peristomial ring; lateral antennae reaching chaetiger 2; median antenna reaching chaetiger 3. Palpophores and ceratophores ring-shaped, short, and thick; palpostyles and ceratostyles tapering, and slender. Prostomial appendage peduncles absent. A pair of faded brown eyes present at posterior base of prostomium, between palps and lateral antennae (Fig. 8 B ). Peristomium larger and wider than prostomium; first ring is 2.5 × longer than second ring, separation between rings distinct on all sides.

Maxillae pale brown (Fig. 8 C ), and maxillary formula as follows: MF = 1 + 1, 5 (4–5) + 5 (5–6), 7 (6–7) + 0, 4 (4–5) + 8 (5–8), 1 + 1. Maxillary carrier ~ 2.5 × shorter than MI, rectangular anteriorly, triangular posteriorly. MI forceps-like, without attachment lamellae, falcal arch extended at sub-right angle, basal outer edge arched, basal inner edge lacking a curvature. Closing system ~ 3 × shorter than MI. Ligament between MI and MII pale brown. MII without attachment lamella, teeth triangular, distributed on <1 / 2 length of the plate. Ligament between MII and MIII pale brown. MIII single, longer than left MIV slightly curved, with equal-sized triangular teeth, without attachment lamella. Left MIV short (<1 / 2 the size of right MIV) with rectangular attachment lamellae. Right MIV long with curved attachment lamellae, teeth triangular, decreasing in size and teeth curved posteriorly. MV paired. Mandible pale brown, with concentric stripes, longer than MI; cutting plates whitish (Fig. 8 D ).

First few parapodia located ventrolaterally but gradually becoming dorsolateral in subsequent segments. Chaetal lobes rounded in anterior and posterior chaetigers, conical in median chaetigers (Fig. 8 E – G ). Prechaetal lobe shorter than chaetal lobe throughout body. Postchaetal lobe digitiform in first three chaetigers then rounded thereafter; longer than chaetal lobe in median chaetigers onwards, become shorter and absent in the posterior-most chaetigers. Dorsal cirri digitiform and slender, longer than ventral cirri anteriorly, slightly longer or similar from mid-body towards posterior-most chaetigers (Fig. 8 E – G ). Ventral cirri thumb-shaped with rounded wide tips in first few chaetigers, basally inflated with digitiform tip from chaetiger 15, and gradually becoming conical posteriorly (Fig. 8 E – G ). Branchiae pectinate, from chaetiger 24 (16–27) and continuing to last ~ 10 chaetigers, branchial filaments 4 × longer than dorsal cirri where best developed; number of filaments increasing from three anteriorly to six in mid-body, decreasing to one in last several chaetigers.

Notoaciculae absent, neuroaciculae black, blunt, and translucent at distal end along most of body, pale brown in posterior-most parapodia; ~ 2 or 3 per parapodium in anterior, one per parapodium in median and posterior chaetigers (Fig. 8 E – G ). Supra-acicular chaetae with limbate capillaries and pectinates. Five types of pectinate chaetae present (types 1, 4, 5, 6, 8) (see Fig. 2 ): type 1: thin, narrow isodont with 7–12 short and slender inner teeth, outer teeth longer, but with varying lengths, present in anterior and median body region (Fig. 9 A, B ); type 4: thick, wide isodont with 12–15 short and slender inner teeth, present only in median and posterior region (Fig. 9 C ); type 5: thick, wide isodont, with 15–18 long and slender inner teeth, only present in posterior region (Fig. 9 D ); type 6: thick, narrow anodont with 11 or 12 long thick teeth, only present in posterior region (Fig. 9 E ); type 8: thick, wide anodont, with five inner long and thick teeth, only present in the posterior region (Fig. 9 F ). Subacicular chaetae with compound spinigers (Fig. 9 G ). Subacicular hooks pale brown, translucent at distal end, emerge from chaetiger 37 (26–42) and then present on all chaetigers, one per parapodium; subacicular hooks unidentate throughout chaetigers (Fig. 9 H ). Pygidium with crenulated margin, with two pairs of tapering pygidial cirri attached to ventral side of pygidium, dorsal pair ~ 4 × longer than ventral (Fig. 8 H ).

Etymology.

The name denotes the type locality (Merchang estuary) where the specimens were collected.

Type locality.

South China Sea, Malaysia, east coast of Peninsular, Terengganu, Merchang mangrove estuary (see Fig. 1 ).

Distribution.

Known only from the type locality and Setiu Wetlands, Terengganu, Malaysia.

Habitat.

Gravelly and slightly gravelly sand (Table 4 ), burrowing in decayed roots of the mangrove E. agallocha (Malay: Bebuta) (Fig. 10 A – C ), burrowing in the sediments within an area populated with Talipariti tiliaceum (Fig. 13 C ) with salinity 26 ‰ during spring low tide.

Remarks.

With the presence of only compound spinigers along the whole body and branchiae along most of the body, Marphysa merchangensis sp. nov. belongs to the Marphysa Group B (Sanguinea). Other Marphysa species from Sanguinea-group occurring in the same water body (South China Sea) as M. merchangensis sp. nov. are M. setiuense sp. nov., M. hongkongensa Wang, Zhang & Qiu, 2018 (type locality: Hong Kong), M. iloiloensis Glasby, Mandario, Burghardt, Kupriyanova, Gunton & Hutchings, 2019 (type locality: Philippines), M. multipectinata Liu, Hutchings & Sun, 2017 (type locality: Shimen, Taiwan of China), M. orientalis Treadwell, 1936 (type locality: Xiamen, China), M. tribranchiata Liu, Hutchings & Sun, 2017 (type locality: Wanli, Taiwan of China), and M. tripectinata Liu, Hutchings & Sun, 2017 (type locality: Beihai, China).

Marphysa merchangensis sp. nov. is similar to M. setiuense sp. nov. in having a pair of eyes and the absence of peduncle on the prostomial appendages. However, they can be differentiated by the number of types of pectinate chaetae, maxillary formula, chaetiger on which the branchiae and subacicular hooks occur, shape of dorsal cirri, chaetal lobes and subacicular hooks. Number of types of pectinate chaetae in M. merchangensis sp. nov. is five (types 1, 4, 5, 6, 8), whereas in M. setiuense sp. nov. there are four (types 1, 2, 7, 8), and they lack the thick, wide isodont pectinate chaetae (types 4, 5). Marphysa merchangensis sp. nov. (L 10: 5.25 (3.45–5.85) mm) has more denticles on MIII 7 (6–7) + 0 compared to M. setiuense sp. nov. (L 10: 2.7 (2.85–4.8) mm) which has MIII: 5 (4–6) + 0. Branchiae and subacicular hook of M. merchangensis sp. nov. occur later (chaetiger 24 (16–27) and 37 (26–42 )), respectively) compared to M. setiuense sp. nov., where they occur from chaetiger 20 (15–25) and 25 (21–38), respectively. Marphysa merchangensis sp. nov. has digitiform dorsal cirri along the whole body, while M. setiuense sp. nov. has both thumb-shaped and digitiform dorsal cirri. Marphysa merchangensis sp. nov. has rounded shaped chaetal lobe in the anterior and posterior, and conical in the median region, whereas M. setiuense sp. nov. has rounded chaetal lobes on all parapodia. Finally, M. merchangensis sp. nov. has unidentate subacicular hook, whereas M. setiuense sp. nov. has unidentate and a few bidentate subacicular hooks present in posterior chaetigers.

Marphysa merchangensis sp. nov. and M. hongkongensa can be differentiated by the presence or absence of eyes, number of types of pectinate chaetae, maximum number of branchial filaments, and the shape of subacicular hooks. Marphysa merchangensis sp. nov. has a pair of eyes but they are absent in M. hongkongensa . Marphysa merchangensis sp. nov. has five types of pectinate chaetae (types 1, 4, 5, 6, 8) compared to four types present in M. hongkongensa (types 1, 2, 7, 8). Marphysa hongkongensa lacks thick, wide isodont and thick, narrow anodont pectinate chaetae (types 4, 5, 6) which are present in the new species. The maximum number of branchial filaments in M. merchangensis sp. nov. (L 10: 5.25 (3.45–5.85) mm) is six and they begin from chaetiger 24 (16–27) whereas M. hongkongensa (L 10: 3.3–7 mm) has a maximum of ten branchial filaments, beginning from chaetiger 15–35. Finally, M. merchangensis sp. nov. only has unidentate subacicular hooks while both unidentate and bidentate subacicular hooks are present in M. hongkongensa .

Marphysa merchangensis sp. nov. is similar to M. iloiloensis and M. multipectinata in having a pair of eyes. However, they can be distinguished by the number of types of pectinate chaetae present, the chaetiger on which branchiae and subacicular hooks occur, number of branchial filaments, shape of subacicular hooks and the maxillae formula. Marphysa merchangensis sp. nov. has five types of pectinate chaetae (types 1, 4, 5, 6, 8) whereas M. iloiloensis and M. multipectinata have three (types 1, 4, 6) and four (types 1, 4, 7, 8) respectively. Marphysa merchangensis sp. nov. and M. iloiloensis have the same type of pectinate branchiae (beginning on the same chaetiger with different range of variation) (chaetiger 24 (16–27) for the new species, and chaetiger 19 (16–20) for M. iloiloensis ). The maximum number of branchial filaments in M. merchangensis sp. nov. (TL: 94 (37–144) mm) is six, while M. iloiloensis (TL: 99 (95–165 +) mm) has a maximum of seven branchial filaments. Marphysa multipectinata (L 10: 13.9 mm) has palmate branchiae with maximum of five branchial filaments from chaetiger 32. Finally, all these species have different formulae for MII, MIII and MIV (see Table 6 ).

The other species from the Sanguinea complex, M. tribranchiata and M. tripectinata differ from M. merchangensis sp. nov. by the absence of eyes. Both M. tribranchiata and M. tripectinata have three types of pectinate chaetae, whereas M. merchangensis sp. nov. has five types. Marphysa tribranchiata lacks thick, wide isodont and thick, narrow anodont pectinate chaetae (types 4, 6), while M. tripectinata lacks thin, narrow isodont pectinate chaetae (type 1) which are present in the new species (types 1, 4, 5, 6, 8). While M. merchangensis sp. nov. and M. tripectinata only have unidentate subacicular hooks, they begin much later (chaetiger 170) in the latter species. Marphysa tribranchiata has both unidentate and bidentate subacicular hooks whereas only unidentate hooks are present in M. merchangensis sp. nov. The maximum number of branchiae filaments present in M. tribranchiata (L 10: 8.7 mm) and M tripectinata (L 10: 12.7 mm) are three and eight respectively, differs from M. merchangensis sp. nov. (L 10: 5.25 (3.45–5.85) mm), which has a maximum of six.

Finally, M. merchangensis sp. nov. is similar to M. orientalis by having unidentate subacicular hooks. Marphysa merchangensis sp. nov. has a pair of eyes and two pairs of anal cirri, while M. orientalis has no eyes and only one pair of anal cirri. Also, branchiae in M. merchangensis sp. nov. begin earlier from chaetiger 24 (16–27) compared to M. orientalis (chaetiger 45). The maximum number of branchial filaments in M. merchangensis sp. nov. is six, while M. orientalis has a maximum of three branchial filaments. Nevertheless, the original description of M. orientalis is incomplete and does not include certain important features such as the number and type of pectinate chaetae. Fresh material of M. orientalis should be collected and redescribed from the type locality at Gulf of Mannar, Sri Lanka.

Figures

Figure 1. Map showing sampling sites of four new Marphysa species in Terengganu mangrove forest, east coast of Peninsular Malaysia A location of Terengganu on the east of Peninsular Malaysia B symbols indicate each sampling site; Setiu Wetlands (red star), Kuala Ibai (red rhombus), Merchang (red triangle), and Kerteh (red oval).

Figure 2. The schematic drawing of type of pectinate chaetae present in Marphysa from Terengganu A thin, narrow isodont with short and slender inner teeth (type 1) B thin, wide isodont with short and slender inner teeth (type 2) C thin, narrow heterodont with short and slender inner teeth (type 3) D thick, wide isodont with short and slender inner teeth (type 4) E thick, wide isodont with short and slender inner teeth (type 5) F thick, narrow anodont with long and thick inner teeth (type 6) G thick, wide anodont with long and slender inner teeth (type 7) H thick, wide anodont with long and thick inner teeth (type 8). Scale bars: 18 µm (A); 35 µm (B, G); 20 µm (C); 38 µm (D); 32 µm (E); 13 µm (F); 30 µm (H).

Figure 8. Marphysa merchangensis sp. nov. Holotype UMTAnn 2149 (B – H), paratype UMTAnn 2148 (A). Light microscopy images and digital drawing A anterior end, lateral view B anterior end, dorsal view. Arrows indicate eyes C maxillae, dorsal view D mandibles, dorsal view E parapodium, chaetiger 10 F parapodium, chaetiger 134 G parapodium, chaetiger 250 H posterior segments and pygidium, ventral view. Arrows show the short pair of pygidial cirri. Abbreviations; MI – MV: maxillae I – V, Ac: aciculae, Dc: dorsal cirrus, Vc: ventral cirrus, PCl: prechaetal lobe, Cl: chaetal lobe, PtCl: postchaetal lobe, Sah: subacicular hook, Bf: branchial filament. Scale bars: 1 mm (A – D, H); 0.1 mm (E – G).

Figure 9. SEM images of Marphysa merchangensis sp. nov. Holotype UMTAnn 2149 (A, B, E, H), paratype AM W. 54044 (C, D, F, G) A, B pectinate chaetae, chaetiger 10 C pectinate chaetae, chaetiger 164 D pectinate chaetae, chaetiger 245 E pectinate chaetae, chaetiger 250 F pectinate chaetae, chaetiger 265 G spiniger chaetae, chaetiger 10 H subacicular hook, chaetiger 128. Numbers denoted by arrows indicate the type of pectinate chaetae; 1. Thin, narrow isodont; 4, 5. Thick, wide isodont; 6. Thick, narrow anodont; 8. Thick, wide anodont. Scale bars: 5 µm (A – C, E); 10 µm (D, F, H); 50 µm (G).

Figure 10. Sampling site in Merchang mangrove estuary A habitat of M. merchangensis sp. nov. B – C worm found in decayed root of Exoecaria agallocha (Malay: Bebuta) D live worms.

Figure 13. Sampling in Setiu Wetlands (river area) A, C habitat of M. setiuense sp. nov. and M. merchangensis sp. nov. within Talipariti tiliaceum B Marphysa setiuense sp. nov. in situ D live M. setiuense sp. nov.