Marphysa setiuense, 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 setiuense sp. nov.

Figs 1 , 2 , 11 , 12 , 13

Material examined.

Holotype. UMTAnn 2177 , complete, antero-ventrally dissected, some parapodia mounted for SEM . Paratypes. AM W. 54050 , complete, some parapodia mounted for SEM. LACM-AHF 13497 to 13499, complete, some parapodia removed; ZRC. ANN. 1607 to 1609, complete, some parapodia removed . All material was collected from the east coast of Peninsular Malaysia, Terengganu, Setiu Wetlands (05 ° 39.183 ' N, 102 ° 45.194 ' 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 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 and wide isodont with short and slender inner teeth, and pectinate thick, wide anodont with long and slender or thick inner teeth. Subacicular chaetae include only compound spinigers. Subacicular hook unidentate, and a few bidentate present in posterior chaetigers. Pygidium with two pairs of anal cirri, without articulation.

Description

(based on holotype, with variation in parentheses for paratypes). Preserved specimens beige (Fig. 11 A ), ~ 154 (141–259) chaetigers, ~ 51 mm (27–75 mm) long, L 10 - 2.7 mm (2.85–4.8 mm), W 10 - 1.8 mm (1.65–2.55 mm), excluding parapodia. Anterior region of the body with dorsum convex and flat ventrum, without groove; body depressed from chaetiger 11, elongated and tapering at the distal end. Live specimens pink (Fig. 13 B, D ).

Prostomium bilobed, anteriorly rounded with two dorsoventrally flattened lobes separated by an anterior notch (Fig. 11 A, B ). Prostomial appendages in a semicircle, median antenna isolated by a gap (Fig. 11 B ). Palps reaching chaetiger 3; lateral antennae reaching chaetiger 4; median antenna reaching chaetiger 5. Palpophores and ceratophores ring-shaped, short, and thick; palpostyles and ceratostyles tapering and slender. Prostomial appendage peduncles absent. Pair of faded brown eyes at posterior base of prostomium, between palps and lateral antennae. Peristomium similar in size (width and length) to prostomium; the first ring is 1.5 × longer than second ring, and separation between rings distinct on all sides.

Maxillae dark brown (Fig. 11 C ) and maxillary formula as follows: MF = 1 + 1, 5 (4–5) + 5 (4–6), 5 (4–6) + 0, 3 (3–4) + 6 (7–8), 1 + 1. Maxillary carrier ~ 2.4 × 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 ~ 5 × shorter than MI. Ligament between MI and MII pale brown. MII without attachment lamella, teeth triangular, distributed along half of plate length. 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 curved attachment lamellae. Right MIV long, with teeth triangular with curved attachment lamellae, decreasing in size and teeth curved posteriorly. MV paired. Mandibles dark brown (Fig. 11 D ), with concentric stripes; longer than MI; cutting plates whitish.

First parapodia occur ventrolaterally, gradually becoming dorsolateral in following segments. Chaetal lobes rounded in all chaetigers (Fig. 11 G – I ). Prechaetal lobe shorter than chaetal lobe along whole body. Postchaetal lobe digitiform in first three chaetigers and rounded thereafter; conical and longer than chaetal lobe in median and posterior chaetigers, becoming shorter and absent in the posterior-most chaetigers. Dorsal cirri thumb-shaped with digitiform tips, shorter than ventral cirri in anterior, digitiform with slender and tapering tips; slightly longer or similar length from mid-body onwards and shorter in posterior-most chaetigers (Fig. 11 G – I ). Ventral cirri thumb-shaped with digitiform tips in the first few chaetigers, basally inflated with digitiform tip from chaetiger 15 onwards, and gradually becoming conical posteriorly (Fig. 11 G – I ). Branchiae pectinate, from chaetiger 20 (15–25) and continuing to near the end (~ 8 last chaetigers without branchiae), branchial filament 4 × longer than dorsal cirri where best developed; number of filaments increasing from two anteriorly to five in mid-body, decreasing to one in last several chaetigers.

Notoaciculae absent, neuroaciculae black, blunt, and translucent at distal end on 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. 11 G – I ). Supra-acicular chaetae with limbate capillaries and pectinates. Four types of pectinate chaetae were identified (types 1, 2, 7, 8) (see Fig. 2 ): type 1: thin, narrow isodont with ~ 18–22 short and slender inner teeth, outer teeth longer, but of varying lengths, present in anterior and median body region (Fig. 12 A, B ); type 2: thin, wide isodont with 14–21 short and slender teeth, outer teeth same length as inner teeth, present only in anterior and posterior region (Fig. 12 C, D ); type 7: thick, wide anodont with 15–18 long and slender inner teeth, only present in posterior region (Fig. 12 E, F ); type 8: thick, wide anodont, with seven inner long and thick teeth, only present in posterior region (Fig. 12 F ). Subacicular chaetae with compound spinigers (Fig. 12 G ). Subacicular hooks unidentate (Figs 11 E , 12 H ), pale brown, translucent at distal end, commencing from chaetiger 25 (21–38) and then present on all subsequent chaetigers, one per parapodium and with a few bidentate hooks in posterior chaetigers (Fig. 11 F ). Pygidium with crenulated margin, with two pairs of tapering pygidial cirri attached to ventral side of pygidium, dorsal pair ~ 4 × longer than ventral one (Fig. 11 J ).

Etymology.

The name refers to the type locality Setiu Wetlands.

Type locality.

South China Sea, Malaysia, east coast of Peninsular, Terengganu, Setiu Wetlands (see Fig. 1 ).

Distribution.

Known only from the type locality.

Habitat.

Slightly gravelly sand sediment (Table 4 ), burrowing in decayed roots of mangrove trees ( Sonneratia spp. ) and area within Talipariti tiliaceum (Fig. 13 A – C ), with salinity 26 ‰ during spring low tide.

Remarks.

With the presence of only compound spiniger along the whole body and branchiae along most of the body, Marphysa setiuense sp. nov. belongs to Group B (Sanguinea). As mentioned earlier, there are seven other Sanguinea-group Marphysa species described from the South China Sea; M. merchangensis sp. nov., M. hongkongensa , M. iloiloensis , M. multipectinata , M. orientalis , M. tribranchiata and M. tripectinata . The most morphologically-similar species to M. setiuense sp. nov. is M. hongkongensa . Both species have four types of pectinate chaetae (two isodont and two anodont; types 1, 2, 7, 8) and have both unidentate and bidentate subacicular hooks in posterior chaetigers. However, they differ in the number of branchial filaments and the distribution of branchiae. Marphysa setiuense sp. nov. (L 10: 2.7 (2.85–4.8) mm) has a maximum of five branchial filaments while M. hongkongensa (L 10: 3.3–7 mm) has up to ten. Also, the species have different maxillae formulae. Marphysa setiuense sp. nov. has fewer denticles on MIII (5 (4–6) + 0) compared to M. hongkongensa which has MIII (7 + 0) (see Table 6 ).

Marphysa setiuense sp. nov. is similar to M. iloiloensis and M. multipectinata in having a pair of eyes, but they can be distinguished by the number of types of pectinate chaetae, the chaetiger on which branchiae and subacicular hooks begin, number of branchial filaments, shape of subacicular hooks and maxillae formula. Marphysa setiuense sp. nov. has four types of pectinate chaetae (types 1, 2, 7, 8) compared to three types present in M. iloiloensis (types 1, 4, 6). Marphysa multipectinata also has four types of pectinate chaetae (types 1, 4, 7, 8), but they are only present on median and posterior chaetigers, whereas in M. setiuense sp. nov., the pectinate chaetae are present throughout the body. The maximum number of branchial filament in M. setiuense sp. nov. (L 10: 2.7 (2.85–4.8) mm) is five, and up to seven for M. iloiloensis . Marphysa multipectinata (L 10: 13.9 mm) has palmate branchiae with maximum five branchial filaments and begin from chaetiger 32 whereas Marphysa setiuense sp. nov. also has a maximum of five branchial filaments but they begin from chaetiger 20 (15–25). Marphysa setiuense sp. nov. and M. multipectinata have unidentate and bidentate subacicular hooks from chaetiger 25 (21–38) and chaetiger 20, whereas M. iloiloensis has unidentate subacicular hooks only from chaetiger 30–38. All these species have different formulae for MII, MIII, and MIV (see Table 6 ).

The other two Marphysa species of the Sanguinea complex occurring within the South China Sea, M. tribranchiata and M. tripectinata differ from M. setiuense sp. nov. by having no eyes. They also can be differentiated by the number of types of pectinate chaetae. Marphysa tribranchiata and M. tripectinata have three types of pectinate chaetae, while M. setiuense sp. nov. has four (types 1, 2, 7, 8). Marphysa tribranchiata lacks thin, wide isodont (type 2), while M. tripectinata lacks thin, narrow isodont pectinate chaetae (type 1). Also, M. tripectinata (L 10: 12.7 mm) only has unidentate subacicular hooks, whereas M. tribranchiata (L 10: 8.7 mm) and M. setiuense sp. nov. (L 10: 2.7 (2.85–4.8) mm) have both unidentate and bidentate subacicular hooks.

Marphysa setiuense sp. nov. and M. orientalis differ by the presence or absence of eyes, shape of subacicular hooks, pair of anal cirri, the chaetiger on which the branchiae begin and the maximum number of branchial filaments. Marphysa setiuense 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. The new species has unidentate and bidentate subacicular hooks while M. orientalis has only unidentate subacicular hooks. Branchiae in M. setiuense sp. nov. begin from chaetiger 20 (15–25) whereas in M. orientalis they occur from chaetiger 45. The maximum number of branchial filaments in M. setiuense sp. nov. is five, while M. orientalis only has three branchial filaments.

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 11. Marphysa setiuense sp. nov. Holotype UMTAnn 2177 (A – J). 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 unidentate hook, chaetiger 136 F bidentate hooded hook, chaetiger 140 G parapodium, chaetiger 10 H parapodium, chaetiger 77 I parapodium, chaetiger 136 J posterior segments and pygidium, dorsal 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, C, D, J); 1 mm (B); 20 µm (E – F); 0.1 mm (G – I).

Figure 12. SEM images of Marphysa setiuense sp. nov. Holotype UMTAnn 2177 (B, D – G), paratype AM W. 54050 (A, C, H) A pectinate chaetae, chaetiger 30 B pectinate chaetae, chaetiger 77 C pectinate chaetae, chaetiger 203 D pectinate chaetae, chaetiger 77 E, F pectinate chaetae, chaetiger 136 G spiniger chaetae, chaetiger 25 H subacicular hook, chaetiger 183. Numbers denoted by arrows indicate the type of pectinate chaetae; 1. Thin, narrow isodont; 2. Thin, wide isodont; 7, 8. Thick, wide anodont. Scale bars: 5 µm (A – C); 10 µm (D – F); 20 µm (G, H).

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.