Namalycastis rhodochorde Glasby, Miura, Nishi and Junardi, 2007

Ibrahim, Nur Fazne, Ibrahim, Yusof Shuaib, Kan, Kotaro & Sato, Masanori, 2024, Nereidid polychaetes (Annelida) inhabiting the inside of decaying fronds of the mangrove palm Nypa fruticans in a tropical estuary in Malaysia, with special reference to the life history of the dominant species, Namalycastis sp., Journal of Natural History 58 (45 - 48), pp. 2043-2074 : 2057-2060

Namalycastis rhodochorde Glasby, Miura, Nishi and Junardi, 2007

( Figures 10–12 )

Namalycastis rhodochorde Glasby, Miura, Nishi and Junardi, 2007: 21–27 , figs 1–8 (type locality: West Kalimantan in Borneo , Indonesia); Idris et al. 2012: 240–241, fig. 2(a–g).

Material examined

In front of Pulau Awang Jin (Sta. 6) (5.643 ° N, 102.757 ° E) in Setiu Wetlands in Terengganu, Malaysia, 27 November 2015, coll. N.F. Ibrahim et al., single specimen ( UMT-Ann 2270 ).

Description

Complete specimen 3.3 mm BW, 445 mm BL, with approximately 650 chaetigers. Approximately uniform in width of anterior to about mid-body, then tapering gradually towards the posterior part. Dorsum convex, ventrally flattened. Colour in alcohol whitish (without pigmentation).

Prostomium trapezoidal (2.0x wider than long), with shallow cleft in anterior margin, with narrow longitudinal groove extending from tip to mid-posterior prostomium ( Figure 10 (a)). Pair of antennae short, sub-conical, aligned at inner edge of palps, extending to one-third of palpophores. Two pairs of eyes (deeply embedded within epidermis, almost invisible), black, arranged obliquely. Jaws black, with several teeth. Proboscis (eversible pharynx) without paragnaths and papillae.

Four pairs of tentacular cirri with cirrophores distinct (1/3 as long as total length of cirri) ( Figure 10 (a)). Anterodorsal and posterodorsal tentacular cirri of almost the same length. Posterodorsal tentacular cirri extending posteriorly to chaetiger 3.

Parapodia consist of triangular dorsal cirrus, acicular ligule and ventral cirrus. Acicular ligule weakly bilobed distally (superior lobe papilliform, inferior lobe globular) throughout except for posterior-most chaetigers ( Figure 10 (d–l)). Dorsal cirri triangular throughout, widest (1.2x wider than long) at mid-body (around chaetiger 300, Figure 10 (i)), longest around chaetiger 10 ( Figure 10 (e)), decreasing in length posteriorly; dorsal cirri of chaetiger 10 twice longer than those of chaetiger 601 ( Figure 10 (l)). Ventral cirri small, slender throughout. Aciculae black.

Notochaetae absent throughout ( Figure 11 ). Neurochaetae type C according to Glasby (1999). Upper neurochaetae have sesquigomph spinigers with finely serrated blade posteriorly ( Figure 12 (a)) and heterogomph falcigers anteriorly ( Figure 12 (b)). Lower neurochaetae have heterogomph falcigers ( Figure 12 (c)) arranged in deep arc around inferior lobe ( Figure 11 ). All heterogomph falcigers with single nose-like projection at base of inner edge of blade lacking serration ( Figure 12 (b,c)).

Pygidium with multi-incised rim, and anus dorsoterminal ( Figure 10 (c)). Pair of anal cirri arising ventrolaterally, half as long as pygidium width.

Habitats

A single specimen was found inside the decaying fronds of Nypa fruticans in the estuary Setiu Wetlands, Terengganu, co-existing with Namalycastis sp. in the present study. The species inhabited the mud banks and mudflats associated with the Nypa palm in estuarine mangrove areas, such as those found in Indonesia, Vietnam ( Glasby et al. 2007; Junardi 2021) and Malaysia ( Idris et al. 2012).

Distribution

Mekong Delta ( Vietnam), West Kalimantan and Sabah in Borneo ( Indonesia and Malaysia) ( Glasby et al. 2007; Junardi et al. 2014a; Junardi 2021); Johor, Kedah and Penang in the western coast of Peninsular Malaysia ( Idris et al. 2012); Terengganu on the eastern coast of Peninsular Malaysia (present study).

Remarks

This is the first record of the species from the eastern coast of Peninsular Malaysia. General morphology of the specimen agrees well with the original description of N. rhodochorde by Glasby et al. (2007), clearly differing from Namalycastis sp. by having toothless blades of heterogomph falcigers and in the absence of notochaetae as well as neuropodial sub-acicular heterogomph spinigers. The specimens reported from the western coast of Peninsular Malaysia by Idris et al. (2012) differ from our specimen in the following characteristics: (1) the presence of heterogomph falcigers having a blade with 10 small serrations in the anterior chaetigers, and (2) the presence of few (1–4) notopodial sesquigomph spinigers in some chaetigers.

Figures

Figure 10. Namalycastis rhodochorde, UMT-Ann 2270. (a) Anterior end with everted proboscis, dorsal view. (b) Middle body, dorsal view. (c) Posterior end, dorsal view. (d–l) Posterior views of parapodia in chaetigers 10 (d), 36 (e), 51 (f), 101 (g), 201 (h), 301 (i), 401 (j), 501 (k), and 601 (l). Scale bars: 1 mm.

Figure 11. Namalycastis rhodochorde, UMT-Ann 2270. Parapodium of chaetiger 101, posterior view. Scale bar: 0.2 mm.

Figure 12. Namalycastis rhodochorde, UMT-Ann 2270. Chaetae in chaetiger 51. (a) Sesquigomph spiniger in upper neurochaetae. (b) Heterogomph falciger in upper neurochaetae. (c) Heterogomph falciger in lower neurochaetae. Scale bars: 0.1 mm.