Composetia tokashikiensis Sato 2020
Creators: name: Sato, Masanori
name: Ebihara, Takumi
name: Satake, Kiyoshi
name: Kojima, Shigeaki
name: Fukumori, Hiroaki
name: Angsupanich, Saowapa
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Animalia
Annelida
Polychaeta
Phyllodocida
Nereididae
Composetia
Composetia tokashikiensis

description: Composetia tokashikiensis Sato, 2020
(Fig. 8)
Composetia tokashikiensis Sato, 2020: 17–20, figs 4B, 6–8. Composetia sp. A: Sato and Sakaguchi 2016: 85.
Composetia sp. 1: Sato 2017: 483.
Materials examined. One single female (PMBC- 29970), the lower reaches of Songkhla Lagoon (7°10′37.4″N, 100°32′26.2″E), southern Thailand, 19 November 2008, coll. S. Angsupanich (Fig. 1; Table 1).
Description. Complete individual, 18 mm BL, 1.0 mm BW, with 57 chaetigers. Colour in preserved specimen whitish cream with brownish pigmentation in anterior dorsum.
Prostomium pear-shaped (Fig. 8A). Antennae short, tapered. Palps with massive palpophores and short subconical palpostyles. Two pairs of eyes arranged trapezoidally, anterior pair reniform, more separated and larger than posterior pair; posterior pair round. Mid-longitudinal white slit present on dorsal anterior surface of prostomium.
Apodous segment (peristomium) with four pairs of tentacular cirri of unequal length; posterior dorsal tentacular cirri longest, reaching back to chaetigers 11.
Proboscis with pair of amber jaws, each with eight marked teeth. Brown paragnaths present only on maxillary ring (Fig. 8A, B). Paragnath numbers on each area as follows: area I: 0; area II: 13 on left and 16 on right in two arched rows, total 29; area III: 21 in wide patch; area IV: 14 on each side in triangular patch, total 28. Oral ring greatly enlarged into trapezoidal shape in full-everted proboscis, without any paragnaths or papillae.
Sub-biramous parapodia of first 2 chaetigers with thin notoacicula (Fig. 8C). Notopodial dorsal ligule conical with tapering tip throughout. Both notopodial prechaetal lobe and notoacicular process absent throughout (Fig. 8 D–G). Notopodial ventral ligule conical with tapering tip throughout, almost subequal to notopodial dorsal ligule. Dorsal cirri slender in most chaetigers (relatively thick in chaetiger 5), tapering, as long as or shorter than notopodial dorsal ligule throughout (Fig. 8 C–G). Three (rarely two) whitish glandular patches present on dorsal edge of notopodia; distalmost glandular patch larger than others, covering whole conical projection of notopodial dorsal ligule throughout (Fig. 8 D–G).
Neuropodial postchaetal lobe with tapering tip present in first 18 chaetigers (Fig. 8C, D), absent in following chaetigers (Fig. 8F, G). Superior lobe in acicular ligule absent throughout. Inferior lobe conical in anterior parapodia, diminishing in middle parapodia, and absent in posterior parapodia. Ventral ligule conical with tapering tip throughout. Ventral cirrus slender with tapering tip.
Notochaetae all homogomph spinigers, having long blades with finely serrated edge; up to 8 spinigers present.
Upper neurochaetae at superior/anterior position in anterior chaetigers (around first 20 chaetigers) consisting of heterogomph spinigers with short finely-serrated blades (3, 7, and 0 spinigers present in chaetigers 1, 5, and 20, respectively), and few heterogomph falcigers with short finely-serrated blades (Fig. 8J) (1, 0, and 2 falcigers present in chaetigers 1, 5, and 20, respectively). Upper neurochaetae at superior/anterior position in posterior chaetigers consisting of only few heterogomph falcigers (0, 2, and 2 falcigers present in chaetigers 44, 46, and 48, respectively), lacking heterogomph spinigers.
Upper neurochaetae at posterior position consisting of homogomph spinigers with long finely-serrated blades (Fig. 8H) throughout (up to 6 spinigers present).
Lower neurochaetae in anterior chaetigers consisting of many heterogomph spinigers with finely-serrated blades (12, 13 and 4 spinigers present in chaetigers 1, 5 and 20, respectively), and few heterogomph falcigers with short serrated blades (0, 1 and 3 falcigers present in chaetigers 1, 5 and 20, respectively); spinigers with long blades located at posterior position; spinigers with short blades (Fig. 8I) and falcigers located at inferior/anterior position. Lower neurochaetae in posterior chaetigers consisting of several heterogomph spinigers at posterior position (5, 5 and 4 spinigers present in chaetigers 44, 46 and 48, respectively), and few heterogomph falcigers at inferior/anterior position (0, 1 and 1 falcigers present in chaetigers 44, 46 and 48, respectively).
The coelom filled with oocytes of 180–200 µm in diameter.
Habitat. Shallow subtidal bottom in the coast of the lower reaches of Songkhla Lagoon, where salinity widely ranges from 1 to 33 psu depending on variable seasonal rainfall; in general, about 1–10 psu in November to March, about 10–20 psu in April to July, about 20–33 in August to October (Angsupanich and Rakkheaw 1997; S. Angsupanich, unpublished data).
Geographical distribution. The middle and southern Ryukyu Islands in southern Japan (north to Amami-oshima, south to Yonagni-jima), the coast of South China Sea in southern Thailand (Fig. 1).
Remarks. The morphological characteristics of the present Thailand specimen agreed well with those of the original description of C. tokashikiensis by Sato (2020) and also of many additional non-type specimens of this species collected from the Ryukyu Islands, southern Japan in the present study. All of the numerical characteristics (BW, BL, numbers of total chaetigers, anterior chaetigers, and paragnaths) of the Thailand specimen were within the ranges of their variations, which were mentioned above for the Japanese populations (Figs 6, 7; Table 3).
However, the notoacicular process was absent in the Thailand specimen that was an ovigerous female with BW of 1.0 mm, whereas it was present in a few parapodia in chaetigers 5–10 in holotype and some large paratypes of C. tokashikiensis with a BW of 1.5 mm or more (Sato 2020). In the present study, the presence and absence of the notoacicular process was regarded as an intraspecific variation depending on the body size.
description: Published as part of Sato, Masanori, Ebihara, Takumi, Satake, Kiyoshi, Kojima, Shigeaki, Fukumori, Hiroaki & Angsupanich, Saowapa, 2020, Distributions and Variations of Two Estuarine Species of Composetia (Annelida: Nereididae) in the Ryukyu Islands, Southern Japan, with a New Record of Composetia tokashikiensis from Thailand, pp. 25-38 in Species Diversity 25 (1) on pages 34-35, DOI: 10.12782/specdiv.25.25, http://zenodo.org/record/4584042