Acartiella nicolae Dussart, 1985

Srinui, Khwanruan & Ohtsuka, Susumu, 2015, Supplementary Description of Three Acartiella Species (Crustacea: Copepoda: Calanoida) from Estuarine Waters in Thailand, Species Diversity 20, pp. 167-181 : 172-175

Acartiella nicolae Dussart, 1985

( Figs 5–6 , 10B )

Acartiella nicolae Dussart, 1985 : pls 49–51, fig. 1 (original description); Mulyadi 2004: 144–151, fig. 85 a–j.

Material examined. Ten females, Prasae Estuary, Gulf of Thailand (station 1 in Fig. 1 ), August 13, 2012, and March 5, 2013 (BIMS-Zoo-0264) .

Female. Total length 0.86–0.99 mm (0.91± 0.03 mm, N=10); prosome length 0.25–0.31 mm (0.29± 0.01 mm); prosome width 0.18–0.25 mm (0.21± 0.01 mm).

Body ( Fig. 5A, B ) similar to that of female A. kempi except genital double-somite ( Fig. 10B ) about seven times longer than anal somite, protruding ventrally near terminal portion of somite, and about twice as long as broad; genital operculum crescent-shaped ( Fig. 10B ), located behind ventro-central midpoint; second urosomite about 1: 1 in length: width ratio; anal somite partly fused with left caudal ramus but separate from right ramus; caudal rami asymmetrical with six setae, right ramus longer than left.

Antennule ( Fig. 5C ) symmetrical, reaching beyond posterior end of third urosomite, 23-segmented. Armature elements as follows: 1=1, 2=(2–4)=3+ae, 3=2, 4=1+ae, 5=1, 6=1+(1 spiniform element), 7=2+ae, 8=0, 9=(1 spiniform element), 10=1+(1 spiniform element), 11=1+(2 spiniform element), 12=1+(2 spiniform element)+ae, 13=1+(2 spiniform element), 14=1+(2 spiniform element)+ae, 15=1+(2 spiniform element), 16=1+(2 spiniform element), 17=1+(3 spiniform element), 18=1+(2 spiniform element), 19=1, 20=2, 21=2, 22=2, 23=4+ae. Segments 15–19 with row of small spinules.

Antenna ( Fig. 5D ) similar to that of A. kempi , but armature slightly different in basis having two setae medially, endopod with fine hairs along both margin; free endopodal segment with four setae at midlength and five terminal setae, and exopod with three setae at midlength and five terminal setae.

Mandible ( Fig. 6A ) similar to that of A. kempi , but armature different in having four cuspidate teeth on gnaththobase, basis unarmed, and exopod completely fused to basis with four setae terminally, all greatly different in length. Endopod fused to basis, represented by single inner seta.

Maxillule ( Fig. 6B ) similar to that of A. kempi , but armature slightly different in praecoxal arthrite having eight approximately equal strong and thin setae, and coxal endite with one thick seta.

Maxilla ( Fig. 6C ) similar to that of A. kempi , but armature slightly different in having syncoxal endite with three long, three medium, and two short setae, and endopod with one short and five long serrate setae.

Maxilliped ( Fig. 6D ) similar to that of A. kempi , but armature slightly different in first coxal endites, single strong seta.

Legs 1–4 ( Fig. 6E–H ) similar to those of A. kempi , but armature slightly different in first endopodal and first exopodal segments having fine hairs along inner margin. Seta and spine formula as shown in Table 2.

Legs 5 ( Fig. 6I ) symmetrical; coxa unarmed and fused with intercoxal sclerite, basis with outer seta, and about two times longer than wide; endopod reduced to small prominence; exopod with curved segment bearing distal outer seta, terminal end with serration on both margins.

Male. Unknown.

Remarks. Acartiella nicolae was originally described by Dussart (1985) as an estuarine species from the Mahakam Estuary, East Kalimantan, Indonesia. The body lengths of females examined in the present study (0.86–0.91 mm) were greater than those in the original description (0.80– 0.85 mm) but similar to those of females from the Mahakam Estuary, Cilacap, and off Tegal Bay, Indonesia (0.90 mm) ( Mulyadi 2004).

The present observations agree with those of Barthélémy (1999) concerning the female genital operculum of A. nicolae , which is located near the posterior edge of the ventral surface of the genital double-somite ( Fig 10B ).

Distribution. This species was previously recorded exclusively from the brackish waters of Indonesia: the Mahakam Estuary ( Dussart 1985; Mulyadi 2004), the Cilacap Estuary, and Tegal Bay ( Mulyadi 2004) ( Fig. 1 ). The present study extends the distribution of the species into other Southeast Asian estuarine waters. The present specimens were collected from the Prasae Estuary, Gulf of Thailand, where the water temperature and salinity ranges were 28– 29.9°C and 1–4‰, respectively.

Figures

Fig. 5. Acartiella nicolae Dussart, 1985, female. A, habitus, dorsal view; B, habitus, lateral view; C, right antennule; D, left antenna. Roman numerals in C indicate numbers of ancestral segments following Huys and Boxshall (1991).

Fig. 6. Acartiella nicolae Dussart, 1985 female. A, right mandible; B, right maxillule; C, left maxilla; D, right maxilliped; E, right leg 1; F, right leg 2; G, right leg 3; H, right leg 4; I, legs 5.

Fig. 10. SEM micrographs of genital double-somites of females of Acartiella, ventral side. A, A. kempi; B, A. nicolae; C, A. sinensis. Scale bars: A, 20µm; B−C: 10µm. Abbreviations: gp, gonoporal plate; op, opercular pad.

Fig. 1. Distribution of the genus Acartiella based on the present and previous data. Three sampling sites in the present study in Thailand: Station 1, Prasae Estuary, Rayong Province, Gulf of Thailand (black triangle); Station 2, Bangpakong Estuary, Chon Buri Province, Gulf of Thailand (black circle); Station 3, Kraburi Estuary, Ranong Province, Andaman Sea (black square);. Previous distributional data: A. nicolae (Dussart 1985; Mulyadi 2004; Razouls et al. 2014); A. sinensis (Shen and Lee 1963; Zheng et al. 1982; Suwanrumpha 1987; Pholpunthin 1997; Orsi and Ohtsuka 1999; Pinkaew 2003; Shang et al. 2007; Razouls et al. 2014); A. kempi (Sewell 1914; Razouls et al. 2014); A. gravelyi (Sewell 1919; Razouls et al. 2014); A. keralensis (Wellershaus 1969; Razouls et al. 2014); A. major (Sewell 1932; Razouls et al. 2014); A. minor (Sewell 1919; Razouls et al. 2014); A. natalensis (Connell and Grindly 1974; Razouls et al. 2014); A. sewelli (Steur 1934; Razouls et al. 2014); A. tortaniformis (Sewell 1932; Razouls et al. 2014); and A. faoensis (Khalaf 1991; Ali et al. 2009; Peyghan et al. 2011; Razouls et al. 2014).