Thalia rhomboides Quoy & Gaimard, 1824

Ishak, Nurul Huda Binti Ahmad, ‘ Aliah, Nur, Adam, Binti & Kassim, Zaleha, 2018, A taxonomic revision of the genus Thalia Blumenbach, 1798; Weelia Yount, 1954; Brooksia Metcalf, 1918 (Salpida: Salpidae) from East Coast of Peninsular Malaysia, Zootaxa 4422 (4), pp. 451-477 : 453-454

1. Thalia rhomboides Quoy & Gaimard, 1824

Salpa rhomboides Quoy & Gaimard, 1824 (cited from van Soest 1973; Kott 2005)

Salpa pyramidalis sensu Quoy & Gaimard, 1834 (cited from van Soest 1973, Kott 2005)

Salpa mucronata Apstein, 1906 (cited from Purushothaman 2017)

Thalia democratica Sewell, 1926

Thalia democratica var. orientalis Tokioka, 1937

Thalia democratica var. orientalis f. echinata Tokioka, 1937

Thalia democratica echinate form Yount, 1954

Thalia democratica intermedia Borgelt, 1968

Thalia rhomboides van Soest, 1973: 199 –200, 1998: 238 fig. 14.3, table 14.3; Godeaux, 1998: 288 fig. 17.17, 293 fig. 17.21; Chihara & Murano, 1997: 1384 -1385; Kim, 2011: 147 –148

Specimens examined. A2: 1 aggregate zooid, 5°39'55.02"N, 103° 0'6.03"E, April 2016; A3: 3 aggregate zooids, 5°40'51.01"N, 103° 1'51.06"E, April 2016; A6: 1 aggregate zooids, 5°39'50.59"N, 103° 9'36.64"E, April 2016; C1: 2 aggregate zooids, 5°20'47.59"N, 103° 8'59.91"E, Jun 2016; C2: 5 solitary zooids, 12 aggregate zooids, 5°25'33.93"N, 103°17'32.72"E, Jun 2016; C3: 3 solitary zooids, 8 aggregate zooids, 5°28'54.80"N, 103°22'55.42"E, Jun 2016; D3; 3 solitary zooid, 3 aggregate zooids, 5°15'50.06"N, 103°17'44.13"E, July 2016. Malaysia: East Cost of Peninsular Malaysia . UMTTn 0 0 0 4.

Description. Solitary ( Fig. 2a–b, 2d ): 3.6–8.4 mm long, excluding posterior projections. Body elongated cylindrical. All test echinate, especially projections, strongly papillated all over the test. Test cylindrical, thickened ventrally around nucleus, with two long posterior projections. Oral opening terminal, atrial opening postero-dorsal. Atrial palps bifurcate. Medioventral projections well developed and lower one longer than upper one. Lateral projections well developed, fairly long. Body muscles thick. Five body muscles, MI to MIV continuous dorsally and ventrally, MV interrupted ventrally. MI to MIII and MIV to MV contiguous or fused in mid-dorsal line. Intermediate muscle interrupted dorsally and converge to MI. the number of muscle fibres varies from 77–106. Dorsal tubercle simple and small, separated from ganglion with short distance. Branchial septum slender, extending from ganglion to gut. Endostyle thin, extending from behind oral to posterior ventrally. Gut forming a compact nucleus, stolon coiled around it.

Aggregate ( Fig. 2c, 2d ): 0.8 mm long. Body pentagonally shaped anteriorly with relatively hard, sharp-edged test. Test echinated. Sharply pointed posterior. The attachment organs vary in number and never protruding beyond test wall left posterior. Body muscles MI– MIII and MIV –MV fused over a short section. Muscle bands are wide, number of muscle fibres is usually 16. Gut forming a compact oval nucleus. Nucleus projection absent. The endostyle is short , only nearing to the MII . Ovary and embryo are situated on MIV, close to the nucleus. The gill are slender.

Remarks. Both solitary and aggregate zooids of this species were collected during this study. Both stages agrees with the description by Yount in 1954, van Soest in 1973 and Purushothaman et al. in 2017.

Distributions. T.rhomboides seems to be restricted to the Indo-Pacific waters (van Soest 1973), and to date there is still no record of this species found to be present in the Atlantic. It was first found by Quoy & Gaimard (1834) and recorded as Salpa pyramidalis on Agulhas Bank in the southeast African waters of the Indian Ocean, as did Borgelt (1968). It has been found in the Red Sea and Gulf of Suez ( Godeaux 1974), Gulf of Aden ( Godeaux 1987). Yount (1954) has recorded the presence of this species in the Central Pacific Ocean while Takioka (1960) found it in the South Pacific Ocean. Distribution from the North Pacific Ocean includes the records from the East coast of middle Japan ( Tokioka 1937), Kaoping Trench of southwestern waters of Taiwan ( Tew & Lo 2005), Eastern Tropical Pacific off Mexico ( Hereu et al. 2010), Korean waters (Kim et al. 2011), the Kuroshio Extension and the Oyashio–Kuroshio mixed Water Region (Takahashi et al. 2013) and Taiwan waters ( Liao et al. 2013 & Franco et al. 2017). The compilation of previous literature and present data distribution of Thalia rhomboides is shown in Figure 3.

Figures

FIGURE 2a. Thalia rhomboides (Quoy & Gaimard, 1824). Top, Solitary, dorsal view; Bottom, ventral view. Br, branchial septum; Dt., dorsal tubercle; End, endostyle; G, ganglion, i.m., intermediate muscle; Lp. Lateral projection,; Mp., medioventral projection; N, nucleus; o.m., oral musculature; Pp., posterior projection.

FIGURE 3. Distribution of Thalia rhomboides (Quoy & Gaimard, 1824). Red dots: specimen examined by the author; black dots: records based on compilation of previous literature data.