Thalia sibogae van Soest, 1973

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 : 454-459

2. Thalia sibogae van Soest, 1973

Thalia democratica var. orientalis (Takioka 1967)

Thalia sibogae van Soest, 1973 : 204 – 205, 1998: 239 fig. 14.3, table 14.3; Kim 2011: 147 – 149; Purushothaman et al. 2017

Specimens examined. A1: 1 solitary zooid, 1 aggregate zooid, 5°38'53.08"N, 102°58'39.07"E, April 2016; A3: 8 aggregate zooids, 5°40'51.01"N, 103° 1'51.06"E, April 2016; A4: 1 solitary zooid, 1 aggregate zooid, 5°38'6.00"N, 103° 3'48.06"E, April 2016; A6: 2 aggregate zooids, 5°39'50.59"N, 103° 9'36.64"E, April 2016; C1: 1 aggregate zooids, 5°20'47.59"N, 103° 8'59.91"E, Jun 2016; C2: 9 solitary zooids, 45 aggregate zooids, 5°25'33.93"N, 103°17'32.72"E, Jun 2016; C3: 8 solitary zooids, 30 aggregate zooids, 5°28'54.80"N, 103°22'55.42"E, Jun 2016; D2: 1 solitary zooid, 5°14'5.20"N, 103°16'36.04"E, July 2016; D3; 1 solitary zooid, 10 aggregate zooids, 5°15'50.06"N, 103°17'44.13"E, July 2016. Malaysia: East Cost of Peninsular Malaysia . UMTTn 0 0 0 5.

Description. Solitary ( Fig. 4a–c, 4e ): 4.8–8.8 mm long. Test firm, rounded, and smooth except for test projections and edge around the oral aperture. Atrial palps is fairly small and bifurcate. Posterior projections fairly short. Lateral projections very short. Medioventral projections are small and of uneven length, upper one shorter than lower one. Muscle bands broad, MII –IV touch dorsally, MV–MVI near but do not touch dorsally. Number of muscle fibres 56–84.

Aggregate ( Fig. 4c, 4e ): 4.8 mm long. Body oval with test bulkily rounding anteriorly . Test smooth. Anterior part is somewhat rounded, with posterior pointed pentagonally. The attachment organs variable 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 nucleus. The endostyle is short , only nearing to the MII. Ovary and embryo is situated on MIV, close to the nucleus. The gill is slender.

Remarks. Solitary and aggregate zooids of this species were collected during this study. For solitary zooid, van Soest describe of his specimen as having no lateral projection, while Kim et al. in 2011 reported that his specimen has a very short lateral projection. In this specimen, because of the presence of the short lateral projection, we would say that this specimen is resembling Kim’s specimen. Aggregate zooid closely resembles the description by van Soest in 1973.

Distribution. T.sibogae occurrence is very scarce. There are very few literature that record the presence of this species in their specimen. Distribution from Pacific Ocean includes the record from East coast of middle Japan ( Tokioka 1937), Bohol and Limosana Island of Philippine archipelago ( Van Soest 1973), Central Indo-Pacific (van der Land 2008) and Korean waters (Kim et al. 2011). The compilation of previous literature and present data distribution of Thalia sibogae is shown in Figure 5.

Figures

FIGURE 4a. Thalia sibogae (van Soest, 1973). 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 5. Distribution of Thalia sibogae (van Soest, 1973). Red dots: specimen examined by the author; black dots: records based on compilation of previous literature data.