Leucetta chagosensis Dendy, 1913

Van, Rob W. M. & De, Nicole J., 2018, Calcareous sponges of the Western Indian Ocean and Red Sea, Zootaxa 4426 (1), pp. 1-160 : 76-77

Leucetta chagosensis Dendy, 1913

Figs 43a–f , 44a–g

Leucetta chagosensis Dendy, 1913: 10 , pl. 1 fig. 6, pl. 4 fig. 2; Van Soest & De Voogd 2015: 51, figs 37a–f, 38a–d, with further synonyms.

Ascoleucetta sagittata Cavalcanti et al., 2013: 308 , figs 21–22; Van Soest & De Voogd 2015: 49, figs 36a–f.

Material examined. RMNH Por. 9171, Saudi Arabia, Al Laith, Quita al Qursh (Shark Reef), 20.1327°N 40.0994°E, depth 7.8–9.1 m, scuba, coll. Diaa Youssef, field nr. KSA-51, 14 May 2013; RMNH Por. 9621, Saudi Arabia, Jeddah, near Thuwal, Al Asoul, 22.265361°N 39.002139°E, coll. N.J. de Voogd, scuba, field nr. THU07/ JED116, 9 November 2014; RMNH Por. 9637, Saudi Arabia, Jeddah, near Thuwal, Um Alsawi, 22.239306°N 38.985139°E, coll. N.J. de Voogd, scuba, field nr. THU08/JED137, 11 November 2014; RMNH Por. 9638, Saudi Arabia, Jeddah, near Thuwal, Um Alsawi, 22.239306°N 38.985139°E, coll. N.J. de Voogd, scuba, field nr. JED138, 11 November 2014; RMNH Por. 9676, Saudi Arabia, Jeddah, near Thuwal, Fsar, 22.229611°N 39.029028°E, scuba, coll. N.J. de Voogd, field nr. THU12/JED181, 13 November 2014; RMNH Por. 10073, Maldives, Faafu Atoll, Wallino, 3.087472°N 72.9567°E, depth 15 m, scuba, coll. N.J. de Voogd, field nr. MAD 02/MAS023, 16 February 2015; RMNH Por. 10114, Maldives, Faafu Atoll, Route 66, 3.07825°N 72.976306°E, depth 20 m, scuba, coll. N.J. de Voogd, field nr. MAD 09/MAS069, 20 February 2015; RMNH Por. 10141, Maldives, Faafu Atoll, Sunny Reef, 3.144639°N 73.012667°E, depth 7 m, scuba, coll. N.J. de Voogd, field nr. MAD 08/MAS099, 18 February 2015; RMNH Por. 10144, Maldives, Faafu Atoll, Route 66, 3.07825°N 72.976306°E, depth 20 m, scuba, coll. N.J. de Voogd, field nr. MAD 09/MAS105, 20 February 2015; RMNH Por. 11601, Mauritius, Rodrigues, La Rampe, 19.65015°S 63,41323333°E, depth 18 m, scuba, coll. N.J. de Voogd, field nr. ROG001, 15 October 2016; RMNH Por. 11656, Mauritius, Rodrigues, Mourouk Ebony, Castel Rock, 19.76203°S 63.46273°E, depth 10 m, scuba, coll. N.J. de Voogd, field nr. ROG060, 17 October 2016; RMNH Por. 11657, Mauritius, Rodrigues, Mourouk Ebony, Castel Rock, 19.76203°S 63.46273°E, depth 10 m, scuba, coll. N.J. de Voogd, field nr. ROG061, 17 October 2016; RMNH Por. 11658, Mauritius, Rodrigues, Mourouk Ebony, Castel Rock, 19.76203°S 63.46273°E, depth 10 m, scuba, coll. N.J. de Voogd, field nr. ROG062, 17 October 2016; ZMA Por. 13480, Israel, Gulf of Aqaba, Coral Garden, in cave at 1.5 m depth, scuba, coll. M. Wunsch field nr. AQ139, 15 July 1998; ZMA Por. 13624, Israel, Gulf of Aqaba, Shark Observatory, depth 15 m, scuba, coll. M. Wunsch field nr. RM201, 22 July 1998; ZMA Por. 21468, Saudi Arabia, Abu Madai Reef, 22.0609°N 38.7679°E, depth 19 m, scuba, coll. J. On On Lee, field nr. 4–8, 14 April 2009; ZMA Por. 12071, Seychelles, Amirantes, Alphonse Atoll, SE part of lagoon, 7.0333°S 52.7333°E, depth 6–8 m, scuba, coll. R.W.M. van Soest, field nr. NIOP-E stat. 788/08, 4 January 1993; ZMA Por. 12442, Seychelles, Amirantes, Platte Island Atoll, lagoon, 5.8333°S 55.35°E, scuba, coll. R.W.M. van Soest, field nr. NIOP-E stat. 797, 7 January 1993; ZMA Por. 16369, Madagascar, Nosy Bé, Ambariobé, N of Nosy Komba, reef, depth 6–8 m, scuba, coll. J.H. Stock, 28 December 1963; ZMA Por. 16372, Madagascar, Nosy Bé, S of Nosy Tanga, reef, depth 7–9 m, scuba, coll. J.H. Stock, 1 January 1964; ZMA Por. 19251, India, Lakshadweep, Minicoy, depth 20 m, scuba, coll. A. George IERSE, field nr. 91, 5 December 2004; ZMA Por. 19279, India, Lakshadweep, Kavaratti, depth 22 m, scuba, coll. A. George IERSE, field nr. 20, 19 February 2005.

Description. Because we recently provided an extensive description of Indonesian specimens of this species (cf. Van Soest & De Voogd 2015), we treat it here in summary format. Habitus in situ ( Figs 43a–f ) is lobate, ovoid or irregularly massive, usually bright yellow in color (dull beige in preservation), with one or several prominent oscules with short rim. The oscule leads to a slit-like or more expanded atrial cavity. Surface optically smooth. Size of specimens up to 11 x 6 x 4 cm, often smaller. Consistency firm to hard.

Aquiferous system. Leuconoid.

Skeleton. ( Figs 44a–b ) The skeleton is formed by a dense mass of spicules surrounding the choanocyte chambers of the leuconoid aquiferous system. At the surface there are giant triactines in tangential position, numbers variable among individuals. The oscular rims are provided with smaller somewhat sagittal triactines, often with undulate paired actines. The atrial surface contains numerous tetractines, with their apical actines protruding into the atrial cavity.

Spicules. ( Figs 44c–g ) Giant triactines, smaller triactines, tetractines.

Giant triactines ( Fig. 44c ) with rather thin, sharply pointed actines, quite variable among the individuals, 480– 789 –1380 x 36 – 61.8 –114 µm.

Small triactines ( Fig. 44d ), similarly sharply pointed, 78– 153 –258 x 6 – 13.3 –23 µm. Sagittal triactines ( Fig. 44e ) of the oscular rim: 105– 123 –144 µm x 6 – 11.1 –17 µm.

Tetractines, with size and shape comparable to the small triactines, basal actines 121– 141 –180 x 8 – 11.3 –16 µm; apical actines, frequently with curved endings, 32– 87 –170 x 3 – 7.4 –12 µm.

Distribution and ecology. Seychelles, Red Sea, India, Maldives, Madagascar, Rodrigues; elsewhere throughout Indo-West Pacific tropical waters (see Wörheide et al. 2008; Van Soest & De Voogd 2015); common on reefs down to 25 m.

Remarks. The actines of the giant triactines in the Western Indian Ocean on average are larger and thicker than those reported for Indonesian specimens (compare with Van Soest & De Voogd’s 2015 measurements). However, the smaller spicules are similar in size, so a conclusion that there is a distinct regional difference is not (yet) warranted. We obtained several partial 28S sequences, both from Indonesian and from Rodrigues specimens.

We also obtained a sequence of the Indonesian holotype of Ascoleucetta sagittata Cavalcanti et al., 2013 . In our phylogenetic tree of Fig. 2C the latter ended up in a larger clade of Leucetta chagosensis , closest to Indonesian specimens of that species. In a separate inspection of a trimmed alignment of 396 sites, the sequence of Ascoleucetta sagittata was found to be identical to three Indonesian specimens (one additional Indonesian specimen had one site different). The three Indonesian sequences and the Ascoleucetta sagittata sequence together differed in 2 sites from Western Indian Ocean specimens obtained from Rodrigues, and in 3 sites from the Maldives sequence of L. chagosensis . These results confirm the already suggested synonymy (cf. Van Soest & De Voogd 2015) of L. chagosensis and Ascoleucetta sagittata .

The differences between sequences from the Western Indian Ocean (excepting the Maldives) and Red Sea sequences obtained from Oliver Voigt showed a consistent single size difference, Indonesian and Red Sea differences amounted to 2 sites.

A sequence of the Australian Leucetta villosa Wörheide & Hooper, 1999 downloaded from GenBank was also found to be included in the larger clade of L. chagosensis (cf. Fig. 2C ). In the separate inspection mentioned above, the sequence of L. villosa differed in five/four sites from Indonesian and Western Indian Ocean L. chagosensis sequences. Because of the habitus differences (villous surface) this is interpreted as evidence of specific difference, indicating a possible species complex in L. chagosensis s.l.

Figures

FIGURE 2. Maximum-likelihood tree based on analysis of sequences of the partial 28S gene (C2–D2 region, comprising 442 sites) of Western Indian Ocean Calcinea newly generated by the Naturalis Biodiversity Center and sequences additionally obtained from GenBank, the Sponge Barcode Project and from Oliver Voigt (München) from the Red Sea, Indonesia, Australia, and a few sequences from other parts of the world, to demonstrate the affiliation of the compared species. Please note that Arturia sequences do not appear in the same clade, indicating Arturia is non-monophyletic. Numbers at the root of clades are bootstrap values of 1000 replicates. Since the high number of sequences were difficult to read in detail, we subdivided the present tree in three detailed sections 2A, 2B, and 2C.

FIGURE 43. Leucetta chagosensis Dendy, 1913, habitus in situ of selected specimens, a, RMNH Por. 10114 from the Maldives, b, ZMA Por. 13480, from Aqaba, Red Sea, c, RMNH Por. 9638 from Jeddah, Red Sea, d, RMNH Por. 11657 from Rodrigues, e, RMNH Por. 11601 from Rodrigues, f, RMNH Por. 11658, from Rodrigues (all photos N.J. de Voogd, except ZMA 12480, photo M. Wunsch).

FIGURE 44. Leucetta chagosensis Dendy, 1913, ZMA Por. 21468 from the Red Sea, N of Jeddah, a, light microscopic overview of the spicule complement, b, light microscopic cross section of the atrial wall showing protruding apical actines of the tetractines, c–g, SEM images of the spicules, c, giant triactine, d, small triactine, e. triactine from the oscular rim, f, tetractine, g, detail of apical actine of the tetractine.