Leucaltis nodusgordii ( Poléjaeff, 1883 ), Van Soest & De Voogd, 2015

Leucaltis nodusgordii ( Poléjaeff, 1883) View in CoL comb. nov.

Figures 28a–c View FIGURE 28 , 29a–d View FIGURE 29 , 30a–e View FIGURE 30

Heteropegma nodusgordii Poléjaeff, 1883 View in CoL (in part, only the Torres Strait material): 45, pl. I fig. 7, pl. IV figs 1a–d; Dendy,

1905: 230; Jenkin, 1908: 453, fig. 103.? Leucaltis bathybia var. mascarenica Ridley, 1884: 628 View in CoL , pl. LIV figs a, a’. Leucaltis clathria sensu Dendy, 1913: 16 View in CoL , pl.2 figs 1–2; Hôzawa, 1940: 136, pl. VI fig. 3; Tanita, 1943: 394, pl. XIII fig. 27;

Borojevic & Klautau, 2000: 190, figs 2–3.

(not: Haeckel, 1872: 159, pl. 29 figs 3a–3c). Leuconia paloensis ; Colin & Arneson, 1995: 61, photo 235; Gosliner et al. 1996: 17, photo 8; Erhardt & Baensch, 1998 Atlas

4: 21, 24–25 (not: Tanita, 1943).

Material examined. RMNH Por. 1772, Indonesia, North Sulawesi, Negeri, Manado Tua South, depth 20 m , SCUBA, coll. N.J. de Voogd, # MD08 /160502/043, 16 May 2002 (several individuals) ; ZMA Por. 17557, Papua New Guinea, Normanby Island, N point, 9.7328°S 150.7402°E, depth 21 m GoogleMaps , SCUBA, coll. R. Schonnenschein , #02136, 30 May 2002 .

Examined for comparison. BMNH 1884.4.22.23a, two slides labeled ‘Type’ and ‘from type’, ‘Challenger Torres Straits, coll. Brit.Mus. 27’ (subsequently labeled as Leucaltis clathria ); ZMA Por. 12443, Seychelles, Amirante Islands, Poivre Atoll, N rim, 5.7333°S 53.3167°E, depth 7–8 m GoogleMaps , SCUBA, coll. R. W.M. van Soest, Netherlands Indian Ocean Program E stat. 768/08, 31 December 1992 ; ZMA Por. 16248, Seychelles, Mahé, SE coast, Anse Royale Bay, 4.7333°S 55.5167°E, depth 2–13 m GoogleMaps , SCUBA, coll. R. W.M. van Soest, Netherlands Indian Ocean Program E stat. 740/04, 24 December 1992 ; RMNH Por. 9314, off Guyana, 7.7°N 57.5°W, depth 65 m, dredged, bottom muddy sand and shells, coll. ‘ Luymes’ Guyana Shelf Expedition stat. 107, 5 September 1970 GoogleMaps .

Description. A clathrate mass of anastomosing tubes ( Figs 28a, c View FIGURE 28 ), largest individual 12 x 6 x 6 cm, individual tubes quite variable in length and diameter, undivided tube lengths up to 2.5 cm, diameter 2–8 mm. Tubes ending in oscules, as wide as the tube (upright) or more often smaller (flush with the surface); oscules naked. Surface smooth, consistency brittle but somewhat compressible. Color white or pinkish white, lavender-colored, becoming yellowish white in preserved condition ( Fig. 28b View FIGURE 28 ).

Histology. The choanocyte chambers ( Figs 29b–d View FIGURE 29 ) are long, broad and branching, somewhat inbetween syconoid and sylleibid.

Skeleton. ( Figs 29a–d View FIGURE 29 ) Cortical skeleton formed by the basal triradiate system of giant tetractines mixed with giant triactines ( Figs 29a, c–d View FIGURE 29 ). Actines of the giant tetractines and triactines protrude into the choanomal skeleton. Next to the actines of the giant tri- and tetractines, the choanosomal skeleton ( Figs 29a–c View FIGURE 29 ) contains scattered intermediate to small-sized regular triactines and tetractines, lining the choanocyte chambers, with free actines of these spicules protruding into the lumen of the choanocyte chambers. The atrial skeleton ( Figs 29a–b View FIGURE 29 ) consists of a single layer of sagittal triactines, and less common tetractines, provided with characteristic abruptly curved paired actines, the paired actines lined up in a single plane. There is a distinct complement of diactinal, triactine-derived, spicules which may be the product of broken-off third actines, but the common occurrence indicates it may be a reduced spicule form. Likewise, there are club-shaped irregular diactinal spicules, probably derived from the abruptly curved sagittal triactines, scattered in the atrial region; occasional forms of these spicules occur with reduced or absent unpaired actines.

Spicules. ( Figs 30a–e View FIGURE 30 ) Giant triactines and tetractines, small regular triactines and tetractines, sagittal ‘abruptly curved’ triactines and tetractines, reduced forms of the latter.

Giant triactines ( Fig. 30a View FIGURE 30 ), equiangular, actines more or less equiactinal, 252– 458.1 –792 x 19– 47.3 –108 µm.

Giant tetractines ( Fig. 30b View FIGURE 30 ), equiangular, actines more or less equiactinal, or occasionally with slightly longer basal actine, 624– 820.1 –1110 x 66– 85.2 –97 µm.

Additionally, a single giant diactine, 846 x 36 µm, was observed. Possibly, it represented a reduced triactine.

Regular equiactinal triactines ( Fig. 30d View FIGURE 30 ), occasionally tripod-shaped, 30– 79.1 –193 x 1.5– 4.7 –13 µm.

Regular tetractines ( Fig. 30d View FIGURE 30 ), actines of the basal radiate system and apical actines more or less similar, 21– 83.9 –138 x 2– 4.4 –7.5 µm.

Sagittal, abruptly angled triactines ( Fig. 30e View FIGURE 30 ), unpaired actine 42– 47.3 –60 x 2.5– 2.9 –3.5 µm, paired actines, 42– 62.1 –72 x 3– 3.8 –4.5 µm.

Sagittal, abruptly angled tetractines ( Fig. 30f View FIGURE 30 ), unpaired actine 60– 64.2 –66 x 4– 4.2 –5 µm, paired actines 78– 79.3 –87 x 6.5– 6.8 –7 µm, apical actine short, difficult to measure, approximately 10 x 3 µm.

Reduced diactinal modifications of sagittal triactines, size of actines 60– 64.4 –69 x 2.5– 3.1 –4 µm (not shown).

Ecology. Coral reefs, among living corals, 15–25 m.

Distribution. At least North Australia, New Caledonia, Indonesia, Papua New Guinea, Seychelles, Zanzibar; possibly South Australia, Japan, Sri Lanka.

Remarks. The Papua New Guinea material (ZMA Por. 17757) included in the above given spicule data, had somewhat smaller spicules: giant triactines 228–602 x 20–47 µm, giant tetractines 570–998 x 65–104 µm, small triactines 54–66 x 2–3 µm, small tetractines paired & unpaired actines 54–66 x 1.5–2.5 µm and apical actines 8–12 x 2 µm, atrial triactines & tetractines with paired & unpaired actines 33–74 x 3–6 µm, apical actines 8–12 x 6 µm, and diactines 50–60 x 4 µm.

We report here also two specimens belonging to this species from outside Indonesia, viz. the Seychelles ( ZMA Por. 12443 and 16248), with essentially similar habitus and spicule size data: giant triactines 111–610 x 18–54 µm, giant tetractines 552–1230 x 90–156 µm, small triactines 48–126 x 2–7 µm, small tetractines with actines of the basal triradiate system 66–115 x 2–5 and apical actines 10–35 x 2–5 µm, atrial triactines and tetractines with paired and unpaired actines 45–60 x 2.5–6 µm and apical actines 10–15 x 6 µm, diactines 67–72 x 3–4 µm .

We name this material Leucaltis nodusgordii , against the consensus in the literature that it should be named Leucaltis clathria ( Haeckel, 1872) (e.g. Dendy 1913; Lévi et al. 1998; Wörheide & Hooper 1999; Borojevic & Klautau 2000). The treatment by previous authors of this and related specimens is rather frustrating. The subsequent authors all refer to Poléjaeff’s admittedly excellent description, but fail to compare it in detail with Haeckel’s type of L. clathria . This should have been done, e.g. by Dendy (1913), who saw fragments of Haeckel’s type brought to the Natural History Museum in London by Mr. R.W.H. Row. Dendy (1913: 17) stated that he examined the fragments carefully, and he gives some comments indicating that Haeckel’s description was incomplete, but failed to provide measurements of the spicules. Unfortunately, we were not able to lay our hands on a slide of Haeckel’s type still remaining in the collections in London, cited by Burton (1963: 598) and Wörheide & Hooper (1999: 877). Both these sources, like Dendy (1913), did not describe the contents of the slide. The external form is apparently so characteristic and convincing that proper description of the spicules and their variation is largely neglected by most authors.

Haeckel (1872: 159, pl. 29 figs 3a–c) described a brownish (alcohol) clathrate mass of tubes, size 3–6 cm, from a depth of 63 m off the coast of Florida, collected by A. Agassiz, as Leucaltis (or alternatively Artynas ) clathria , with the spicules described and measured as:

Triactines (‘mittelgross’ = middlesized) 400–600 x 30–50 µm. Tetractines (‘colossal’) 800– 1200 x 100–150 µm, occasionally as long as 2000 µm. Sagittal tri- and tetractines (drawn with paired actines in 180° degree angle and with bluntly rounded ends), paired actines 50–70 x 2–3 µm, unpaired actines 30–40 µm. Triactines more common than tetractines. Occasional subregular triactines 400–700 x 1–2 µm. Although in his description he mentions small choanosomal tri- and tetractines supporting the choanocyte chambers he does not provide measurements. Dendy (1913) stated that these were amply present in the London fragments of the type.

We report here a specimen in the collections of the Naturalis Biodiversity Center, RMNH Por. 9314, from the Guyana shelf (7.7°N 57.5°W, depth 65 m), which may be considered representative for the Western Atlantic population to which Haeckel’s type is assumed to belong. The habitus ( Fig. 31a View FIGURE 31 ) and the spiculation ( Figs 31b–g View FIGURE 31 ) (actines of giant tri- and tetractines: 210–530 x 15–63 µm, actines of small equiangular tri- and tetractines: 40–55 x 2–3 µm, abruptly angled tri- and tetractines with unpaired angles 40–45 x 3–4 µm, paired actines 50–65 x 3–4 µm) of this specimen are indeed strikingly similar to the Indo-West Pacific specimens listed and described above. However, there is one obvious difference in the spicule complement (see Fig. 31d View FIGURE 31 ), namely the presence in the Guyana specimen of a second category of large ‘abruptly angled’ triactines with paired actines 122–141 x 8.5–10 µm and unpaired actines 111–126 x 6–10 µm, clearly twice as long and thick as the usual spicules reported by us above. These spicules are not very common, so they might have been overlooked by Haeckel and Dendy. It appears to us that this difference supports the specific distinctness of specimens from West Pacific and West Atlantic localities. Klautau et al. (2013) found considerable DNA sequence distance between Leucaltis clathria from the Caribbean and individuals assigned to L. clathria from Australia, and on that basis pleaded for making a specific distinction. This confirms that both morphologically and genetically a separate species Leucaltis nodusgordii is valid.