Leucandrilla wasinensis

Leucandrilla wasinensis (Jenkin, 1908)

Leucilla wasinensis: Jenkin 1908: 454, text-fig. 104

Leucandra wasinensis: Dendy 1913: 24, plate 2—fig. 5; Dendy & Row 1913: 772; Burton 1963: 306, text-fig. 160

Leucandrilla wasinensis: Borojević et al. 2000: 226, fig. 23; Borojević et al. 2002: 1168, fig. 6A; Cóndor-Luján et al. 2018: 42; Van Soest & De Voogd 2018: 106, figs. 64, 65

Material examined: Slides of the holotype BMNH 1908.9.25.59 (6 slides containing sections of the skeleton and 4 containing dissociated spicules). Wasin, Kenya, East Africa.

Description: The specimen could not be analysed but according to the original description it has ovoid shape and white colour in ethanol. A short fringe of trichoxea surrounds the osculum (Fig. 1A). The aquiferous system is leuconoid. The body wall is thick, and the skeleton is well developed, with several layers of spicules. Giant diactines perforate the sponge surface and can reach through most of the choanosome (Figs. 1A, B). They occur separately or in groups of four to five spicules. Three small microdiactines were also found. While one of them was protruding through the surface, the other two were imbedded in the skeleton close to the cortex (Fig. 1C). It is not clear if they are part of the sponge, as they were not found in any other section besides that used for illustration. The cortical skeleton is formed of a tangential layer of thin triactines (Figs. 1B, D, F) and by tetractines (Figs. 1 C- F). The latter vary in size, but they are never giant as in Amphoriscidae. Below the cortex, there are some pseudosagittal triactines, some of them surrounding subcortical lacunae (Figs. 1E, F). Inner, giant triactines are present, many of them pointing the unpaired actines to the cortex, in opposition to the cortical tetractines or (less common) to the pseudosagittal triactines (Figs. 1 B-D). This layer may not be so evident because of the presence of the subcortical lacunae. The choanosomal skeleton is mainly composed of the same giant triactines mentioned before and of some giant tetractines. Spicules of both categories may be in disarray, but there are also several layers of them pointing the unpaired actines to the cortex, forming an articulated skeleton (Figs. 1B, G). Tetractines are present surrounding the canals. The proximal region is even more organised, and an evident subatrial layer is present. It is formed of tetractines and triactines, the latter being less abundant (Figs. 1G, H). The atrium is surrounded by tetractines that project their long apical actines into the lumen (Figs. 1G, H). Reproductive elements are present.

Spicules: The tips of the spicules could not reliably be described as most of them were corroded.

Microdiactines (Fig. 1B): They are not abundant. Fusiform, with sharp tips (139.2–172.3 ± 46.8–205.4/7.1 ± 0.3 µm; N = 2).

Diactines (Fig. 2A): Most of them are broken. They are straight and fusiform (875.6–1133.9 ± 209.1–1539.8/ 40.0 ± 5.2 µm; N = 18).

Cortical triactines (Fig. 2C): Very thin. Unpaired actines shorter than the paired ones, which are curved. Cylindrical with sharp tips (paired: 223.9–305.2 ± 42.8–391.6/14.7 ± 3.2 µm; unpaired: 136.1–201.9 ± 34.5–262.4/ 15.2 ± 3.7 µm; N = 30).

Cortical tetractines (Fig. 2B): Basal actines are curved, while the apical one is straight. Actines are cylindrical with blunt or sharp tips (paired: 119.8-322.5 ± 57.1–367.9/-18.2 ± 5.4 µm; unpaired: 118.6–311.1 ± 118.8–411.9/ 19.0 ± 5.2 µm; apical: 105.5–7108.8 ± 29.5–200.2/14.8 ± 2.0 µm; N = 30).

Pseudosagittal triactines (Fig. 2D): Variable in thickness. Their shape is typical of pseudosagittal spicules. Actines are cylindrical to slightly conical, with sharp tips (large paired: 188.7–237.8 ± 68.2–400.2/25.5 ± 5.8 µm; short paired: 124.1–180.2 ± 33.3–332.0/23.8 ± 5.3 µm; unpaired: 220.1–365.2 ± 103.2–512.2/24.8 ± 4.8 µm; N = 30).

Choanosomal triactines (Fig. 2E): Size of the actines is variable. They can be equiradiated, the unpaired actine can be shorter or paired actines can have different sizes. A slight undulation at one of the actines is also common. Slightly conical with sharp tips (paired: 280.0–546.8 ± 105.7–737.7/30.7 ± 4.6 µm; unpaired: 252.0–417.3 ± 95.4– 570.6/30.8 ± 4.9 µm; N = 30).

Choanosomal tetractines (Fig. 2F): Actines are cylindrical to slightly conical. Paired actines curved in opposition to the unpaired one, which can be short or can reach the same size as that of the paired actines. Apical actine is short (paired: 227.8–328.1 ± 70.1–493.1/19.5 ± 4.8 µm; unpaired: 247.1–330.8 ± 69.7–473.1/20.7 ± 5.9 µm; apical: 22.0–45.7 ± 15.6–81.1/13.4 ± 3.9 µm; N = 18).

Subatrial triactines (Fig. 2H): They are not abundant. Similar to the subatrial tetractines (paired: 236.6–325.0 ± 47.8–405.5/21.2 ± 5.5 µm; unpaired: 391.7–504.2 ± 71.4–639.9/22.1 ± 2.8 µm; N = 15).

Subatrial tetractines (Fig. 2G): The difference between these spicules and the choanosomal tetractines is not clear, but it seems that in the present spicule category, the unpaired actines are commonly longer than the paired ones. Apical actine is short (paired: 163.0–298.2 ± 80.8–498.0/17.1 ± 3.0 µm; unpaired: 334.2–465.2 ± 87.3–612.5/ 17.6 ± 3.2 µm; apical: 34.5–53.2 ± 16.4–87.4/12.2 ± 2.7 µm; N = 30).

Atrial tetractines (Fig. 2I): Actines are thin and long. Paired actines are curved, as typically observed for atrial spicules. Apical actine is smooth, long and commonly slightly curved. Cylindrical with sharp tips (paired: 101.1– 359.5 ± 140.0–709.5/19.0 ± 9.3 µm; unpaired: 23.5–77.5 ± 47.2–173.6/18.7 ± 10.6 µm; apical: 56.2–200.4 ± 105.7–552.5/20.3 ± 44.1 µm; N = 30).

Remarks: According to the original description, there are few tetractines among the cortical triactines, and the choanoskeleton is a closely packed mass of irregularly placed spicules (Jenkin 1908). We observed in the slides of the holotype that the tetractines are in fact abundant and most of the spicules of the choanosome form an articulated skeleton. In addition, the presence of microdiactines, pseudosagittal subcortical triactines and subatrial spicules was not mentioned before. Finally, differences in size of some spicule categories were detected. Spicule sizes provided by Jenkin (1908) for the cortical tetractines (maximum 700 x 26 µm for the basal actines and 500 x 26 µm for 205 the apical one) and atrial tetractines (unpaired: 300–560 x 10–12 µm, paired: 240–450 x 206 8–10 µm, apical: 180–260 x 8 µm) are considerably larger than our measurements of these spicules. We also compared our results with the description of L. wasinensis from the Seychelles (Van Soest & De Voogd 2018). In the Seychelles specimen, the shape of cortical and atrial spicules differs from the holotype, and atrial triactines occur only in that specimen, suggesting that its taxonomic identification needs to be confirmed.