Leucandra falakra Klautau, Imešek, Azevedo, Pleše, Nikolić & Ćetković, 2016, sp. nov.

Leucandra falakra sp. nov.

urn:lsid:zoobank.org:act: 3DEBFC2C-2E7E-4D8E-A7FA-7FE971CFEDB2

Figs 8–9; Table 8

Etymology From the Greek falákra (φαλάκρα), meaning bald, for the absence of diactines.

Material examined

Holotype

ADRIATIC SEA: near the Island of Blitvenica, 43°37'31.96" N, 15°34'25.94" E; 5 m, collected by V. Nikolić, 10 Oct. 2012 (PMR-13748 = UFRJPOR 8349, in ethanol).

Colour

White in life and in ethanol.

Description

The sponge is massive and vase-shaped, with one apical osculum without crown. The atrium is central and large. The aquiferous system is leuconoid (Fig. 8A). The sponge surface is smooth, but harsh. The cortical skeleton is composed of small, tangentially arranged triactines. The choanosomal skeleton has no organisation (Fig. 8B). It is composed of two categories of triactines (giant triactines and triactines larger than those of the cortex) (Fig. 8C). There are also tetractines and some triactines surrounding the canals (Fig. 8D). The atrial skeleton is smooth, composed mainly of triactines, with a few tetractines also present (Fig. 8E).

Spicules (Table 8)

CORTICAL TRIACTINES. Subregular to sagittal, equiradiate and small. Actines are cylindrical, blunt and curved (Fig. 9 A–B). Size: 136.4/ 11.1 µm (paired actine); 106.0/ 11.4 µm. (unpaired actine).

CHOANOSOMAL SMALL TRIACTINES. Subregular to sagittal. Actines are conical and sharp (Fig. 9 C–D). Size: 214.2/ 18.3 µm (paired actine); 189.7/ 19.8 µm. (unpaired actine).

CHOANOSOMAL GIANT TRIACTINES. Subregular to sagittal, equiradiate. Actines are conical and sharp (Fig. 9 E–F). Size: 624.5/ 81.5 µm.

CHOANOSOMAL TETRACTINES. Sagittal. These spicules are present only surrounding the canals. Actines are cylindrical, sharp and curved. The unpaired actine is a little shorter than the paired ones. The apical

actine is straight, short, conical and sharp (Fig. 9 G–H). Size: 154.0/ 12.4 µm (paired actine); 143.0/ 12.4 µm (unpaired actine); 80.6/ 9.6 µm (apical actine).

ATRIAL TRIACTINES AND TETRACTINES. Strongly sagittal. Triactines are the most abundant spicules (Fig. 9I). Actines are cylindrical and blunt. The unpaired actine is shorter than the paired ones. The apical actine of the tetractines is conical, straight, sharp and short. Frequently they are longer and thicker than the apical actine of the choanosomal tetractines (Fig. 9J). Size (triactines): 222.7/ 15.1 µm (paired actine); 111.2/ 12.3 µm (unpaired actine). Size (tetractines): 191.4/ 14.9 µm (paired actine); 92.0/ 13.1 µm (unpaired actine); 110.3/ 11.9 µm (apical actine).

Ecology

The specimen was collected on a shaded, semi-vertical, hard limestone bottom.

Remarks

To our knowledge, there are only three described species of Leucandra without diactines and with triactines being the main atrial spicules: L. consolida Tanita, 1943, L. glabra Hôzawa, 1940 and

I.

Atrial triactine. J. Atrial tetractine. Scale bar A–J = 100 µm. L. okinoseana Hôzawa, 1929, all three from Japan. Leucandra falakra sp. nov. can be differentiated from L. consolida by the presence of an oscular crown in the latter (although “feebly developed”), by the absence of tetractines in the choanosome, and by the absence of the large triactines in the cortex. Moreover, the size of some spicules is different (cortical triactines: 240–350/ 20–25 µm; choanosomal triactines - paired actines: 590–740/ 60–86 µm, unpaired actine: 550–720/ 60–86 µm; atrial triactines - paired actines: 220–270/ 15–18 µm, unpaired actine: 250–300/ 15–18 µm; atrial tetractines: same size of the atrial triactines but with an apical actine of 80/ 14 µm).

Leucandra glabra has a different external morphology, with several oscula in a single individual. Besides, the size of some spicules is different (cortical triactines: 120–240/ 14–28 µm; small choanosomal triactines: 100–200/ 10–20 µm; large choanosomal triactines: 400–950/ 42–110 µm; choanosomal tetractines: similar to the small choanosomal triactines but with an apical actine of 80/ 10 µm; atrial triactines: 90–200/ 12–20 µm).

Leucandra okinoseana can be differentiated from L. falakra sp. nov. by the presence of “small protuberances for attachment” in L. okinoseana and by the size of some spicules, which are larger in the Japanese species (cortical triactines - paired actines: 120–250/ 16–24 µm, unpaired actine: 150–350/ 14– 16 µm; cortical and choanosomal large triactines: 400–1400/ 32–120 µm; tetractines of the canals - paired actines: 150–200/ 16–20 µm, unpaired actine: 120–570/ 12–16 µm, apical actine: 70–200/ 8–12 µm; atrial triactines - paired actines: 190–370/ 20–32 µm, unpaired actine: 70–270/ 16–24 µm; atrial tetractines - same size as the atrial triactines but with an apical actine of 50–110/ 8–16 µm).

the cortex. E. Choanosome. F. Atrial skeleton. Abbreviations: at = atrium; cx = cortex.