Leucosolenia sp. A

Lavrov, Andrey, Ekimova, Irina, Schepetov, Dimitry, Koinova, Alexandra & Ereskovsky, Alexander, 2024, The complex case of the calcareous sponge Leucosolenia complicata % Porifera: Calcarea): hidden diversity in Boreal and Arctic regions with description of a new species, Zoological Journal of the Linnean Society 200, pp. 876-914 : 900

Leucosolenia sp. A

( Figs 17 , 18 ; Table 7)

Material studied: Three specimens. Molecular data— three specimens %WS11692* WS11752* WS11770)* external morphology— three specimens %WS11692* WS11752* WS11770) * skeleton organization— two specimens %WS11752* WS11770)* spicules %SEM)— two specimens %WS11692* WS11770) %Supporting Information* Table S1).

External morphology: Studied specimens small in size. Length of cormus up to 1 cm. Cormus represented by compact reticulation of tubes* from which several oscular tubes arising. Oscular tubes erect and almost straight. Surface minutely hispid. Coloration of living and preserved specimens greyish white % Fig. 17A ).

Spicules: Diactines % Fig. 18 A-C). Two populations: %i) curved* spiny* lanceolate diactines % Fig. 18B )* mean length 189.1 µm* mean width 7.2 µm % Table 7)* small* from almost straight to slightly curved and undulating* with lanceolate and spiny outer tip* spines in distinct rows % Fig. 18C ); %ii) curved* smooth diactines % Fig. 18A )* mean length 515.0 µm* mean width 11.6 µm % Table 7)* rare* long* slightly curved* without spines and lanceolate tips % Fig. 18C ).

Triactines % Fig. 18D * E). Predominantly T-shaped* sagittal %mean angle 146.5°) % Table 7). Unpaired actines variable in size: equal to* shorter* or longer than paired actines* but shorter unpaired actines most common %mean length: 118.5 µm—unpaired* 125.1 µm—paired) % Table 7). Both straight and bent paired actines common. Abnormal triactines in high numbers % Fig. 18E )* sometimes with undulated actines. Unpaired actines usually slightly slender than paired %mean width: 11.1 µm—unpaired* 11.6 µm—paired) % Table 7).

Tetractines % Fig. 18F ). Quite rare. Predominantly T-shaped %mean angle 140.8°) % Table 7)* variable in size. Unpaired actines equal to paired ones %mean length: 114.3 µm—unpaired* 113.2 µm—paired* 30.0 µm—apical) % Table 7). Unpaired actines straight* paired actines straight or undulating* apical actines curved or undulating* smooth. Paired and unpaired actines equal in width* apical actine more slender %mean width: 8.6 µm—unpaired* 8.5 µm—paired* 7.1 µm—apical) % Table 7).

Skeleton : Skeleton of both oscular rim and cormus tubes predominantly formed by triactines* tetractines rare % Fig. 17C * D). In oscular tubes* spicules constitute organized array with their unpaired actines directed toward cormus and oriented more or less in parallel to proximo-distal axis of oscular tube % Fig. 17C ). In cormus tubes spicule array completely disordered % Fig. 17D ). Prominent oscular crown absent % Fig. 17B ). Both populations of diactines cover tubes’ surface* orienting in different directions and extending outside.

Cytology: No material was available for cytological studies.

Distribution: Arctic species. Molecular identity confirmed only for the White Sea and Greenland. Found subtidal up to 15 m on rocks and red algae.

Reproduction: No data about reproduction time for this species.

Remarks: Although both our species’ delimitation analysis based on the H3 dataset and morphological data suggest that this species represents a distinct species-level unit* we avoid describing a new species as this case requires additional studies for several reasons. Leucosolenia sp. A shares some features with Leucosolenia corallorrhiza : %i) the external appearance is similar* %ii) the angle between unpaired actines in tri- and tetractines is similar %the mean angle is 142.9° in L. corallorrhiza and 146.5° in Leucosolenia sp. A )* and %iii) the unpaired actines in tri- and tetractines are commonly shorter than the paired ones.

However* these two species show several differences. Firstly* Leucosolenia sp. A has two populations of diactines* the smaller with lanceolate tips and the rare* large* curved* smooth* non-lanceolate diactines* whereas in L. corallorrhiza only the first type is present. Also* the tetractines are rare in both the cormus and oscular regions of Leucosolenia sp. A * while they are commonly present in the osculum of L. corallorrhiza . Leucosolenia sp. A commonly has triactines with bent* unpaired actines* which are straight in L. corallorrhiza . Finally* the mean length of actines in tri- and tetractines of L. corallorrhiza is shorter than those of Leucosolenia sp. A % L. corallorrhiza : 70.5 µm—unpaired actines mean length* 82.7 µm—paired actine mean length; Leucosolenia sp. A : 118.5 µm—unpaired mean length* 125.1 µm—paired mean length). At the same time* the limited material of Leucosolenia sp. A %only three specimens were collected and studied) does not allow us to study the possible interspecific variation and ontogenetic variation. Therefore* we avoid the designation of this species as a distinct one* until more material would be available for study.

Figures

Figure 17. Leucosolenia sp. A external morphology and skeleton. A* general morphology %Wº11752); B* skeleton of oscular rim %Wº11770); C* skeleton of oscular tube %Wº11770); D* skeleton of cormus %Wº11752). Abbreviations: c* cormus; d* diverticulum; o* osculum; or* oscular rim; ot* oscular tube.

Figure 18. Leucosolenia sp. A spicule types* scanning electron microscopy. A* curved smooth diactines; B* curved spiny lanceolate diactines triactines; C* tips of diactines* I and II refer to the zones marked on A and B* white arrowheads mark spines; D* triactines; E* abnormal triactines; F* tetractine.