Leucosolenia complicata (Montagu, 1814)

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 : 884-888

publication ID	https://doi.org/ 10.1093/zoolinnean/zlad104
DOI	https://doi.org/10.5281/zenodo.11265601
persistent identifier	https://treatment.plazi.org/id/039D223D-FFA8-FFFF-FF68-FA406245FE46
treatment provided by	Plazi
scientific name	Leucosolenia complicata (Montagu, 1814)
status

Treatment

Leucosolenia complicata (Montagu, 1814) View in CoL

( Figs 3–6 View Figure 3 View Figure 4 View Figure 5 View Figure 6 ; Table 4 View Table 4 )

Type material: Not known* probably lost.

Type locality: British Isles * Devon coast % Montagu 1818 ).

Material studied: Three specimens. Molecular data— three specimens %WS11661* WS11662* WS11663)* external morphology— three specimens %WS11661* WS11662* WS11663) * skeleton organization— one specimen %WS11662)* spicules %SEM)— three specimens %WS11661* WS11662* WS11663)* cytology % TEM )— three specimens %WS11661* WS11662* WS11663) %Supporting Information* Table S1).

External morphology: Cormus more or less spherical* bearing multiple* erect* oscular tubes with short* lateral diverticula in basal part % Fig. 3A View Figure 3 ). Prominent perioscular spicular crown absent % Fig. 3B View Figure 3 ). Surface minutely hispid. Coloration of living and preserved specimens greyish white % Fig. 3A View Figure 3 ).

Spicules: Diactines % Fig. 4A–C View Figure 4 ). Two populations: %i) curved lanceolate diactines % Fig. 4A View Figure 4 )* mean length 263.7 µm* mean width 9.5 µm % Table 4 View Table 4 )* slightly curved* smooth* with lanceolate outer tip* variable in length and %ii) trichoxeas % Fig. 4B View Figure 4 )* mean length 127.3 µm* mean width 2.4 µm % Table 4 View Table 4 )* thin* straight* narrowing toward outer end* both ends pointed* not lance-shaped. Numerous irregularly distributed spines* number and size of spines decrease toward inner end % Fig. 4C View Figure 4 ).

Triactines % Fig. 4D View Figure 4 ). Predominantly parasagittal V-shaped %mean angle 125.7°)* with unpaired actines usually longer than paired %mean length: 113.5 µm—unpaired* 94.9 µm—paired) % Table 4 View Table 4 )* but equal and shorter unpaired actines also occur. Unpaired actines usually slightly slender than paired %mean width: 6.3 µm—unpaired* 6.8 µm—paired) % Table 4 View Table 4 ). T-shaped sagittal triactines absent.

Tetractines % Fig. 4E View Figure 4 ). Predominantly parasagittal V-shaped %mean angle 123.5°). Unpaired actines usually longer than paired* rarely equal %mean length: 109.3 µm—unpaired* 93.9 µm—paired* 23.8 µm—apical) % Table 4 View Table 4 ). Paired and unpaired actines equal in width* apical actine more slender %mean width: 6.7 µm—unpaired* 6.9 µm—paired* 5.3 µm—apical) % Table 4 View Table 4 ). Apical actine curved and smooth.

Skeleton : Skeleton of both oscular and cormus tubes predominantly formed by tetractines; triactines quite rare % Fig.3C View Figure 3 * 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. 3C View Figure 3 ). In cormus tubes* spicule array less organized % Fig. 3D View Figure 3 ). Lanceolate diactines cover tubes’ surface* orienting in different directions and extending outside by lance-shaped tip. Trichoxeas sparsely distributed on outer surface. No prominent spicular crown on oscular rim % Fig. 3B View Figure 3 ).

Cytology: Body wall* 6–9 µm thick* three layers: exopinacoderm* loose mesohyl* and choanoderm % Fig. 5A View Figure 5 * B; Supporting Information* Table S2). Flat endopinacocytes located in only distal part of oscular tube %oscular ring) replacing choanocytes. Inhalant pores scattered throughout exopinacoderm* except the oscular ring area.

Exopinacocytes non-flagellated T-shaped* rarely flat % Fig. 5C View Figure 5 ). External surface covered by glycocalyx. Cell body %height 4.8 µm* width 2.8 µm)* containing nucleus %diameter 2.2 µm)* submersed in mesohyl % Fig. 5C View Figure 5 ). Cytoplasm with specific spherical electron-dense inclusions %0.3–0.4 µm diameter) % Fig. 5C View Figure 5 ).

Endopinacocytes non-flagellated flat cells* size 20–30 µm × 2–2.5 µm % Fig. 5D View Figure 5 ). External surface covered by glycocalyx. Nucleus %2.4 × 1.8 µm) oval with or without nucleolus. Cytoplasm without specific inclusions % Fig. 5D View Figure 5 ).

Choanocytes flagellated trapeziform or prismatic %height 6 µm* width 3.7 µm) % Fig. 5E View Figure 5 ). Flagellum surrounded by collar of microvilli. Characteristic pyriform nucleus %diameter 2.3 µm) in apical position. Cytoplasm with phagosomes and small vacuoles % Fig. 5E View Figure 5 ).

Porocytes tubular cylindrical %height 4.5 µm* width 2 µm)* connecting external milieu with choanocyte tube % Fig. 5B View Figure 5 * F).

Nucleus oval to spherical* diameter 1.8 µm* sometimes with nucleolus. Cytoplasm with phagosomes and small vacuoles % Fig. 5F View Figure 5 ).

Sclerocytes amoeboid* size 4 µm × 2 µm % Fig. 6A View Figure 6 ). Nucleus usually oval or pear-shaped %diameter 1.6 µm)* containing single nucleolus. Well-developed Golgi apparatus and rough endoplasmic reticulum. Cytoplasm usually with phagosomes and/or lysosomes % Fig. 6A View Figure 6 ).

Amoebocytes of different shape %from oval to amoeboid) without special inclusions* size 5.8 µm × 3.4 µm % Fig. 6B View Figure 6 ). Nucleus spherical %diameter 2.2 µm)* sometimes with nucleolus.

Two morphotypes of bacterial symbionts in mesohyl. Morphotype 1 most abundant. Bacteria large* rod-shaped* slightly curved* diameter 0.3 µm* length 2.2 µm % Fig. 6C View Figure 6 ). Double-cell wall* cytoplasm transparent* nucleoid region filamentous.

Morphotype 2 rare. Bacteria rod-shaped* diameter 0.18 µm* length 1.2 µm % Fig. 6D View Figure 6 ). Double-cell wall* cytoplasm transparent* nucleoid region filamentous.

Distribution: Boreal species. Molecular species identity confirmed for specimens from France %Roscoff). Live in low intertidal and subtidal zones up to 20 m depth* on rocks and kelps %Borojevic et al.* 1968).

Reproduction: The specimens collected in February 2017 in Roscoff contained oocytes at the early stages of development.

Remarks: Leucosolenia complicata was one of the most undoubted species described in the 19th century. According to our data* it shows stable internal characters and easily diagnosable external features* i.e. erect multiply oscular tubes extending from the small cormus. The species’ identity and validity of L. complicata are strongly supported by our molecular data as well. It represents a distinct monophyletic lineage on all phylogenetic trees* and p- distance values to other Leucosolenia species are very high %more than 5% in LSU and 3.8% in SSU). Extensively studied morphology allows clarification of the species diagnosis* which varied from author to author %Haeckel 1872* Minchin 1904* Jones 1954* Rapp 2015): small cormus* erect multiple oscular tubes* two populations of diactines %curved lanceolate diactines and small trichoxea)* parasagittal tri- and tetractines with predominately longer unpaired actines * skeleton of tubes predominately formed by tetractines. Leucosolenia complicata is easily differentiated from other Leucosolenia species % Leucosolenia variabilis * L. somesii * and others) in these traits. In addition* the mesohyl cell composition of L. complicata is very poor compared to other studied Leucosolenia species: the mesohyl contains only sclerocytes and amoebocytes %Supporting Information* Table S2). The composition of symbiotic bacteria %two morphotypes of rod-shaped bacteria) differs in L. complicata from L. corallorrhiza and L. variabilis %Supporting Information* Table S2).

888 • Lavrov et al.

Although the type material of this species is not available* if it ever existed* we studied spicule slides from Minchin’s type collections % BMNH 1910.1.1.415a and BNMH 1910.1.1.435. Aa). They are listed as the type material of L. complicata in the BMNH collection. These slides contain handwritten information on the corresponding paragraphs in Minchin %1904) with relevant collection information %slides nos. 1* 2; Minchin 1904: 372). Accordingly* both slides appeared from Canon Normans’s Collection. The specimen BMNH 1910.1.1.415a was collected at Scarborough %the North Sea) by Bean and sent to Haeckel for examination. The specimen BNMH 1910.1.1.435.Aa was collected at the Guernsey Islands %the English Channel) by J. Bowerbank and probably represents a syntype of Ascandra contorta %Bowerbank * 1866). According to Minchin %1904)* this slide contains an admixture of L. complicata spicules with A. contorta . All this indicates that slides BMNH 1910.1.1.415a and BNMH 1910.1.1.435.Aa are not the type material of L. complicata * and the label ‘type’ probably refers to the Minchin’s type collection* which contained most typical specimens. Since no type material exists* the designation of neotype is needed once the material from the type locality %British Isles* Devon coast) becomes available for molecular study.

Ascandra pinus Haeckel * 1872 and Leucosolenia fabricii Schmidt* 1869 are regarded herein as minor synonyms. Ascandra pinus lacks small trichoxeas* which were most probably overlooked by Haeckel %Minchin 1904)* and in Leucosolenia fabricii * the skeleton is formed mostly by triactines* which was considered intraspecific variation by many authors %Minchin 1904* Burton 1963 * Rapp 2015). However* our data show that these characters may be regarded as diagnostic interspecific features* as shown for the L. variabilis species complex %see below); therefore* both of these species names should be taken into account for future research on European Leucosolenia .

Our data also suggest the absence of L. complicata in the White Sea. In works by Breitfuss %1898a)* three Leucosolenia species were found at different localities in the White Sea and are described under the names Ascandra variabilis Haeckel * 1872* Ascandra contorta %Bowerbank* 1866)* and Ascandra fabricii %Schmidt* 1869). Minchin %1904) later considered the latter two species sensu Breitfuss %1898a) as minor synonyms of Leucosolenia complicata due to external morphological characters* while spicular characters were ignored in most cases. However* Ascandra contorta sensu Breitfuss %1898a) possesses tri- and tetractines with short* unpaired actines* which is most likely a diagnostic feature for L. variabilis . Due to the absence of L. complicata in our material from the White Sea* and uncertainties in previous research* more material is required from different localities in the White and Barents Seas to clarify the distribution ranges of this species in Arctic waters.