Leucosolenia creepae Lavrov, Ekimova, Schepetov, Koinova & Ereskovsky, 2024, sp.nov.
Creators: name: Lavrov, Andrey
name: Ekimova, Irina
name: Schepetov, Dimitry
name: Koinova, Alexandra
name: Ereskovsky, Alexander
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Porifera
Calcarea
Leucosolenida
Leucosoleniidae
Leucosolenia
Leucosolenia creepae

description: Leucosolenia creepae sp.nov.
(Figs 19–22; Table 8)
ZooBank LSID: urn:lsid:zoobank.org:act: D60461BE-F215- 4BE2-AFB5-25AF542FC4B9.
Type material: Holotype: WS11702* White Sea* Kandalaksha Bay * Velikaya Salma Strait* vicinity of the N.A. Pertsov White Sea Biological Station* 0–2 m depth * 28.viii.2018 * coll. A.I. Lavrov. Paratypes: WS11703* 1 specimen * White Sea* Kandalaksha Bay * Velikaya Salma Strait* vicinity of the N.A. Pertsov White Sea Biological Station* 0–2 m depth * 28.viii.2018 * coll. A.I. Lavrov. WS11728 paratype agrees in locality* date and collector with holotype WS11702 and paratype WS11703. WS11655 was collected in 30.viii.2017 * and WS11725* WS11726* WS11771 were collected in 24.viii.2018 * but all agree in locality and collector with holotype WS11702 and paratype WS11703.
Type locality: White Sea* Kandalaksha Bay* Velikaya Salma Strait* vicinity of the N.A. Pertsov White Sea Biological Station %66°34ʹN* 33°08ʹE).
Material studied: Fifty-four specimens. Molecular data— 54 specimens * external morphology— 54 specimens * skeleton organization— three specimens %WS11655* WS11728* WS11762)* spicules %SEM)— five specimens %WS11579* WS11605* WS11704* WS11729* WS11775)* cytology % TEM)— three specimens %WS11579* WS11600* WS11698) %Supporting Information* Table S1).
Etymology: From English ‘creep’* referring to specific decumbent cormus and unusual growth form of this species in contrast to sympatrically living Leucosolenia corallorrhiza.
External morphology: Length of cormus up to 5 cm. Cormus formed by basal reticulations of creepy tubes with one or several oscular tubes % Fig. 19A). Tubes brittle. Oscular tubes creepy* trailing over substrate with slightly curved and erecteddistal end* sometimes with few diverticula. Oscular rim gradually narrows* possessing prominent spicular crown % Figure 19A * B). Surface echinate. Coloration of living and preserved specimens greyish white % Fig. 19A).
Spicules: Diactines % Fig. 20A * B). Spiny diactines* mean length 194.9 µm* mean width 5.1 µm % Table 8). Extremely variable in length* without lanceolate tips* spiny. Largest diactines slightly curved; intermediate and short diactines straight. Spines in distinct rows at one end of diactines* more or less reduced in large ones %Fig. 20B).
Triactines % Fig. 20C * D). Sagittal* T-shaped and V-shaped %mean angle 131.1°) % Table 8)* usually recurved* unpaired actines variable in length:most frequently shorter then paired actines* but equal and longer unpaired actines rarely occur %mean length: 80.7 µm—unpaired* 94.9 µm—paired) % Table 8). Aberrant T- and V-shaped triactines present* sometimes with undulated rays % Fig. 20D). Unpaired actines often more slender than paired actines %mean width: 5.4 µm—unpaired* 5.9 µm—paired) % Table 8).
Tetractines % Fig. 20E). Quite rare. Sagittal* T-shaped and V-shaped %mean angle 139.5°) % Table 8)* variable in size and proportions. Unpaired actines variable in length: longer* shorter* and equal to unpaired actines %mean length: 85.1 µm—unpaired* 95.3 µm—paired* 25.6 µm—apical) % Table 8). Paired and unpaired actines equal in width %mean width: 6.2 µm—unpaired* 6.3 µm—paired) % Table 8). Apical actine curved* smooth* and slender %mean width 5.2 µm) % Table 8).
Skeleton: Skeleton of oscular rim predominantly formed by both tri- and tetractines* while in other body parts tetractines absent % Fig. 19C * 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. 19C). In cormus tubes* spicule array completely disordered % Fig. 19D). Diactines form extending oscular crown up to 500 µm % Fig. 19B) and cover tubes’ surface in large numbers* orienting in different directions and making it hispid.
Cytology: Bodywall*9–14µmthick*threelayers:exopinacoderm*loose mesohyl* and choanoderm % Fig. 21A * B; Supporting Information* Table S2). Flat endopinacocytes located only in 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. 21C). External surface covered by glycocalyx. Cell body %height 5.8 µm* width 2.8 µm) containing spherical to oval nucleus %diameter 2.7 µm)* submersed in mesohyl. Cytoplasm with specific* spherical* electron-dense inclusions %0.25–0.35 µm diameter) %Fig. 21C).
Endopinacocytes non-flagellated* flat cells* size 16.2 µm × 2.7 µm % Fig. 21D). External surface covered by glycocalyx. Nucleus %diameter 2.7 µm) spherical without nucleolus. Cytoplasm without specific inclusions % Fig. 21D).
Choanocytes flagellated trapeziform or prismatic %height 11.4 µm* width 3.6 µm) % Fig. 21E). Flagellum surrounded by collar of microvilli. Characteristic pyriform nucleus %diameter 2.3 µm) in apical position. Cytoplasm with phagosomes and small vacuoles % Fig. 21E).
Porocytes tubular cylindrical %height 4.6–8.9 µm* width 2.8– 2.9 µm)* connecting external milieu with choanocyte tube % Fig. 21F). Nucleus oval to spherical %diameter 2.5 µm)* sometimes with nucleolus. Cytoplasm with spherical* electron-dense inclusions* identical with inclusions of exopinacocytes* phagosomes* and small vacuoles % Fig. 21F).
Sclerocytes amoeboid* size 7.6 µm × 2.9 µm % Fig. 22A). Nucleus usually oval or pear-shaped %diameter 2.3 µm)* sometimes with single nucleolus. Well-developed Golgi apparatus and rough endoplasmic reticulum. Cytoplasm usually with phagosomes and/or lysosomes % Fig. 22A).
Amoebocytes of different shape %from oval to amoeboid) without special inclusions* size 5.7 µm × 2.6 µm % Fig. 22B). Nucleus spherical %diameter 2.5 µm)* sometimes with nucleolus.
Myocytes fusiform cells* size 16.5 µm × 3.3 µm* located in mesohyl. Nucleus oval %2.4 µm × 1.9 µm)* without nucleolus % Fig. 21D). Cytoplasm with mitochondria* ribosomes* small vesicles* and cytoplasmic myofilaments. Myofilaments grouped in bundles %diameter 0.25–0.32 µm) that are located along the long axis of the cell % Fig. 21D).
Two morphotypes of bacterial symbionts in mesohyl. Morphotype 1 numerous % Fig. 22C * D). Bacteria large* rod-shaped* slightly curved* diameter 0.4–0.5 µm* length 2.7 µm. Cell is double* smooth* and covered with fibres* cytoplasm transparent with vacuolar inclusions* nucleoid region filamentous %Fig. 22C* D).
Morphotype 2 abundant % Fig. 22E * F). Bacteria small* rodshaped* diameter 0.19 µm* length 1.9–2.1 µm. Cell wall smooth* cytoplasm transparent* nucleoid region filamentous % Fig. 22E * F).
Distribution: Arctic species. In the White Sea quite rare* found in low intertidal and upper subtidal zones up to 5–10 m depth* on kelps and rocks.
Reproduction: In White Sea specimens* collected in mid-June to the end of the August contained oocytes at different stages %mostly* early) of development % Figs 21B * 22G).
Remarks: Leucosolenia creepae sp. nov. differs from other Leucosolenia species in both external characters and the morphology of spicules. In L. somesii * diactines are of two types: %i) smooth diactines* which are variable in length* and %ii) short and highly spined ones. In Leucosolenia creepae sp. nov. * we identified only one type of diactine* which has spines on the outer tip and variable in length. However* in Leucosolenia creepae sp. nov. * spines are more expressed in small and medium-sized diactines but become hardly visible in longer diactines of ~250–300 µm in length. In L. somesii * all medium-sized diactines have smooth tips % Fig. 24B). Leucosolenia creepae sp. nov. forms a sparse* basal reticulation with few oscular tubes* while the cormus of L. somesii is formed by a dense reticulation of extremely branched* winding tubes. From all other North Atlantic and Arctic Leucosolenia species * Leucosolenia creepae sp. nov. differs by the absence of lanceolate diactines. The mesohyl cell composition of Leucosolenia creepae sp. nov. includes only amoebocytes* myocytes* and sclerocytes* which differs it from the sympatrically living L. corallorrhiza and L. variabilis %Supporting Information* Table S2).
description: Published as part of 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, pp. 876-914 in Zoological Journal of the Linnean Society 200 on pages 901-906, DOI: 10.1093/zoolinnean/zlad104, http://zenodo.org/record/11248861