Plakinastrella nicoleae, Lage & Muricy & Ruiz & Pérez, 2018

Lage, Anaíra, Muricy, Guilherme, Ruiz, César & Pérez, Thierry, 2018, New sciaphilic plakinids (Porifera, Homoscleromorpha) from the Central-Western Pacific, Zootaxa 4466 (1), pp. 8-38 : 16-19

Plakinastrella nicoleae sp. nov.

( FIg. 6 , TAbLE 3)

Definition. LIgHT gREyISH-bROWN, MASSIVE TO dROP-SHAPEd Plakinastrella WITH SHORT TUbULAR OScULES, UNEVEN SURfAcE, ANd gENERALLy SMALL SPIcULES: dIOdS 27–125 µM LONg, TRIOdS AcTINES 12–59 µM, cALTHROPS AcTINES 10–30 µM. MIcRORHAbdS AbSENT.

Type Material. HOLOTyPE: MNRJ 19726 (MQ32GR-TP10-b1), cOLLEcTEd IN HATUTU ISLANd, MARqUESAS ISLANdS, FRENcH POLyNESIA (7°54.387'S, 140°07.240’W), IN A LARgE OVERHANg WHIcH cONTINUES INTO A dARk UNdERWATER cAVE, AT 10 M dEPTH. JANUARy 27, 2012, cOLL. THIERRy PÉREZ .

Description. SHAPE IRREgULAR, WITH AN ENcRUSTINg bASIS ANd THIN IRREgULAR OR dROP-SHAPEd LObES HANgINg fROM THE cEILINg Of A cAVE, 3.8 cM LONg by 0.1–1.2 cM WIdE ANd 0.5–1.0 cM THIck ( FIg. 6A ). COLOUR LIgHT gREyISH-bROWN WITH LIgHT bEIgE TINgES, bOTH in vivo ANd AfTER fIXATION ( FIgS. 6A–B ). SURfAcE SMOOTH bUT UNEVEN. SPARSE OScULES, SMALL, 0.5–1.0 MM IN dIAMETER, cIRcULAR, WITH AN ELEVATEd MEMbRANE UP TO 1.3 MM HIgH. CONSISTENcy RELATIVELy fIRM bUT cOMPRESSIbLE.

Anatomy. THE SkELETON IS cOMPOSEd Of dIOdS, TRIOdS ANd cALTHROPS fORMINg A dENSE ALVEOLAR RETIcULATION IN THE cHOANOSOME ( FIg. 6C ) ANd A PALISAdE Of SMALL dIOdS IN THE SURfAcE ( FIg. 6D ). THE TANgENTIAL EcTOSOMAL SkELETON IS A dOUbLE RETIcULATION Of MULTISPIcULAR TRAcTS fORMINg SMALL ROUNdEd MESHES 12–49 µM IN dIAMETER INSIdE LARgER MESHES 49–148 µM IN dIAMETER ( FIg. 6E ). AqUIfEROUS SySTEM LEUcONOId. BOTH EcTOSOMAL ANd bASAL cAVITIES AbSENT.

Spicules ( TAbLE 3). DIOdS cOMMON, IRREgULAR, ALMOST STRAIgHT, SMOOTH, AcERATE, WITH cENTRAL IRREgULARITy INcONSPIcUOUS, OfTEN ONLy SLIgHTLy cENTROTyLOTE-LIkE; HIgHLy VARIAbLE IN SIZE ANd THIckNESS ( FIg. 6F ): FULL SIZE 27– 81–125 / 2.5–6.1–7.5 µM.

TRIOdS AbUNdANT, REgULAR, SMOOTH, WITH AcERATE ENdS, USUALLy Y-SHAPEd ( FIg. 6G ): AcTINES 12–25–59 / 2.5–6.1– 7.5 µM.

CALTHROPS AbUNdANT, REgULAR, SMOOTH, WITH AcERATE ENdS ( FIg. 6H ): AcTINES 10–19–30 / 2.5–5.3–7.5 µM.

–, absent. Measurements are min-med-max length or length / width in micrometres. Numbers of measurements in parentheses

Reproduction. CINcTObLASTULA LARVAE APPROXIMATELy 500 µM IN dIAMETER WERE fOUNd NEAR THE bASIS Of THE SPONgE.

Ecology. Plakinastrella nicoleae sp. nov. cOLONIZES SEMI-dARk cAVES, ANd LIVES IN SyNTOPy WITH Plakinastrella pseudolopha sp. nov. ANd Plakortis ruetzleri sp. nov. THIS SPONgE WAS cOLLEcTEd AT 10 M dEPTH ON THE ROOf Of A LARgE OVERHANg dOMINATEd by bLAck cORAL cOLONIES (PÉREZ et al. 2016). NO SIgN Of EPIbIOSIS OR PREdATION WERE ObSERVEd.

Distribution. MARqUESAS ISLANdS, FRENcH POLyNESIA ( FIgS. 1 , 3 ).

Etymology. THE SPEcIfIc EPITHET nicoleae IS gIVEN IN HONOUR Of DR. NIcOLE BOURy-ESNAULT fOR HER EXcEPTIONAL cONTRIbUTION TO THE SySTEMATIcS Of THE HOMOScLEROMORPHA ANd fOR HER ENTHUSIASTIc EffORTS fOR THE dEVELOPMENT Of SPONgE bIOLOgy ANd THE fORMATION Of NEW ScIENTISTS.

Taxonomic remarks. Plakinastrella cURRENTLy INcLUdES 14 SPEcIES WITH UNIfORM SPIcULATION Of dIOdS, TRIOdS ANd cALTHROPS (VAN SOEST et al. 2018). MANy SPEcIES ARE POORLy dEScRIbEd, ANd THE MAIN MORPHOLOgIcAL cHARAcTER USEd fOR SPEcIES dIScRIMINATION IN Plakinastrella IS SPIcULE SIZE. Plakinastrella nicoleae sp. nov. SHARES THE SMALL SIZE Of THE SPIcULES—ALL SHORTER THAN 150 µM—WITH Plakinastrella copiosa , P. clippertonensis VAN SOEST et al., 2011, P. globularis DOMINgOS et al., 2013, P. osculifera sp. nov., P. microspiculifera MORAES & MURIcy, 2003 ANd P. mixta MALdONAdO, 1992. HOWEVER, P. copiosa , P. clippertonensis , ANd P. mixta dIffER by THE SMALL SIZE (MAXIMUM 2 cM LONg) ANd EXTERNAL cOLOURS (WHITE, yELLOW, OR cREAM). Plakinastrella globularis dIffERS by THE MASSIVE SHAPE, dARk bLUE cOLOUR in vivo, ANd PRESENcE Of MIcRORHAbdS, AbSENT IN THE NEW SPEcIES. Plakinastrella osculifera sp. nov. dIffERS fROM Plakinastrella nicoleae sp. nov. by THE ENcRUSTINg SHAPE, cHOcOLATE-bROWN cOLOUR, cONSPIcUOUS OScULES, ANd LARgER cALTHROPS. THE SPEcIES MOST SIMILAR TO Plakinastrella nicoleae sp. nov. IS P. microspiculifera fROM THE TROPIcAL SOUTHWESTERN ATLANTIc, WHIcH SHARES THE SMALL SPIcULE SIZE, THE MASSIVE dROP-SHAPEd HAbIT, THE EcTOSOMAL SkELETON ARcHITEcTURE, ANd THE PRESENcE Of EcTOSOMAL cAVITIES. Plakinastrella microspiculifera dIffERS by THE dARk gREy TO bLAck cOLOUR, IRREgULAR SURfAcE, PRESENcE Of EcTOSOMAL cAVITIES, RARITy Of TRIOdS, ANd by THE REgULAR SHAPE Of ITS cALTHROPS ( MORAES & MURIcy 2003). THESE dIffERENcES ARE RELATIVELy SMALL bUT ARE cONgRUENT, ANd TOgETHER WITH THE HIgHLy dISjUNcT dISTRIbUTIONS THEy SUPPORT THE dISTINcTION Of Plakinastrella nicoleae sp. nov. AS A NEW TAXON.

Figures

FIGURE 1. Location of collection sites. A, Pacific Ocean showing New Caledonia and Marquesas Islands. B, Marquesas Islands showing Nuku Hiva and Hatutu Island (red circles). C, New Caledonia showing Bourail and Hienghène (red circles)

FIGURE 3. Distribution of Homoscleromorpha species in the Pacific Ocean. Records identified only to genus level (as sp., cf., or aff.) and from Antarctica were not included. See Table 4 for locality names and references

FIGURE 6. Plakinastrella nicoleae sp. nov. A, holotype MNRJ 19726 in vivo. B, fragment of the holotype after fixation. C, Transverse section showing the dense, alveolar choanosomal skeleton, the dense surface layer, and canals. D, transversal section of the ectosome showing the palisade of small diods. E, Tangential section showing ectosomal reticulation with rounded primary and secondary meshes. F, diods. G, triods. H, calthrops (F–H, SEM). Key: ca, canals; ch, choanosomal skeleton; pa, palisade; s, surface.