Plakinastrella pseudolopha, 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 : 22-24

Plakinastrella pseudolopha sp. nov.

( FIgS. 9–10 , TAbLE 3)

Definition. Plakinastrella WITH A SMALL cOLUMNAR SHAPE ANd WITH dIOdS, TRIOdS, cALTHROPS, ANd UNIqUE SPIcULES WITH 2–4 AcTINES THAT RAMIfy IN 2–8 cONIcAL, fUSEd RAyS (PSEUdOLOPHOSE SPIcULES).

Type Material. HOLOTyPE: MNRJ 18463 (MQ32GR-TP10-b2), cOLLEcTEd IN HATUTU ISLANd, MARqUESAS ISLANdS , FRENcH POLyNESIA (7°54.387'S, 140°07.240’W), IN A LARgE OVERHANg WHIcH cONTINUES IN A dARk UNdERWATER cAVE AT 10 M dEPTH. JANUARy 27, 2012, cOLL. THIERRy PÉREZ .

Description. SMALL cOLUMNAR SPONgE WITH ROUNdEd TOP, 1.5 cM HIgH by 0.5 cM IN dIAMETER, HANgINg UPSIdE dOWN fROM THE cAVE cEILINg ( FIg. 9A ). COLOUR in vivo cREAM, bEcOMINg LIgHT bROWN AfTER fIXATION ( FIgS. 9A–B ). SURfAcE SMOOTH, WITH THIN SUb-SURfAcE cANALS. OScULES cIRcULAR, ELEVATEd, 0.5–1 MM IN dIAMETER ANd UP TO 1 MM HIgH, cONTRAcTEd AfTER fIXATION. CONSISTENcy RELATIVELy fIRM, cARTILAgINOUS.

Anatomy. THE cHOANOSOMAL SkELETON IS A dISORgANIZEd ALVEOLAR RETIcULATION SURROUNdINg cHOANOcyTE cHAMbERS, WITH A dENSE TANgENTIAL LAyER AT THE MARgINS Of AqUIfEROUS cANALS ANd AT THE bASAL SURfAcE Of THE SPONgE ( FIgS. 9C–E ). PSEUdOLOPHOSE SPIcULES ARE dISPERSEd THROUgHOUT THE cHOANOSOME bUT ARE SLIgHTLy MORE AbUNdANT NEAR THE bASE ( FIg. 9E ). SUbEcTOSOMAL LAcUNAE ANd bASAL cAVITIES AbSENT, bUT THE cHOANOSOME IS PIERcEd by LARgE cyLINdRIcAL cANALS, 100–650 µM IN dIAMETER ( FIg. 9C ). IN TRANSVERSE SEcTIONS, THE EcTOSOMAL SkELETON IS A PALISAdE Of SMALL dIOdS OVER A THIN LAyER Of TANgENTIAL SPIcULES ( FIg. 9F ). IN TANgENTIAL SEcTIONS, THE EcTOSOMAL SkELETON IS A RETIcULATION Of MULTISPIcULAR TRAcTS fORMINg UNIfORM, ROUNdEd MESHES 20–40 µM IN dIAMETER ( FIg. 9G ).

Spicules ( FIgURE 10 , TAbLE 3). DIOdS Of TWO SIZE cATEgORIES, bUT NOT cLEARLy SEPARATEd ( FIgS. 10A–B ). DIOdS I THIN, SMOOTH, SLIgHTLy S-bENT AT THE cENTRE, EXTREMITIES bLUNT OR TERMINALLy MIcROSPINEd. FULL SIZE 30–43–60 µM / 1.0–1.5–2.0 µM. DIOdS II AbUNdANT, RObUST, STRAIgHT OR cURVEd ANd SLIgHTLy S-bENT AT THE cENTRE, WITH AcERATE OR bLUNT ENdS. FULL SIZE 60–82–120 / 3.0–4.0–5.0 µM.

TRIOdS Of TWO SIZE cATEgORIES, bUT NOT EASILy SEPARATEd ( FIg. 10C ). TRIOdS I SMALL, THIN, REgULAR, Y- OR T-SHAPEd, WITH SMOOTH AcTINES ANd bLUNT OR TERMINALLy MIcROSPINEd TIPS. AcTINES 10–17–20 / 1.0–1.5–2.0 µM. TRIOdS II AbUNdANT, REgULAR, MOST OfTEN Y-SHAPEd, SMOOTH, WITH AcERATE ENdINgS. AcTINES 20–29–36 / 3.0–3.7–5.0 µM.

CALTHROPS RELATIVELy UNcOMMON, SMALL, REgULAR, SMOOTH, WITH AcERATE ENdINgS ( FIg. 10D ). AcTINES 9.0–15–22 / 1.0–2.3–4.0 µM.

PSEUdOLOPHOSE SPIcULES ( FIg. 10E ) cOMMON, WITH 2–4 IRREgULAR, OfTEN SLIgHTLy SPIRALLEd AcTINES THAT RAMIfy MEdIALLy IN 2–8 SHORT, PARTLy fUSEd, cONIcAL RAyS WITH AcERATE ENdINgS: FULL SPIcULE SIZE 10–16–25 µM.

Reproduction. EMbRyOS 150–300 µM IN dIAMETER WERE fOUNd THROUgHOUT THE cHOANOSOME Of THE ONLy SPEcIMEN, cOLLEcTEd IN JANUARy. ALL EMbRyOS WERE IN MORULA STAgE ANd WERE bROOdEd IN ROUgHLy SPHERIcAL cHAMbERS SURROUNdEd by A TANgENTIAL LAyER Of SPIcULES ( FIgS. 9C, H ).

Ecology. Plakinastrella pseudolopha sp. nov. LIVES IN SEMI-dARk cAVES IN SyNTOPy WITH Plakinastrella nicoleae sp. nov. ANd Plakortis ruetzleri sp. nov. (SEE bELOW). THIS SPONgE WAS cOLLEcTEd AT 10 M dEPTH ON THE cEILINg Of A LARgE OVERHANg dOMINATEd by LARgE 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 NAME pseudolopha REfERS TO THE UNIqUE SPIcULE TyPE NAMEd HERE 'PSEUdOLOPHOSE SPIcULES’.

Taxonomic remarks. Plakinastrella pseudolopha sp. nov. dIffERS fROM ALL OTHER PLAkINIdS by THE PRESENcE Of UNIqUE SPIcULES WITH RAMIfIEd AcTINES ANd fUSEd cONIcAL RAyS NAMEd HERE ‘PSEUdOLOPHOSE SPIcULES’. THE SyMMETRy Of THESE SPIcULES IS VARIAbLE ANd THE SPIcULES MAy HAVE TWO, THREE OR fOUR AcTINES ( FIg. 10E ). THE AcTINES RAMIfy IN fUSEd, cONIcAL RAyS IN A PATTERN THAT IS SOMETIMES SIMILAR TO THE SMOOTH AcTINES Of THE cANdELAbRA Of Corticium ( FIgS. 2E–F ), ANd Of THE LOPHOSE cALTHROPS Of SOME Plakina SPEcIES SUcH AS P. weinbergi MURIcy, BÉZAc, BOURy-ESNAULT ANd VAcELET, 1998 ANd P. anomala LAgE, GEROVASILEIOU, VOULTSIAdOU ANd MURIcy, 2018. HOWEVER, THE AbSENcE Of TRUE cANdELAbRA PREcLUdES ITS ALLOcATION IN Corticium , ANd A POSSIbLE HOMOLOgy bETWEEN TRULy LOPHOSE ANd THE PSEUdOLOPHOSE SPIcULES IS dIffIcULT TO dETERMINE. ALTHOUgH THEIR SHAPE IS SLIgHTLy SIMILAR, THE dISTRIbUTION Of PSEUdOLOPHOSE SPIcULES THROUgHOUT THE cHOANOSOME Of THE NEW SPEcIES cONTRASTS WITH THE cONcENTRATION Of LOPHOSE SPIcULES IN THE EcTOSOME ANd AROUNd cANALS IN Plakina SPEcIES. ON THE OTHER HANd, THE NEW SPEcIES SHARES WITH Plakinastrella THE EcTOSOMAL PALISAdE Of SMALL dIOdS, THE TANgENTIAL RETIcULATION WITH ROUNdEd MESHES, ANd THE PRESENcE Of TWO SIZE cATEgORIES Of dIOdS ANd TRIOdS. ONE SPEcIES Of Plakinastrella , P. globularis DOMINgOS, MORAES ANd MURIcy, 2013 HAS MIcRORHAbdS, WHIcH cOULd bE RELATEd TO THE dIAcTINAL PSEUdOLOPHOSE SPIcULES. A cLOSE RELATIONSHIP Of THE NEW SPEcIES WITH Plakinastrella WAS ALSO SUPPORTEd by PRELIMINARy cox-1 gENE SEqUENcE dATA (NOT SHOWN). THE cLASSIfIcATION Of THIS SPEcIES, HOWEVER, SHOULd bE VERIfIEd THROUgH MOLEcULAR ANd MORPHOLOgIcAL PHyLOgENETIc ANALySES Of THE WHOLE fAMILy PLAkINIdAE , WHIcH ARE OUT Of THE ScOPE Of THIS cONTRIbUTION.

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 2. Corticium vaceleti sp. nov. A, holotype MNRJ 18050 in vivo. B, paratype MNRJ 18051 in vivo. C, ectosome and part of choanosome in transversal section. D, transversal section through the whole sponge, showing the system of basal cavities, straight transversal inhalant canals, and cinctoblastula larvae. E, candelabra in upper view. F, candelabra in side view (E–F, SEM).

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 9. Plakinastrella pseudolopha sp. nov. A, holotype MNRJ 18463 in vivo. B, holotype after fixation. C, transversal section showing the dense choanosomal reticulation, canals and an embryo. D, tangential layer of spicules around a canal. E, basal layer of tangential spicules and part of the choanosome with pseudolophose spicules. F, ectosome with a palisade of small diods over a tangential layer of diverse spicule types. G, tangential ectosomal reticulation with simple, uniform, rounded meshes. H, embryo. Key: bl, basal layer; ca, canal; em, embryo; pa, palisade; ps, pseudolophose spicules; s, surface; tl, tangential layer.

FIGURE 10. Plakinastrella pseudolopha sp. nov. Spicules (SEM). A–B, diods. C, triods. D, calthrops. E, pseudolophose spicules.