Bathypathes patula Brook, 1889

Horowitz, Jeremy, Opresko, Dennis M. & Bridge, Tom C. L., 2018, Black corals (Anthozoa: Antipatharia) from the deep (916 m - 2542 m) Coral Sea, north-eastern Australia, Zootaxa 4472 (2), pp. 307-326 : 312-317

Bathypathes patula Brook, 1889

( FIgS. 1 , 3–4 )

Bathypathes patula, Molodtsova (2006): 141 –142 (complete synonymy).

Bathypathes seculata Opresko (2005): 130 –133.

Material examined: MTQ MATeRIAL (PReSeRVed IN eTHYL ALCOHOL): G35428, G35430, G61917, G73228, G61948, G61966, G61967, G61977, G61978, G61979, G61980, G61981, ANd G62049 (STATION dATA IN TAbLe 1).

Diagnosis (after Molodtsova 2006 -emended): COLONY MONOPOdIAL, PINNULATe; SICkLe-SHAPed STeMS. PINNULeS SIMPLe; ARRANged ALONg THe STeM IN TWO LATeRAL OR ANTeROLATeRAL ROWS, RANgINg fROM 7 MM TO 9 MM APART IN eACH ROW.

PINNULeS INCReASe IN LeNgTH fROM THe LOWeST PAIR Of PINNULeS, ReACH MAXIMUM LeNgTH AT AbOUT THe MId-PAIR TO jUST AbOVe THe MId-PAIR, ANd THeN deCReASe IN LeNgTH TOWARdS THe APeX.

SPINeS SIMPLe, SMOOTH WITH bLUNT TIPS, TRIANgULAR OR SLIgHTLY COMPReSSed OR eLONgATed, 0.03 MM TO 0.075 MM TALL, eITHeR AT 90° TO THe SURfACe Of THe PINNULe OR SLIgHTLY SLANTed dISTALLY, WITH bIfURCATION Of A feW SPINeS; THRee TO fIVe ROWS VISIbLe IN LATeRAL VIeW WITH AbOUT THRee SPINeS PeR 1 MM. POLYPS UP TO 9 MM IN TRANSVeRSe dIAMeTeR, ARRANged IN A SINgLe ROW.

IN AddITION TO THe AbOVe dIAgNOSIS, We Add THe fOLLOWINg: RATIO Of THe LeNgTH Of THe LONgeST PINNULe TO LeNgTH Of THe PINNULATed PORTION Of THe STeM LARgeST AMONg YOUNg COLONIeS (1.5 TO 2 fOR COLONIeS WITH PINNULATed PORTION Of STeM LeNgTHS LeSS THAN 10 CM) ANd deCReASINg WITH Age (<1 fOR COLONIeS WITH PINNULATed PORTIONS Of THe STeM gReATeR THAN 15 CM). THe eqUATION ReLATINg THIS RATIO (Y) TO LeNgTH Of THe PINNULATed PORTION Of THe STeM IN CM [X] IS Y= 2.081 - 0.059X.

Description of the CIDARIS Specimens: TWO COLONIeS ReSeMbLe B. patula ANd 11 COLONIeS ReSeMbLe B. seculata bASed ON THe deSCRIPTION Of THe HOLOTYPeS. THeSe SPeCIMeNS HAVe CURVed TO SICkLe-SHAPed STeMS WHeN VIeWed fROM THe SIde ( FIgUReS 3A–b ) THAT RANge fROM 3.3 CM TO 24 CM IN TOTAL LeNgTH. THe LeNgTH Of THe LONgeST PINNULe RANgeS fROM 1.6 CM TO 10.5 CM ANd THIS PINNULe IS POSITIONed AT, OR jUST AbOVe, THe MId PAIR Of PINNULeS ( FIgUReS 3A–b ). THe LeNgTH Of THe UNPINNULATed STeM RANgeS fROM 2.2 CM TO 7.9 CM ANd THe LeNgTH Of THe PINNULATed STeM RANgeS fROM 1.1 CM TO 16.1 CM. THe RATIO Of THe LeNgTH Of THe LONgeST PINNULe TO THe TOTAL COLONY SIze RANgeS beTWeeN 0.32 ANd 1.15. TWO COLONIeS HAVe RATIOS CLOSe TO, OR LeSS THAN, 0.5 ANd 11 COLONIeS HAVe RATIOS CLOSe TO, OR gReATeR THAN, 0.9, IdeNTIfYINg THeM AS eITHeR B. patula OR B. seculata , ReSPeCTIVeLY. THe RATIO Of THe LeNgTH Of THe LONgeST PINNULe TO THe LeNgTH Of THe PINNULATed PORTION Of THe STeM RANgeS beTWeeN 0.48 ANd 1.94. THe PINNULe deNSITY ON eACH SIde Of THe STeM RANgeS beTWeeN THRee ANd fIVe PINNULeS PeR 3 CM; HOWeVeR, THIS RANge MIgHT be AS MUCH AS SIX PINNULeS PeR 3 CM AS ONe SPeCIMeN HAS A PINNULATed PORTION 2 CM IN LeNgTH WITH fOUR PINNULeS ON eACH SIde Of THe STeM. STeM THICkNeSS jUST AbOVe THe bASAL PLATe RANgeS beTWeeN 0.1 MM ANd 0.9 MM. THe STRIATUM ON THe STeM VARIeS IN POSITION ANd LeNgTH, STARTINg ANYWHeRe beTWeeN THe LOWeST POINT Of THe STeM TO MIdWAY UP THe UNPINNULATed PORTION Of THe STeM, ANd eNdINg ANYWHeRe fROM MIdWAY UP THe UNPINNULATed PORTION Of THe STeM TO THe APeX Of THe COLONY. THe NUMbeR Of RIdgeS ON THe STRIATUM RANgeS beTWeeN TWO ANd SIX fROM ONe VIeW, ANd THe dISTINCTIVeNeSS Of THe STRIATUM RANgeS fROM NOT dISTINCT TO VeRY dISTINCT. THRee TO SeVeN ROWS Of SPINeS CAN be COUNTed IN ONe VIeW ON THe PINNULeS, ANd THe SPINeS ARe ARRANged IRRegULARLY IN eITHeR SPIRALS OR IN AXIAL ROWS ( FIgUReS 3C–d ). THe dIffeReNCe beTWeeN POLYPAR ANd AbPOLYPAR SPINeS ARe VISIbLe IN SOMe SPeCIMeNS, WHeRe POLYPAR SPINeS ARe ~0.07 MM ANd AbPOLYPAR SPINeS ARe ~0.03 MM ( FIgURe 3d ). SPINeS ARe SMOOTH WITH bLUNT TIPS, eLONgATed, ANd ARe eITHeR AT 90° TO THe SURfACe Of THe PINNULe OR SLIgHTLY SLANTed dISTALLY ( FIgURe 3e ), WITH ONe SPeCIMeN SHOWINg SOMe bIfURCATION Of THe SPINeS ( FIgURe 3f ). AMONg THe feW SPeCIMeNS THAT HAVe WeLL PReSeRVed POLYPS, THe TRANSVeRSe dIAMeTeR IS ~6 MM, THe TeNTACLeS ReACH A MAXIMUM LeNgTH Of 3 MM, ANd THe INTeRPOLYPAR SPACe IS ~2 MM. POLYP deNSITY IS ~1.5 PeR 1 CM ( FIgURe 3g ).

Remarks: THe dISCOVeRY Of 11 SPeCIMeNS IdeNTIfIed AS B. seculata bASed ON SIMILARITIeS WITH THe TYPe SPeCIMeN ALLOWS US TO INVeSTIgATe WHeTHeR THe PRIMARY MORPHOMeTRIC CHARACTeR THAT defINeS THe TAXONOMIC bOUNdARY beTWeeN B. seculata ANd B. patula (RATIO Of PINNULe LeNgTH TO STeM LeNgTH) CAN be eXPLAINed bY COLONY Age, USINg LeNgTH Of THe PINNULATed PORTION Of THe STeM AS A PROXY fOR Age. PRIOR TO THIS PUbLICATION, B. seculata WAS defINed AS HAVINg A LeNgTH Of LONgeST PINNULe TO STeM LeNgTH RATIO Of 0.9, ANd B. patula ~ 0.3 TO 0.5. WHeN COMPARINg THe LeNgTH Of THe LONgeST PINNULe TO THe PINNULATed PORTION Of THe STeM (THIS IS A MOdIfIed RATIO TO ACCOUNT fOR VARIATIONS IN THe LeNgTH Of THe UNPINNULATed PORTION Of THe STeM) AMONg THe 11 B. seculata ANd TWO B. patula SPeCIMeNS IN OUR COLLeCTION, THe B. seculata ANd B. patula HOLOTYPe SPeCIMeNS, ANd 8 B. patula SPeCIMeNS deSCRIbed IN THe LITeRATURe, ReSULTS SHOW A SIgNIfICANT ReLATIONSHIP beTWeeN THIS RATIO ANd COLONY SIze (F 1,21 = 51.87, P<0.001). THe eqUATION ReLATINg RATIO (Y) TO COLONY SIze (I.e., TOTAL LeNgTH Of THe PINNULATed PORTION Of THe STeM) IN CM [X] IS Y= 2.081 - 0.059X. THIS eqUATION SUCCeSSfULLY eXPLAINS APPROXIMATeLY 70% Of THe TOTAL VARIATION IN THe PINNULe TO COLONY SIze RATIO. THe TYPe SPeCIMeN Of B. seculata HAS A TOTAL COLONY SIze Of 9 CM ANd A RATIO Of 1.5, ANd B. patula SPeCIMeNS IN THe LITeRATURe HAVe TOTAL COLONY SIzeS THAT RANge fROM 6 CM TO 25 CM ANd RATIOS RANgINg fROM 1.6 TO 0.48. PRIOR TO THIS STUdY, THe dIffeReNT RATIOS ANd COLONY SIzeS beTWeeN THe B. seculata TYPe SPeCIMeN ANd B. patula SPeCIMeNS SUggeSTed POTeNTIALLY dIffeReNT SPeCIeS. HOWeVeR, WHeN CONSIdeRINg SPeCIMeNS fROM OUR COLLeCTION ( TAbLe 2), THeRe IS A STRONg NegATIVe CORReLATION beTWeeN RATIO ANd COLONY SIze ( FIgURe 4 ), WHICH MeANS THAT THe RATIO deCReASeS WITH INCReASINg COLONY SIze ANd B. seculata IS THeRefORe A jUVeNILe B. patula . We PROPOSe THAT THe NegATIVe CORReLATION beTWeeN RATIO ANd COLONY SIze IS dUe TO PINNULeS HAVINg SLOWeR gROWTH RATeS THAN THe STeM,

a Type specimen

WHICH IS WHY AS COLONY SIze geTS LARgeR, THe RATIO Of THe PINNULe TO COLONY SIze deCReASeS. ALLOMeTRIC gROWTH AMONg CORALS HAS beeN SHOWN TO MAXIMIze THeIR CHANCeS Of SURVIVAL ANd RePROdUCTION (DORNeLAS et al. 2017), ANd HAS PReVIOUSLY beeN dOCUMeNTed IN THe bLACk CORAL Leiopathes ( ANTIPATHARIA : LeIOPATHIdAe ) (LARTAUd et al. 2016). THe AdVANTAge THAT OUR Bathypathes SPeCIMeNS HAVe bY gROWINg ALLOMeTRICALLY CAN ReLATe TO A LAW Of MOdULAR ORgANISMS, WHeRe PROPORTIONAL gROWTH RATeS deCReASe WITH SIze dUe TO geOMeTRIC, STRUCTURAL, ANd eNeRgeTIC CONSTRAINTS (DORNeLAS et al. 2017).

ANOTHeR feATURe THAT WAS THOUgHT TO be dIffeReNT beTWeeN THe TWO SPeCIeS IS THe POSITION Of THe LONgeST PINNULe, WHeRe THe LONgeST PINNULe fOR B. patula IS POSITIONed MId-WAY UP THe PINNULATed PORTION Of THe STeM ( BROOk 1889) WHILe THe LONgeST PINNULe fOR B. seculata IS POSITIONed AT THe APeX ( OPReSkO 2005). HOWeVeR, THe MAjORITY Of SPeCIMeNS IdeNTIfIed AS B. seculata ANd B. patula HAVe THeIR LONgeST PAIR Of PINNULeS NeAR THe MId-PAIR OR jUST AbOVe THe MId-PAIR Of PINNULeS. OTHeR MORPHOLOgICAL feATUReS SIMILAR AMONg THeSe SPeCIMeNS INCLUde: PINNULe deNSITY (THRee TO fIVe PeR 3 CM ON ONe SIde Of THe STeM), SPINe deNSITY (~3 SPINeS PeR 1 MM), SPINe HeIgHT (0.03 MM TO 0.075 MM), SPINe SHAPe (bLUNT TIP, eLONgATed, ANd TRIANgULAR OR SLANTed), ANd SPINe ARRANgeMeNT (THRee TO fIVe AXIAL ROWS PeR VIeW, SOMeTIMeS IRRegULAR OR SPIRAL) ( TAbLe 2).

ONe dIffeReNCe beTWeeN THeSe 13 SPeCIMeNS THAT CAN NOT be eXPLAINed bY COLONY SIze IS THe POSITION, dISTINCTIVeNeSS, ANd LeNgTH Of THe STRIATUM. FOR eXAMPLe, THe SMALLeST SPeCIMeN (G35430) HAS AN INdISTINCT STRIATUM THAT COVeRS THe WHOLe STeM, THe SeCONd SMALLeST SPeCIMeN (G61917) HAS VeRY dISTINCT STRIATUM THAT IS AbOUT 1.6 CM IN LeNgTH ANd STARTS AT THe bASe ANd eNdS MIdWAY-UP THe UNPINNULATed PORTION Of THe STeM, ANd A MId-SIzed SPeCIMeN (G61948) HAS VeRY dISTINCT STRIATUM 6 CM IN LeNgTH THAT STARTS AbOUT 0.5 CM fROM THe bASe ANd eXTeNdS TO THe fIRST SeT Of PINNULeS ( TAbLe 2). ANOTHeR UNeXPLAINAbLe dIffeReNCe AMONg THeSe SPeCIMeNS IS THe LeNgTH Of THe UNPINNULATed PORTION Of THe STeM. ALTHOUgH THeRe SeeMS TO be A geNeRAL deCReASe IN THe RATIO beTWeeN THe LeNgTH Of THe UNPINNULATed PORTION Of THe STeM ANd TOTAL STeM LeNgTH, WHeRe THe SMALLeST SIzed SPeCIMeN HAS A RATIO Of ~0.66, ANd THe LARgeST SIzed SPeCIMeN (G61980) HAS A RATIO Of ~0.33, THe CHANge IN RATIO WITH COLONY SIze dOeS NOT SeeM TO be CONSISTeNT AMONg ALL THe SPeCIMeNS. FOR eXAMPLe, SPeCIMeNS G61917, G62049, G61979, G61978, ANd G61948 HAVe TOTAL STeM LeNgTHS Of 5.8 CM, 7.5 CM, 7.75 CM, 8.6 CM, ANd 11 CM, ReSPeCTIVeLY, WITH RATIOS RANgINg fROM 0.46 TO 0.41; HOWeVeR, ONe SPeCIMeN fROM Siboga STATION 74A (VAN PeSCH 1914) ANd G61966 HAVe TOTAL STeM LeNgTHS Of 6 CM ANd 7 CM ANd RATIOS Of 0.58 ANd 0.35, ReSPeCTIVeLY. GIVeN THAT STRIATUM CHARACTeRISTICS ANd LeNgTH Of THe UNPINNULATed PORTION Of THe STeM SeeM TO be HIgHLY VARIAbLe CHARACTeRISTICS, ANd NO OTHeR dISTINCT dIffeReNCeS CAN be fOUNd beTWeeN OUR B. seculata ANd B. patula SPeCIMeNS, THe HOLOTYPe SPeCIMeNS, ANd B. patula SPeCIMeNS deSCRIbed IN THe LITeRATURe, We HeRebY SYNONYMIze B. seculata WITH B. patula .

Distribution: SPeCIMeNS ASSIgNed TO THIS SPeCIeS HAVe beeN RePORTed fROM THe PACIfIC, ATLANTIC, ANd INdIAN OCeANS fROM dePTHS Of 100 M TO 5,500 M. THIS STUdY eXPANdS THe kNOWN dISTRIbUTION TO THe CORAL SeA, AUSTRALIA ( FIgURe 1C ). DeSPITe THe MANY ReCORdS Of Bathypathes patula LISTed IN OBIS, MOST ARe bASed ON in-situ ObSeRVATIONS WITHOUT THe SPeCIMeNS HAVINg beeN COLLeCTed. GIVeN THAT IT IS dIffICULT TO IdeNTIfY THIS SPeCIeS bASed ON in situ ObSeRVATION ALONe, We ARe UNAbLe TO CONfIdeNTLY CALCULATe THe dISTANCe Of THe RANge eXPANSION.

Figures

FIGURE 1. a, Map of collection sites for the specimens in this study and other locations globally where the same species have been collected; b, view of the Central and Eastern Indo-Pacific region; c, new black coral records from the Coral Sea.

FIGURE 3. Bathypathes patula: a, G61948; b, G35430, anterolateral views of corallums showing curvature of stem and pinnule lengths; c, G61917; d, G61978, spines on sections of pinnules where c shows longer polypar spines (topside of pinnule in image) than abpolypar spines (bottomside of pinnule in image); e, G61978, single spine on pinnule; f, G61917, single spine showing bifurcation; g, G61978, polyps on section of pinnule.

FIGURE 4. Ratio of the longest pinnule and length of the pinnulated section of stem against length of pinnulated section of stem.