Folsomotoma octooculata (Willem, 1901)

Fanciulli, Pietro Paolo, Leo, Chiara, Convey, Peter, Frati, Francesco & Carapelli, Antonio, 2018, Redescription and neotype designation of the Antarctic springtail Folsomotoma octooculata (Collembola: Isotomidae), Zootaxa 4392 (2), pp. 392-400 : 393-394

Folsomotoma octooculata (Willem, 1901)

( FIgS. 1–4 )

Isotoma octooculata Willem, 1901

Parisotoma octooculata (Willem, 1901) : Salmon 1949 Isotoma (Folsomotoma) octooculata Willem, 1901 : Greenslade 1995 Folsomotoma octooculata (Willem, 1901) : Greenslade 2010

Neotype designation. Folsomotoma octooculata WAS FIRST dEScRIbEd bY WILLEM (1901, 1902) bASEd ON SPEcIMENS FROM ThE GERLAchE STRAIT, ANTARcTIc PENINSULA (cOLLEcTINg SITES: HARRY ISLANd, DANcO COAST ANd CUVERVILLE ISLANd) . IT IS PRObAbLE ThAT WILLEM’S ORIgINAL cOLLEcTION WAS dEPOSITEd AT GhENT UNIVERSITY, BELgIUM ; NEVERThELESS, EFFORTS TO TRAcE IT FAILEd, ANd ThE TYPE MATERIAL PRObAbLY NO LONgER EXISTS. ThUS, FOLLOWINg ARTIcLE 75.3.4 OF ThE INTERNATIONAL COdE OF ZOOLOgIcAL NOMENcLATURE (INTERNATIONAL COMMISSION ON ZOOLOgIcAL NOMENcLATURE 1999), WE hERE dESIgNATE A FEMALE AS NEOTYPE, cOLLEcTEd FROM SPERT ISLANd, GERLAchE STRAIT, ANTARcTIc PENINSULA (63°51’S, 60°57’W) .

Additional material examined. FOUR FURThER SPEcIMENS (ThREE FEMALES; ONE MALE) FROM ThE SAME NEOTYPE LOcALITY. FURThER SPEcIMENS OF F. octooculata , INcLUdEd IN ThE ANALYSIS, WERE ObTAINEd FROM ThE FOLLOWINg LOcALITIES NEAR ThE GERLAchE STRAIT: FOUR FEMALES FROM WIENckE ISLANd (64°50’S, 63°23’W); TWO FEMALES FROM BERThELOT ISLANd (65°20’S; 64°9’W); SIX INdIVIdUALS ( FOUR FEMALES; TWO MALES) FROM GANd ISLANd (64°24’S; 62°51’W). OThER SPEcIMENS FROM dIFFERENT SAMPLINg SITES ALONg ThE ANTARcTIc PENINSULA (ANd OFFShORE ISLANdS) WERE ALSO EXAMINEd: ONE FEMALE FROM POTTER COVE, KINg GEORgE I. (62°14’S, 58°42’W); FIVE FEMALES FROM RIP POINT, NELSON I . (62°15’S, 58°59’W); FOUR FEMALES FROM HARMONY POINT, NELSON I. (62°18’S, 59°14’W); ThREE FEMALES FROM COPPERMINE PENINSULA, RObERT I. (62°22’S, 59°42’W); FOUR INdIVIdUALS (TWO FEMALES; TWO MALES) FROM HANNAh POINT, LIVINgSTON I. (62°39’S, 60°36’W); ThREE FEMALES FROM DEVILS POINT, LIVINgSTON I. (62°40’S, 61°10’W); FOUR INdIVIdUALS (TWO FEMALES; TWO MALES) FROM HURd PENINSULA, LIVINgSTON I. (62°40’S, 60°21’W). ALL SLIdES ARE dEPOSITEd IN ThE COLLEMbOLA cOLLEcTION OF ThE DEPARTMENT OF LIFE ScIENcES, UNIVERSITY OF SIENA.

Redescription. MEAN bOdY LENgTh 1.25 MM; bOdY cOLOUR VARIAbLE ANd dEPENdENT ON AgE OF SPEcIMENS, FROM LIghT gREY TO dARk bLUE, USUALLY LIghTER VENTRALLY; EYE SPOTS ALWAYS dARk. CUTIcLE gRANULATION FINE ANd REgULARLY dISTRIbUTEd; dORSAL TERgITES Th. II–Abd. IV cLEARLY SEPARATEd FROM EAch OThER, Abd. V–VI FUSEd. Abd. III ANd IV APPROXIMATELY OF ThE SAME WIdTh. ChAETOTAXY PLURIchAETOSE cONSISTINg OF MIcRO-, MESO- ANd MAcROSETAE, ThESE LATTER WELL dIFFERENTIATEd ON LAST AbdOMINAL TERgA (IV–VI), bUT NOT WELL dISTINgUIShEd FROM ORdINARY SETAE ON OThER TERgITES ( FIgS 1A ANd 4D ). BOTh MESO- ANd MAcROSETAE ARE POINTEd ANd WITh UNSMOOTh SURFAcE. RATIO bETWEEN MAcROSETAE ON ThE LAST AbdOMINAL TERgITES ANd ThE cLAW III RANgES bETWEEN 2.5 ANd 2.8 ( FIgS. 2D , 4B ANd 4D ). AXIAL chAETOTAXY FOR Th. II – Abd. II AS: 7–8, 6, 4–5 ANd 5. NUMbER ANd POSITION OF AXIAL MESOSETAE ARE QUITE hOMOgENEOUS WIThIN ANd bETWEEN POPULATIONS ( FIgS. 2B, C, E, F ) . SENSORY chAETOTAXY IS cONSTITUTEd bY MIcROSENSILLA (MS), AccP ANd AS SENSILLA. MIcROSENSILLAR FORMULA (MS): 1,0/1,0,0 ( FIgS. 2A ); AL , AS ANd AccP SENSILLA FORMULA (S): 1,2/1,1,2,4,6 ( FIgS 2A, D ANd G ), IN PARTIcULAR, Th. II: ShORT AL–S; Th. III: ShORT AL–S ANd 1 ShORT AccP–S; Abd. I: ShORT AccP-S; Abd. II: 1 ShORT AccP-S; Abd. III : ONE ShORT ANd ONE LONg AccP–S; Abd. IV: 3 LONg ANd ONE ShORT AccP–S; Abd. V: ONE TUbULAR AS –S ANd 3 TUbULAR ANd 2 ShORT AccP–S ( FIgS. 2A , 4E, F ANd G ). DISTRIbUTION OF SETAE ANd SENSILLA IN P–ROW IS: ½S1S2S0S (Abd. IV); 1S1S1S1S0S, WITh 1 AS ON Abd. V ( AFTER POTAPOV 1989 ) . ANTENNAE LONgER ThAN ThE cEPhALIc dIAgONAL (D/A = 0.54). ANT. I WITh 48–52 SETAE, FOUR VENTRO-LATERAL SENSILLA INcLUdINg TWO MIcROSENSILLA ( FIgS. 1F ANd 4H ) ANd TWO SETA-LIkE SENSILLA. ANT. II WITh 88–97 SETAE ANd ONE VENTRO-LATERAL SETA-LIkE SENSILLUM. ANT. III WITh 95–115 SETAE; SENSORY FIELd INcLUdES TWO cURVEd SENSILLA INSERTEd IN A cUTIcULAR PIT (AOIII), TWO cYLINdRIcAL bASAL SENSILLA, TWO LATERAL MIcROSENSILLA ANd ThREE SETA-LIkE SENSILLA ( FIgS 1G ANd 3D ). ANT. IV PLURIchAETOSE WITh MORE ThAN 260 SETAE; cA. 60 OF ThE LATTER ARE cURVEd SETA-LIkE SENSILLA FORMINg A VENTRAL SENSORY FIELd ( FIg. 4C ), ONE SUbAPIcAL ORgANITE PIN-LIkE cLOSE TO A LONg cURVEd SUb-APIcAL MIcROSENSILLUM; OThER SETAE QUITE dIFFIcULT TO dEFINE AS SENSILLA OR ORdINARY SETAE . EYE SPOTS WITh 4+4 OcELLI STRONgLY dARk PIgMENTEd; PAO ELLIPTIcAL, WITh A MEdIAN cONSTRIcTION, SLIghTLY NARROWER ThAN ThE OcELLUS A ANd WITh 4–5 gUARd SETAE ( FIg. 3C ). LAbRAL FORMULA AS 4–5, 5 , 4 ANd 4 ShARP PAPILLAE ( FIg. 3A ) . MAXILLARY PALP TRIFURcATE ANd MOL WITh FOUR SUbLObAL hAIRS. LAbIUM WITh 4+4 SETAE ON BMF, 5 SETAE ON BLF, 4 PROXIMAL SETAE ( FIg. 1C ). LP WITh 5 PAPILLAE ANd A TOTAL OF 16 gUARd SETAE ( FjELLbERg 1999) SO dISTRIbUTEd: A1, B4, C0, D4, E7 ( FIg. 3B ). VENTRAL LINE OF ThE hEAd WITh 5+5 SETAE ( FIg. 1B ). MANdIbLE WITh WELLdEVELOPEd MOLAR PLATE ANd WITh 3 dISTAL TEETh. MAXILLA WITh LAMELLA 1 LONgER ThAN cAPITULUM. VENTRAL TUbE WITh 4+4 LATERAL, 4+4 ANTERIOR ANd 3 POSTERIOR SETAE ( FIgS 1D ANd 3F ). RETINAcULUM WITh 4 TEETh ANd 4–5 SETAE ON ThE bOdY ( FIg. 3E ). FURcA WELL-dEVELOPEd; RATIO OF MUcRON/dENS/MANUbRIUM = 1/22/15 ( FIg. 1I ). ANTERIOR SIdE OF MANUbRIUM WITh AbOUT 40 SETAE ANd 3+3 SPINE-LIkE SETAE IN ThE APIcAL PART ( FIg. 1E ); POSTERIOR SIdE WITh cA. 15 SETAE. ANTERIOR SIdE OF dENS WITh AbOUT 65 SETAE, POSTERIOR WITh cA. 9. ANTERIOR FURcAL SUbcOXA WITh AbOUT 30 SETAE, POSTERIOR ONE WITh 10–15 SETAE. MUcRO WITh 3 TEETh ( FIg. 4A ). TIbIOTARSI I, II ANd III WITh AbOUT 35, 35 ANd 70 SETAE, RESPEcTIVELY ( FIg. 1H ). CLAW SIMPLE, WIThOUT INTERNAL TEETh, EMPOdIAL APPENdAgE AS LONg AS hALF OF cLAW ( FIg. 4B ) . FEMALE gENITAL PLATE WITh 3+3 PREgENITAL, AbOUT 6 cIRcUMgENITAL ANd 2 EUgENITAL SETAE ( FIg. 1K ); gENITAL PLATE OF MALE WITh 3+3 PREgENITAL, 10–12 cIRcUMgENITAL ANd 3+3 EUgENITAL SETAE ( FIg. 1L ).

Taxonomic considerations. ThE dESIgNATION OF AN F. octooculata NEOTYPE WAS NEcESSARY gIVEN ThE FAILURE TO RELOcATE WILLEM’S ORIgINAL TYPE MATERIAL ANd ThE INcREASINg INTEREST IN ThE STUdY OF ANTARcTIc SPRINgTAIL EVOLUTION ANd AdAPTATION TO ThE TERRESTRIAL EcOSYSTEM, PARTIcULARLY cONSIdERINg ThE REcENT ENVIRONMENTAL chANgES ThAT ThREATEN POLAR REgIONS ( CONVEY 2013; CONVEY et al. 2014). CONSEQUENTLY, IN ORdER TO STAbILIzE NOMENcLATURE, ONE SPEcIMEN ObTAINEd FROM SPERT ISLANd (GERLAchE STRAIT) WAS SELEcTEd AS ThE NEOTYPE OF F. octooculata WILLEM (1901).

ThE SPEcIMENS OF F. octooculata EXAMINEd IN ThIS ANALYSIS dId NOT ShOW ANY cONSISTENT dIFFERENcES IN ThEIR MORPhOLOgY ANd WERE hOMOgENEOUS, bOTh WIThIN ANd AcROSS ThE dIFFERENT SAMPLINg LOcATIONS EXAMINEd, FURThER cONFIRMINg ThE SLOW RATE OF gENETIc dIVERgENcE hIghLIghTEd bY hAPLOTYPE ANALYSIS (CARAPELLI et al. 2017). COMPARISONS OF F. octooculata WITh cONgENERIc SPEcIES MAdE hERE ARE bASEd ON LITERATURE. COMPARISON WITh F. anomala (SALMON 1948) ANd F. minuta (SALMON 1949) MAY bE OF LIMITEd UTILITY gIVEN ThAT ThESE SPEcIES WERE PRObAbLY dEScRIbEd bASEd ON jUVENILE SPEcIMENS ( DEhARVENg 1981). HOWEVER, ThE NUMbER OF OcELLI OF ThESE SPEcIES (bOTh 2+2) dIFFERS FROM ThAT OF F. octooculata (4+4); ThE NUMbER OF OcELLI ON ThE OcULAR PLATE ALSO dISTINgUIShES F. octooculata FROM OThER cONgENERIc SPEcIES: 1+1 IN F. boerneri ( ENdERLEIN 1903) , F. marionensis ( DEhARVENg 1981) , F. punctata (WAhLgREN 1906), F. subflava (SALMON, 1949), ANd 3+3 IN F. bioculata (WOMERSLEY 1939). ThE MOST cLOSELY RELATEd SPEcIES TO F. octooculata IS F. kerguelensis ( ENdERLEIN 1903) (SEE REdEScRIPTION IN DEhARVENg 1981). ThE LATTER SPEcIES ShARES ThE SAME NUMbER OF OcELLI (4+4), bUT hAS A dIFFERENT NUMbER OF VENTRO-APIcAL SETAE ON ThE MANUbRIUM (2+2 AMPOULE SETAE IN F. kerguelensis vs. 3+3 SPINE-LIkE SETAE IN F. octooculata ). FURThER, F. kerguelensis hAS 20–30 SETAE ON ThE VENTRAL SIdE OF ThE MANUbRIUM, WhEREAS ThE NUMbER IS cLOSER TO 40 IN F. octooculata . MAjOR dIFFERENcES ARE APPARENT IN ThE SENSORIAL chAETOTAXY OF Abd. III–V. BOTh SPEcIES ShOW SIMILAR TYPES OF SENSORIAL SETAE (VERY LONg ThIN SETAE-LIkE AccP ANd ShORT “FAT” AccP ANd AS SETAE, WITh ROUNdEd/bLUNT APEX), bUT ThEIR NUMbER ANd POSITION ON TERgITES ARE dIFFERENT. ON Abd. III, F. kerguelensis hAS ONE SETA-LIkE AccP IN ThE dORSO-cENTRAL AREA OF ThE TERgITE, WhEREAS IN F. octooculata ThIS IS LOcATEd MUch MORE LATERAL ANd cLOSE TO AN MS SENSILLUM (ThESE LATTER SENSILLA WERE NOT REPORTEd IN ThE REdEScRIPTION OF F. kerguelensis ); ON Abd. IV, ThERE ARE TWO AccP SETA–LIkE ANd ONE AS SETA–LIkE IN F. kerguelensis , WhILE IN F. octooculata ThERE ARE ThREE AccP SETA-LIkE. SENSILLARY chAETOTAXY OF Abd. V IS SIMILAR IN ThE TWO SPEcIES: bOTh hAVE FOUR ShORT SENSILLA (ThREE AccP ANd ONE AS), WhIch hAVE SLIghTLY dIFFERENT LENgTh IN F. kerguelensis , WhILE bEINg OF ThE SAME SIzE IN F. octooculata . AS NOTEd bY GREENSLAdE (1986b), SIzE, ShAPE ANd POSITION OF AccP ANd AS ON AbdS. III–V cOULd bE cONSIdEREd TYPIcAL chARAcTERS OF ThE gENUS Folsomotoma . ThUS, gENERAL cOMPARISON OF SENSORY ANd ORdINARY chAETOTAXY SUPPORTS ThE EXISTENcE OF cONSIdERAbLE dIFFERENTIATION AMONg Folsomotoma SPEcIES, ANd cONFIRMS ThE IdENTIFIcATION OF IMPORTANT dIAgNOSTIc chARAcTERS USEFUL FOR cONgENERIc TAXONOMY.

ThE SYSTEMATIc kEY OF ThE Folsomotoma SPEcIES PROPOSEd hERE IS MAINLY bASEd ON EXISTINg LITERATURE (SALMON 1948, 1949; DEhARVENg 1981; GREENSLAdE 1986b); ThEREFORE, SOME chARAcTERS ARE dIFFIcULT TO cOMPARE, ANd LIkELY cASES OF SYNONYMY MAY bE hYPOThESIzEd. IN PARTIcULAR, SOME dOUbTS RISE FOR ThE SPEcIES WITh 2+2 EYES ( F. anomala ANd F. minuta ) ANd WITh 1+1 EYES ( F. boerneri ANd F. subflava ), WhIch ShOULd bE FURThER VALIdATEd cOMPARINg TYPIcAL OR TOPOTYPIcAL MATERIAL.

Figures

FIGURE 1. Folsomotoma octooculata: A, Dorsal chaetotaXy;, Ventral chaetotaXy of the head; C, Labium; Lp–Labial palp; Bmf–Basomedian field (submentum); Blf–Basolateral field (mentum); D, Ventral tube; E, Manubrium anterior VieW shoWing 3+3 spine–like setae, F, Ant. I lateral sensilla; G, Ant. Organ III; H, ChaetotaXy of tibiotarsus III; I, ChaetotaXy of the furca; K, Female genital opening; L, Male genital opening. Scale bars: 200 µm (A), 100 µm (B, I), 50 µm (D, K, L), 25 µm (C, E–H).

FIGURE 2. Folsomotoma octooculata; A, Number and distribution of dorsal sensilla (accp–s, al–s and as) and microsensilla (ms); B, C, E, F, Number and distribution of dorsal aXial setae along Th. II (E), Th. III (F), Abd. I (B) and Abd. II (C); asterisks indicate setae alWays present in all the specimens obserVed; D, ChaetotaXy of Abd. V–VI; G, Abd. IV p roW shoWing the position of the accp–s. Scale bar: 50 µm (D, G).

FIGURE 3. Folsomotoma octooculata; scanning electron microscopy. A, Mouth region shoWing labrum (Lbr), labium (Lbm) and maXillary outer lobe (Mol); scale bar, 20 µm; B, Labial palp With labial papilla (A, B, C, D and E); C, Ocular plate and PAO; D, Antennal organ III; E, Retinacle; F, Ventral tube. Scale bars: 20 µm (A, C, E), 10 µm (B, F), 5 µm (D).

FIGURE 4. Folsomotoma octooculata; scanning electron microscopy. A, Mucro; B, ClaW and empodial appendage; C, Ant. IV shoWing seVeral seta–like sensilla; D, Macrochaeta on the last abdominal tergites; E, EXample of long accp–s of the p–roW on Abd. III–IV; F, Lateral microsensilla (ms) and al–s of Th. II; G, EXample of long tubular accp–s of the p–roW on Abd. V; H, Ant. I lateral microsensilla (ms). Scale bars: 10 µm (A–E), 5 µm (F).