the third labidostommatid genus from Baltic amber has subtropical kin

18 Pages·2017·3.68 MB·English

ACAROLOGIA
A quarterly journal of acarology, since 1959
Publishing on all aspects of the Acari
All information:
http://www1.montpellier.inra.fr/CBGP/acarologia/
[email protected]
Acarologia is proudly non-profit,
with no page charges and free open access
Please help us maintain this system by
encouraging your institutes to subscribe to the print version of the journal
and by sending us your high quality research on the Acari.
Subscriptions: Year 2017 (Volume 57): 380 €
http://www1.montpellier.inra.fr/CBGP/acarologia/subscribe.php
Previous volumes (2010-2015): 250 € / year (4 issues)
Acarologia, CBGP, CS 30016, 34988 MONTFERRIER-sur-LEZ Cedex, France
The digitalization of Acarologia papers prior to 2000 was supported by Agropolis Fondation under
the reference ID 1500-024 through the « Investissements d’avenir » programme
(Labex Agro: ANR-10-LABX-0001-01)

Acarologia is under free license and distributed under the terms of the
Creative Commons-BY-NC-ND which permits unrestricted non-commercial use, distribution, and
reproduction in any medium, provided the original author and source are credited.
Acarologia55(3):321–336(2015)
DOI:10.1051/acarologia/20152170
Before the summer turns to winter: the third labidostommatid genus from
Baltic amber has subtropical kin
MichelBERTRAND1,EkaterinaSIDORCHUK2andCHOFFEINS3
(Received24April2015;accepted18June2015;publishedonline30September2015)
1UniversitéMontpellierPaulValéry34199Montpelliercedex5,[email protected]
2BorissiakPaleontologicalInstitute,RussianAcademyofSciences,Profsoyuznayaulitsa123,117997Moscow,[email protected]
3Liseistieg10,D-22149Hamburg,Germany
ABSTRACT — Followingthediscoveryofthegenera LabidostommaandSellnickiellainPaleogeneamber, afossilofthe
genusEunicolinawasfoundforthefirsttimeinapieceofBalticamberfromtheHoffeinscollection.Thegenusisknown
by four extant species: three European and one American. Eunicolina is distinguished notably by the multiplication
of the pustules around the posterior part of the dorsal shield. The presence of this genus in Baltic amber confirmed
thatthefamilywasrepresentedintheearlyCenozoicbygenerawhosemembersarepresentlyconfinedtoratherwarm
or cool, or Mediterranean climatic conditions, either in the South or in the North hemisphere, or cosmopolitan. The
past and present distributions of the labidostommatid genera known from Baltic amber are discussed with respect to
environmental changes. A key for orienting the identification of the genera and subgenera of Labidistommatidae is
provided,includingthefossilspecies.
KEYWORDS—Balticamber;Labidostommatidae;Eunicolina;Eocene;biogeography
INTRODUCTION jorgroupsofAcari,Labidostommatidaehaveprob-
ably existed well before the major adaptive break-
throughthathadhappenedbetweenthelateMeso-
Fossil record of edaphic predatory mites is rather
zoicandCenozoic,from60to100Ma(Krantz2009).
impressive, with about 20 valid species of Par-
To date, less than twenty fossil labidostommatid
asitiformes and more than 250 species of Acari-
specimensareidentifiedfromEuropeanEoceneam-
formes (Dunlop et al. 2015). Of the latter, the fos-
ber. Twogenera, SellnickiellaFeider&Vasiliu, 1969
silrepresentativesofthefamilyLabidostommatidae
(with one species) and Labidostomma Kramer, 1879
may help to understand the historical biogeogra-
areknownfromBalticamber,andoneunidentified
phyofthisgroup. TheextantLabidostommatoidea
memberofthefamily–fromUkrainianamber(Sell-
(Prostigmata)arerepresentedbyasingleandprim-
nick 1931a; Dunlop and Bertrand 2011; Sidorchuk
itive family of Prostigmata, exhibiting plesiomor-
andBertrand2013,Dunlopetal. 2015).
phic characters (i.e. plesiomorphic dorsal chaeto-
taxy, shapeofthefamulus, etc.), characterizedbya EoceneamberofEuropeisaserendipitouswin-
heavilyarmoreddorsalshieldandacompleteven- dow to the European environment just before the
tralarmature(Walteretal.2009).Asmostofthema- Eocene-Oligocenetransition, markedbythelossof
http://www1.montpellier.inra.fr/CBGP/acarologia/ 321
ISSN0044-586-X(print).ISSN2107-7207(electronic)
BertrandM.etal.
many tropical and subtropical elements. During ber was prepared by E.S., who identified the fam-
thisperiod,theglobalchangefromawarmclimate ily, then was examined (M.B.) by light microscopy
(= late Eocene with dominant evergreen subtropi- mounted in a slide with glycerol with large con-
cal flora) to a cooler temperate seasonal climate (= cavity and conserved in a solution of thymol. Im-
early Oligocene with mixed evergreen and decid- age stacks were obtained using the Optikam B3
uous flora) eradicated from north latitudes many cameramountedonthecompoundmicroscopeOp-
species, whereas vast stretches of seas breaking up tika B600ti and Olympus CH2 with additional in-
thelandcontinuitydisturbedthegeneticcommuni- cident illumination. Measurements were made on
cationbetweentheterrestrialecosystems(Collinson imageswithcameracalibration,anddrawingswith
1992). thehelpofthesoftwareInkscapeTM(v.0.48.0).Mea-
surements are given with a rather large estimated
AninclusioninapieceofBalticamberfromthe
intervalofconfidencebecauseinclusionwithinthe
Hoffeinscollectionrevealedanewputativelabidos-
piece of amber induced deformation and because
tommatid specimen. This fossil was more deeply
orientationisnotaseasyasthatofafreespecimen
examined: itwasthefourthspeciesofLabidostom-
inaslide.
matidaefoundinEoceneamber,andthefirstrepre-
sentative of the genus Eunicolina Berlese, 1911. Its Terminology—Inourpreviousarticle,weused
extantcongenersarelargeandrobustmites,preda- an emendation of the original name (Labidostomma
tory on soft-bodied arthropods of the upper layers Kramer, 1879) by Oudemans (1904): Labidostoma,
in soils. They are infrequently collected but eas- and its derivations. Oudemans emended the in-
ily identified, notably by neotaxy of the laterodor- correct latinization of the Greek root "στoµα", but,
sal pustules and by ankylosis of the femora of the according to the International Code of Zoological
firstpairoflegs. Allextantspeciesarefoundunder Nomenclature(ICZN,art.32.5.1.),thisisunjustified
warmtemperatetosubtropicalclimaticconditions: emendation: it was not a lapsus calami, as the orig-
threeinMediterraneanEuropeandoneinVirginia inal spelling was twice repeated in Kramer’s work
(USA). The discovery of this first fossil Eunicolina (Kramer 1879, p. 13), and as Kramer himself did
brings new data for a more comprehensive histor- not refer to the origin of the name from the word
ical biogeography of the family. Our objectives by "στoµα". Unjustified emendation is an available
thiscontributionaretodescribethespecimen,anal- name and has its own author and date — Labidos-
yseavailabledataonthepastandpresentdistribu- tomaOudemans,1904—,whichisajuniorobjective
tions of Labidostommatidae, and provide an iden- synonymofthenameinitsoriginalspelling(ICZN,
tification key to their genera, subgenera and fossil art. 32.5.2.). Itcanberetainedonlyinonecase: ifits
species. usageisprevailing(ICZN,art.33.2.3.1.).Itisnotso:
originalspelling,Labidostomma,iswidely,albeitnot
universally, used (see References). The name in its
MATERIALS AND METHODS
original spelling, Labidostomma Kramer, 1879, thus
shouldbeused,andweuseitinthepresentarticle.
A piece of Baltic amber (Collection Hoffeins, pri-
vate collection CHHC piece 588-13), in all likeli- The family-group name that we used, Labidos-
hood produced by Pinus succinifera, dated accord- tomatidae Oudemans, 1904, also needs to be cor-
ing to the sediments from Lower to Mid Eocene rected, (ICZN art. 35.4.1.) because this name
i.e. 37 to 54.5 Ma (Poinar 1992; Weitschat, Wichard was originally derived from the unjustified emen-
2010). Amberwiththemiteinclusionwastrimmed dation (see above) – thus, double-m spelling is
and polished to obtain a small (approximately 1 correct. The spelling is also different from the
mm) lozengic piece (for description of method see original (Labidostomidae) in that the stem of the
Sidorchuk(2013)). Thesamplewasstoredinaque- name was corrected by Krantz (1978) to comply
ous thymol solution (one or two drops of satu- with ICZN art. 29.3.: as genitive singular of
ratedsolutionper1mlofwater). Thepieceofam- "στoµα"is"στoµατoς",thestemis"στoµατ-": fam-
322
Acarologia55(3):321–336(2015)
FIGURE1: Eunicolinaglaesin. sp. —A.Lateralview,rightside. B.Oculo-pustularzone,details. C.Detailofthecuticle,patterninthe
lateralzone. D.EnlargedviewoftheacetabulaIV,showingthevillosityinpitPT("puitstégumentaire"inCoineau1964). Abbrevi-
ations:BO.A,BO.P:anteriorandposteriortrichobothria;la,lb:lateralsetaeofthedorsalshield;da,db,dc:dorsalsetaeofthedorsal
shield;EPIIV:fourthepimeralplate;PI,PIV:firstandfourthlegs.Star:possiblelateraleye.
ily Labidostommatidae Oudemans, 1904, super- thefixeddigitofthechelicerawhichfitsinacorre-
family Labidostommatoidea Oudemans, 1904, co- sponding hollow of the mobile digit. Type species
hort/infraorder Labidostommatina Krantz, 1978. —EunicolinatuberculataBerlese,1911(redescription
Thisisthespellingtobeused,andweuseitbelow. inVistorin,1980: 376).
Notation follows the works on this family by
Grandjean (1942 a, b, c), and on the genus by Eunicolinaglaesin. sp.
Coineau(1964). (Figs1-5,6B,6C)
Type designation and repository — The holotype
RESULTS and only described specimen is an inclusion in
Baltic amber from the private C. & H.W. Hof-
GenusEunicolinaBerlese,1911
feins Collection (specimen CHHC 588-13, which
Diagnosis — Heavily armoured labidostommatid will be eventually transferred to the Museum für
miteswithpronouncedneotaxyofpustulesoneach Naturkunde, Berlin). This specimen is an adult,
sideofthedorsalshield,thedeephollowatthelevel having the entire dorsal shield (nymphal stases of
of thefourth pairof legs, where the reticulatedcu- labidostommatidsarelesschitinized, withthedor-
ticleisreplacedbyadensecarpetofvillosities, the sal shield divided into paired lateral and dorso-
trichobothriawithfewlongbranches,theanterolat- lateralsclerotizedzones), and, havingtherounded
eral margins of the dorsal shield projected as cor- genital ring (Fig. 6), it is a male (labidostommatid
nua, the regressive famulus, the proximal tooth on femaleshaveanovalano-genitalring).
323
BertrandM.etal.
FIGURE2: Eunicolinaglaesin. sp.: A–Genuandtibia,firstpairoflegs,rightside,dorsalview;B–Firstleg,leftside,lateralview;C
–Ventralview,detailoftheproximalarticlesoflegI,IIandacetabulumoffourthleg(thelegIVisnotrepresentedhere);D–The
tridactyloustipofthetarsusII,lateralview.Abbreviations:epI:firstepimeralplate;ge:genu;PI,PII,PIII,PIV:Legs1to4;ti:tibia.
324
Acarologia55(3):321–336(2015)
FIGURE 3: . Eunicolinaglaesin. sp.: A–Dorsalshield,anteriorpart; B–Detailoftheposteriortrichobothrium; C–Ventralviewof
epimeralplatesanddetailofornamentation.Abbreviations:AS:additionalposteriorseateoftheinfracapitulum;bo.a,bo.p:anterior
andposteriorbothridia;CH:Chelicera;cha,chbcheliceralsetae;gr,la:ocularandlateralsetaeofthedorsalshield;PI,PII:legsIand
II;Pp:palp.ω1:tarsalsolenidionofthepalp.
325
BertrandM.etal.
FIGURE 4: Eunicolinaglaesin. sp.: A–Theholotypepiece, CHHC588-13(Hoffeinscollection); B–Lateralviewofthespecimenof
Eunicolinaglaesisp.nov.;C–VentralviewofinfracapitulumandlegI.
FIGURE 5: Eunicolinaglaesin. sp.: A–Oculo-pustularzone. bo.p: trichobthria, la?: supposedinsertionofthelaseta; lb: setalb; ly:
post-ocularlyriformorgan;B–DetailofthePItarsusshowingthebidactylusclaw,oneofthetwotarsalsolnidia(ω). F?: possible
famulusofthetarsus.Someinsertionsofsetaearemarkedbycircles.
326
Acarologia55(3):321–336(2015)
FIGURE6: Genito-analarea: A–Dispositionofgenitalandanalshields(drawnfromtheextantspeciesE.travei)Aa,Ab: ventralview,
female(a),male(b);Ac:malelateralview.Eunicolinaglaesin.sp.:B-C–extremityoftheopisthosoma,lateralview(B)andinterpre-
tation(Ca,Cb,Cc).
Description — The habitus is that of an animal polygonal pattern extends onto the articles of the
with a rounded body, robust, well-sclerotized, yel- legsandonthechelicerae,butnotonthepalps.
lowtobrownincoloration.
Dorsal shield — Chaetotaxy as for the genus
(Figs 1A, 3A), the dorsal setae are long, (la – le c.
Dimensions and proportions — Body length (c.
75 – 100 µm, da – de c. 75 – 80 µm), anterior setae
580–600µm)isabout1.7timesitsmaximumwidth
ga, ge,andgmlessvisibleorbroken, theirpresence
(c. 390 – 400 µm), about as wide as high (Figs 1A,
revealedonlybythemarkofinsertion. Thesetaegr
3B,3C).
areshort(<40µm). Thetrichobothriaaresimilarto
Cuticleornamentationandcerotegument—The those of E. travei Coineau, 1964, with 3-4 branches.
cuticle is ornamented with more or less rounded Withmorethan100µminlength,thebothridialse-
alveoli: the dorsal shield is covered with a regular tae are longer than the lateral and the dorsal setae
polygonal pattern laterally, whereas partitions are (Figs 3A, B). The frontal edge of the dorsal shield
more rounded on the central zone of the dorsum, bears two cornua. Close to twenty pustules were
and on the ventral shields. The borders of alveoli counted on the lateral fields of the dorsal shield.
are crossed with more or less large costules (Fig. Oneachside,thefieldofthepustulesbeginsatthe
1C). As in other representatives of the genus, the level of the second coxal plate. In the usual posi-
327
BertrandM.etal.
tionofthelateraleyes,closetothe(gr)setae,acon- ticlesofthefirstpairoflegsarethick,andnotelon-
vex structure (Figs 1A, 1B, star) could be either a gated as in the other genera of labidostommatids.
pustuleorthelateraleye(theusualstriationofthe However,asymmetrybetweenrightandleftlegsof
lens surface, different from the smooth surface of thefirstpairatteststhateitherthefossilisationpro-
thepustules,isnotvisible). Nomediananterioreye cess or optical properties of amber induced some
wasdiscernible. Thelaterallyrifissure, poorlypre- deformation,thelegsoftherightsidekeepingmore
served, may be located between the most anterior "natural" proportions. The third leg is missing on
pustules. The density of the pustules is maximal the left side. The alveolate ornamentation of the
behindthesupposedlateraleye(Figs1A,1B,5A). legsissimilartothatoftheshields,butlocallyitis
resolvedincristulesasontheedgesofthegenuand
Ventralview—Theposteriorendoftheventral
tibiaoflegI(Fig. 2A).Thegenu,isshorterthanthe
shieldisdamaged,hencetheanalscleriteswerenot
telofemurandtheseparationofthefemorainthree
seen and the genital ones were only partially ob-
articles is functionally reduced to basi- and [meso-
servable. Theinfracapitulum(162µmlong,150µm
telo]femora, dueto"ankylosis"ofthedistalarticle
wide)isornamentedbyalveoli,thepairofsetaemb
ofthefemora(Figs2A,2B)alreadydescribedinthe
is well visible, plus at least one pair of additional
extantspecies(Coineau1964).
posteriorsetae(ASonFig. 3C).Thelaterallipsare
narrowerthantheanteriormarginoftheinfracapit- Tarsiasforthegenus,tarsiII,III,IVaretridacty-
ulum. The palps (the right palp was well observ- lous, and tarsi of legs I bidactylous. The tarsi I
ableinventralview)arecharacteristicforthegenus areprovidedwithlongdorsalsetae,andontheleft
(1-1-3-4+ω), with the palpal solenidion identifiable leg,oneofthetwousualrecumbentsolenidia(ω)is
andthelongapicalseta(eupathidium?) (45–60µm clearlyvisible,andaspinewhich,byboththeposi-
long) (Figs 3C & 4C). The chelicerae are partially tionanditsshape,couldbeidentifiedasthefamu-
hidden by the first pair of legs and the palps, and lus(Fig.5B,F?).
cannot be observed in lateral view. The chelicerae
Differential diagnosis — By the characters de-
are robust (c. 250 µm long) and are strongly scle-
scribedhereabove,thereisnodoubtthatthisspec-
rotized,theproximalpartcoveredwithalveolaror-
imen belongs to the genus Eunicolina. The fossil
namentation. Examination in alternate dorsal and
species is distinct from the extant members of the
ventral views permitted identification of the ante-
genus by the supposed absence of frontal eye, re-
riorseta(chb)ofthefixeddigitandthelongposte-
ducedlateraleyesandbythelowernumberofpus-
riorsetacha,whoseinsertionwasnotseen(Figs3A,
tulesthaninmodernspecies. Itclearlydiffersfrom
3C).Thecoxisternalarea(Fig.3C)isarmoured,scle-
E. nova (Sellnick, 1931b), which has 20 to 35 pus-
rotized and ornamented with strong alveoli (Fig.
tules, by absence of neotrichy; from E. travei – by
3C), the epimeral setae are poorly preserved, and
the absence of modified integument near the pos-
onlysomesimplesetaewereidentifiedontheante-
terior trichobothria. On the ventral surface of the
riorfringeofthefirstepimeralplates.
infracapitulum it clearly differs from both E. travei
Atthelevelofthefourthepimera,oneachside, andE.nova,theselatterspecieshavingrespectively
the integument forms a large cavity, a pit, that re- (ma)and(mb)and4-5or7pairsofinfracapitularse-
ceivesthebasalpartsofthelegsIV("puitstégumen- tae,whileE.glaesishowstwopairsofinfracapitular
taire"inCoineau1964).Thecuticleofthesehollows setae: (mb) and one other pair with discernible in-
iscoveredwithdensevilloseintegumentsimilarto sertionmarks.
whathasbeenobservedincongenericspecies(PT,
Remark — The pustules of Eunicolina mites are
Figs1D,2C)(cf. Coineau1964;Feider,Vasiliu1968).
distributed "on each side from the level of the leg
Legs(Figs1A,2A,2D)—Thelegsarerobustand IIand extending uninterrupted caudad andabsent
sclerotized,thepolygonalpatternornamentationof from a short space of the posterior end of the dor-
thebodyiscontinuedonthearticlesanddiscernible sal shield" (Greenberg 1952), but each species dif-
onfemoraandgenuaonthefirstpairoflegs.Thear- fers by their number (Table 1). Berlese (1911) has
328
Acarologia55(3):321–336(2015)
TABLE1:ThetuberclesanddistributionsoftheEunicolinaspecies(datafromBerlese1911;Sellnick1931b;FeideretVasiliu1968;Vistorin,
1980;Coineau1964;Bertrand,1988)
Species Number of pustules Distribution Habitat
E. tuberculata ca 28–32. 5–6 anterior, 25 North Italy, Adriatic coast. fields, natural vegetal cover,
posterior to the eye. shrubs
E. porifera 30. None anterior to the eye. Virginia (USA) leaf mold
E. nova 20–35. First four are anterior to East Mediterranean basin, leaf litter, sclerophyllous
the seta gr Greece, Romania. Mediterranean forest
E. travei More than 40. More than 7 Mediterranean France under tree cover, under
anterior to the lateral eye. Mediterranean and temperate
climatic conditions, upper layer
of litter
E. glaesi n. sp. 18–20. None anterior to the Fossil, in Baltic amber unknown
seta gr
noted the arrangement of the pustules in two "se- DISCUSSION
ries" "tuberculi seriei marginalis 6 numero; marginal-
The family Labidostommatidae is homogeneous,
ibusserieusqueadmarginalisposticumproducta,ad25
and all the species are free-living, robust edaphic
numero",i.eatotalof31pustules,inE.tuberculata.E.
hunters, feeding on soft-bodied edaphic organ-
travei presents the largest neotaxy, with more than
isms, and living under dry tropical, subtropical or
40 pustules on each side, in E. nova the number of
temperate climates. The Labidostommatidae have
pustulesvariesfrom20to35oneachside(Sellnick
poor abilities of dispersion, with no phoretic be-
1931b;FeiderandVasiliu1968). Thefourthspecies,
havioureverrecorded. Labidostommatidsarepro-
theAmericanE.poriferaGreenberg,1952,fromVir-
tected by a cuticle ornamented with alveolar mi-
ginia,averages30pustulesoneachside(Greenberg
crosculpture interpreted as an adaptation to heavy
1952).
rains: this alveolated structure prevents the cuti-
clefromcomingintodirectcontactwithwater(Al-
berti 2013). This clade is primitive, and may de-
rive from the most ancient lineages, the older fos-
Etymology — from "glaesum", term, used by
sil material of which, currently assigned to other
PlinytheElder(77)foramber".../... certumestgigni
primitive Prostigmata (Sphaerolichida and Eupod-
in insulis septentrionalis oceani et ab germanis appel-
ina) comes from the early Devonian (c. 410 Ma)
lariglaesum,itaqueetabnostrisobidunaminsularum
Rhynie Chert of Scotland (Hirst 1923; Dunlop and
glaesariam appellatam, .../... nascitur autem defluente
Selden2009).
medulla pinei generis arboribus .../...". Translation: It
is well established that the amber is a product of The genus Eunicolina Berlese, 1911 successfully
islands in the Northern Ocean, that the Germans navigatedthemid-Eocene-Oligocenetransitionand
named"glaesum",andthat,asaresult,oneofthese later environmental changes. By application of the
islandswasnicknamed"Glaesaria"byour(legion), principle that the life environment of extant or-
.../... (Amber is) formed of a liquid seeping from ganisms allows understanding the life conditions
theinteriorofaspeciesofpine.../... [adaptedfrom of neighbour extinct species, the discovery of E.
Woolley’stranslation(1969)]. glaesi n. sp. is congruent with the classic recon-
329