Table Of ContentPROCEEDINGSOFTHEBIOLOGICALSOCIETYOFWASHINGTON
Ul(l):153-157. 1998.
Pagurus retrorsimanus (Crustacea: Decapoda: Paguridae), a new and
distinctive hermit crab from the eastern Pacific
Mary K. Wicksten andPatsy A. McLaughlin
(MKW)DepartmentofBiologyTexasA&MUniversityCollegeStation,
Texas77843-3258,U.S.A.;
(PAM)ShannonPointMarineCenterWesternWashingtonUniversity 1900ShannonPointRoad
Anacortes,Washington98221-4042,U.S.A.
—
Abstract. Pagurusretrorsimanus,anewanddistinctivehermitcrabspecies
from the eastern Pacific ofthe genus Pagurus Fabricius, is described and il-
lustrated. Itis immediately distinguishedfromotherrepresentativesofthege-
nus in the regionby its extremelymassiveright cheliped.
While sorting and identifying specimens 3.8). Naples Reef, ca. 18 mi. N. of Santa
ofhermit crabs from the collections ofthe Barbara, 11-15m,Jun-Jul 1976,coll.Gary
AllanHancockFoundation,nowtransferred Robinson, female ov. (SL 3.1), male (SL
totheLosAngelesCountyMuseumofNat- 3.6), male (SL 4.0). Becher's Bay, Santa
uralHistory(LACM),wediscoveredavery Rosa Is., 18 m, sand, 2 Aug 1938, Velero
unusual and undescribed hermit crab. One IIIsta. 881-38,femaleov. (SL3.2),female
of us (MKW) and other divers observed (SL4.3).Becher'sBay, 18m,sandandcor-
andphotographedthe crab inlife onrocky allines, 10 Aug 1939, Velero III sta. 995-
reefs ofCalifornia. The hermit crab is de- 39, femaleov. (SL2.8), male (SL2.5), fe-
scribedherein. male(SL2.8),female(SL2.4),female(SL
The material used for this study is de- 1.4), male (SL 1.5). Becher's Bay, 26 m,
posited in the collections of the Los An- sandandshell, 18Aug 1939, VeleroIIIsta.
geles County Museum of Natural History. 1003-39, male (SL 2.6). 2.6 mi. 360°True
The shield length, abbreviated as SL, has to E. Point, Santa Rosa Is., 50 m, 7 Nov
been measured in millimeters from the tip 1975, VeleroTVsta. 23206,femaleov. (SL
ofthe rostrum to the midpoint ofthe pos- 2.8). 2.6mi. 230°TruetoDiabloPt., Santa
teriormarginofthe shield, andisindicated CruzIs., 85-90m, 27 Apr 1976, VeleroTV
inparenthesisinthematerialexamined;ov. sta.24867,male(SL2.9).2.6mi. 105°True
indicates ovigerous female. to FraserPt., Santa Cruz Is., 44-66 m, 28
Apr 1976, Velero IVsta. 24873, male (SL
Pagurus retrorsimanus, new species 2.5).OffRedondoBeach,20-37m,gravel,
Figs. 1, 2 6 May 1940, Velero III sta. 1139-40, fe-
Pagurus sp. 2: Jensen 1995: 67, fig. 126. dmoalBeea(cShL,3.436),mf,emgaralveel(,SLMa3.y8).19O4f1f,Rceoldlo.nJ-.
Holotype.—Male (SL4.8),LACMnum- Burch, female (SL 3.2). Off Redondo
ber 40-113.13. Off Redondo Beach, Los Beach, 18-36 m, 31 Aug 1940, coll. T
Angeles County, California (33°49'55"N, Burch, female (SL4.7), male (SL5.5). Off
118°23'50"W), 20-37 m, gravel, 6 May Redondo Beach, 16 Jul 1939, Burch sta.
1940, VeleroI—IIsta. 1139-40. 3919, male (SL 3.1). Point Loma, San Di-
Paratypes. California, U.S.A.: Off ego, 12 m, "Grid 15," 23 Oct 1975, male
CanneryRow, Monterey, 11 m, onreef, 25 (SL6.2), withparasiticrhizocephalan.Baja
Jan 1975, coll. M.K. Wicksten, 1 male(SL California Norte, Mexico: Los Coronados
PROCEEDINGSOFTHEBIOLOGICALSOCIETYOFWASHINGTON
Fig. 1. Pagurus retrorsimanus, new species. A, shield and cephalic appendages ofmale; B, shield and
cephalicappendagesoffemale;C,maxilluleofmale;D,anteriorlobeofsterniteofthirdpereopodsofmale;E,
sterniteoffifthpereopodsofmale;F,telsonofmale;G,telsonoffemale.Scalesequal 1.0mm.
Islands, 28 m, 19 Jul 1901, Elsie sta. LIX- produced, and with small marginal or sub-
Hl, female ov. (SL 3.6), male (SL 3.4), marginal spine. Interocular lobes weakly
male (SL 3.8),—male (SL5.7). developed.Ocularpedunclesapproximately
Description. Shield(Fig. 1A,B)longer 2/3lengthofshield,butoverreachedbyboth
than broad (females) to slightly broader antennularandantennalpeduncles;corneae
thanlong (males); anteriormarginbetween slightlydilated. Ocularaciclestriangularor
rostrum and lateral projections usually subovate, with moderate to strong submar-
slightly concave; posterior margintruncate ginal spine; separated basally by less than
or rounded. Dorsal surface of shield with basalwidth of 1 acicle.
scatteredsetae,anteriorhalfgranulate.Ros- Antennular peduncles overreaching cor-
trum triangular, broadly rounded, or obso- neaebyVitoVilengthofultimatesegment;
lete. Lateralprojections obsoleteorweakly unarmed.
VOLUME 111,NUMBER
5mm 3mm
Fig.2. Pagurusretrorsimanus,newspecies. A,rightcheliped(dorsolateralview);B,leftcheliped(dorsal
view);C,rightsecondpereopod(lateralview);D,leftthirdpereopod(lateralview);E,dactylandpropodusof
leftsecondpereopod(mesialview);F,dactylandpropodusofleftthirdpereopod(mesialview);G,merusof
rightcheliped(mesialview). Scalesequal3.0mm(E,F)and5.0mm(A-D,G).Note:2Gwasdrawnfroma
differentspecimenthanthatillustratedinA-F
Antennal peduncle overreachingcorneae spine and often with 2 or 3 accessory spi-
by '/8toValengthofultimatesegment.Fifth nules on mesial margin; dorsomesial distal
and fourth segments unarmed. Third seg- angle with small spine. First segment with
mentwithspineatventrodistalmargin.Sec- small spine on dorsolateral distal margin;
ond segment with dorsolateral distal angle ventral margin produced and with 3 or 4
produced, terminating in simple or bifid smallspineslaterally.Antennalaciclemod-
PROCEEDINGSOFTHEBIOLOGICALSOCIETYOFWASHINGTON
erately short, terminating in small spine, with row ofclosely-spacedcorneous teeth,
and with row of tufts of setae on mesial terminating in small corneous claw; dorsal
margin. Antennal flagellum with very few surfaceunarmed,butwithfewscatteredse-
scatteredsetae. taedistally,ventralsurfacewithrowoftufts
Palpofmandible3-segmented.Maxillule of stiff setae. Fixed finger with 2 or more
(Fig. 1C) with external lobe of endopod rows oftufts of stiff setae on ventral sur-
somewhat produced, slightly recurved. face, dorsal surface withfewtufts adjacent
Maxillawithendopodslightlyoverreaching tocuttingedge,latterwithrowofsmallcal-
scaphognathite. Firstmaxillipedwithmod- careous teeth interspersed with corneous
erately slender exopod; endopod approxi- teeth and terminating in small corneous
mately 2/3 length ofexopod. Third maxilli- claw. Palm and fixed finger roundly trian-
pedwith well developed cristadentataand gular in cross section, margins not delim-
1 accessory tooth; merus and carpus un- ited; dorsal surface sometimes with few
armed. Sternite of third maxillipeds with minutespinulesortuberclesonmesialhalf.
small spineon eithersideofmidline. Carpusapproximatelytwicelengthofpalm
Rightcheliped (Fig. 2A) extremelymas- andequaltolengthofmerus;subtriangular;
sive; dactyl % to Vi length ofpalm; articu- dorsal surface withirregularsingleordou-
lating obliquely with very short fixed fin- ble row of very small spines, extending
ger; cutting edge of dactyl with 1 very ontomesiodistalmargin; ventrolateralmar-
broad calcareous tooth proximally and 3 gin with few spines distally. Merus sub-
smaller calcareous teeth distally, terminat- triangular; ventromesial and ventrolateral
ing in strong calcareous claw; cuttingedge margins each with row of small to minute
offixed finger withbroad calcareous tooth spinules. Ischiumunarmed.
proximallyandfewsmallercalcareousteeth Secondleftandrightpereopods(Fig.2C,
distally, terminating in strong calcareous E) and third right pereopod similar; third
claw. Palm very broad and dorsoventrally left with distinctly different dactyl and
compressed, dorsomesial and dorsolateral propodus from these (Fig. 2D, F). Dactyls
margins not delimited. Dorsal and ventral ofsecond andright third approximately as
surfacesofdactyl,fixedfinger,andpalmall long andbroadaspropodi; ventralmargins
with flattened, plate-like tubercles, particu- with 10-14corneousspinesonventralmar-
larly densely packed marginally. Carpus gins; dorsal margins with irregular row of
short and broad, with lateral face strongly small corneous spinules or bristles, mesial
produced ventrally, dorsolateral and dor- faces each with dorsal and ventral rows of
somesialmargins notdelimited, distalmar- corneous spinules. Propodi each with 2 or
gin tuberculate; all surfaces covered with 3 corneous spines atventrodistalangleand
densely packed flattened tubercles at least row of small corneous spines on ventral
in distal halves. Meral-carpal articulation margins. Carpiwithrowofvery smallspi-
twisted at approximately 75° counterclock- nules on dorsal margins, strongest on sec-
wise. Merus approximately as long as car- ond. Meri with 1 or2rows ofminute spi-
pus, withfewblunt spinulesondorsodistal nules on ventral margins. Ischia unarmed.
margin and row of small spinules on dis- Thirdleftpereopodwithdactylslightlylon-
tomesial margin; ventrolateral margin with gerthanpropodus,broader(inlateralview)
row ofsmall acute orblunt spinulesdistal- proximally and tapering to claw; ventral
ly;ventromesialmarginwithstrong,broad, marginwith 13 or 14corneous spines;me-
blunttubercle.Ischiumwithrowofbluntor sialfacewithsinglerow(dorsally)anddou-
acutetubercleson ventromesialmargin. ble row (ventrally) of small corneous
Left cheliped (Fig. 2B) reaching only to spines. Propodus also broad (in lateral
proximal halfofright palm. Dactyl nearly view), ventral margin with row of minute
1 Vz times longer than palm; cutting edge corneous spinules, 3 or4 strongerspinules
—
atdistal angle. Carpus, merus, andischium danus, it is the carpal-propodal articulation
as inthirdright. that is twisted from the perpendicular. InP.
Sterniteofthirdpereopodswithsubsemi- retrorsimanus, itis inthemeral-carpalartic-
circular,setoseanteriorlobe(Fig. ID).Ster- ulationthatthetwistingoccurs.
nite of fifth pereopods (Fig. IE) with 2 This species exhibits sexual dimorphism,
broadly separated, setoselobes. butinamannerdifferentfromotherPagurus
Fourth pereopods without definitive species.Ratherthantherightchelipedexhib-
preungualprocessatbaseofclaw.Proposal itingdimorphicattributes,inP.retrorsimanus
raspconsistingofseveralrowsofcorneous largemales(SL>5.0mm)arecharacterized
scales. byanobsoleteormarkedlyreducedrostrum,
Uropods markedly asymmetrical. Telson ashieldthatisbroaderthanlongandhaving
(Fig. IF G) with distinct transverse suture; anearlystraightoronlyveryweaklyconcave
posteriorlobes separated by shallowmedian anterior margin, and a telson with only the
cleft; terminal margins oblique, each armed outermost spines appreciably larger. In con-
with 3-5 strong spines and several smaller trast, females have triangular, acute rostra,
spines, outermost, andsometimesalsoinner- shields that are appreciably longer than
most, strongest; lateral margins weakly chi- broad, with distinctly concave anterior mar-
tinized. — gins, andtelsonwith strong spinesinthein-
Color in life. Ocular peduncles and an- nermostas wellas outermostpositions.
tennules dark, translucent blue. Dark blue Pagurus retrorsimanus does not appear
ring at base of ocular peduncles. Antennal to have any close relatives among eastern
flagellum translucent reddish. Third maxilli- Pacific Pagurus species. It shares withPa-
peds orange-red. Shield flesh-colored, with gurus hemphilli (Benedict 1892) the ven-
two large and few smaller brown spots. trallyproducedcarpusoftherightcheliped
Walking legs, entireminorchelipedandma- and the slightly recurved external endopo-
jor cheliped except for propodus and dactyl dal lobe ofthe maxillule (cf. McLaughlin,
covered with dark red specks, giving crab a 1974), butthere the similarityends.
reddish color when seen from a distance.
Palmandfingersofmajorchelausuallybone Acknowledgments
white,rarelyals—ocoveredwithred specks. The late Janet Haig ofthe University of
Distribution. Monterey, California to Southern California was the first to recog-
Los Coronados Islands, Baja California nizethishermitcrabasanundescribedspe-
NorEttey,moMleoxgiyc.o—; T1h1e-90spmec.ific name is de- ccioelsl,ecatnidonlsocoaftetdhespAelcliamnenHsanocfoitckamFoonugndtah-e
rivedfromtheLatinretrorsusmeaningbent tion. The figures were drawn by G. Fain
or turned backward, and manus meaning Hubbard. This is a scientific contribution
hand. Thenameis anouninapposition. In fromthe ShannonPointMarine Center.
life, the majorchelaisbentunderneaththe
body and a—ppears to beturnedbackwards. LiteratureCited
Remarks. Pagurus retrorsimanus is dis-
btuitngaulissohebdynottheovnleyrybybriotasdm,abslsuinvtetruibgehrtclceheolna Benedictntyu,-ssJ.eEvuDep.nagn1u8er9wu2.sspiPenrceitlehsiemUoi.fnSah.reyNramdtieitsoccnrraialpbtMsiouonsfsetouhfmet.hgier--
the ventromesial margin ofthe merus ofthe ProceedingsoftheUnitedStatesNationalMu-
right cheliped. At first glance, the shape, seum 15:1-26.
structure and positioning of the right chela Jensen,G.C. 1995. Pacificcoastcrabsandshrimps.
with the dorsal surface in a lateral position SeaChallengers,Monterey,California.87pp.
aCraelcrienmuisnisspceecniteso.fHtohewelvefetr,cheilnipCeadlscionfuss,omaes McLaughADlmeiecnra,ipcoaPd..a—A,.ZPoao1g9l7uo4rg.iidsecTahh)eeVoheferrhmnaiontrdtechlrwiaenbsgsetne(rCNnrou.sNtoa1rc3t0eh:a
wellasinotherdiogenidgenerasuchasDar- 1-396.
