Contribution to the knowledge of the family Caecidae: 16. Revision of the Caecidae of Easter Island (Chile) (Caenogastropoda: Rissooidea Gray J. E.,1847)

2005·11.4 MB·English

by  Bret Raines

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SociedadEspañola deMalacología Iberus, 23 (1): 49-65, 2005
Contribution to the knowledge ofthe family Caecidae: 16.
Revisión of the Caecidae of Easter Island (Chile)
(Caenogastropoda: Rissooidea Gray E., 1847)
J.
Contribución al conocimiento de la familia Caecidae: 16. Revisión
de los Caecidae de la Isla de Pascua (Chile) (Caenogastropoda:
Rissooidea E. Gray, 1847)
J.
Bret RAINES* and Mauro PIZZINI**
Recibido el26-X-2004. Aceptadoel11-11-2005
ABSTRACT
With the exception oftwo species, members ofthefamilyCaecidae from Easter Island have
been previously neglected. Based on type and additional material, a revisión ofthe species
known to date from Easter Is. is herein proposed, with the description of 5 new species:
Caecum rehderi spec. nov., C. heterochromum spec. nov., C. pascuanum spec. nov., C.
rapanuiense spec. nov., C. campanulatum spec. nov.
RESUMEN
Con la excepción de dos especies, los miembros de la familia Caecidae de la Isla de
Pascua han sido previamente desatendido. Basado en el tipoyen el material adicional, se
propone aquí dentro, una revisión de las especies conocidas hasta la fecha de la Isla de
Pascua, y incluye la descripción de 5 nuevas especies: C. rehderi esp. n., C. heterochro-
mum esp. n., C. pascuanum esp. n., C. rapanuiense esp. n., C. campanulatum esp. n.
KEY WORDS: Mollusca, Caenogastropoda, Rissooidea, Caecidae, taxonomy, new species, Easter Island,
WesternPacific.
PALABRAS CLAVE: Mollusca, Caenogastropoda, Rissooidea, Caecidae, taxonomía, nuevas especies, Isla de
Pascua, PacíficoOccidental.
INTRODUCTION
Easter Island (Fig. 1) is found inato- graphical province from the Polynesian
tally isolated position approximately province. The submarine seascape fea-
3,500KmfromthecoastofChile. Froma tures widely scattered coráis affixed to
zoogeographicalpoint ofview, Easter Is. the rugged volcanic substrate. The de-
is inaverypeculiar áreawithintheeast- paupératebenthiccommunityemploysa
ern Indo-Pacific región, and to thepoint varietyofadaptivestrategiesforsurvival
that, in 1965, Schilder proposed the Ra- in an environment stressed by waves,
panuian province as a sepárate biogeo- currents and the absence ofmineral nu-
* ResearchAssociate, Natural HistoryMuseum ofLosAngelesCounty, P.O. Box612Victorville, CA92393
USA. e-mail: [email protected]
**LargodellaCaffarelletta, 6, 00179 ROME (Italy). e-mail: [email protected]
49
Iberus, 23 (1), 2005
trients. Mostofthe coráis and otherbot- been completed during the last ten
tominvertebratesaretypicaloftheIndo- years. With regard to Caecidae, during
Pacificreefs,butreefshavenotformed. the three trips to Easter Island, the
The circulation pattern, and espe- authors of the present work collected
cially the marked upwelling between more than 350 specimens of this family.
the South Pacific and Mentor currents, Rehder mentions only two species:
contributes to the isolation of the área. Caecum cf. solitarium Oliver, 1915, and C.
In terms of marine ecosystems, this in- amydroglyptum Rehder, 1980. In all other
sularityhas alsoproduced ahighdegree publications, which we have reviewed,
ofradiationinmany groups, and partic- Caecidae are listed simply as 'Caecum
ularly in the caenogastropods. Thus the species'. No other descriptions or illus-
fauna can essentially be described as trationswereprovided.
typical Pacific fauna with a relatively So we present herein a revisión of
highnumber ofendemic species. The is- the species known to date from Easter
land's marine benthic fauna is generally Is., based on type and additional mater-
characterised by a high degree of ial, with the description of five new
species diversity and a low abundance, species.
and this is true for both hard and soft
bottoms. The meiobenthic family Caeci- Abbreviationsused:
daealsofollowsthispattern.
The Caecidae of the Easter Island AMS: Australian Museum Sydney,
have been scarcely studied in the past, Sydney (Australia)
with the exception of the work of CM: Canterbury Museum, Christchurch
Rehder (1980). Past surveys have (NewZealand)
reported endemicity rates within the LACM: Natural HistoryMuseum ofLos
molluscan fauna ranging from 37% to AngelesCounty,LosAngeles(U.S.A.)
42% (Rehder, 1980, DiSalvo, Randall MNHN: Museum National d'Histoire
and Cea, 1988, Raines, 2002). Rehder Naturelle,Paris (France)
also indicates that some species appear MPR: MauroPizzinicollection.
to have a dual relationship with certain NHML: Natural History Museum,
species from Hawaii, as well as species London(U.K.)
from the Kermadec Islands. In prepara- NMNZ: Museum of New Zealand Te
tion for his 1980 publication, Rehder Papa Tongarewa, Wellington (New
reviewed all previous studies and expe- Zealand)
ditions. In addition to examining all the NSMT: National Science Museum,
Easter Is. material in US museums, he Tokyo (Japan)
also examined the full store of material USNM: National Museum of Natural
housed in the Museo National de Histo- History,WashingtonD.C. (U.S.A.)
ria Natural in Santiago, Chile. In all, WAM: Western Australian Museum,
Rehder examined over 7,000 specimens, Perth(Australia)
ofwhich 3480 were collected during his
triptotheislandin 1974. Terminology:
In the mid 1980's, DiSalvo and his
teamconductedacomprehensivesurvey Abapical: towards the ápices (of the
of Easter Island's sublittoral marine septum)
environment. The authors ofthepresent Adapical: opposite to the ápices direc-
work had the good fortune of having tion(oftheseptum)
access to examples of all the molluscan Aperture, aperturalend: theroundante-
material collected during DiSalvo's rioropeningoftheshell.
investigation. Other than the few publi- Apex, apical,end: the smaller, narrower,
cations that we have been working on closedposteriorendofthetube.
(Oliver, 1915, Schilder, 1965, Rehder, Cutting plañe: the plañe individuated
1980,DiSalvoetal., 1988,Raines,2002) by the edge of the shell at the apex
no other serious work on molluscs has (excludingseptumandmuero).
50
RAINESAND PlZZINI: Revisión ofthe Caecidae ofEaster Island (Chile)
UNITED STA
Figure 1. Biogeographical provinces within the tropical eastern Indo-Pacific as proposed by
SCHILDER (1965), andas illustratedbyREHDER (1980): Micronesian: M; Hawaiian: H; Fijian: F;
Polynesian: P; Rapanuian: R; KermadecIslands: K(addedbytheauthors).
Figura 1. Lasprovincias biogeographicas dentro delIndo-Pacífico orientaltropicalpropuestaspor
SCHILDER (1965) eilustradasporREHDER (1980):Micronesian: M;Hawaiano: H;Fijian: F;Poline-
K
sio: P;Rapanuian: R;KermadecIslands: (añadidaporlosautores).
Interspace: área between rings, with / Rings, annular sculpture: transverse,
withoutmicrosculpture. raised sculpture (equivalent to the
Meiobenthic: referred to all interstitial axial sculpture of the normally
molluscs living in sediment of coiledgastropods).
varyinggranulesize. Septum: closure of the shell at the apex,
Microsculpture: usually visible at very asitshedsearlierstages.
highmagnificationorunderSEMcan Shell(s): the shell, beached without gas-
betransverse,longitudinalorboth. tropod.
Muero: small to large prong projecting Spm(s): live collected specimen(s), with
fromtheseptum. softpartsand/oroperculum(a).
RESULTS
SuperfamilyRissooideaGrayJ. E., 1847
Family Caecidae Gray E., 1850
J.
Genus Caecum Fleming, 1813
Diagnosis (Bandel, 1996): "The shell of the teleoconch is a small, slightly curved tube orna-
mentedonlywithgrowthlines,numerousring-likecollabralliraead/oraxialribs. Theposte-
riorendofthetubeisclosedbyaconicalseptum.Theprotoconchistrochospirallyorplanispi-
rallycoiled.Uncoilingoftheshellbeginsaftermetamorphosis".
Type species (Bandel, 1996): Dentalium imperforatum Kanmaker, 1798 (= trachea Montagu, 1803)
fromEurope,MediterraneanSeaandAtlantictosouthernEngland.
51
Iberus, 23 (1), 2005
Figure 2. Caecum rehderi spec. nov. A: holotype LACM 3019, gold coated, length 2.08 mm; B:
detailofseptum; C: microsculpture; D: detailofaperture. SEM imagingbyD. Geiger.
Figura2. Caecum rehderi spec. nov. A: holotipoLACM3019, metalizado en oro, longitud2,08 mm;
B: detalledelsepto; C: microescultura; D: detalledelaabertura. ImágenesalMEBporD. Geiger.
Caecum rehderi spec. nov. (Fig. 2)
Caecumcf.solitarium;Rehder,1980:31-32,pl.5,fig. 11.
Type material: Holotype, LACM 3019; 1 paratype, LACM 3020; 1 paratype, USNM 756269; 1
paratype,MNHN.
Materialexamined: 1 specimen,Onetea,Hotuiti(length:2.42mm,USNM756269) (Oct. 1974,leg.
H.Rehder);4specimens,PuntaRosalia,eastofAnakena(Apr. 1998,leg.B.Raines),
Type locality: In sand collected along thebase ofcliffs at 10-20m, offPunta Rosalia, east of
Anakena,EasterIs.,Chile.27°04' 18"S,109°19'45"W.
Description: Shell small (holotype withincised annular rings. Aperture cir-
measures, length: 2.08 mm; width: 0.42 cular, but slightly constricted. Posterior
mm), tube-like, slender, gently arched, end with tapered rim. Septum not
semi-translucent to opaque white. Tube retracted, subquadrate lateral outline
seemingly smooth almost glassy, sub- inclinedwithelevatededgeslightlyright
cylindrical, with posterior end only ofcenterwhenviewedfrontally. Opercu-
slightly smaller than anterior end. lumandsoftpartsunknown.
Microsculpture nearly obsolete, with Original description ofC. cf. solitar-
onlyfineannulargrowthlinessometimes ium Rehder, 1980: ''Diagnosis. Shell
mm
present under magnification. Anterior small, 2.4 to 2.7 in length, glassy,
end somewhatflaredjustaboveaperture grayish-white towhitish, slender, gently
52
RAINES AND PIZZINI: Revisión ofthe Caecidae ofEaster Island (Chile!
Figure 3. Caecum cf. solitarium Rehder (1980). A: USNM 756269, uncoated, length 2.42 mm; B:
detailofseptum; C: microsculpture; D: detailofaperture. SEM imagingbyD. Geiger.
Figura3. Caecumcf.solitariumRehder(1980).A: USNM756269, nometalizado, longitud2,42mm;
B:detalledelsepto; C: microescultura;D:detalledelaabertura. ImágenesalMEBporD. Geiger.
curved, diameter at posterior end only identified as Caecum cf. solitarium Oliver,
slightly smaller than at anterior end, 1915. However, itseems thatRehderun-
where the aperture is slightly con- fortunatelyoverlookedseveralkeychar-
stricted and somewhat opaque above acteristics within Oliver's description.
the aperture; the sculpture consists of The first being the septum of C. solitar-
fine, rather crowded, subobscure ium, which Oliver (1915) described as
(worn?) annular riblets that gradually "...hemispherical, making an abrupt
and slightly increase in strength toward shoulder at the junction of the shell";
the aperture; septum exserted, sub- even the septum of Rehder's specimen
quadrate with a slightly convex surface (Fig. 3) could be associated to a tale ty-
inclined from an elevated edge at the pology. Oliver also mentions, that the
right dorsal sector to the edge of the sculpture ofC. solitarium consists ofsim-
posterior rim of the shell at the left ple growth lines, while Rehder refers to
ventralsector. the sculpture as consisting of suboscure
Range. Kermadec Islands (and (worn?) annular riblets that gradually
EasterIsland ?). and slightly increase in strength toward
Material. 1 specimen from sta E-27A, the aperture. Other main difference be-
USNM756269. tween C. solitarium Oliver, 1915 and C.
Measurements (mm). USNM 756269: solitarium sensu Rehder is that the first
length,2.42;diameteratanteriorend,0.4". hasanearlyuniformdiameter,whilethe
Discussion: Rehder reported a caecid second shows the diameter at posterior
from Easter Island, which he tentatively end only slightly smaller than at ante-
53
Iberus, 23 (1), 2005
Figure 4. Caecum solitarium Oliver, 1915. A: Holotype CM M2867, uncoated, length 1.68 mm;
B: detailofaperture; C: microsculpture; D: detailofposterior. SEM imagingbyN.Andrews.
Figura4. Caecumsolitarium Oliver, 1915.A:Holotipo CMM2867, nometalizado, longitud1,68mm;
B:detalledelaabertura; C: microescultura;D:detalletrasero. ImágenesalMEBporN.Andrews.
rior end. Furthermore, it appears Re- small rings along the entire tube; and
hder did not examine Oliver's type ma- apart from the relativity of the term's
terial, because if he would have done, significance, we hold that the difference
hewouldhavenoted thatthe two speci- between our specimens and those de-
mens have significantly different ante- scribed by the two authors falls within
rior ends (Figs. 3D, 4B), and that the the species' range ofvariability, in light,
holotype ofC. solitarium isbadlybroken above all else, of the high degree of
and lacks the entire posterior end (Fig. adaptation of the local molluscs to the
4). The damage to the holotype is oíd island's distinguishing geo-climatic con-
and worn, and possibly occurred in situ ditions. It is known that a number of
suggesting thatOliver mayhave chosen species of Caecidae (i.e. C. lightfootae
an imperfect specimen as the type and Pizzini, Nofroni and Oliverio, 1994),
actually described another in his de- though they have the same general
scription. (Scofield, 2002, pers. commu- shape (septum, tube and aperture),
nication). Rehder's specimen is, how- could show a very wide range of vari-
ever, consistent with C. rehderi, and abilityintermsofthetypeofsculpture.
therefore, has been designated as the Remarks: Caecum rehderi seems to be
paratype. Although Rehder broke the an unusually fragüe species. Of the five
anterior end ofhis specimenwhile mea- known specimens, Rehder chipped the
suring it, all the pieces were available aperture of his specimen (USNM
for examination. The specimens which 756269)whilemeasuringit,theholotype
we found, actually showed a series of has a small longitudinal crack toward
54
RAINESAND PIZZINI: Revisión ofthe Caecidae ofEaster Island (Chile)
Figure5. CaecumamydroglyptumRehder, 1980.A: holotypeUSNM757977, uncoated, length 1.67
mm; B: detailofseptum; C: microsculpture; D: detailofaperture. SEM imagingbyD. Geiger.
Figura5. CaecumamydroglyptumRehder, 1980.A:holotipo USNM757977, nometalizado, longitud
1,67mm;B:detalledelsepto; C:microescultura;D:detalledelaabertura. ImágenesalMEBporD. Geiger.
the aperture end, the otherparatype has the Kermadec Islands, while Rehder
a chip in the aperture, and the júnior tentatively indicated the species as
author completely crushed another being from Easter Is. In our opinión,
specimenwhileexaminingit. according to the present knowledge, C.
Geographical distribution: Oliver solitarium is restricted to the Kermadec
described Caecum solitarium only from Is.
Caecum amydroglyptum Rehder, 1980 (Figs. 5, 6)
Caecumamydroglyptum;Rehder,1980:32,pl.5,fig. 12.
Typematerial:Holotype,USNM757977;1paratype,USNM757978
Materialexamined:Originaltypes.Holotype,USNM757977;paratype,USNM757978,(Oct.1974,
leg.H.Rehder).132specimensinsandcollecWtedalongthebaseofcliffsat10-20m,offPuntaRosalia,
eastofAnakena,27°04'18"S,109°19'45" (Apr. 1998,leg.B.Raines).
Vouchermaterial:4specimensweredepositedineachofthefollowinginstitutions:LACM;USNM
1018792;MNHN;NHML;NMNZM.273207;NSMTMo73562;AMSC.205278;WAMS13783,and
6specimens(3adults/3juveniles),MPR.13shells,beachofAnakenaBay,onthenortherncoastof
EasterIs.,pickedupamongtherockybottomonthewestsideofthebayatlowtide,amongcom-
munitiesofDictyotales,withGalaxauraobtusata. (12-1-1995,leg.E.Rolan),MPR.
Typelocality:StationE-27A,Onetea,Hotuiti:inpatchofsandabovehightidelevel.
55
Iberus, 23 (1), 2005
Figure 6. Caecum amydroglyptum Rehder, 1980. A: Voucherspecimen LACM, gold coated, length
1.53 mm; B: detail ofseptum; C: microsculpture; D: detail ofaperture. SEM imaging by D.
Geiger.
Figura6. Caecum amydroglyptumRehder, 1980.A:ElespécimendelvaleLACM, metalizadoenoro,
longitud1,53 mm; B: detalledelsepto; C: microescultura;D: detalledelaabertura. ImágenesalMEB
porD. Geiger.
Original description: "Shell small, the shell being less raised and changing
mm
from 1.3 to 1.7 in length, curved, their shape, until they resemble very
rather evenly cylindrical with the ante- fine growth lines. Microsculpture
rior end in fully grown specimens formedbylongitudinalworm-like striae
slightly swollen above the aperture; visible at enlargement of at least 180x.
glassy grayish white to light orange Septum dome-shaped, slightly raised
yellow in color; sculpture consists of overthe cuttingplañe. Aperture consist-
rather strong, somewhat distantly ing of a large protuberance crossed by
spaced annular ribs that become more slightly raised rings. Operculum and
or less obscure in the middle part of the softpartsunknown.
shell, with microscopic, longitudinal Remarks: We agree totally with
wavy striae that are obscure at the ante- Rehder's conclusions; because we have
rior and posterior ends; septum, low, "...been unable to identify this species with
dome-shaped. " any published taxon" from either the
Additional description: Shell small Indo-Pacific Provinces, the Panamic
(mean length: 1.7 mm; width: min. 0.3 Prov. or the Chilean Prov. We have
mm, max 0.4 mm), curved, colour foundonlyonespeciesthatresembles C.
grayish white. The tube is perfectly amydroglyptum, which is C. vertébrale
cylindrical, except near the aperture, Hedley, 1899, from Funafuti Is. It is
and its sculpture consists of about 36-40 quite similar to amydroglyptum in terms
rings, with some in the middle part of ofthesculpture ofthetube,longitudinal
56
RAINESAND PlZZINI: Revisión ofthe Caecidae ofEaster Island (Chile)
Figure 7. Caecum heterochromum spec. nov. A: holotype LACM 3021, gold coated, length 1.42
mm; B: detailofseptum; C: microsculpture; D: detailofaperture. SEM imagingbyD. Geiger.
Figura7. Caecumheterochromumspec. nov.A:holotipoLACM3021, metalizadoenoro, longitud1,42
mm;B:detalledelsepto; C:microescultura;D:detalledelaabertura. ImágenesalMEBporD. Geiger.
microsculpture and septum, but the tube, a very strong microsculpture
Rehder's species shows a much greater consisting of worm-like, longitudinal
swelling of the tube above the apertural striae, covering also the top ofthe rings,
end, which is crossed by small sculp- while that of vertébrale is an indistinct
tured rings, while the adapical part of microsculpturenotsurelycomparableto
vertébrale has almost the same diameter arealstriation (pers. observ.).
of the tube. In addition, C. amydroglyp- Geographical distribution: This species
tum presents, along the entire length of would appeartobelimited toEasterIs.
Caecum heterochromum spec. nov. (Figs. 7, 8)
Type material: Holotype,LACM3021;6paratypes, LACM3022;6Paratypes,USNM 1018789;6
Paratypes,MNHN; 6Paratypes,NHML; 6Paratypes,NMNZM.273205; 6Paratypes,NSMTMo
73560;6Paratypes,AMSC.205275;6Paratypes,WAMS13780;9Paratypes,MPR.
Material examined: 168 specimens: offHanga Nui; and 8 specimens offthe western coastline
near Tahai (Dec. 2000, leg. B. Raines). 39 shells,beach ofAnakena Bay, on the northern coast of
Easter Is., picked up among the rockybottom on the west side ofthebay at low tide, among
communitiesofDictyotales,withGalaxauraobtusata.(12-1-1995,leg.E.Rolan)MPR.
Vouchermaterial:39shells,beachofAnakenaBay,onthenortherncoastofEasterIs.,pickedup
among the rockybottom on the westside ofthebay atlow tide, among communities ofDicty-
otales,withGalaxauraobtusata. (12-1-1995,leg.E. Rolan)MPR.
57
Iberus, 23 (1), 2005
Figure 8. Caecumheterochromumspec. nov.A: paratypefromlotLACM 3022, goldcoated, length
1.53 mm; B: detailofseptum; C: microsculpture; D: detailofaperture. SEMimagingbyD. Geiger.
Figura8. Caecumheterochromumspec. nov.A:paratipodelaporciónLACM3022, metalizadoenoro,
longitud1,53 mm; B:detalledelsepto; C: microescultura; D: detalledelaabertura. ImágenesalMEB
porD. Geiger.
Type locality: In sand collected along thebase ofcliffs at20m offHanga Nui, EasterIs.,Chile.
27°07'46"S,109°16'35"W.
Derivationoftheñame:Fromthegreekeiepoc,:otherandxpcojxa:colour.
Description: Shell small (mean sponding breadth and depth, particu-
length: 1.6 mm; mean width: 0.4 mm) larly in the upper portion of the tube
with the tube subcylindrical in shape in andneartheaperture,toothersthatlack
the abapical part and cylindrical up to anytypeofsculpture;thesetwoextreme
the vicinity of the aperture (Fig. 8), representthe limits ofthe species' range
where there is a slight swelling, fol- of variability, given that they were
lowed by a narrowing of the tube; the found in intermedíate specimens whose
apertureisperfectlycircular, simple and rings arebarelyvisible. The microsculp-
rimmedby a very slightflaring towards ture also presents a wide range of vari-
theoutside. Theseptumisdome-shaped ability, with some specimens not
and slightly raised over the cutting showing any trace of microsculpture,
plañe. Its sculpture is extremely vari- while the surface of other specimens, at
able, ranging from specimens with an enlargement of 30x, presents a
approximately50 smallraised rings that microsculpture consisting of a large
are separated by interstices of corre- number of very fine, worm-like striae
58