The terrestrial Isopoda (Crustacea, Oniscidea) of Rapa Nui (Easter Island), with descriptions of two new species

Abstract

Nine species of terrestrial isopods are reported for the Polynesian island of Rapa Nui (Easter Island) based upon museum materials and recent collections from field sampling. Most of these animals are non-native species, but two are new to science: Styloniscus
manuvaka
sp. n. and Hawaiioscia
rapui
sp. n. Of these, the former is believed to be a Polynesian endemic as it has been recorded from Rapa Iti, Austral Islands, while the latter is identified as a Rapa Nui island endemic. Both of these new species are considered ‘disturbance relicts’ and appear restricted to the cave environment on Rapa Nui. A short key to all the oniscidean species presently recorded from Rapa Nui is provided. We also offered conservation and management recommendations for the two new isopod species.

Full text

e terrestrial Isopoda (Crustacea, Oniscidea) of Rapa Nui (Easter Island)... 27
The terrestrial Isopoda (Crustacea, Oniscidea)
of Rapa Nui (Easter Island), with descriptions
of two new species
Stefano Taiti1, J. Judson Wynne2
1 Istituto per lo Studio degli Ecosistemi, Consiglio Nazionale delle Ricerche, Via Madonna del Piano 10, 50019
Sesto Fiorentino (Florence), Italy 2 Department of Biological Sciences, Colorado Plateau Biodiversity Center,
Northern Arizona University, Box 5640, Flagsta, Arizona 86011-5614, USA
Corresponding author: Stefano Taiti (stefano.taiti@ise.cnr.it)
Academic editor: D. Bouchon|Received 28 February 2015|Accepted 18 May 2015 |Published 30 July 2015
http://zoobank.org/56B35C30-E575-402C-8480-E73A7E463137
Citation: Taiti S, Wynne JJ (2015) e terrestrial Isopoda (Crustacea, Oniscidea) of Rapa Nui (Easter Island), with
descriptions of two new species. In: Taiti S, Hornung E, Štrus J, Bouchon D (Eds) Trends in Terrestrial Isopod Biology.
ZooKeys 515: 27–49. doi: 10.3897/zookeys.515.9477
Abstract
Nine species of terrestrial isopods are reported for the Polynesian island of Rapa Nui (Easter Island) based
upon museum materials and recent collections from eld sampling. Most of these animals are non-native
species, but two are new to science: Styloniscus manuvaka sp. n. and Hawaiioscia rapui sp. n. Of these, the
former is believed to be a Polynesian endemic as it has been recorded from Rapa Iti, Austral Islands, while
the latter is identied as a Rapa Nui island endemic. Both of these new species are considered ‘disturbance
relicts’ and appear restricted to the cave environment on Rapa Nui. A short key to all the oniscidean spe-
cies presently recorded from Rapa Nui is provided. We also oered conservation and management recom-
mendations for the two new isopod species.
Keywords
Crustacea, Isopoda, Oniscidea, new species, Rapa Nui, Easter Island, disturbance relicts, caves
ZooKeys 515: 27–49 (2015)
doi: 10.3897/zookeys.515.9477
http://zookeys.pensoft.net
Copyright Stefano Taiti, J. Judson Wynne. This is an open access article distributed under the terms of the Creative Commons Attribution License
(CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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Stefano Taiti & J. Judson Wynne / ZooKeys 515: 27–49 (2015)
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Introduction
Rapa Nui (Easter Island) is one of the most ecologically degraded islands in Polynesia.
A number of factors including geographic isolation, island size and low topographic
relief (Rolett and Diamond 2004) predisposed Rapa Nui to dramatic human-induced
environmental change. Between Polynesian colonization (800–1200 CE; Hunt and
Lipo 2006, Shepardson et al. 2008) and prior to European contact in 1722 (McCall
1990), a catastrophic ecological shift occurred where the palm-dominated shrubland
shifted to grassland (Wynne et al. 2014). By the mid-nineteenth century, most of the
island was converted into a century-long sheep-grazing operation (Fischer 2005).
Contemporarily, few native plant species remain and all terrestrial vertebrates have gone
extinct (Wynne et al. 2014). Researchers have described the arthropod communities of Rapa
Nui as being equally impoverished (Kuschel 1963, Campos and Peña 1973, Desender and
Baert 1997). Of the nearly 400 known arthropod species, only 30 species (~5%) have been
identied as either endemic or indigenous with the remaining species either intentionally or
accidentally introduced to the island (Wynne et al. 2014, Bernard et al. 2015).
rough eldwork led by the second author, at least eight island endemic and
two Polynesian endemic arthropod species have been recently identied (Wynne et
al. 2014). ese include one psocopteran (Mockford and Wynne 2013), six species
of collembolans (including ve new species and one Polynesian endemic; Bernard et
al. 2015), one recently described collembolan later identied as endemic (Jordana and
Baquero 2008; Wynne et al. 2014), and the two new species of terrestrial isopods de-
scribed in this paper. All of these animals are presumed to be cave-restricted and repre-
sent disturbance relicts – organisms now restricted to a fraction of their former range
due to extensive anthropogenic disturbance (Wynne et al. 2014). Given that one-third
of the island’s endemic arthropod fauna appear restricted to the cave environment, this
oers a unique opportunity for conservation and management.
With the exception of the Hawaiian islands (Taiti and Ferrara 1991, Taiti and
Howarth 1996, 1997, Taiti 1999, Rivera et al. 2002, Taiti et al. 2003, Santamaria
et al. 2013), terrestrial isopods from Polynesia are poorly known (see Jackson 1941
for a review). For Rapa Nui, only three species of terrestrial isopods were previously
recorded (Fuentes 1914): Ligia exotica Roux, 1828, Porcellio scaber Latreille, 1804,
and Armadillidium vulgare (Latreille, 1804). All of these isopods are non-native spe-
cies. e purpose of this paper is to identify the terrestrial isopod fauna of Rapa Nui,
including the descriptions of two new species.
Material and methods
Study area
Fieldwork was conducted on the Roiho lava ow, ~5 km north of the village of Hanga
Roa during three research trips in 2008, 2009 and 2011. e study area is characterized

e terrestrial Isopoda (Crustacea, Oniscidea) of Rapa Nui (Easter Island)... 29
by gently rolling hills (i.e., extinct scoria cones) with coastal cli faces anking the
western-most boundary. Vegetation was grassland and invasive guava (Psidium guajava)
shrub. Within the collapse pit and skylight entrances of most caves, several non-native
tree species occurred, including g (Ficus sp.), avocado (Persea americana), apple
banana (Musa × paradisiaca), roseapple (Syzygium jambos), guava (Psidium guajava)
and Eucalyptus spp.
e cave environment
Caves are zonal environments often consisting of four principle zones: (1) an entrance
(or light) zone representing a combination of both surface and cave climatic condi-
tions; (2) a twilight zone where light is diminished and surface climate conditions are
progressively dampened; (3) a transition zone characterized by complete darkness with
a further diminished inuence of surface climate conditions; and, (4) a deep zone (usu-
ally the deepest portion of the cave) where environmental conditions (e.g., complete
darkness, temperature, and air ow) remain relatively stable over time and the evapora-
tion rate is negligible (Howarth 1980, 1982). For each isopod detected within caves,
we provide a zone designation in the “type material examined” section.
Sampling
Cave and surface sampling was conducted. Research teams (led by the second author)
systematically sampled 10 caves during three research trips (16–21 August 2008; 28
June–17 July 2009; and 01–07 August 2011). Four methodologies (pitfall traps, time-
constrained searches, opportunistic collecting, and timed direct intuitive searches)
were applied to sample 10 caves during the rst two trips. Pitfall trap construction
consisted of two 946-ml stacked plastic containers (13.5 cm high, 10.8-cm-diameter
rim and 8.9-cm base). A teaspoon of peanut butter placed in the bottom of the exte-
rior container was used as bait. e bottom of the interior container had several dozen
holes to allow the bait to “breathe” to attract arthropods. Traps were deployed for three
to four days.
Time-constrained searches involved estimating a one-meter radius around each
pitfall trap sampling station and then conducting a timed search. Searches were con-
ducted for one to three minutes (one minute if no arthropods were observed, three if
arthropods were detected) before pitfall trap deployment and prior to trap removal.
Opportunistic collection involved collecting arthropods as encountered – while
deploying and removing pitfall traps, and between timed searches. During these in-
tervals, personnel searched the ground, walls and ceilings as they walked the length
of each cave. In ve caves (where all the collecting methodologies were applied), we
also conducted timed direct intuitive searches (DIS) of fern-moss gardens by gently
combing through the fern and moss and looking beneath rocks for 40 search-minutes

Stefano Taiti & J. Judson Wynne / ZooKeys 515: 27–49 (2015)
30
per garden (two observers × 20 minutes per observer). In four additional caves, we
limited sampling to DIS within fern-moss gardens only (two observers × 20 minutes
per observer).
During the last research trip to the island, the deep zones of four of the caves were
sampled via bait sampling and DIS. ree types of baits were placed directly on the
ground and within cracks and ssures on cave walls, ceilings and oors: sweet potato
(Ipomoea batatas), chicken and sh entrails, and small branches from local hibiscus
(Hibiscus rosa-sinensis) and Gaoho (Caesalpinia major) shrubs. Two to three stations
of each bait type were deployed, for four to ve days, within the deep zone(s) of each
cave. At proximity to bait sampling arrays, we also conducted one DIS by searching
the cave oor for 10 minutes within a 1-m2 area.
From 28 June through 08 July 2009 (total of 10 days), we deployed two 15 x 20
meter surface pitfall trapping grids. Surface Grid 1 (with trap numbers 1 - 20) was
established inland at the approximate center of our study area. Surface Grid 2 (with
trap numbers 21 - 40) was deployed at the western extent of the study area (~250 m
from the coastal cli face). All pitfall traps were countersunk to ground surface with
trap spacing at 5 m between each trap.
For additional information on sampling refer to Wynne et al. (2014) at: http://
www.bioscience.oxfordjournals.org/lookup/suppl/doi:10.1093/biosci/biu090/-/DC1
Cave codes
We recognize standard practice for locality information is to provide geographical
coordinates to facilitate future collecting and interpretation. However, Chilean park
ocials have requested that neither cave names nor coordinates be included due to
cultural and natural resource sensitivities of caves. In place of cave names, we used cave
codes supplied by CONAF – Parque Nacional Rapa Nui. A copy of this paper, which
includes a table of cave names with associated cave codes, is on le with CONAF –
Parque Nacional Rapa Nui headquarters Hanga Roa, Easter Island, and CONAF, Jefe
Departamento, Diversidad Biológica, Gerencia de Areas Protegidas y Medio Ambi-
ente, Santiago, Chile.
Preservation, mounting, observation
All material was preserved in 95% ethanol. Identications were based on morphologi-
cal characters with the use of micropreparations. Line drawings were made with the
aid of a camera lucida mounted on Wild M5 and M20 microscopes. Whole-specimen
images were captured using a 1.1 MP Canon 5D Mark II (with a 65 mm zoom lens)
mounted on a Visionary Digital BK Lab Plus camera mounting system. We used the
program Zerene Stacker to merge images into a composite image. Photoshop CS5 was
used for image post-processing.

e terrestrial Isopoda (Crustacea, Oniscidea) of Rapa Nui (Easter Island)... 31
Museum abbreviations
AMNH American Museum of Natural History, New York, USA;
BPBM Bernice P. Bishop Museum, Honolulu, Hawai‘i, USA;
MNHN Museo Nacional de Historia Natural, Santiago, Chile;
MZUF Museo di Storia Naturale, sezione di Zoologia, dell’Università di Firenze,
Florence, Italy;
YPM Peabody Museum of Natural History, Yale University, New Haven, Con-
necticut, USA.
Systematic account
Family Ligiidae
Genus Ligia Fabricius, 1798
Ligia exotica Roux, 1828
Ligyda exotica; Fuentes 1914: 315.
Remarks. e record of this species by Fuentes (1914) needs to be conrmed since this
littoral species has often been confused with other species in the past. Unfortunately,
no specimens of Ligia have been recently collected from Rapa Nui, most likely due to
lack of investigations along the littoral zones of the island.
Distribution. Pantropical.
Family Styloniscidae
Genus Styloniscus Dana, 1853
Styloniscus manuvaka sp. n.
http://zoobank.org/00706DDB-9E9C-4DEF-AEA5-E9289287B7AB
Figs 1A, 2–4
Styloniscus sp.; Wynne et al. 2014: 713, 714, g. 2b.
Type material examined. Chile, Rapa Nui: 1 ♂ holotype, 2 ♂♂, 2 ♀♀, 1 juv. para-
types (MNHN), Mahunga Hiva Hiva, Cave Q15-070, fern-moss garden (entrance
zone), direct intuitive search, 10.VII.2009, leg. J.J. Wynne; 2 ♂♂, 1 ♀, 2 juvs. para-
types (MZUF), same location, 50 m from entrance, direct intuitive search (on de-
composing tree branches; twilight zone), 6.VIII.2011, leg. J.J. Wynne; 1 ♀ paratype
(MNHN), same data; 1 ♂, 1 ♀ paratypes (BPBM), Mahunga Hiva Hiva, Cave Q15-
074, skylight entrance (1st entrance NE of main entrance; entrance zone), 3.VII.2009,

Stefano Taiti & J. Judson Wynne / ZooKeys 515: 27–49 (2015)
32
Figure 1. Styloniscus manuvaka sp. n.: A ♀ paratype in dorsal view. Hawaiioscia rapui sp. n.: B ♀ paratype
in dorsal view.
leg. J.J. Wynne; 1 ♀ paratype (BPBM), Mahunga Hiva Hiva, Cave Q15-119, timed
search at trap 4A, 5.VII.2009, leg. J.J. Wynne; 1 ♂ paratype (BPBM), same location,
Zone 2 (approx. cave deep zone), trap, sh entrails 1, 6.VIII.2011, leg. J.J. Wynne; 1
♀ paratype (BPBM), Mahunga Hiva Hiva, Cave Q15-071, Zone 2 (approx. cave deep
zone), bait trap, sh entrails 1, 7.VIII.2011, leg. J.J. Wynne; 1 ♀ paratype (BPBM),
Cave Q15-067, fern-moss garden (entrance zone), direct intuitive search, 4.XII.2008,
leg J.J. Wynne.
Additional material examined. French Polynesia, Bass Islands (Austral Islands),
Rapa Iti Island: 4 ♂♂ (YPM), Pumarua-Maurua Ridge, Pumarua and some west, 500-
620 m, from dead leaves of the bird’s nest fern, Asplenium nidus, 9.I.1980, leg. G. Paulay.
Description. Maximum length: ♂ 4 mm, ♀ 4.2 mm. Dorsum brown with the
usual yellow muscle spots (Fig. 1A). Body ovoid with pleon narrower than pereon

e terrestrial Isopoda (Crustacea, Oniscidea) of Rapa Nui (Easter Island)... 33
Figure 2. Styloniscus manuvaka sp. n., ♀ paratype: A adult specimen in dorsal view B dorsal scale-seta
C cephalon in dorsal view D cephalon in frontal view E pleonite 5, telson and uropods F antennula
Gantenna.

Stefano Taiti & J. Judson Wynne / ZooKeys 515: 27–49 (2015)
34
Figure 3. Styloniscus manuvaka sp. n., ♀ paratype: A left mandible B right mandible C maxillula Dmaxilla
E maxilliped.
(Figs 1A, 2A). Vertex and pereon distinctly granulated with granulations arranged on
three rows on pereonite 1 and two rows on pereonites 2-7; pleon and telson smooth.
Dorsal surface with scale-setae as in Fig. 2B. Cephalon (Fig. 2C, D) with obtuse mid-
dle lobe slightly protruding frontwards compared with rounded lateral lobes; eye con-
sisting of three ommatidia in a triangle. Pleonites 3-5 reduced with small posterior
points. Telson (Fig. 2E) with concave sides and truncate apex. Antennula (Fig. 2F)
with second article shorter than rst and third; third article with 6 long aesthetascs at
apex. Antenna (Fig. 2G) with agellum as long as fth article of peduncle; agellum

e terrestrial Isopoda (Crustacea, Oniscidea) of Rapa Nui (Easter Island)... 35
cone-shaped, consisting of 5 articles with the second, third and fourth article bearing
two aesthetascs each. Left mandible (Fig. 3A) with 2 penicils; right mandible (Fig. 3B)
with 1 penicil. Maxillula (Fig. 3C) outer branch with 10 simple teeth and 2 long stalks;
inner branch with 3 penicils. Maxilla (Fig. 3D) apically bilobate, inner lobe wider than
outer lobe and bearing strong setae on its margin. Maxilliped (Fig. 3E) endite with a
stout apical penicil; basal article of the palp with 2 setae. Pereopods 6 and 7 with a
distinct water conducting system (Fig. 4B,C) on merus, carpus and propodus, and on
basis, ischium and merus, respectively.
Male. Pereopod 1 (Fig. 4A) merus and carpus with a line of short scales on sternal
margin. Pereopod 7 (Fig. 4C) ischium enlarged in the distal part, forming a at round-
ed lobe with two short and stout setae on tergal margin, sternal margin almost straight;
propodus with numerous long and thin setae on tergal margin. Genital papilla (Fig.
4D) with rounded and enlarged distal part. Pleopod 1 (Fig. 4D) exopodite triangular,
as wide as long, with rounded posterior margin; endopodite with agelliform distal
segment, about twice as long as basal one and slightly enlarged at apex. Pleopod 2
(Fig. 4E) exopodite very short, rectangular, about twice wider than long; endopodite
with distal segment about seven times longer than basal one, with tapering apical part
slightly bent outwards, acute apex.
Etymology. e species name is a combination of two Rapanui terms, manu and
vaka. Manu is “bug” and vaka is “canoe” or “boat”; when combined this translates to
“canoe bug.” Based upon the identication of this species, and a collembolan (Lepi-
docyrtus olena Christiansen & Bellinger, 1992) previously known from the Hawaiian
Islands only, Wynne et al. (2014) suggested both of these animals may have been
dispersed by the ancient Polynesians as they transported and transplanted cultivars
(called “canoe plants”), such as banana, taro and sugar cane, throughout the South
Pacic islands.
Remarks. At present the genus Styloniscus includes about 45 species distributed in
the tropics and the southern hemisphere (Schmalfuss 2003; Nunomura 2007; Taiti
2014). e new species is characterized by the male pereopod 7 ischium enlarged in the
distal part with a at rounded lobe. A similar character is present also in a species from
Omaio, North Island, New Zealand, identied by Vandel (1952) as Styloniscus otakensis
(Chilton, 1901). e specimens redescribed and illustrated by Vandel certainly do not
belong to S. otakensis according to the redescription of this species provided by Green
(1971) on the basis of the type material studied by Chilton (1901) and on topotypic
material (Dunedin, South Island). In fact, the male pereopod 7 ischium does not show
any distinct lobe (compare g. 31 in Green 1971 with g. 37 in Vandel 1952), and the
shapes of the male pleopod 1 exopodite and pleopod 2 endopodite are signicantly dif-
ferent (compare gs 29 and 30 in Green 1971 with gs 38 and 39A in Vandel 1952).
us, the specimens from Omaio must belong to a distinct species yet to be named.
Styloniscus manuvaka sp. n. diers from S. otakensis sensu Vandel nec Chilton in having
6 instead of 5 aesthetascs at the apex of the antennula, 5 instead of 4 agellar articles of
the antenna, the male pereopod 7 ischium with two, instead of one, stout setae on the
tergal margin, and the male pleopod 2 endopodite with a thicker distal part.

Stefano Taiti & J. Judson Wynne / ZooKeys 515: 27–49 (2015)
36
Figure 4. Styloniscus manuvaka sp. n., ♂ paratype: A pereopod 1 B pereopod 6 C pereopod 7 D genital
papilla and pleopod 1 E pleopod 2.
On Rapa Nui, Styloniscus manuvaka sp. n. is presently restricted to the cave envi-
ronment, but is not troglomorphic (cave-adapted). is animal was detected within
the fern-moss gardens (entrance zone) of three caves, but also occurred within the

e terrestrial Isopoda (Crustacea, Oniscidea) of Rapa Nui (Easter Island)... 37
twilight and cave deep zones. is species was not detected during the surface sampling
work conducted in 2009, nor has it been identied during previous invertebrate in-
ventory work (e.g., Fuentes 1914, Olalquiaga 1946, Kuschel 1963, Campos and Peña
1973). e species also occurs on Rapa Iti, Bass Islands, where it is not restricted to
the cave environment. is species is considered a Polynesian endemic and it might be
present also on other Pacic islands.
Distribution. Presently known from Rapa Nui and Rapa Iti.
Family Philosciidae
Genus Hawaiioscia Schultz, 1973
Hawaiioscia rapui sp. n.
http://zoobank.org/56E14D72-3CF5-4E39-A655-15659F01B67A
Figs 1B, 5–7
Hawaiioscia sp.; Wynne et al. 2014: 714, 716, g. 2a.
Type material examined. Chile, Rapa Nui: 1 ♂ holotype, 2 ♀♀ paratypes (MNHN),
Mahunga Hiva Hiva, Cave Q15-034, pitfall trap 5A (twilight zone) 12.VII.2009, leg.
J.J. Wynne; 1 ♀ paratype (MZUF), 1 ♀ paratype (BPBM), same data, pitfall trap
7A (approx. deep zone); 1 ♂ Paratype (MZUF), Mahunga Hiva Hiva, Cave Q15-
076/078, pitfall trap 2C (light zone), 4.VII.2009, leg. J.J. Wynne.
Description. Maximum length: ♂ and ♀ 7.5 mm. Dorsum light brown with the
usual muscle spots (Fig. 1B). Body at, ovoidal, with pleon narrower than pereon, out-
line as in Fig. 5A. Dorsal body surface nely granulated with small triangular scale-setae
(Fig. 5B). Pereonites with no sulcus marginalis, gland pores absent. Noduli laterales (Fig.
5C, G) clearly visible, inserted on a small tubercle and disposed as follows: two on the
cephalic vertex, one per side on pereonites 1-6 with that on the fourth pereonite much
more distant from the lateral margin of the segment, and two per side on pereonite
7. Cephalon (Fig. 5D–F) with short triangular lateral lobes not protruding frontwards
compared with the obtuse middle lobe; frontal and supra-antennal lines absent; eyes
small, consisting of eight ommatidia. Pleon epimera reduced but with distinct poste-
rior points (Fig. 5A,H). Telson (Fig. 5H) triangular, about twice as wide as long, with
broadly rounded apex. Antennula (Fig. 5I) of 3 articles, second article slightly shorter
than rst and third; third article bearing two rows of 7 and 2 aesthetascs each, and 2 api-
cal aesthetascs. Antenna (Fig. 6A) long and thin, reaching back rear margin of pereonite
6; agellum as long as fth peduncular article, rst agellar article distinctly longer than
second and third, with two rows of 4 to 6 aesthetascs on each second and third article.
Mandibles (Fig. 6B,C) with molar penicil semidichotomized, i.e. consisting of 3-4 setae
on a common stem; left mandible with 2+1 and right mandible with 1+1 free penicils.
Maxillula (Fig. 6D) outer branch with 5+6 teeth, all simple; inner branch with two stout
subequal penicils. Maxilla (Fig. 6E) apically setose and bilobate with outer lobe wider

Stefano Taiti & J. Judson Wynne / ZooKeys 515: 27–49 (2015)
38
Figure 5. Hawaiioscia rapui sp. n., ♂ holotype: A adult specimen in dorsal view. ♀ paratype: B dorsal
scale-seta C co-ordinates of noduli laterales D cephalon in dorsal view E cephalon in frontal view Fcepha-
lon in lateral view G pereonites with noduli laterales H pleonite 5, telson and uropods I antennula.

e terrestrial Isopoda (Crustacea, Oniscidea) of Rapa Nui (Easter Island)... 39
Figure 6. Hawaiioscia rapui sp. n., ♀ paratype: A antenna B left mandible C right mandible D maxillula
E maxilla F maxilliped.

Stefano Taiti & J. Judson Wynne / ZooKeys 515: 27–49 (2015)
40
Figure 7. Hawaiioscia rapui sp. n., ♂ paratype: A pereopod 1 B pereopod 7 C genital papilla and pleo-
pod 1 D pleopod 2 E pleopod 3 exopodite F pleopod 4 exopodite G pleopod 5 exopodite.
than inner one. Maxilliped (Fig. 6F) endite apically setose and bearing a large penicil at
medial corner, proximal article of palp bearing 2 strong setae. Pereopods with elongated
articles and agelliform dactylar and ungual setae (Fig. 7A). Pleopodal exopodites with

e terrestrial Isopoda (Crustacea, Oniscidea) of Rapa Nui (Easter Island)... 41
no trace of respiratory structures. Uropod (Fig. 5H) protopod with a /\-shaped groove on
outer margin; insertion of endopodite slightly proximal to that of exopodite.
Male. Pereopod 1 carpus with a brush of trid spines on sternal margin (Fig. 7A).
Pereopod 7 (Fig. 7B) with no peculiar modications, ischium with sternal margin
straight. Pleopod 1 (Fig. 7C) exopodite cordiform, with a broadly rounded apex; en-
dopodite with thickset distal part, straight with rounded apex. Pleopod 2 (Fig. 7D)
with exopodite triangular, shorter than endopodite and bearing 5 setae on ouer mar-
gin. Pleopods 3-5 exopodite as in Fig. 7E–G.
Etymology. e new species is named after Sergio Rapu Haoa, a humanitarian
who has furthered cultural and archeological knowledge of Rapa Nui. Sergio was Rapa
Nui’s rst governor of Rapanui descent and the rst director and curator of Museo
Antropológico P. Sebastián Englert on Rapa Nui. He is also a world-renowned Rapa
Nui archaeologist and purveyor of Rapa Nui culture. He graciously provided logistical
support to the second author and his research teams while on Rapa Nui.
Remarks. Prior to discovering this new species, the genus Hawaiioscia consisted of
four troglomorphic species restricted to lava tube caves on the Hawaiian Islands (Schultz
1973; Taiti and Howarth 1997): H. parvituberculata Schultz, 1973 from Maui, H. mi-
crophthalma Taiti & Howarth, 1997 from O‘ahu, H. paeninsulae Taiti & Howarth,
1997 from Moloka‘i, and H. rotundata Taiti & Howarth, 1997 from Kaua‘i. No epigean
species in this genus were previously known. e new species shows all the characters of
the genus Hawaiioscia with the sole exception of the molar penicil of the mandible which
is semidichotomized instead of simple as in all the others species from Hawai‘i. Consid-
ering that all the most important characters (number and position of noduli laterales,
maxillular teeth, penicil on maxillipedal endite, uropod and shape of male pleopod 1) are
shared with all the other Hawaiioscia species, we include the new species in this genus.
Specimens from this new species were collected from both within the entrance
zone of one cave and the twilight zone of another cave. It is important to note, this
species does not have troglomorphic characteristics, such as body depigmentation or
eye reduction as do other congeners within Hawaiioscia. However, as with Styloniscus
manuvaka sp. n., this new species was not detected during the surface sampling eort,
nor has it been previously identied by earlier entomological surveys of the island.
us, we believe this animal to be restricted to cave environment on Rapa Nui.
Distribution. Presently endemic to Rapa Nui.
Family Platyarthridae
Genus Trichorhina Budde-Lund, 1908
Trichorhina tomentosa (Budde-Lund, 1893)
Material examined. Chile, Rapa Nui: 1 ♀ (BPBM), Mahunga Hiva, Cave Q15-074,
pitfall trap 1B (light zone), 30.VI.2009, leg. J.J. Wynne.
Distribution. Pantropical. Introduced to greenhouses worldwide.

Stefano Taiti & J. Judson Wynne / ZooKeys 515: 27–49 (2015)
42
Family Porcellionidae
Genus Porcellionides Miers, 1877
Porcellionides pruinosus (Brandt, 1833)
Material examined. Chile, Rapa Nui: 2 ♂♂, 3 ♀♀ (AMNH 18360), Cannibal Cave,
21.VIII.1999, leg. C. Boyko, J. Tanacredi, S. Reanier, H. Tonnemacher and S. Lopez;
1 ♀ (BPBM), Mahunga Hiva Hiva, Cave, Q15-074, time search at 1A (light zone),
30.VI.2009, leg. J.J. Wynne; 1 ♂, 3 ♀♀ (BPBM), same location, leaf litter beneath
skylight, (3rd entrance NW of main entrance; entrance zone), direct intuitive search,
2.VIII.2011, leg. J.J. Wynne; 1 ♀ (BPBM), Mahunga Hiva Hiva, Cave Q15-067, fern-
moss garden (entrance zone), direct intuitive search, 10.VII.2009, leg. J.J. Wynne; 1
♂ (BPBM), Mahunga Hiva Hiva, Cave Q15-070, fern-moss garden (entrance zone),
direct intuitive search, 10.VII.2009, leg. J.J. Wynne.
Distribution. Cosmopolitan species of Mediterranean origin.
Genus Porcellio Latreille, 1804
Porcellio scaber Latreille, 1804
Porcellio scaber; Fuentes 1914: 315; Wynne et al. 2014: 716.
Material examined. Chile, Rapa Nui: 1 ♀ (AMNH 18362), VIII.1999, leg. C.
Boyko, J. Tanacredi, S. Reanier, H. Tonnemacher and S. Lopez; 2 ♂♂, 1 ♀ (AMNH
18363), Maunga Tangaroa, 20.VIII.1999, leg. C. Boyko, J. Tanacredi, S. Reani-
er, H. Tonnemacher and S. Lopez; 2 ♂♂, 3 ♀♀ (AMNH 18365), Ana te Pahu,
21.VIII.1999, leg. C. Boyko, J. Tanacredi, S. Reanier, H. Tonnemacher and S.
Lopez; 2 ♂♂, 13 ♀♀ (AMNH 18364), Poike region, 25.VIII.1999, leg. C. Boyko,
J. Tanacredi, S. Reanier, H. Tonnemacher and S. Lopez; 1 ♂ (BPBM), Mahunga
Hiva Hiva, surface in front of Cave Q15-038, opportunistic collection (eastern-most
collapse pit, southern extent near cave entrance), 18.VIII.2008, J.J. Wynne; 1 ♂
(BPBM), Mahunga Hiva Hiva, surface grid 2, 27°06'41.3"S, 109°25'09.2"W, pitfall
trap 21, 10.VII.2009, leg. J.J. Wynne; 1 juv. (BPBM), Mahunga Hiva Hiva, surface
in front of Cave Q15-038, timed search at 1C (eastern-most collapse pit on south-
ern extent near cave entrance), 20.VIII.2008, leg. J.J. Wynne; 3 ♂♂ (BPBM), Cave
Q15-038, fern-moss garden (entrance zone), direct intuitive search, 4.XII.2008,
leg. J.J. Wynne; 1 ♂, 2 ♀♀ (BPBM), Mahunga Hiva Hiva, Cave Q15-076/078,
opportunistic collection, 4.VII.2009, leg. J.J. Wynne; 1 ♂, 2 ♀♀ (BPBM), Ma-
hunga Hiva Hiva, Cave Q15-070, fern-moss garden (entrance zone), direct intuitive
search, 13.VII.2009, leg. J.J. Wynne; 2 ♂♂, 1 ♀ (BPBM), Mahunga Hiva Hiva,
Cave Q15-074, skylight entrance (1st entrance NW of main entrance; entrance
zone), opportunistic collection, 3.VII.2009, leg. J.J. Wynne; 1 juv. (BPBM), Ma-

e terrestrial Isopoda (Crustacea, Oniscidea) of Rapa Nui (Easter Island)... 43
hunga Hiva Hiva, Cave Q15-067, fern-moss garden (entrance zone), direct intui-
tive search, 10.VII.2009, leg. J.J. Wynne; 1 ♀ (BPBM), Mahunga Hiva Hiva, Cave
Q15-127, entrance zone, pitfall trap 1A, 5.VII.2009, leg. J.J. Wynne; 1 ♂ (BPBM),
same data, pitfall traps 1B; 1 ♂, 1 ♀ (BPBM), Mahunga Hiva Hiva, surface grid 1,
27°06'53.1"S, 109°24'20.3"W, pitfall trap 3, 10.VII.2009, leg. J.J. Wynne; 1 ♂, 1 ♀
(BPBM), same location, pitfall trap 10, 10.VII.2009, leg. J.J. Wynne; 2 ♂♂, 5 ♀♀
(BPBM), same location, pitfall trap 12, 10.VII.2009, leg. J.J. Wynne.
Distribution. Cosmopolitan species of western European origin.
Porcellio laevis Latreille, 1804
Material examined. Chile, Rapa Nui: 2 ♂♂ (AMNH 18362), VIII.1999, leg. C.
Boyko, J. Tanacredi, S. Reanier, H. Tonnemacher and S. Lopez; 2 ♂♂, 1 juv. (AMNH
18363), Maunga Tangaroa, 20.VIII.1999, leg. C. Boyko, J. Tanacredi, S. Reanier,
H. Tonnemacher and S. Lopez; 1 ♂, 1 ♀ (AMNH 18365), Cave Q15-074, loca-
tion within cave not reported, 21.VIII.1999, leg. C. Boyko, J. Tanacredi, S. Reani-
er, H. Tonnemacher and S. Lopez; 2 ♂♂, 7 ♀♀ (AMNH 18361), La Pérouse Bay,
21.VIII.1999, leg. C. Boyko, J. Tanacredi, S. Reanier, H. Tonnemacher and S. Lopez.
Distribution. Cosmopolitan species of Mediterranean origin.
Family Armadillidiidae
Genus Armadillidium Brandt, 1831
Armadillidium vulgare (Latreille, 1804)
Armadillidium vulgare; Fuentes, 1914: 315.
Material examined. Chile, Rapa Nui: 1 ♂ (AMNH 18362), VIII.1999, leg. C.
Boyko, J. Tanacredi, S. Reanier, H. Tonnemacher and S. Lopez; 6 ♂♂, 5 ♀♀
(AMNH 18365), Cave Q15-074, location within cave not reported, 21.VIII.1999,
leg. C. Boyko, J. Tanacredi, S. Reanier, H. Tonnemacher and S. Lopez; 3 ♂♂, 9
♀♀ (AMNH 18366), Hotel Hanga Roa, Hanga Roa, 21.VIII.1999, leg. C. Boyko, J.
Tanacredi, S. Reanier, H. Tonnemacher and S. Lopez; 2 ♂♂, 2 ♀♀ (AMNH 18364),
Poike region, 25.VIII.1999, leg. C. Boyko, J. Tanacredi, S. Reanier, H. Tonnemach-
er and S. Lopez; 1 ♂, 1 ♀ (BPBM), Mahunga Hiva Hiva, surface in front of Cave
Q15-038, timed search at 1B (eastern-most collapse pit, southern extent near cave
entrance), 20.VIII.2008, leg. J.J. Wynne; 1 ♀ (BPBM), Cave Q15-038, fern-moss
garden (entrance zone), direct intuitive search, 21.XIII.2008, leg. J.J. Wynne; 2 ♀♀
(BPBM), Mahunga Hiva Hiva, surface grid 2, 27°06'41.3"S, 109°25'09.2"W, pitfall
trap 23, 10.VII.2009, leg. J.J. Wynne; 1 ♂ (BPBM), surface grid 1, 27°06'53.1"S,
109°24'20.3"W, pitfall trap 17, 10.VII.2009, leg. J.J. Wynne; 3 ♀♀ (BPBM), same

Stefano Taiti & J. Judson Wynne / ZooKeys 515: 27–49 (2015)
44
location, pitfall trap 19, 10.VII.2009, leg. J.J. Wynne; 1 ♂, 3 ♀♀ (BPBM), same loca-
tion, pitfall trap 4, 10.VII.2009, leg. J.J. Wynne.
Distribution. Cosmopolitan species of Mediterranean origin.
Family Armadillidae
Genus Venezillo Verhoe, 1928
Venezillo parvus (Budde-Lund, 1885)
Material examined. Chile, Rapa Nui: 2 ♂♂ (BPBM), Mahunga Hiva Hiva, surface
grid 2, 27°06'41.3"S, 109°25'09.2"W, pitfall trap 39, 10.VII.2009, leg. J.J. Wynne; 1
♂ (BPBM), same location, pitfall trap 32, 10.VII.2009, leg. J.J. Wynne.
Distribution. Widespread in tropical and subtropical regions. It has been intro-
duced to European greenhouses. For diagnostic gures of this species see Schmidt
(2003).
Key to species of terrestrial isopods from Rapa Nui
1 Antennal agellum with >10 articles; eye with >100 ommatidia ...Ligia exotica
– Antennal agellum with <6 articles, eye with <30 ommatidia .....................2
2 Antennal agellum of 5 articles .................................Styloniscus manuvaka
– Antennal agellum of 3 or 2 articles ...........................................................3
3 Antennal agellum of 3 articles .......................................Hawaiioscia rapui
– Antennal agellum of 2 articles ...................................................................4
4 Body depigmented; eye consisting of a single ommatidium ..........................
................................................................................Trichorhina tomentosa
– Body pigmented; eye consisting of several ommatidia .................................5
5 Body slightly convex, unable to roll up into a ball .......................................6
– Body strongly convex, able to roll up into a perfect ball ..............................8
6 Cephalon with a V-shaped suprantennal line; pereonite 1 with posterior mar-
gin straight and posterior corners rounded ............ Porcellionides pruinosus
– Cephalon without suprantennal line; pereonite 1 with posterior margin more
or less concave at sides and posterior corners right-angled or acute .............7
7 Dorsal body surface smooth ..................................................Porcellio laevis
– Dorsal body surface distinctly granulated .............................Porcellio scaber
8 Cephalon with a triangular frontal scutellum; telson trapezoidal; uropod exo-
podite attened, lling the gap between telson and pleonite 5 ......................
............................................................................... Armadillidium vulgare
– Cephalon with no frontal scutellum; telson hour-glass shaped; uropod protopo-
dite attened, lling the gap between telson and pleonite 5 ......Venezillo parvus

e terrestrial Isopoda (Crustacea, Oniscidea) of Rapa Nui (Easter Island)... 45
Discussion
Nine species of terrestrial isopods are known from Rapa Nui: Ligia exotica, Styloniscus
manuvaka sp. n., Hawaiioscia rapui sp. n., Trichorhina tomentosa, Porcellionides pruino-
sus, Porcellio laevis, P. scaber, Armadillidium vulgare, and Venezillo parvus.
Only one species (Ligia exotica) is littoral, halophilic, and widely distributed along
coastal habitats in the tropics. We have not examined any specimens belonging to
this species and its identication needs to be conrmed. Littoral habitats have not
been adequately sampled on Rapa Nui and other littoral species may also be present
on the island. Two species (Trichorhina tomentosa and Venezillo parvus) have a wide
distribution in the tropics, and four species of European or Mediterranean origin (Por-
cellionides pruinosus, Porcellio laevis, P. scaber, and Armadillidium vulgare) are now cos-
mopolitan. All of these species were introduced to Rapa Nui due to human activities.
Styloniscus manuvaka sp. n. and Hawaiioscia rapui sp. n. are Polynesian and Rapa Nui
endemics, respectively.
Given that few native arthropod species remain on Rapa Nui (Wynne et al. 2014),
the two new isopod species are a signicant contribution to the island’s natural history.
Together with the other eight endemics described by Bernard et al. (2015), Mockford
and Wynne (2013) and Jordana and Baquero (2008), these disturbance relicts have
persisted despite several hundred years of extreme environmental change and interac-
tions with non-native species (Wynne et al. 2014).
Despite their persistence, these endemic species are considered imperiled (Wynne
et al. 2014). S. manuvaka and H. rapui may be operating under extinction debts (Tri-
antis et al. 2010). is may occur once a population has become isolated following a
signicant environmental perturbation, such as habitat loss or fragmentation (Tilman
et al. 1994). Habitat loss has occurred dramatically and at an island-wide scale on Rapa
Nui. Both S. manuvaka and H. rapui were detected in low numbers. Neither of these
species were detected during earlier inventory work (see Fuentes 1914, Olalquiaga
1946, Kuschel 1963, Campos and Peña 1973) or our surface sampling eort.
Further, the combined eects of global climate change and interactions with non-
native species may further threaten the persistence of these endemic isopods. Com-
petition with non-native species has been identied as threatening the persistence of
surface-dwelling endemic arthropods on other island ecosystems (see Chown et al.
2007, Fordham and Brook 2010, Vitousek et al. 1997). Increased drought conditions
are predicted for the sub-tropics (IPCC 2013) and other Polynesian islands (Chu et
al. 2010). We also know non-native species represent the majority of known arthro-
pods on Rapa Nui. For example, of the seven known non-native isopod species, the
cosmopolitan P. scaber was detected in the greatest numbers in both surface sampling
and within caves (Wynne et al. 2014). Additionally, P. scaber is a well-established non-
native species being rst detected by Fuentes (1914). In Hawai‘i, P. scaber is consid-
ered to be an invasive species and one of the most damaging non-native arthropods in
the native ecosystems (Howarth et al. 2001).

Stefano Taiti & J. Judson Wynne / ZooKeys 515: 27–49 (2015)
46
Conservation and management of these endemic terrestrial isopods (as well as the
other endemic species) and their habitats should be a high priority for the Rapanui
community, policy makers and resource managers. Given the concerns associated with
global climate change and non-native invasive species, a captive breeding program of
these new species is recommended. Captive breeding of isopods is relatively easy and
inexpensive (Sutton 1972). Such a program may be developed in collaboration with
CONAF, Museo Antropológico P. Sebastián Englert de Rapa Nui and potentially
secondary school classrooms on the island. By captively breeding these animals in a
variety of locations, their long-term persistence may be somewhat safeguarded, and
will facilitate the establishment of viable populations for future reintroduction eorts.
Additionally, this will provide an opportunity for researchers to obtain information
associated with the life history characteristics of these endemic species. Also, once large
captive populations are established, experiments examining competition with the non-
native isopods may be performed.
Northup and Welbourn (1997) proposed that moss garden habitats in New Mex-
ico lava tube caves may serve as a source habitat for arthropods colonizing cave deep
zones. Fern-moss gardens within Rapa Nui caves may provide this same function.
All known congeners of H. rapui sp. n. are cave-adapted isopods from the Hawaiian
Islands. H. rapui sp. n. was detected within both entrance and twilight zones. If this
species persists, it is possible parapatric speciation may occur as has been suggested for
other Hawaiioscia species from the Hawaiian Islands (Rivera et al. 2002).
Finally, we know little concerning the distributions of these endemic isopods. We
recommend additional surveys be conducted in other caves on the island, as well as in
other habitats likely to support terrestrial isopods (and endemic arthropods, in gener-
al). is nal step will provide resource managers with the ability to better characterize
endemic isopod habitat, and to further improve our understanding of the distribution
of these animals on Rapa Nui.
Acknowledgements
JJW wishes to thank Ninoska Cuadros Hucke, Susana Nahoe, and Enrique Tucky
of CONAF-Parque Nacíonal Rapa Nui and Consejo de Monumentos, Rapa Nui, for
administrative and logistical support. Cristian Tambley of Campo Alto Operaciones
and Sergio Rapu provided additional logistical assistance. Javier Les of the Sociedad de
Ciencias Espeleológicas and Andrzej Ciszewski of the Polish Expedition team provided
cave maps. Kyle Voyles co-developed the cave-dwelling arthropod sampling protocol.
Christina Colpitts, Lynn Hicks, Bruce Higgins, Alicia Ika, Talina Konotchick, Scott
Nicolay, Knutt Petersen, Lázero Pakarati, Victoria Pakarati Hotus, Pete Polsgrove, Dan
Ruby, and Liz Ruther were invaluable in the eld. e Explorers Club and the National
Speleological Society partially funded the eld research. Color images of S. manuvaka
sp. n. and H. rapui sp. n. were provided by Caitlin Chapman and Neil Cobb, Colorado
Plateau Museum of Arthropod Biodiversity (CPMAB), Northern Arizona University.

e terrestrial Isopoda (Crustacea, Oniscidea) of Rapa Nui (Easter Island)... 47
Jacob Higgins formerly of CPMAB assisted with identications of known isopod spe-
cies. Julianna Rapu provided suggestions on etymology and conrmations of Rapa Nui
place names. We are also grateful to Dr. Christopher Boyko and Dr. Eric A. Lazo-
Wasem for the loan of the material deposited in AMNH and YPM, respectively.
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