An enigmatic Holocene podocopid ostracod from a submarine cave, Okinawa, Japan: ‘living fossil’ or adaptive morphotype?

Abstract

Submarine cave faunas remain poorly understood, and only a few stygobite podocopid ostracods are known. We describe an enigmatic submarine cave ostracod, Tabukicypris decoris gen. et sp. nov., from Holocene sediment cores taken from the Daidokutsu submarine cave off Ie Island, Okinawa, Japan. This species is endemic to the submarine cave environment. At least part of its enigmatic morphology, especially the distinct pore clusters in the anterior and posterior parts, is probably an adaptation to the submarine cave environment. There is no clear morphological evidence to indicate that Tabukicypris decoris is a ‘living fossil’. The morphological characters of this stygobite indicate three possible origins of this species: from a deep-sea, interstitial or tropical open shallow-marine environment.

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An enigmatic Holocene podocopid ostracod from
a submarine cave, Okinawa, Japan: ‘living fossil’ or
adaptive morphotype?
Wing-Tung Ruby Chiu, Moriaki Yasuhara, Hokuto Iwatani, Akihisa Kitamura &
Kazuhiko Fujita
To cite this article: Wing-Tung Ruby Chiu, Moriaki Yasuhara, Hokuto Iwatani, Akihisa Kitamura
& Kazuhiko Fujita (2015): An enigmatic Holocene podocopid ostracod from a submarine cave,
Okinawa, Japan: ‘living fossil’ or adaptive morphotype?, Journal of Systematic Palaeontology
To link to this article: http://dx.doi.org/10.1080/14772019.2015.1094754
Published online: 26 Oct 2015.
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An enigmatic Holocene podocopid ostracod from a submarine cave, Okinawa,
Japan: ‘living fossil’ or adaptive morphotype?
Wing-Tung Ruby Chiu
a
*, Moriaki Yasuhara
b
, Hokuto Iwatani
a
, Akihisa Kitamura
c
and Kazuhiko Fujita
d
a
School of Biological Sciences, Swire Institute of Marine Science, The University of Hong Kong, Kadoorie Biological Sciences Building,
Pokfulam Road, Hong Kong SAR, China;
b
School of Biological Sciences, Department of Earth Sciences, Swire Institute of Marine
Science, The University of Hong Kong, Kadoorie Biological Sciences Building, Pokfulam Road, Hong Kong SAR, China;
c
Institute of
Geosciences, Shizuoka University, Shizuoka, 422-8529, Japan;
d
Department of Physics and Earth Sciences, University of the Ryukyus,
Okinawa, 903-0213, Japan
(Received 11 April 2015; accepted 24 July 2015)
Submarine cave faunas remain poorly understood, and only a few stygobite podocopid ostracods are known. We describe
an enigmatic submarine cave ostracod, Tabukicypris decoris gen. et sp. nov., from Holocene sediment cores taken from the
Daidokutsu submarine cave off Ie Island, Okinawa, Japan. This species is endemic to the submarine cave environment. At
least part of its enigmatic morphology, especially the distinct pore clusters in the anterior and posterior parts, is probably
an adaptation to the submarine cave environment. There is no clear morphological evidence to indicate that Tabukicypris
decoris is a ‘living fossil’. The morphological characters of this stygobite indicate three possible origins of this species:
from a deep-sea, interstitial or tropical open shallow-marine environment.
http://zoobank.org/urn:lsid:zoobank.org:pub:25E37E49-C0A0-4A49-A8D8-E4AE9D85DB74
Keywords: submarine cave; Ostracoda; Holocene; Okinawa; Japan
Introduction
Submarine caves are unique environments that are dark,
food-limited, semi-isolated from the outside and shel-
tered from wave action (Iliffe et al. 1984;Fichez1991;
Kano & Kase 2008), and where, it has been suggested,
predation and competition are reduced (Vermeij 1987;
Tabuki & Hanai 1999). These environm ental conditions
allow submarine caves to serve as refuges or ha bitats for
‘living fossil’ and other enigmatic stygobites that often
show affinity with deep-sea taxa (Hayami & Kase 1996;
Tabuki & Hanai 1999; Kano & Kase 2008). Howeve r,
less attention has been paid to submarine cave fauna com-
pared to more isolated anchialine fauna (Iliffe &
Kornicker 2009).
Ostracoda are small bivalved crustaceans, and their
shells, composed of calcite, are well preserved as fossils.
Their excellent fossil record offers a unique opportunity
to rigorously compare morphological characters of ‘living
fossil’ and other enigmatic stygobites to those of ancient
fossil taxa. Tabuki & Hanai (1999) discovered a ‘living
fossil’ submarine cave ostracod, Kasella ryukyuensis
Tabuki & Hanai, 1999 from Ie, Irabu and Shimoji islands,
Ryukyu Islands, Japan, and discussed its origin,
macroevolution and adaptation to the submarine cave
environment using fossil records of sigillid ostracods.
Here, we present a new enigmatic submarine cave
ostracod, Tabukicypris decoris gen. et sp. nov., from
Holocene sediment cores taken in the Daidokutsu subma-
rine cave on the east coast of Ie Island, Okinawa, Japan.
This is the first discovery of a submarine cave podocopid
ostracod showing substantial morphological differences
from ordinary marine ostracods, other than the ‘living fos-
sil’ sigillid ostracod Kasella ryukyuensis discovered by
Tabuki & Hanai (1999). The new genus described here
belongs to a different superfamily and even a different
suborder of Podocopida from Kasella (Tabukicypris: Pon-
tocypridoidea, Cypridocopina; Kasella: Sigilloidea, Sigil-
locopina). Our results suggest that the enigmatic
morphological characters of Tabukicypris decoris gen. et
sp. nov. are adaptations to the submarine cave environ-
ment rather than primitive features of a ‘living fossil’.
Locality
Daidokutsu (meaning ‘large cave’ in Japanese) is a sub-
marine limestone cave on the east coast of Ie Island,
*Corresponding author. Email: rubychiu@ymail.com
Ó The Trustees of the Natural History Museum, London 2015. All rights reserved.
Journal of Systematic Palaeontology, 2015
http://dx.doi.org/10.1080/14772019.2015.1094754
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Okinawa, Japan (Fig. 1). The walls and cei ling of the cave
are composed of Pleistocene Ryukyu Limestone and the
floor is covered by calcareous mud (Hayami & Kase
1993; Tabuki & Hanai 1999; Kitamura et al. 2007a;
Omori et al. 2010; Yamamoto et al. 2010). The cave
entrance is at 19 m below sea level, and the cave floor
gradually deepens to 29 m water depth towards the inte-
rior of the cave (Omori et al. 2010). The inside of the
cave is dark, but the temperature and salinity are similar
to those of the outside (Tabuki & Hanai 1999; Yamamoto
et al. 2010; Kitamura et al. 2013). Ostracods, larger ben-
thic foraminifera, bivalves and other organisms have been
studied in this cave (Kase & Hayami 1992; Hayami &
Kase 1993; Tabuki & Hanai 1994; Hayami & Kase 1996;
Tabuki & Hanai 1999; Kitamura et al. 2007a, b;
Yamamoto et al. 2009, 2010; Omori et al. 2010).
Material and methods
Sediment cores and surface sediments were used in the
present study. Two sediment cores (5 cm in diameter),
Core 06 (148 cm long) and Core 19 (233 cm long), were
obtained from 29 m water depth inside the Daidokutsu
submarine cave (Fig. 1; Kitamura et al. 2007b; Yamamoto
et al. 2009). These cores cover the last »7000 years based
on radiocarbon dating (Yamamoto et al. 2009; Kitamura
et al. 2013). Surface sediments collected outside the cave
at 46.2 m water depth (sample IR1; Fig. 1C) and collected
from the open-water sites with similar water depth to the
cave (samples 116, 118 and 11; Fig. 1B; Ujiie et al. 1979)
were used for comparison of ostracods between the inside
and the outside of the cave.
Uncoated ostracod specim ens were digitally imaged
with a Hitachi S-3400N variable pressure scanning elec-
tron microscope (SEM) in low-vacuum mode (at the Elec-
tron Microscope Unit, University of Hong Kong), and
with a Leica M205C stereomicroscope (at M.Y. labora-
tory) using a Leica LAS Multifocus system that produced
a composite, all-in-focus, extended-depth-of-focus image.
Figured specimens are deposited in the National Museum
of Natural History (Washington, DC, USA; catalogue
numbers USNM 612800807). We follow the higher
classification scheme of the World Ostracoda Database
(Brand
~
ao et al. 2015).
Abbreviations
LV, left valve; RV, right valve; L, length; H, height.
Systematic palaeontology
Subclass Podocopa Sars, 1866
Order Podocopida Sars, 1866
Suborder Cypridocopina Jones, 1901
Superfamily Pontocypridoidea M
€
uller, 1894
Family Pontocyprididae M
€
uller, 1894
Genus Tabukicypris gen. nov.
Figure 1. Location of sampling sites. A, B, location of Daido-
kutsu cave and surface sediment samples 116, 118 and 11; C,
simplified cross section of Daidokutsu cave showing the position
of Core 06, Core 19 and surface sediment sample IR1. A and B
were created using Ocean Data View (Schlitzer 2015); C is from
Omori et al. (2010) with permission from Elsevier.
2 W. T. R. Chiu et al.
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Type species. Tabukicypris decoris sp. nov., the only
known species.
Diagnosis. A small, subtriangular-shaped Pontocypridi-
dae genus with a flattened ventral surface, conspicuous
anterior and posterior vestibula, and subcentral muscle
scars composed of a rosette-shaped cluster of six scars.
Derivation of name. In honour of Ryoichi Tabuki (Uni-
versity of the Ryukyus, Japan) for his work on submarine
cave ostracods.
Tabukicypris decoris sp. nov.
(Figs 25)
Derivation of name. From the Latin decoris (genitive
noun) D ornament, with reference to surface ornamenta-
tion in this species.
Material. Holotype: USNM 612800, adult left valve
(Figs 2C, G, 4C, G, 5A, B). Paratypes: USNM 612801,
adult left valve (Figs 2A, 3A, E, 4A, E); USNM 612802,
adult right valve (Figs 2B, 3B, 4B, F).
Type locality and horizon. Core 19, 9091 cm core
depth; Daidokutsu submarine cave, Ie Island, Okinawa,
Japan; 26.727

N, 127.831

E, 29 m water depth.
Dimensions. Holotype: USNM 612800 (L D 496 mm,
H D 212 mm). Paratypes: USNM 612801 (L D 524 mm,
H D 222 mm); USNM612802 (L D 468 mm, H D 192 mm).
Other material examined. Five more specimens were
examined: USNM 612803, adult RV; USNM 612804,
adult carapace; USNM 612805, adult RV; USNM
612806, juvenile LV; USNM 612807, juvenile RV.
Diagnosis. A species of Tabukicypris ornamented with
fine longitudinal ridges.
Description. Carapace comparatively well calcified,
small, highest at anterior cardina l angle. Outline elongate
and subt riangular in lateral view; anterior margin rounded,
more angular in right valve, weakly denticulate in left
valve; posterior margin acuminate, pointed subventrally;
dorsal margin straight; ventral margin almost straight.
Anterodorsal and posterodorsal corners (cardinal angles)
weakly angular. Lateral surface ornamented with fine,
longitudinal ridges; clusters of distinct pores distributed in
anterior quarter, especially along anterior margin, and in
ventral half of posterior quarter. Juveniles have less obvi-
ous surface ornamentation. Left valve overlaps right
valve. Po sterior and anterior inner lamellae broad; anterior
and posterior vestibules well developed; marginal pores
simple and unbranched. Hingement adont. Subcentral
muscle scars consist of rosette-shaped cluster of six scars.
Sexual dimorphism not evident.
Remarks. The subtriangular outline (especially its acu-
minate posterior margin) and the adont hingement of Tab-
ukicypris decoris gen. et sp. nov. suggest its taxonomic
affiliation to the Pontocyprididae or Paracyprididae (see
Moore 1961). Howeve r, the simple unbranched marginal
pore canals of this species suggest that it belongs to the
family Pontocyprididae rather than Paracyprididae,
because species of Paracyprididae mostly retain branched
marginal pore canals (Maddocks 1988). Furthermore,
Tabukicypris has rosette-shaped subcentral muscle scars,
a characteristic of Pontocyprididae, although the number
of scars is six instead of five, the typical number in Ponto-
cyprididae (Maddocks 1969). Although pontocypr idid
species usually have the right valve overlapping the left
valve, some pontocypridids (e.g. some species of Austral-
oecia) have left-valve overlap (Maddocks 1969, 1977).
Thus, we consider that this genus belongs to the family
Pontocyprididae, in spite of enigmatic external morpho-
logical characters including the fine longitudinal ridges,
the flat ventral surface especially in the posterior half, and
the distinct pore clusters in the anterior and posterior
parts, which are rarely seen in pontocypridids.
The general outline is similar to that of Pontocypris and
Propontocypris, but the anterior margin of this species is
more sharply acuminate than that of Pontocypris and Pro-
pontocypris, and the size of Tabuki cypris is generally
smaller than Pontocypris and Propontocypris (Maddocks
1969; Maddocks & Iliffe 1986). Furthermore, surface
ornamentation, such as the longitudinal ridges and disti nct
clusters of pores, is unknown in any genera of the families
Pontocyprididae or Paracyprididae. Rosette-shaped sub-
central muscle scars composed of six scars is also not
known in any genera with similar subtriangular outline in
these families, except Peripontocypris which has a
smooth valve surface (Wouters
1997). Paracypris has six
scars but they are not in rosette shape, and Paracypris has
a smooth valve surface without any distinct ornamentation
(Maddocks 1988). Thus, we consider that this species
belongs to a new genus, for which we propose
Tabukicypris.
Distribution. This species is known only from Holocene
sediment of the Daidokutsu submarine limestone cave
located on the east coast of Ie Island. Although one speci-
men is known from just outside of the cave, it is most
likely reworked from the cave (see below).
Discussion
Submarine cave endemic species
The absolute abundance (number of specimens per gram
of dry sediment) of Tabukicypris decoris gen. et sp. nov.
has gradually increased, especially in the innermost part
of the Daidokutsu cave (i.e. Core 19), during the last
Enigmatic Japanese Holocene ostracod 3
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Figure 2. Scanning electron microscopy images of Tabukicypris decoris gen. et sp. nov. A, USNM 612801, paratype, lateral view of
adult left valve, core 19, 33 34 cm core depth; B, USNM 612802, paratype, lateral view of adult right valve, core 06, 01 cm core
depth; C, USNM 612800, holotype, lateral view of adult left valve, core 19, 9091 cm core depth; D, USNM 612803, lateral view of
adult right valve, core 19, 01 cm core depth; E, USNM 612806, lateral view of juvenile left valve, core 19, 1819 cm core depth; F,
USNM 612807, lateral view of juvenile right valve, core 19, 01 cm core depth; G, USNM 612804, dorsal view of adult carapace, core
19, 34 cm core depth; H, USNM 612804, ventral view of adult carapace, core 19, 34 cm core depth. All specimens from the Holo-
cene Daidokutsu submarine cave, Ie Island, Ryukyu Islands.
4 W. T. R. Chiu et al.
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Figure 3. Scanning electron microscopy images of Tabukicypris decoris gen. et sp. nov. A, USNM 612801, paratype, internal view of
adult LV, core 19, 3334 cm core depth; B, USNM 612802, paratype, internal view of adult RV, core 06, 01 cm core depth; C,
USNM 612800, holotype, internal view of adult LV, core 19, 9091 core depth; D, USNM 612805, internal view of adult RV, core 19,
1718 cm core depth; E, USNM 612801, paratype, internal view of hinge of adult LV, core 19, 3334 cm core depth; F, USNM
612805, internal view of hinge of adult RV, core 19, 1718 cm core depth; G, USNM 612800, holotype, internal view of anterior part
of adult LV, core 19, 9091 cm core depth; H, USNM 612805, internal view of anterior part of adult RV, core 19, 1718 cm core depth.
All specimens from the Holocene Daidokutsu submarine cave, Ie Island, Ryukyu Islands.
Enigmatic Japanese Holocene ostracod 5
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Figure 4. Composite stereomicroscopy and scanning electron microscopy images of Tabukicypris decoris. AD, composite stereomi-
croscopy image of Tabukicypris decoris gen. et sp. nov.; A, USNM 612801, paratype, lateral view of adult left valve, core 19,
3334 cm core depth; B, USNM 612802, paratype, lateral view of adult right valve, core 06, 01 cm core depth; C, USNM 612800,
holotype, lateral view of adult left valve, core 19, 9091 cm core depth; D, USNM 612803, lateral view of adult right valve, core 19,
01 cm core depth. EH, scanning electron microscopy images of Tabukicypris decoris; E, USNM 612801, paratype, internal view of
muscle scar of adult left valve, core 19, 3334 cm core depth; F, USNM 612802, paratype, internal view of muscle scar of adult right
valve, core 06, 01 cm core depth; G, USNM 612800, holotype, internal view of muscle scar of adult right valve, core 19, 9091 cm
core depth; H, USNM 612805, internal view of muscle scar of adult right valve, core 19, 1718 cm core depth. All specimens from the
Holocene Daidokutsu submarine cave, Ie Island, Ryukyu Islands.
6 W. T. R. Chiu et al.
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»7000 years (Fig. 6). It is known that the inside of the
cave has gradually become darker and more isolated from
the outside during this period (Omori et al. 2010). Only
one Tabukicypris decoris valve was found in the sediment
sample IR1 (4.03 g dry weight) from the outside of the
cave at 46.2 m water depth (Fig. 1C). No specimens of
Tabukicypris decoris were found in the surface sediment
samples 116, 118 and 11 collected around Sesoko Island
(near Ie Island and the Daidokutsu submarine cave) at
similar water depths of 2030 m (Fig. 1B). These results
strongly suggest that Tabukicypris decoris is endemic to
the submarine cave environment. We consider that the
one specimen found outside the cave is a reworked speci-
men from the cave. This is reasonable given the steep
slope outside the cave.
‘Living fossil’ or morphological adaptations?
Pontocypridid and paracypridid ostracods have been
widely reported from Mesozoic and Cenozoic strata (e.g.
Moore 1961; Maddocks 1988). As far as we know , none
of them share the enigmatic characteristics of Tabukicyp-
ris decoris gen. et sp. nov., including fine longitudinal
ridges, distinct pore clusters in the anterior and posterior
parts, and a flat ventral surface in the posterior half.
Another enigmatic ostracod, Kasella ryukyuensis (Sigilli-
dae), is known from this cave (Tabuki & Hanai 1999).
These two species share the character of a flat venter in
the posterior half even though they are in different super-
families, suggesting that this character may be a morpho-
logical adaptation to the submarine cave environment,
Figure 5. Tabukicypris decoris gen. et sp. nov., USNM 612800, holotype, Holocene, Daidokutsu submarine cave, Ie Island, Ryukyu
Islands. A, composite stereomicroscope (transmitted light) image, lateral view of adult left valve, core 19, 9091 cm core depth; B,
drawing of adult left valve, showing subcentral muscle scars, well-developed anterior and posterior vestibules, and simple unbranched
marginal pores.
Enigmatic Japanese Holocene ostracod 7
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although the function is uncertain. Tabuki & Hanai (1999)
suggested that the strongly flattened and overlapping ven-
tral surface of Kasella may be effective to protect their
soft parts, because they open their valves widely when
they crawl. But it is uncertain whether the flattened ventral
surface of Tabukicypris has a similar function, because
their left and right valves are not strongly overlapped.
Tabuki & Hanai (1999) considered Kasella ryukyuensis to
be mainly living on hard substrates in caves, especially in
the crevices on cave walls and ceilings. We speculate that
some of the enigmatic morphological characters of Tabuki-
cypris may be an adaptation to the same or a similar habi-
tat. However, the flat ventral surface (as well as the small
size) of Kasella and Tabukicypris may also be indicative
of an interstitial origin or lifestyle, as discussed below. In
fact, both sigillid and pontocypridid ostracods are known
from interstitial environments (Wouters 1987; Danielopol
& Wouters 1992; Tsukagoshi 2004).
Pore canals often equipped with sensilla (pore systems;
Tsukagoshi 1990) are known as (mechano- or chemo-)
receptors (see Kamiya 1989; Tsukagoshi 1990). Anterior
and posterior pore clusters in Tabukicypris are probably
for sensory development, which is a typical constructive
adaptation to the submarine cave envi ronment (Iliffe &
Kornicker 2009). Given the food-limited nature of subma-
rine caves and the dominant scavenging feeding style
found within them (Hayami & Kase 1996; Kornicker
et al. 2007), we speculate that Tabukicypris may be a sen-
sitive scavenger in a dark environment. The small size of
Tabukicypris decoris is also typical of stygobites (Iliffe &
Kornicker 2009). In summary, available evidence sug-
gests that Tabukicypris is a well-ada pted stygobite rather
than a ‘living fossil’.
Origin of Tabukicypris
Given a » 120 m lower sea level in the Last Glacial Maxi-
mum (Yokoyama et al. 2000), the Daidokutsu cave is
young. Yamamoto et al.(2009) and Omori et al. (2010)
indicate that the cave was completely submerged at
»8000 years ago. However, it is unlikel y that Tabukicyp-
ris decoris gen. et sp. nov. suddenly evolved during the
Holocene, because of its occurrence throughout the last
»7000 years (Fig. 6) and its enigmatic morphology which
is not similar to that of any other pontocypridids. As Iliffe
et al. (2011) suggested for Bermuda’s caves, alternative
caves must have existed in the low-sea-level periods dur-
ing the Pleistocene as former habitats of this species. As
discussed below, there are three possibilities for the origin
of Tabukicypris.
Deep-sea origin. Comparatively well-calcified pontocy-
pridids, including Argilloecia, Australoecia and Aratro-
cypris, are abundant in deep-sea environments, especially
in upper bathyal depths (e.g. Whatley et al. 1985 ; Didi

e&
Bauch 2000 ; Yasuhara et al. 2008, 2009). Thus, the rela-
tively well-calcified carapace of Tabukicypr is within the
Pontocyprididae may suggest a deep-sea origin of this
genus. In addition, fine longitudinal ridges (or similar
structures such as striations or plications) are often found
in deep-sea species of genera in which most species have
a smooth valve surf ace (e.g. Paracytherois, Pseudocy-
there, Xestoleberis; Didi

e & Bauch 2000; Alvarez
Zarikian 2009; Yasuhara et al. 2009 ). In fact, a species
with longitudinal surface ornam ent, very similar to Tabu-
kicypris decoris, was misidentified (in our opinion) and
reported as Microcythere medistriatum (Alvarez Zarikian
2009). However, the internal view of this species was not
Figure 6. Temporal changes in absolute abundance (number of specimens per gram of dry sediment) of Tabukicypris decoris gen. et sp.
nov. for the last »7000 years. Number of specimens refers to valves (i.e. counting one valve as one specimen, and one articulated cara-
pace as two specimens). yr BP: year before present (D 1950).
8 W. T. R. Chiu et al.
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shown, precluding further discussion, and its size was
much smaller than that of Tabukicypris decoris.
Interstitial origin. The flat ventral surface in the poste-
rior half and the small size are prevailing characters in
interstitial ostracods, even in different families including
Pontocyprididae [e.g. Cobanocythere (Cobanocytheridae),
Parvocythere (Parvocytheridae), Comontocypris (Pontocy-
prididae); see Wouters 1987; Higashi & Tsukagoshi 2011,
2012]. In fact, one small pontocypridid species (similar to
Argilloecia) with a flat ventral surface was reported in
open nomenclature from an anchialine cave in Bermuda
(‘Pontocyprididae n. gen., n. sp.’ of Maddocks & Iliffe
1986). Maddocks & Iliffe (1986) suggested that this spe-
cies is specialized for an interstitial lifestyle. The evidence
listed above may suggest an interstitial origin of Tabuki-
cypris. The ancestor of Tabukicypris may have migrated to
a submarine cave during a low sea-level period.
Tropical shallow-marine origin. Wouters (1997)
reported Peripontocypris from the tropical shallow-
marine IndoPacific region. Although Peripontocypris
does not have any surface ornamentation or a flat ventral
surface, it has a very similar outline to Tabukicypris. Fur-
thermore, both of these genera have rosette-shaped sub-
central muscle scars composed of six scars. Given the
subtropical location of the Daidokutsu cave, it is plausible
that Tabukicypris has evolved from a species of Peripon-
tocypris or its close relative that invaded the submarine
cave environment.
Acknowledgements
We thank David J. Horne, Thomas M. Cronin and an
anonymous reviewer for valuable comments; Ryoichi
Tabuki for providing surface sediments and information;
Laura Wong for continuous support; HKU Electron
Microscope Unit for technical support; Hayato Tanaka for
giving advice on taxonomy; and Gene Hunt and Daniel
Levin for depositing type and figured specimens. This
study is supported by the Early Career Scheme of the
Research Grants Council of Hong Kong (project code:
HKU 709413P) and the Seed Funding Programme for
Basic Research of the University of Hong Kong (project
code: 201111159140) (to MY). Collaboration with KF
was partly supported by the International Research Hub
Project for Climate Change and Coral Reef/Island
Dynamics of University of the Ryukyus.
ORCID
Moriaki Yasuhara http://orcid.org/0000-0003-0990-
1764
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