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Restructuring the Traditional Suborders in the Order Scleractinia Based on
Embryogenetic Morphological Characteristics
Author(s): Nami Okubo
Source: Zoological Science, 33(1):116-123.
Published By: Zoological Society of Japan
DOI: http://dx.doi.org/10.2108/zs150094
URL: http://www.bioone.org/doi/full/10.2108/zs150094
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© 2016 Zoological Society of JapanZOOLOGICAL SCIENCE 33: 116–123 (2016)
Restructuring the Traditional Suborders in the Order Scleractinia
Based on Embryogenetic Morphological Characteristics
Nami Okubo*
Department of Economics, Tokyo Keizai University, 1-7-34 Minamimachi,
Kokubunji, Tokyo 185-8502, Japan
The order Scleractinia includes two distinct groups, which are termed “complex” and “robust” as
indicated by the molecular phylogeny of mitochondrial 16S ribosomal gene sequences. Since this
discovery, coral taxonomists have been seeking morphological characters for grouping this deep
division in the order Scleractinia. Recently, morphological characteristics during embryogenesis
that facilitate grouping the two clades as “complex” and “robust” were reported, thus clarifying a
deep division in the Scleractinia. In the present report, I establish two new suborders, Refertina and
Vacatina, on the basis of the embryogenetic morphological characteristics, molecular data, and
new observations of Tubastraea coccinea and Cyphastrea serailia embryogenesis. In particular, the
embryo of T. coccinea has a possible fertilization membrane that was first observed in the phylum
Cnidaria. The new suborder Refertina consists of the families that belong to the “complex” clade
and have no or little blastocoel. The new suborder Vacatina is composed of the families that fall into
the “robust” clade and have an apparent blastocoel.
Key words: coral, suborder, embryogenesis, hyaline layer, complex, robust
INTRODUCTION
Scleractinian corals are found in oceans around the
world. The classification of these animals, including those in
the fossil record, has been for a long time confused. The
development of molecular and morphological tools devel-
oped now enables a better understanding of the evolution-
ary history of scleractinians. Our understanding of skeletal
growth and homology is limited, because rampant conver-
gent evolution limits the usefulness of morphological phylo-
genetics. Molecular phylogenetic analyses however have
revealed the multi-level systematics of the Scleractinia, giv-
ing rise to new hypotheses regarding relationships among
suborders, families, and genera that do not agree with those
proposed on the basis of traditional classification. Moreover,
many families of Scleractinia have not been established by
molecular methods, and phylogenies often vary depending
on the number of samples and which genes were used
(Fukami et al., 2008; Huang et al., 2011; Arrigoni et al., 2012;
Kayal et al., 2013). However, morphology is also very impor-
tant, and has broad utility, especially for the field biologists.
Before launching a long debate between morphology-
and molecular-phylogeny researchers, Romano and Palumbi
(1996) found that the order Scleractinia includes two dis-
crete lineages that originate in the early evolutionary history
of the group, termed “complex” and “robust” on the basis of
mitochondrial 16S ribosomal gene sequences. Coral taxon-
omists have for a long time been seeking morphological
characteristics for grouping this deep division in the order
Scleractinia, but morphological support for the robust and
complex dichotomy was deficient (Kitahara et al., 2010).
Recently, however, Okubo et al. (2013) have reported on a
morphological characteristic during embryogenesis that
facilitates grouping the two clades as “complex” and
“robust”, thus clarifying a deep division in the Scleractinia.
Corals in “complex” clade have a blastocoel, while those in
“robust” clade have no blastocoel during embryogenesis
(Okubo et al., 2013). In addition, we have already found that
gene expression patterns relating gastrulation are different
between representatives in each group (Okubo, Hayward,
Foret and Ball, in preparation).
Originally, “complex” corals were described as having
comparatively porous and light-calcified complex skeletons
with branching and various growth forms, while “robust”
have relatively heavy-calcified ones with plate or massive
growth forms (Romano and Palumbi, 1996). However, many
studies have implied that the names “complex” and “robust”
do not fit the morphological characteristics of the two
groups; thus Veron (2013) mentioned “these two nicknames
are somewhat inappropriate”. Besides, molecular analyses
suggest that more than half of the traditional suborders
(Fungiina Verrill, 1865; Caryophylliina Vaughan & Wells,
1943; Astrocoeniina Vaughan & Wells, 1943; Dendrophylliina
Vaughan & Wells, 1943; plus the Meandriina and Poritiina
proposed by Veron, 1995) contain the suborders that belong
to both “complex” and “robust” groups. In addition, the
“robust” coral clade is a lineage that is embedded in the
“complex” clade (Fukami et al., 2008; Kitahara et al., 2010).
In this paper, I propose two new suborders, Refertina
and Vacatina, restructured from the traditional suborders, on
the basis of molecular data and the key morphological char-
acteristics of the type genus for grouping the two clades: the
* Corresponding author. Tel. : +81-42-328-7789;
Fax : +81-42-328-7767;
E-mail:
nokubo@tku.ac.jp
Supplemental material for this article is available online.
doi:10.2108/zs150094
Restructuring suborders in Scleractinia 117
presence or absence of a coeloblastula and the mode of
gastrulation. In addition, embryogenesis in Tubastraea
coccinea from the “complex” clade and Cyphastrea serailia
from the “robust” clade was described. In particular, in the
current study, embryogenesis was first observed in the fam-
ily of T. coccinea, namely Dendrophylliidae, as T. coccinea
has been known as a brooding species. The new suborder
Refertina consists of the families that belong to the “com-
plex” clade and have no or little blastocoel. The new subor-
der Vacatina is mainly composed of the families, which fall
into the “robust” clade and have an apparent blastocoel.
MATERIALS AND METHODS
Collection of Tubastraea coccinea and Cyphastrea serailia
embryos
Two colonies of T. coccinea were collected from Kagoshima
prefecture, Japan, during December 2014. The colonies were cul-
tured in aquaria for five months. C. serailia was collected from
Wakayama prefecture, Japan, before the predicted date of spawn-
ing in 2013. Collected embryos were fixed in 10% formaldehyde
and then embedded in glycol methacrylate (Technovit 7100;
Heraeus Kulzer GmbH, Germany). Sections of 8-μm thickness were
cut using a microtome (Leica RM2125; Leica Microsystems). All
Fig. 1. Embryogenesis of Tubastraea coccinea. (A) First cleavage. (B) Morula stage. (C) Embryo has gradually flattened. (D–F) Cell cleavage
has proceeded. (G) The embryo has an appearance of a rough stone. Arrowheads indicate possible hyaline layers. (H) The embryo has grad-
ually swollen. (I) The outer cells surround an inner mass consisting of cellular fragments and cells. (J) Spheroidal embryo with a closing blasto-
pore. (K) Section of (J). (L) A round-shaped gastrula with a possible hyaline layer (arrowhead). (M) The embryo seems to have hatched out.
(N) Mesoglea was formed (arrow), and distinct endoderm (en) and ectoderm (ec) layers were apparent. (O) Pear-shaped planula. (P) Elongated
planula. Scale bar of (A–F, H–O) = 100 μm; (G, P) = 500 μm.
N. Okubo118
sections were mounted on glass slides and stained using methylene
blue.
RESULTS
Embryogenesis of Tubastraea coccinea
The release of buoyant eggs started at approximately
22:30 on 28 March (n = 40) and on 18 May (n = 3), and 22
May (n = 10) 2015. Planulae were released on 19 May (n =
1), 21 May (n = 1), and 23 June (n = 3), 2015. The water
temperature was 22.5°C. Although only one colony
spawned during each period, cell cleavage initiated at 1:50
on 29 March, 19 May, and 23 May 2015, indicating that
internal self-fertilization or parthenogenesis had occurred.
Microscopic analysis did not reveal sperms and polar bodies
around the eggs. The early cleavage was holoblastic (Fig.
1A). Cleavage proceeded and the embryo entered the
morula stage 6 h after spawning (Fig. 1B). The embryo
gradually flattened (Figs. 1C–F) and then became a rough
stone-shaped mass without a coelom by 12–16 h (Fig. 1G).
At this stage, the presence of a fertilization membrane
around the embryo (Fig. 1G, arrowheads) was observed.
The embryo gradually thickened after 27 h (Figs. 1H). The
outer cells surrounded an inner mass consisting of cellular
fragments and cells (Fig. 1I), indicating that gastrulation had
occurred. The surface of the embryo became smooth and a
blastopore (asterisk) was observed (Figs. 1J, K). The possi-
ble hyaline layer was still apparent (Fig. 1L), but then the
embryo appeared to have hatched out (Fig. 1M). The gas-
trula started swimming after approximately 140 h and the
hyaline layer disappeared. The mesoglea formed (arrow),
and distinct endoderm and ectoderm layers became appar-
ent (Fig. 1N). By 6 April 2015, the gastrula formed a pear-
shaped planula larva, which was actively swimming (Fig.
1O). By 16 April 16 2015, the planula had become elon-
gated and displayed a slow, creeping motility (Fig. 1P).
Embryogenesis of Cyphastrea serailia
Spawning of egg-sperm bundles occurred at approxi-
mately 20:00 on 11 July 2013. The first cleavage started 2.5
h after spawning. Cleavage proceeded, forming a blastocoel
(Fig. 2A, B). The embryo entered the cushion-shaped stage
by 5 h (Fig. 2C). The embryo became further flattened after
7 h (Fig. 2D). A pseudo-blastopore (Okubo et al., 2013) then
arose in the center of the disc-shaped embryo as it once
again formed a spherical shape with an apparent blastocoel
by 8–9 h (Fig. 2E–J, arrow head). After 10–11 h, the embryo
was a completely hollow sphere (Fig. 2K). Gastrulation by
invagination initiated after approximately 15 h (Fig. 2L).
Invagination proceeded and the blastopore (asterisk)
became smaller (Fig. 2M). Two germ layers, the ectoderm
(ec) and endoderm (en), were formed and separated by the
mesoglea at approximately 18–21 h (arrow, Fig. 2N). The
endodermal layer ruptured and it’s cells moved into the
space formed by invagination. The gastrula started swim-
ming by ca. 24 h (Fig. 2O). The blastopore became the oral
pore (Fig. 2P).
DISCUSSION
Tubastraea coccinea from the “complex” clade has no
blastocoel and becomes a stereogastrula. Prior to gastrula-
tion, the prawn-chip stage, which is common in Acropora,
Montipora, and Galaxea, is not found in this species.
Instead, a rough stone-shaped T. coccinea embryo was
observed, resembling that of Porites cylindrica, although the
P. cylindrica embryo has little blastocoel (Hirose and
Hidaka, 2006). The reason for this similarity may be that
Dendrophylliidae, to which T. coccinea belongs, is more
closely related at a molecular level to Poritidae than to
Acroporidae (Fukami et al., 2008; Kitahara et al., 2010).
Surprisingly, a possible fertilization membrane was
observed around the T. coccinea embryo, despite Cnidaria
being the only known phylum in the animal kingdom to have
no fertilization membrane (Dan, 2000). The observed layer
was quite translucent; therefore, was not distinctly visible
under the microscope until a part of the observation was
complete. However, the layer could have been present
when spawning occurred, because the embryos maintained
a certain distance from each other at that time (Fig. 1A). The
fertilization membrane is thought to prevent polyspermy, and
the hyaline layer may play an important role in holding blas-
tomeres together during cleavage. In this species, there is
no evidence whether reproduction by self-fertilization or by
parthenogenesis has occurred. In corals, self-fertilization
was identified histologically in Isopora bruggemanni (Okubo
et al., 2007), whereas parthenogenesis was suggested by
Lively and Johnson (1994) on the basis of the observations
of Pocillopora damicornis (Ward, 1992) and T. coccinea
and T. diaphana (Ayre and Resing, 1986).
Cyphastrea serailia from the “robust” clade has an
apparent blastocoel, and gastrulation occurred by invagina-
tion. The process of embryogenesis with a pseudo-blastopore
is similar to the other “robust” corals (Okubo et al., 2013). In
C. serailia, invagination occurred after a pseudo-blastopore
disappeared, such that the relationship between the location
of the pseudo-blastopore and invagination could not be
determined. In Favites abdita and F. pentagona, invagination
occurs in a different location from the pseudo-blastopore
(Okubo et al., 2013).
In corals, there is no reported evidence on how mesen-
teries and mesenterial filaments are formed. Study of C.
serailia may histologically show that the formation starts
when the endodermal layer is ruptured and the endodermal
cells move into the space formed by invagination during the
“robust” mode of embryogenesis (Fig. 2N). Thereafter, ver-
tical histological sections revealed that the moving cells
formed a mesentery-like shape (figure not shown). In con-
trast, it could not be determined how the thin layer, which
included a number of nuclei (Fig. 1N), had formed from the
T. coccinea stereogastrula (Fig. 1K). It is unknown whether
mesenteries and mesenterial filaments typically form from
the cells in the thin layer or the cells gathered at the center
of an embryo.
In conclusion, the observations in the present study, the
initial wide analyses reported by Okubo et al. (2013), and
the published literature all indicate that the order Scleractinia
has two distinct groups based on its mode of embryogenesis:
one consists of corals with no or little blastocoel, and the
other consists of corals with an apparent blastocoel. These
results clarified a deep division in the Scleractinia that facil-
itates grouping the two clades as “complex” and “robust”
with one exception (see discussion below). In this paper,
therefore, I establish two new suborders restructured from
Restructuring suborders in Scleractinia 119
the traditional suborders, on the basis of morphological
embryogenetic characteristics and molecular data.
Taxonomy
Phylum Cnidaria Verrill, 1865
Class Anthozoa Ehrenberg, 1834
Subclass Hexacorallia Haeckel, 1896
Order Scleractinia Bourne, 1900
Suborder Refertina new suborder
Definition.—The embryo has no or little blastocoel.
After spawning and fertilization, the cleavage proceeded and
the embryo became the prawn-chip or the rough stone-
shape stage (Fig. 3a). The embryo resulted in smooth sur-
face due to continued cell division, as the cells elongate to
the flattened disc, and it became spherical as the sides of
the bowl fold inward to form the blastopore (Fig. 3b, c).
Simultaneously, cells, yolk granules and zooxanthellae (in
the case of zooxanthellate corals) are released from the
inner side of the cell membrane into the central cavity to
Fig. 2. Embryogenesis of Cyphastrea serailia. (A) 32-cell stage. (B) Section of (A). The blastocoel was formed. (C) Embryo flattened to
become the cushion-shaped stage (D) Cushion-shaped embryo with a smooth surface further flattened. (E–H) Cushion-shaped embryo has
gradually swollen with a pseudo-blastopore (arrow head). (I) A pseudo-blastopore gradually disappeared. (J) Section of g with an apparent
blastocoel. (K) Embryo has become a hollow sphere. (L) Gastrulation has started by invagination. The asterisk in this and succeeding panels
shows a blastopore. (M) The blastopore has become smaller. (N) Mesoglea (arrow) formed, and distinct endoderm (en) and ectoderm (ec)
were becoming apparent. (O) The blastopore/oral pore began to close. (P) The endodermal layer ruptured and its cells moved into the space
formed by invagination. Scale bar = 50 μm.
N. Okubo120
form a stereogastrula (Fig. 3d). The outer cells formed a sin-
gle layer of epidermis and a central area contained cellular
fragments and lipid bodies. The boundary between the inner
and outer germ layers becomes clear, forming mesoglea (Fig.
3d). The oral pore (mouth) is formed by invagination (Fig. 3e).
Corals in this suborder belong to the “complex” clade.
Etymology.—The name Refertina is derived from the
Latin word refertus, meaning “filled”. The name refers to the
inner side of an embryo filled with cells and yolk granules.
Remarks.—At present, this suborder is composed of
Family Acroporidae Verrill, 1902, Family Agariciidae Gray,
1847, Family Astrocoeniidae Koby, 1890, Family
Dendrophylliidae Gray, 1847, Family Euphylliidae Alloiteau,
1952, Family Flabellidae Bourne, 1905, Family
Fungiacyathidae Chevalier, 1987, Family Gardineridae
Stolarski, 1996, Family Guyniidae Hickson, 1910, Family
Micrabaciidae Vaughan, 1905, Family Poritidae Gray, 1842,
Family Siderastreidae Vaughan and Wells, 1943, Family
Turbinoliidae Milne-Edwards and Haime, 1848.
Suborder Vacatina new suborder
Definition.—The embryo has an apparent blastocoel.
Cleavage proceeds after fertilization and a depression
appeared in the side of the sphere, becoming a flattened or
a cushion shape (Fig. 3f). Then, the embryo became swell-
ing (Fig. 3g, h), formed an apparent hollow sphere, i.e., the
formation of an apparent blastocoel (Fig. 3i). Cell fragments
then start to move into the blastocoel by invagination (Fig.
3j), which leads to formation of the endoderm. As invagina-
tion proceeds, the blastocoel gradually disappeared (Fig.
3k). Ectoderm and endoderm are separated by mesoglea,
and the blastopore becomes the oral pore/mouth (Fig. 3l).
Corals in this suborder belong to the “robust” clade.
Etymology.—The name Vacatina is derived from the
Latin word vacatus, meaning “empty”. The name refers to
the blastocoel of an embryo.
Remarks.—At present, this suborder is composed of
Family Caryophylliidae Dana 1846, Family Pocilloporidae
Gray, 1842, Family Fungiidae Dana, 1846, Family
Meandrinidae Gray, 1847, Family Oculinidae Gray, 1847,
Family Rhizangiidae d’Orbigny, 1851, Family Merulinidae
Verrill, 1865, Family Mussidae Ortmann, 1890, Family
Diploastreidae Chevalier and Beauvais, 1987, Family
Anthemiphylliidae Vaughan, 1907, Family Montastraeidae
Yabe and Sugiyama, 1941, Family Psammocoridae Chevalier
and Beauvais, 1987, Family Stenocyathidae Stolarski, 2000,
Family Lobophylliidae Dai and Horng, 2009, Family
Coscinaraeidae Benzoni et al., 2012, Family Deltocyathidae
Kitahara et al., 2013.
Incertae sedis: Family Montlivaltiidae Dietrich, 1926,
Family Schizocyathidae Stolarski, 2000, Family
Trochosmiliidae.
Restructuring the traditional suborders in the Sclerac-
tinia
The new suborder Vacatina corals formed a hollow
coeloblastula at the morula stage at the time when the new
suborder Refertina corals, such as Acropora had formed a
so-called prawn chip, with little or no space between the two
layers of which the embryo was composed (Fig. 4). The fam-
ilies Montlivaltiidae, Schizocyathidae and Trochosmiliidae,
whose positions are equivocal, were placed in incertae
sedis because there is no information on their molecular
composition or sufficient information about their morphology.
It has recently been suggested that the families
Gardineriidae and Micrabaciidae have a basal position in
corals (Kitahara et al., 2010; Stolarski et al., 2011). The
clade was termed “basal” (Stolarski et al., 2011), and Huang
(2012) follows this grouping. In this paper, however, the two
families could remain in the “complex” clade as the genetic
distance between basal and complex is relatively short com-
pared with that between complex and robust (Kitahara et al.,
2010). Thus, the two families have been grouped in the new
suborder Refertina.
The mode of gastrulation of Pavona decussata, a mem-
ber of the family Agariciidae, is “robust” (Okubo et al., 2013).
However, the molecular analyses strongly suggest that P.
decussata should be classified as a “complex” coral (Fukami
et al., 2008); therefore, I placed the family Agariciidae in the
new suborder Refertina as an exception. Kitahara et al.
(2010), with their more recent phylogenetic analyses of a
larger number of species, based only on the mitochondrial
CO1 gene, concluded that the “robust” coral clade originated
Fig. 3. Embryogenesis of the new suborders Refertina and
Vacatina.
Restructuring suborders in Scleractinia 121
Fig. 4. Phylogeny and the presence of blastocoel from the results of the past studies. The studied species are overlaid onto the coral phylogeny
of Kitahara et al. (2010), which is based on the sequence of the mitochondrial CO1 gene. See also other phylogenies that show each complex and
robust clade is monophyletic from the analyses using various different genes (Stolarski et al., 2011; Huang, 2012). The family names revised in
recent (Budd et al., 2012; Huang et al., 2014a, b) are explained using arrows. ACR: Acroporidae, AGA: Agariciidae, CAR: Caryophylliidae, DEN:
Dendrophylliidae, EUP: Euphylliidae, FAV: Faviidae, FLA: Flabellidae, FUN: Fungiidae, LOB: Lobophylliidae, MEL: Meruliniidae, MUS: Mussidae,
PEC: Pectiniidae, POC: Pocilloporidae, POR: Poritidae, RHI: Rhizangiidae, SID: Siderastreidae.
N. Okubo122
from within a clade that includes the agariciids and the cary-
ophylliid genus Dactylotrochus. There are thus at least two
possibilities regarding the “Pavona exception”. One possibil-
ity is that only P. decussata and a few other species in the
family Agariciidae have the “robust” embryogenesis mode,
and the rest of the species mainly have the “complex” mode;
in this case, it indicates that “robust” embryogenesis may
have been secondarily acquired in Agariciidae. The other
possibility is that all members of the family Agariciidae have
the same embryological “robust” mode. In this case, the
“robust” embryogenesis mode acquired before separating
robust clade and Agariciidae. Then, the taxonomic validity that
the new suborder Refertina includes the family Agariciidae
will
be discussed, considering other potential taxonomic charac-
ters such as reproductive modes (Baird et al., 2009).
The oculinids were polyphyletic (Romano and Cairns,
2000; Le Goff-Vitry et al., 2004), with Galaxea falling into the
“complex” clade (Kitahara et al., 2010). Budd et al. (2012)
moved Galaxea and Ctenella into the family Euphylliidae, so
I assigned the family Euphylliidae including these two gen-
era to the new suborder Refertina. Accordingly, the family
Meandrinidae becomes monophyletic and thus I assigned
the family Meandrinidae to the suborder Vacatina. The fam-
ily Guyniidae is grouped in the new suborder Refertina
based on the results of Romano and Cairns (2000). So far in
the family Astrocoeniidae,
Stephanocoenia
and
Stylocoeniella
have been molecularly analyzed and the former falls into
“complex” group and the latter into “robust” group. Stylocoe-
niella is related to pocilloporids (Kitahara et al., 2010), but
the type genus for the family is a fossil genus (Astrocoenia)
could be morphologically similar to Stephanocoenia (Fukami
et al., 2008), so that I grouped this family in the new subor-
der Refertina.
The family Siderastreidae is assigned to the new subor-
der Refertina based on the results of Benzoni et al. (2012).
The families Acroporidae, Dendrophylliidae, Flabellidae,
Fungiacyathidae, Poritidae, Turbinoliidae are grouped in the
new suborder Refertina, and the families Anthemiphyllidae,
Fungiidae, Merulinidae, Mussidae, Pocilloporidae,
Rhizangiidae, Stenocyathidae in the new suborder Vacatina
based on the results of Kitahara et al. (2010) and Okubo et
al. (2013). The families Coscinaraeidae, Deltocyathidae,
Diploastreidae, Lobophylliidae, Montastraeidae and
Psammocoridae are grouped into the suborder Vacatina
based on the results of Benzoni et al. (2007), Huang et al.
(2011), Benzoni et al. (2012), Kitahara et al. (2010), Dai and
Horng (2009), Budd et al. (2012) and Okubo et al. (2013).
The family Caryophylliidae is assigned to the new sub-
order Vacatina based on the result of molecular position of
Lophelia pertusa, which should be close to the type genus
Caryophyllia (Le Goff-Vitry et al., 2004), and its embryogen-
esis, which has hollow blastula (Larsson et al., 2014).
Goffredo et al. (2012) reported on the embryogenesis of
Caryophyllia, and they described the embryo has no blasto-
coel and gastrulation occurs by delamination. However, the
early cleavage stages, especially between the morula stage
to the blastula, which are the important stages to find the
blastocoel, are not shown in their paper. In Fig. 6B of
Goffredo et al. (2012), they describe the early embryos,
however, the surface of embryos, which they show, is very
smooth and no cellularization was observed from the pic-
ture. The embryos seem to be at the early gametogenesis
stage, or even if they are embryos as they describe, the
early cleavage stage including morula has already finished.
So it is difficult to say that Caryophyllia has no blastocoel. I
look forward to further studies on the early cleavage stages
before delamination starts in Caryophyllia. It is very interest-
ing if delamination occurs in Caryophyllia because Pocil-
lopora damicornis and P. eydouxi also show delamination
(Hirose et al., 2000) and they are close in the molecular phy-
logeny (Kitahara et al., 2010).
While the classification of corals remains in flux, several
additional hypotheses flow from the results of embryogenesis.
First, it would conclude that patterns of early development
and gastrulation do make phylogenetic sense, rather than
being correlated with other factors such as habitat or mode
of reproduction. Second, it would appear that the mode of
gastrulation in the new suborder Refertina is the original
mode of gastrulation within the Scleractinia. Having
discovered this apparent correlation between the pattern of
embryonic development and the robust/complex clades, I
turned to the literature to see whether this apparent correla-
tion held up to broader scrutiny. The results are summarized
(Supplementary Table S1 online). For some of these
papers, the data are inadequate for unequivocal assignment
to either a robust or complex pattern but Okubo et al. (2013)
made the best predictions based on text descriptions plus
figures. Some of the descriptions strongly support the corre-
lation between phylogeny and pattern of development. So,
in an era when scleractinian systematics is still in flux, pat-
terns of embryonic development can supplement data as a
tool for determining systematic and taxonomic position.
Gastrulation mode such as delamination, invagination,
ingression etc. could be used for grouping at the family or
genus level, because the gastrulation mode is different at
least among genera (Okubo et al., 2013). Also, in the early
stages of polyp formation, the beginning of skeletogenesis
might be useful as the morphology is different among fami-
lies (Okubo unpublished).
ACKNOWLEDGMENTS
The author is grateful to Tohru Iseto for critical reading of early
drafts with many helpful taxonomic comments, Helmut Schuhmacher
and Yoshihiko Kutsukake for their help on Latin, Hironobu fukami
and Marcelo V Kitahara for valuable information, Makoto Omori,
Eldon Ball, David Hayward and Patricia Morse for their help on pre-
paring the manuscript, Yuna Zayasu for her help on sampling of C.
serailia, and two anonymous reviewers for valuable comments. This
work was supported by JSPS KAKENHI 24710275 and 15K18599
to Nami Okubo. Further support was received from Tokyo Keizai
University (Research Grant 14-06) and Research Institute of Marine
Invertebrates (Research Grant 2015KO-3).
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(Received June 24, 2015 / Accepted August 16, 2015)
