International Journal of Marine Science, 2016, Vol.6, No.14, 1-10
7
3.3 Transition some features
In support of the above-said, it is necessary to consider the similarity of growth forms of some species groups
(
Caulastrea-Favia-Favites- Goniastrea-Platygyra Goniastrea-Platygyra
), which was spoken about in the previous
chapter when discussing variability and the transition of many features from one genus to the other one. Now we
shall see to what extent a two-way transition of such features as “placoid”, “cerioid” and meandroid” growth
forms in the series
Caulastrea-Favia-Favites-Goniastrea-Platygyra
is real. All
Caulastrea
have only phaceloid
colonies, and however close to each other corallites may be located, each of them has epitheca and its colony
has no coenosteum. And it must be so, proceeding from the definition of a phaceloid colony (Wells, 1956). In a
placoid colony all corallites have a common coenosteum, and phaceloid colonies are not known among
Favia
.
This means that in this case an indicator between
Caulastrea
and
Favia
, showing transition of features of colony
forms, does not work in both directions. As was shown above, placoid colonies fundamentally differ from cerioid
ones. The former have round discrete corallites with endo- and exotheca developed on a smooth or vesicular
coenosteum. The latter are characterized by polygonal corallites with a common exotheca, adjoining septa and the
absence of coenosteum. This is why a strict approach to the definitions of “placoid” and “cerioid,” taking into
account that all
Favia
are placoid, and all
Favites
are cerioid, goes a long way toward removing the problem of
transition of these features from one genus to the other one. Among
Favites
the species
F. bennettae
, having a
tendency for corallites to form meanders, is now attributed to the genus
Oulophyllia
(Veron, 1986), thus, the
transition of the feature “meandroid colonies” to the genus
Goniastrea
and back to
Favites
is removed.
For the remaining three genera the feature “meandroid colonies” is not really the most reliable character. They all
have cerioid and meandroid corallites in some of their species.
Goniastrea
in most cases are cerioid,
Platygyra
are
both, and
Oulophyllia
are meandroid with individual polygonal corallites. It means that this feature cannot serve
as a diagnostic feature. But, if a characteristic of cerioid-meandroid colonies were added that “well formed large
pali, forming a crown, always projecting over the corallite indentation,” then these features would be typical only
for the genus
Goniastrea
. Neither
Platygyra
nor
Oulophyllia
have a distinctly developed crown. The spongy
columella of
Platygyra
merges into one line, passing through all corallites within a valley. In
Oulophyllia
the
columella always designates the centers of corallites. In addition, broad trough-shaped valleys or corallites of the
Oulophyllia
are 1.5 times wider than the funnel-shaped valleys of
Platygyra
.
3.4 Placoid or cerioid
The characteristics “massive placoid” and “massive-cerioid” are as insufficient for the identification of
Favia
and
Favites
without mentioning that they are
Faviidae
as the characteristic “massive cerioidmeandroid” is insufficient
for identification of
Goniastrea, Platygyra
and
Oulophyllia
. As it is known from the principles of zoological
systematization, a character or a sum of characters become taxonomic characters only in relation between two taxa.
And when they are unambiguously limited qualitatively or quantitatively, then specimens of a species will be
identified easier, and there will always have to be a gap in the values of one or more characters between different
species, no matter whether the characters are morphological, ecological, biochemical or genetic.
Difficulties in identification, and especially in the separation of
Favia speciosa
from
F. pallida
, have been
discussed repeatedly (Chevalier, 1971, 1975; Veron et al. 1977; Scheer and Pillai, 1983). Now we shall analyze a
complex of characters of both species (Table 1). As can be seen, there are distinctions for every character. At the
same time, many characters will overlap even though a sample of colonies of the two species is not large.
But F.
pallida has no highly prominent corallites, and F. speciosa has no corallites joined together.
There are also
characters with a larger gap. Horizontal skeletal elements of these species corals differ greatly. The difference in
lamina size is not very great, but the rates that laminae are laid down in the process of corallite growth differ
substantially. In
F. speciosa
dissepiments are laid 2-3 times more often than in
F. pallida
. It seems that this
genetically determined character is functionally connected and morphologically developed in highly prominent
corallites, which are absent in
F. pallida
corals, having different rates of vertical growth.
