1. Introduction
G
rowth and form of marine organisms inhabiting hard substrata, the
"marine sessile organisms", is characterized by a number of remarkable
properties. One remarkable feature of these organisms is that many of them
can be characterized as modular organisms. Modular organisms are typically
built of repeated units, the modules, which might be a polyp in a coral colony
or a frond in seaweeds. In most cases, the module has a distinctive form, while
the growth form of the entire colony is frequently an indeterminate form.
Indeterminate growth indicates that the same growth process may result in an
infinite number of different realizations of the growth form . This is in contrast
to unitary organisms such as vertebrates and insects, in which a single-celled
stage develops into a well-defined, determinate structure. In many cases the
growth process in modular organisms leads to complex shapes, which are
often quite difficult to describe in words. In most of the biological literature
these forms are only described in qualitative and rather vague terms, such as
"thinly branching", "tree-shaped" and "irregularly branching".
Another major characteristic of marine sessile organisms is that there is
frequently a strong impact of the physical environment on the growth process,
leading to a variety of growth forms. Growth by accumulation of modules
allows the organism to fit its shape to its environment i.e., have plasticity.
In many seaweeds, sponges, and corals, differences in exposure to water
movement cause significant changes in morphology. A good example of this
plasticity is the Indo-Pacific stony coral Pocillopora damicornis (Veron and
Pichon 1976) shown in Plg.r.i. In very sheltered environments, this species
has a thin-branching growth form. The growth form gradually transforms
to a more compact shape when the exposure to water movement increases.
Without knowledge of this relationship between the physical environment
and the growth process, the enormous variety in growth forms found in this
species does not make any sense . Early taxonomists were often confused by
this diversity; very often different growth forms of the same species were
classified as different species. Ortmann (1888) wrote about this genus :
"haben wir hier ein Chaosvon Formen,,1
since he was not able to decide to which of the described species his specimens
could be attributed.
People have been studying the growth and form of marine sessile organisms for many decades. For example, the classic work by D'Arcy Thompson
(1917) describes the packing of the cups containing the polyps, the corallites
on the surface of a coral colony. In the work of lackson (1979) six basic shapes
1 Wehave a chaos of forms here.
J. A. Kaandorp et al., The Algorithmic Beauty of Seaweeds, Sponges and Corals
© Springer-Verlag Berlin Heidelberg 2001
G
rowth and form of marine organisms inhabiting hard substrata, the
"marine sessile organisms", is characterized by a number of remarkable
properties. One remarkable feature of these organisms is that many of them
can be characterized as modular organisms. Modular organisms are typically
built of repeated units, the modules, which might be a polyp in a coral colony
or a frond in seaweeds. In most cases, the module has a distinctive form, while
the growth form of the entire colony is frequently an indeterminate form.
Indeterminate growth indicates that the same growth process may result in an
infinite number of different realizations of the growth form . This is in contrast
to unitary organisms such as vertebrates and insects, in which a single-celled
stage develops into a well-defined, determinate structure. In many cases the
growth process in modular organisms leads to complex shapes, which are
often quite difficult to describe in words. In most of the biological literature
these forms are only described in qualitative and rather vague terms, such as
"thinly branching", "tree-shaped" and "irregularly branching".
Another major characteristic of marine sessile organisms is that there is
frequently a strong impact of the physical environment on the growth process,
leading to a variety of growth forms. Growth by accumulation of modules
allows the organism to fit its shape to its environment i.e., have plasticity.
In many seaweeds, sponges, and corals, differences in exposure to water
movement cause significant changes in morphology. A good example of this
plasticity is the Indo-Pacific stony coral Pocillopora damicornis (Veron and
Pichon 1976) shown in Plg.r.i. In very sheltered environments, this species
has a thin-branching growth form. The growth form gradually transforms
to a more compact shape when the exposure to water movement increases.
Without knowledge of this relationship between the physical environment
and the growth process, the enormous variety in growth forms found in this
species does not make any sense . Early taxonomists were often confused by
this diversity; very often different growth forms of the same species were
classified as different species. Ortmann (1888) wrote about this genus :
"haben wir hier ein Chaosvon Formen,,1
since he was not able to decide to which of the described species his specimens
could be attributed.
People have been studying the growth and form of marine sessile organisms for many decades. For example, the classic work by D'Arcy Thompson
(1917) describes the packing of the cups containing the polyps, the corallites
on the surface of a coral colony. In the work of lackson (1979) six basic shapes
1 Wehave a chaos of forms here.
J. A. Kaandorp et al., The Algorithmic Beauty of Seaweeds, Sponges and Corals
© Springer-Verlag Berlin Heidelberg 2001