Page 256 - (DK) Ocean - The Definitive Visual Guide

254 FUNGI

Fungi

FUNGI FORM A GREAT KINGDOM OF SINGLE-CELLED and filamentous
DOMAIN Eucarya LICHEN ENCRUSTATION
life-forms, including yeasts and moulds. Some organise their filaments Fungi thrive on the
KINGDOM Fungi coast if they grow in
into complex fruiting structures, such as mushrooms. Truly marine
PHYLA 5 association with algae, in
fungi are rare, but a few fungus-like organisms survive within a slime an intimate symbiosis
SPECIES 46,574 called lichen. Here,
covering, avoiding contact with salt water. Fungi are abundant on encrusting and foliose
shorelines, but only in close association with certain algae. Alga and fungus grow in partnership lichens cover sandstone
cliffs in the Shetland
in a kind of symbiotic, compound organism called a lichen. Lichens proliferate in the hostile, Isles, Scotland.
wave-splashed zone of bare rock just above high tide.

Anatomy

A lichen’s body (thallus) is composed mainly of fungal
filaments called hyphae. The cells of the fungus’s algal
partner are restricted to a thin layer below the surface,
where they cannot dry out. Lichens grow in one of
four ways: bushy (fruticose); leaf-like (foliose); tightly
clustered (squamulose); or lying flat (crustose).
Marine fungus-like organisms, such as slime nets
(labyrinthulids) and thraustochytrids, are microscopic,
usually transparent, and encased in a network of slimy
threads. The cells move up and down within the threads
and react positively towards food. They are increasingly
recognized as protists, however, rather than fungi.

LICHEN COMPOSITION
This false-colour micrograph of a
lichen (below) shows the smooth
surface of the thallus, to the left,
and fungal hyphae, to the right.

ENCASED IN SLIME
This thraustochytrid (above)
is a fungus-like organism that
lives as a parasite within certain
bivalves. Its slime net forms a
complete cover.

Habitats
Most lichens require alternating dry and wet periods,
but marine lichens can withstand continuous drought or
dampness. On most rocky shores, yellow and grey lichens
dominate surfaces splashed by waves at high tide (the
splash zone). They endure both the drying Sun and wind,
and the salt spray of the sea. Below, in the tidal zone, the
brightly coloured lichens give way to black encrusting
lichen, such as Verrucaria maura, which covers the bedrock
and any large, stable boulders. Verrucaria serpuloides lives
yet further down the shore and is the only lichen to
survive permanent immersion in sea water.
Slime nets can live in the sea
because they are protected
from the dehydrating effects of
OCEAN LIFE seagrasses, green algae, or clams.
salt water by slime, or because
they live as parasites within

BELOW THE SPLASH ZONE
Some lichens, such as this crustose black
Verrucaria, live below the splash zone, and
may be surrounded by seaweeds.