Page 239 - (DK) Ocean - The Definitive Visual Guide

CHROMISTS 237

PHYLUM RADIOZOA geometric pattern. The spines aid PHYLUM FORAMINIFERA covered with cytoplasmic strands
buoyancy and the pores provide (pseudopodia) for collecting food.
Cladococcus viminalis outlets for cell material, called Hastigerina pelagica Hasterigina pelagica is unique in
pseudopodia, which engulf any food surrounding its test with a gelatinous
DIAMETER 0.08mm that becomes trapped on the spines LENGTH / 4 in (6 mm) capsule of tiny frothy bubbles,
1
HABITAT Surface waters and carry it to the centre of the cell HABITAT Warm waters at depth of 660 ft (200 m) which is thought to aid buoyancy.
to be digested. Cladococcus viminalis Dinoflagellates sometimes live on the
DISTRIBUTION Mediterranean DISTRIBUTION Subtropical and tropical waters of
is a polycystine radiolarian, which North Atlantic and western Indian Ocean surface of the capsule and up to
Radiolarians produce extremely are the most commonly fossilized 79 have been counted on a single
complex silica tests of spines and pores radiolarians and are frequently found Foraminiferans are unicellular individual, although 6–10 is more
that are laid down in a well-defined in chalk and limestone rocks. organisms found only in marine usual. The relationship between
habitats. Hastigerina pelagica is one of the two organisms is not clearly
the larger forms. It is often pinkish understood because Hasterigina
PHYLUM HAPTOPHYTA very quickly in favorable conditions red and has a calcareous test with pelagica is carnivorous, yet the
and form blooms that can cover several globular-shaped chambers dinoflagellates are unharmed.
Emiliania huxleyi areas of up to 38,600 square miles from which radiate calcite spines globular-shaped
(100,000 square km). These blooms chamber of
DIAMETER 0.006 mm are visible from space because the calcareous test
HABITAT Surface waters coccoliths act like tiny mirrors
and reflect sunlight so the water
DISTRIBUTION Atlantic, Pacific, and Indian Oceans
they are in appears a milky white.
By reflecting light and heat and
Emiliana huxleyi is a protist belonging by “locking up” carbon in their
to a group of haptophytes commonly calcite coccoliths, they help reduce
known as coccolithophores. The name ocean warming. They have been calcite spines
comes from a covering of intricately found worldwide in chalk deposits aid buoyancy
sculptured calcite plates called dating from 65 million years ago.
coccoliths with patterns that are The famous white cliffs of Dover
unique to each species. Like some in the UK are mainly formed from
other protists, E. huxleyi can multiply coccolith plates.

PHYLUM OCHROPHYTA products of photosynthesis into oily
Ethmodiscus rex substances that increase their buoyancy.
Ethmodiscus rex can reproduce sexually
but, if conditions are favorable, it
1
1
DIAMETER / 16– / 8 in (2–3 mm)
multiplies rapidly, simply by dividing
HABITAT Warm, nutrient-poor water
into two. Over a 10-day period, one
DISTRIBUTION Open ocean worldwide individual that divides three times a
day can theoretically have more than
Ethmodiscus rex is the largest of all 1.5 billion descendants.
diatoms and can be seen with the
naked eye. It is a single cell with a
rigid cell wall, called a test, which
is impregnated with silica and covered
in regular rows of pits. The test is
made up of two disk-shaped
halves, called valves, which fit
tightly together. Because
each diatom has a
unique test, Ethmodiscus
rex can be easily valve forms one
half of test
identified in the fossil
record. It is found in rocks
that date from the Pliocene
and the fossils can be up to
5 million years old. The cells
need to remain near the water
surface in order to utilize the
Sun’s energy for food, which
rigid cell
they do by transforming the wall (test)
PHYLUM OCHROPHYTA are all that remains of a group of
organisms that flourished more than
PHYLUM OCHROPHYTA because it has highly distinctive long, Dictyocha fibula 5 million years ago. Their fossils are
stiff hairs, called setae, which project abundant in some Miocene deposits.
Chaetoceros danicus perpendicularly from the margins of LENGTH 0.045 mm
its test. and have prominent secondary HABITAT Surface waters golden yellow
LENGTH 0.005–0.02 mm spines along their length. Chloroplasts,
DISTRIBUTION Atlantic, Mediterranean, Baltic Sea, pigments used in
HABITAT Surface waters which contain pigments used in and eastern Pacific off coast of Chile photosynthesis
DISTRIBUTION Worldwide photosynthesis, are numerous and
found inside both the cell and the The golden-yellow pigments visible
setae. The setae are easily broken and in this image of Dictyocha fibula are
First described in 1844, Chaetoceros if large quantities lodge in the gills typical of two groups of golden algae
is one of the largest and most diverse of a fish, they may kill it. The known as Chrysophyceae and
genera of marine diatoms, containing secondary spines anchor the setae Dictyochophyceae (this species). OCEAN LIFE
nearly 200 species. Chaetoceros danicus to the sensitive gill tissue causing The word Dictyocha means “net”
is a colonial form, and groups of irritation, and the fish reacts by and refers to the large windows in projection
seven cells are not uncommon producing mucus. Eventually, it the silica test. Fewer than 20 species from
(as shown here). It is easily recognized dies from suffocation. of Dictyocha are alive today. They silica test