ctenidium
80
pressure electrically, and from the latter two the salinity and depth are computed. The advantage of this instrument over the older techniques with
Nansen bottles and reversing thermometers is that it gives the data directly with a
very high vertical resolution, although calibration with the older instruments
stays necessary.
ctenidium (pI. ctenidia) ciliated organ of Bivalvia, consisting of many filaments,
and suspended in the mantle cavity. The ctenidia (also called gills, because of
their resemblance to the gills of fish) are mainly filters for sieving food particles from the water, and are to a lesser extent involved in the oxygenation of
blood in the gill veins. The ctenidia effectuate by ciliary movement (~cilia) a
water current from the inhalant opening or siphon, through the ctenidia,
towards the exhalant opening or siphon. The suspended particles retained by
the ciliated filament are transported over the ctenidium surface towards the
mouth lobes (or labial palps), which pass the selected fraction to the mouth for
ingestion. The remaining, not ingested material is removed as pseudofeces.
Ctenophora (ctenophores, comb-jellies) subphylum of the phylum Cnidaria. A small
group of marine, mostly planktonic species, in principle with the same body
structure as medusae with ectoderm, endoderm, mesogloea, and gastro-vascular
cavity. The body is generally spherical, with eight rows of combs with cilia, by
the movements of which the comb-jellies swim. Two branched, and sticky
tentacles, which are used to collect small planktonic prey animals like
Copepoda, can be retracted into tentacular sheaths in the sides. Tentacles in a
I-cm-wide comb-jelly can be 50 cm long. In some species the tentacles are
reduced and the prey is taken directly from the water with the mouth lobes.
Ctenophores are divided into the classes Tentaculata (e.g., Pleurobrachia, a cosmopolitan species especially abundant in coastal waters, and the open-sea
species Mnemiopsis and Bolinopsis) and Nuda (no tentacles, e.g., Beroe, a
comb-jelly feeding exclusively on Pleurobrachia).
Ctenostomata order of the class Gymnolaemata (phylum Bryozoa). The body walls
are not calcified. Example: Alcyonidium, which forms cartilagenous colonies,
that are locally common in the North Sea and can cause to people who handle it the so-called "fisherman's" itch.
Cubozoa (sea wasps) class of the phylum Cnidaria, which sometimes is included
in the class Scyphozoa (jellyfish). These often cubic medusae are powerful
swimmers and have four simple or four clusters of tentacles. They live in
tropical and subtropical seas, and are notorious for their powerful sting,
which can be fatal to humans. Example: Chironex.
culture techniques the complex of technical measures for the cultivation and
propagation of living organisms or tissues. This comprises optimization of
80
pressure electrically, and from the latter two the salinity and depth are computed. The advantage of this instrument over the older techniques with
Nansen bottles and reversing thermometers is that it gives the data directly with a
very high vertical resolution, although calibration with the older instruments
stays necessary.
ctenidium (pI. ctenidia) ciliated organ of Bivalvia, consisting of many filaments,
and suspended in the mantle cavity. The ctenidia (also called gills, because of
their resemblance to the gills of fish) are mainly filters for sieving food particles from the water, and are to a lesser extent involved in the oxygenation of
blood in the gill veins. The ctenidia effectuate by ciliary movement (~cilia) a
water current from the inhalant opening or siphon, through the ctenidia,
towards the exhalant opening or siphon. The suspended particles retained by
the ciliated filament are transported over the ctenidium surface towards the
mouth lobes (or labial palps), which pass the selected fraction to the mouth for
ingestion. The remaining, not ingested material is removed as pseudofeces.
Ctenophora (ctenophores, comb-jellies) subphylum of the phylum Cnidaria. A small
group of marine, mostly planktonic species, in principle with the same body
structure as medusae with ectoderm, endoderm, mesogloea, and gastro-vascular
cavity. The body is generally spherical, with eight rows of combs with cilia, by
the movements of which the comb-jellies swim. Two branched, and sticky
tentacles, which are used to collect small planktonic prey animals like
Copepoda, can be retracted into tentacular sheaths in the sides. Tentacles in a
I-cm-wide comb-jelly can be 50 cm long. In some species the tentacles are
reduced and the prey is taken directly from the water with the mouth lobes.
Ctenophores are divided into the classes Tentaculata (e.g., Pleurobrachia, a cosmopolitan species especially abundant in coastal waters, and the open-sea
species Mnemiopsis and Bolinopsis) and Nuda (no tentacles, e.g., Beroe, a
comb-jelly feeding exclusively on Pleurobrachia).
Ctenostomata order of the class Gymnolaemata (phylum Bryozoa). The body walls
are not calcified. Example: Alcyonidium, which forms cartilagenous colonies,
that are locally common in the North Sea and can cause to people who handle it the so-called "fisherman's" itch.
Cubozoa (sea wasps) class of the phylum Cnidaria, which sometimes is included
in the class Scyphozoa (jellyfish). These often cubic medusae are powerful
swimmers and have four simple or four clusters of tentacles. They live in
tropical and subtropical seas, and are notorious for their powerful sting,
which can be fatal to humans. Example: Chironex.
culture techniques the complex of technical measures for the cultivation and
propagation of living organisms or tissues. This comprises optimization of