current ripple
82
rent speed. The direction is measured by recording the position of a current
vane with respect to a compass. As the first measurement gives a time average and the other a momentaneous value, caution is required in interpreting
the results. A further problem may arise from fouling when instruments are
deployed too long. Other sensors, such as the Doppler current meter (---?Doppler
effect), are acoustic or electromagnetic and have a high time resolution.
current ripple ---?ripple.
cuticula (cuticle) superficial, noncellular layer covering certain organism,
secreted by the hypodermis. ---?exoskeleton.
Cyanobacteria (syn. Cyanophyceae, blue-green algae) phylum of the kingdom
Monera. Their cell nucleus has no envelope (---?prokaryotes), in contrast to the
eukaryotic true algae (---?eukaryotes), and they lack plastid membranes and
mitochondria. Chlorophyll-a, p-carotene and phycobilin are their pigments for photosynthesis. Many species owe their characteristic blue-green color to phycocyanin. Some cyanobacteria, however, are more yellowish green and some
are even red due to phycoerythrin. There are four major subgroups of
cyanobacteria. First the chroococcales, which are unicellular rods or cocci.
They reproduce either by binary fission or by budding. Second, the pleurocapsales, which are single cells enclosed in a fibrous layer. The third group
contains the nostocales, which form filamentous structures, exclusively
composed of vegetative cells, known as trichomes. The fourth group exists
of the stigonematales, which form differentiated cells known as heterocysts,
when growing in the absence of fixed forms of nitrogen. In picoplankton the
chroococcacean Synechococcus plays a significant role in the primary production of the oceans.
Cyanophyceae ---?Cyanobacteria.
cycle (1) a time interval (day, year, tide, etc.) during which a sequence of recurrent (successions of) events is completed; (2) a course of a series of events
that recur regularly and often lead to the starting point: carbon cycle, nutrient
cycle, life cycle, biogeochemical cycle.
Cycliophora recently (1995) described phylum of small « 1 mm), acoelomate
(without coelom), epizoic animals, with affinities to Bryozoa and Entoprocta. Until
now only one species is known, which is found on the mouth parts of the
Norwegian lobster. The body is sac-like and attached to the host by an adhesive disk. A funnel with a ring of cilia collects the food. By internal budding
free-swimming larvae and dwarf males develop, but by the same process
also a regular regeneration of the individual takes place. The dwarf males
attach to the female.
82
rent speed. The direction is measured by recording the position of a current
vane with respect to a compass. As the first measurement gives a time average and the other a momentaneous value, caution is required in interpreting
the results. A further problem may arise from fouling when instruments are
deployed too long. Other sensors, such as the Doppler current meter (---?Doppler
effect), are acoustic or electromagnetic and have a high time resolution.
current ripple ---?ripple.
cuticula (cuticle) superficial, noncellular layer covering certain organism,
secreted by the hypodermis. ---?exoskeleton.
Cyanobacteria (syn. Cyanophyceae, blue-green algae) phylum of the kingdom
Monera. Their cell nucleus has no envelope (---?prokaryotes), in contrast to the
eukaryotic true algae (---?eukaryotes), and they lack plastid membranes and
mitochondria. Chlorophyll-a, p-carotene and phycobilin are their pigments for photosynthesis. Many species owe their characteristic blue-green color to phycocyanin. Some cyanobacteria, however, are more yellowish green and some
are even red due to phycoerythrin. There are four major subgroups of
cyanobacteria. First the chroococcales, which are unicellular rods or cocci.
They reproduce either by binary fission or by budding. Second, the pleurocapsales, which are single cells enclosed in a fibrous layer. The third group
contains the nostocales, which form filamentous structures, exclusively
composed of vegetative cells, known as trichomes. The fourth group exists
of the stigonematales, which form differentiated cells known as heterocysts,
when growing in the absence of fixed forms of nitrogen. In picoplankton the
chroococcacean Synechococcus plays a significant role in the primary production of the oceans.
Cyanophyceae ---?Cyanobacteria.
cycle (1) a time interval (day, year, tide, etc.) during which a sequence of recurrent (successions of) events is completed; (2) a course of a series of events
that recur regularly and often lead to the starting point: carbon cycle, nutrient
cycle, life cycle, biogeochemical cycle.
Cycliophora recently (1995) described phylum of small « 1 mm), acoelomate
(without coelom), epizoic animals, with affinities to Bryozoa and Entoprocta. Until
now only one species is known, which is found on the mouth parts of the
Norwegian lobster. The body is sac-like and attached to the host by an adhesive disk. A funnel with a ring of cilia collects the food. By internal budding
free-swimming larvae and dwarf males develop, but by the same process
also a regular regeneration of the individual takes place. The dwarf males
attach to the female.