mammals, marine
186
ed for swimming, burying, effectuating water currents for ventilation, or
carrying eggs (in females). The Malacostraca include along the primitive
Leptostraca, the superorders Syncarida (with no marine representatives),
Hoplocarida, Peracarida and Eucarida.
mammals, marine different groups of originally terrestrial mammals that have
returned to the sea over the last 80 million years, probably attracted by
abundant food, or to escape from predators or climatic changes. They
include Cetacea (whales and dolphins), pinnipeds (seals, sea-lions and walruses), sirenians (manatees, dugongs and Steller sea-cows) and mustelids (a few
otters, and the extinct sea-mink) and sometimes the polar bear is included.
Respiratory, circulatory, locomotory, thermo-regulating, and communicative systems are all significantly different from the typical terrestrial mammalian pattern. Man has used marine mammals as a source of food, fuel,
and clothing for at least 5000 years; with extending size and range of hunting vessels man began to affect populations, some species being hunted to
extinction: the Steller sea-cow was discovered in the Bering Sea in 1741 and
eradicated about 30 years later, the bowhead and right whales were almost
eradicated in the 18th and 19th centuries, the blue whale and humpback in
this century.
manganese nodules (syn. ferromanganese nodules) spherical or semi-spherical or
irregular concretions, largely consisting of oxides of iron (Fe) and manganese (Mn), but containing in addition metals like titanium, chromium,
copper, nickel, cobalt, and zinc, often found on the surface of deep-sea
marine sediments. Most likely of diagenetic origin. First reported during the
Challenger Deep-Sea Expedition. These nodules form very slowly, over millions of
years. ~mineral resources.
mangrove swamps (or mangal, also mangroves) salt marshes in the tropics covered by shrubs and trees. ~salt marsh.
mantle (1) (bioI.) ~Mollusca; (2) (geol.) ~earth's internal structure.
marginal basin (syn. back-arc basin) basin of intermediate (ca. 2000 m) to normal
oceanic (ca.4S00 m) depth, behind island arc systems and separating the trenches and island arcs from continents or other (usually inactive) island arcs.
marginal seas more or less enclosed seas along the continents.
Mariana Trench the deepest point in the ocean (12-15° N; 143-147° E). At this
depth an accurate measurement meets difficulties. The best available estimate is about 11030 m depth. ~bathyscaphe, ~trench, ~sea-floor topography.
186
ed for swimming, burying, effectuating water currents for ventilation, or
carrying eggs (in females). The Malacostraca include along the primitive
Leptostraca, the superorders Syncarida (with no marine representatives),
Hoplocarida, Peracarida and Eucarida.
mammals, marine different groups of originally terrestrial mammals that have
returned to the sea over the last 80 million years, probably attracted by
abundant food, or to escape from predators or climatic changes. They
include Cetacea (whales and dolphins), pinnipeds (seals, sea-lions and walruses), sirenians (manatees, dugongs and Steller sea-cows) and mustelids (a few
otters, and the extinct sea-mink) and sometimes the polar bear is included.
Respiratory, circulatory, locomotory, thermo-regulating, and communicative systems are all significantly different from the typical terrestrial mammalian pattern. Man has used marine mammals as a source of food, fuel,
and clothing for at least 5000 years; with extending size and range of hunting vessels man began to affect populations, some species being hunted to
extinction: the Steller sea-cow was discovered in the Bering Sea in 1741 and
eradicated about 30 years later, the bowhead and right whales were almost
eradicated in the 18th and 19th centuries, the blue whale and humpback in
this century.
manganese nodules (syn. ferromanganese nodules) spherical or semi-spherical or
irregular concretions, largely consisting of oxides of iron (Fe) and manganese (Mn), but containing in addition metals like titanium, chromium,
copper, nickel, cobalt, and zinc, often found on the surface of deep-sea
marine sediments. Most likely of diagenetic origin. First reported during the
Challenger Deep-Sea Expedition. These nodules form very slowly, over millions of
years. ~mineral resources.
mangrove swamps (or mangal, also mangroves) salt marshes in the tropics covered by shrubs and trees. ~salt marsh.
mantle (1) (bioI.) ~Mollusca; (2) (geol.) ~earth's internal structure.
marginal basin (syn. back-arc basin) basin of intermediate (ca. 2000 m) to normal
oceanic (ca.4S00 m) depth, behind island arc systems and separating the trenches and island arcs from continents or other (usually inactive) island arcs.
marginal seas more or less enclosed seas along the continents.
Mariana Trench the deepest point in the ocean (12-15° N; 143-147° E). At this
depth an accurate measurement meets difficulties. The best available estimate is about 11030 m depth. ~bathyscaphe, ~trench, ~sea-floor topography.