No species are listed by the IUCN Red List. For most Hy-drozoa, the distribution and the abundance are not known and only the few remaining specialists know about their presence. Many species are endemic simply because they are not searched for and only the areas of activity of specialists are covered. The only groups mentioned in regional or national red lists are the calcified, coral-like Milleporidae and Stylas-teridae, which are also listed by CITES. Inclusion of these taxa on conservation lists is linked to the assessment of species value according to appearance.
Milleporidae and Stylasteridae have been subjected to trade, as are some hydroids (known as "white weeds" in the North Sea). Their decline is linked to habitat degradation.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.