*1.6. Marine Animals*

Oceans dominate planet Earth: approximately 70% of the Earth's surface is covered by water, and from that, 96.5% of this water is from the oceans [115]. More than 480,000 species of marine animals have been discovered and identified according to the World Register of Marine Species [116]. However, such a figure may be even larger: the Ward Appeltans of the Intergovernmental Oceanographic Commission of UNESCO (https://en.unesco. org/news/ocean-life-marine-age-discovery-0, accessed 19 November 2021) estimates that oceans may hold 700,000 species. These data represent what the ocean can become: a molecular library! Molecules that belong to an organism's physiology, act on hunting and prey digestion and/or chemical defense may ultimately lead to the discovery of new compounds with biotechnological or pharmaceutical uses.

Regarding bioprospection, marine animals have provided several molecules for a wide range of therapeutic applications. Some of them have already been approved by regulatory agencies and are being commercialized. The most known is ziconotide (Prialt), a ω-conotoxin peptide from *Conus magus*, applied by intrathecal route as analgesic for chronic and intense pain, whose mechanism of action is the selective blocking of neuronal N-type voltage-sensitive calcium channels [117,118]. Another known drug from marine animals is trabectedin (Yondelis), initially isolated from the marine ascidian *Ecteinascidia turbinata*, used to treat sarcomas and ovary cancer [119].

For cancer, other drugs have been developed, such as Ara-C (Cytarabine), a nucleoside isolated from a Caribbean sponge, *Cryptotheca crypta*. It is used for certain types of leukemia, including acute myeloid leukemia, acute lymphocytic leukemia and chronic myelogenous leukemia [120].

Brazilian sponges and cnidarians, such as *Zoanthus sociatus*, *Exaiptasia pallida* and *Carijoa riisei*, have yielded promising molecules active on cancer cells. Some of these authors have showed that *C. riisei* and the porifera *Tedania brasiliensis* extracts were effective in reducing the cell viability of glioblastoma, and that *C. riseii* also acts on breast and ovary cancer. Moreover, *Z. sociatus* and *E. pallida* were able to diminish leukemic cell viability [121]. Regarding the envenomation field, some of these authors have contributed for the understanding of marine animal venoms, from a biochemical and pathophysiological perspective.
