Indian Journal of Geo-Marine Sciences Vol. 40(1), February 2011, pp. 13-27 Cephalopod research and bioactive substances J. Rajasekharan Nair* ,1 , Devika Pillai 1 , Sophia M Joseph 2 , P. Gomathi 3 , Priya V Senan 4 & P.M. Sherief 1 1 College of Fisheries, Kerala Agricultural University, Panangad, Kochi 682506, India 2 Rajiv Gandhi Centre for Biotechnology, Poojapura, Thycaud P.O, Trivandrum-695014, India 3 Department of Fisheries, TNHB Complex, Ashok Nagar, Chennai, Tamil Nadu- 83, India 4 Dept. of Biotechnology, SNDP Yogam College, Konni, Kerala, India *[E-mail: nairjr@rediffmail.com] Received 20 October 2010; revised 11 January 2011 Marine environment comprises complex ecosystems and many of the organisms are known to possess bioactive components as a common means of self-defense or for the protection of eggs and embryos. In recent years, many bioactive compounds have been extracted, characterized and purified from various marine animals like bacteria, algae, dinoflagellates, tunicates, sponges, soft corals, bryozoans, cephalopods, and echinoderms. Present review consists of the research work done on the biology of the cephalopods, mainly pertaining to the feeding strategies (the salivary gland toxins, body and liver oils), the reproductive strategies (the ovarian-peptides, the nidamental gland products, accessory nidamental gland products and the associated symbiotic bacteria), and the defence mechanisms (the ink glands and their bioactive products, the squid-vibrio association, the camouflage colouration mechanisms and the reflectin-proteins). The learning capabilities and personalities of octopods have been a matter of great interest in cephalopod ethology. The aspect of cephalopod welfare in laboratory and field studies merits scientific debate because of the biological and behavioural complexities exhibited by these highly evolved, lovable invertebrates. [Key Words: cuttlefish, squid, octopus, nidamental glands, symbiotic bacteria, salivary toxins, ink-peptidoglycan, reflectin-proteins] Introduction The marine environment comprises complex ecosystems and many of the organisms are known to possess bioactive components as a common means of self-defense or for the protection of eggs and embryos. Some organisms derive the chemistry from dietary sources, while others synthesise the compounds de novo. Some compounds may be produced by associated organisms, while others may require an association between the host and microorganisms to produce the compounds 1 . In recent years, many bioactive compounds have been extracted, characterized and purified from various marine animals like bacteria, algae, dinoflagellates, tunicates, sponges, soft corals, bryozoans, cephalopods, and echinoderms 2,3 . The word Mollusca comes from the Latin word mollus, meaning ‘soft’. The phylum Mollusca includes animals that are usually soft-bodied but have hard external shells of calcium carbonate. Some molluscs like the cephalopods have evolved to having reduced, internalized shells, or to entirely losing their shells. The class Cephalopoda (Gr. Kephale =head and pod = foot) includes squids, cuttlefishes, octopuses and nautilus. The subclass Nautiloidea has external shells, while in the Coeleoidea, the shell is either considerably internal or has been completely lost 4 . The Coeleoidea includes squids, cuttlefishes, octopods and vampire squids, which are represented by around 700 species (Fig. 1). Cephalopods occur in all marine habitats of the world like benthic-cryptic or burrowing in coral reefs, grass flats, sand, mud and rocks; epibenthic; and pelagic in bays, seas and in the open ocean. They are found at depths ranging from the surface to over 5000 m. Many species of oceanic cephalopods undergo vertical migration, where in they occur at depths of about 400 to 800 m during the day, then ascend into the uppermost 200 m or so during the night. Shallow living cephalopods are able to conceal themselves by chromatophore-produced colour patterns and chameleon like colour changes, while many deep-sea forms camouflage themselves by producing bioluminescent light from photophores. Cephalopods are famous for their defences, from their fast jetting escape movements to changes in colouration that can ___________ *Correspondent author