|Biological Diversity 2001|
order (photos above and below) includes the common 'octopus,' and the
finned octopods found deep in the oceans and sometimes in shallow polar
waters. Finned octopods, or Cirrata, have cirri (hair-like structures,
probably for feeding) lining each of their arms. The Incirrata have no
fins, and their arms are lined exclusively with suckers.
One species of Vampyromorpha is known to exist - the vampire squid. These creatures share traits with both octopods and decapods, but have special adaptations for deep-sea life. They are gelatinous and their second pair of arms are special sensory filaments. Their chromatophores cannot change color as quickly as other cephalopods', and they do not have ink sacs; instead, they have photophores, which exude glowing particles!
The name cephalopod ("head foot") comes from the proximity of the muscular foot to the head. As an adaptation to being predators the foot of octopuses and squids has developed into a funnel that can be used to quickly direct water out of their mantle as a type of "jet propulsion". Octopuses have 8 tentacles, squids and cuttlefish have 10 tentacles, and nautilus have 80-90 tentacles (McGraw Hill 1998, Wood 2001).
With special pigment cells called chromatophores cephalopods can change their color to match a new environment. Another form of self defense is the ability to form a "smoke screen" out of ink to allow a fast escape (University of Michigan 1996, Wood 2001).
Cephalopods have a highly developed nervous system with sensory organs and the most complex brain of any invertebrate. Many species have highly developed eyes that are comparable to the eyes of vertebrates. This advanced development is an example of convergent evolution. All species have a closed, or nearly closed, circulatory system with three hearts and gills. Their coelem is restricted to a bag around their hearts (McGraw Hill 1998).
Cephalopods are dioecious. The spermatophore is passed from the male to the female, and the eggs are then fertilized as they leave the oviduct. Cephalopod young go through a stage as trochophore larvae, as do most mollusks (McGraw Hill 1998).
The feeding patterns of cephalopods vary according to the species, however very few specifics are known. All mollusks have a radula, a tongue-like structure used for different feeding purposes in different species (McGraw Hill 1998).
South Australia is home to the breeding site of the Australia Giant Cuttlefish
(Sepia apama). In 1997 and 1998, the population was decimated as over
400,000 cuttlefish were taken for the commercial market. In 1998 the season
was closed early by the Primary Industries Minister, Mr. Kerin, and a
three year study of the cuttlefish population was initiated. Fishing was
also closed in 1999 and 2000. Concerned local sport divers have been instrumental
in promoting eco-tourism and diving as a renewable way to profit from
the annual cuttlefish aggregation in Whyalla and have rallied for the
establishment of permanent refuges and long-term conservation plans (Smith,
Research on cephalopods is important for their conservation because relatively little is known about their life history, development, and reproductive behavior, particularly of deep ocean species. The following are some sites that describe current or recent cephalopod research.
to March of 1999, scientists from New Zealand and the United States collaborated
on a deep sea expedition dive in search of the giant squid, Architeuthis
dux. The goal of the expedition was to observe the giant squid in its
natural habitatsomething never before accomplished. (Smithsonian,
1999). The website about the expedition is very interesting and informative
about the giant squid, but unfortunately there is no concise summary of
the expeditions findings. You can, however, read the daily dispatches
April 2001, a research project began to study the octopus that inhabit
the waters around Santa Cruz Island, in the Galapagos Islands (Ecuador).
The study aims to produce concrete information on the biology, ecology,
and distribution of octopus so that proper protection and conservation
of the species. Currently, octopus is considered and incidental catch
in the Galapagos, but local demand for consumption is increasing. Octopus
is an important species in the food chainparticularly as prey for
the flightless cormorant.
Department of Zoology at the University of Aberdeen, Scotland,
The phylogeny of the Decapodiformes is not very clear or widely agreed upon. What is clear is that this group includes cuttlefish, all of the many kinds of squid, including the elusive Giant Squid. Decapods are highly visual creatures, having the largest eyes proportional to their body size of any other creatures!! The suckers of decapods sometimes have sharp claws that may be used for grasping prey.
Check out the following links for a lot more information and some great photographs.
Alan Kazlev's Cehpalopod Page
California Department of Fish and Game. 2001 May 01. Status of the Market Squid Fishery with Recommendations for a Conservation and Management Plan. http://www.dfg.ca.gov/mrd/mlma/reports/squid.html Accessed 2001 November 09.
The Charles Darwin Foundation for the Galapagos Islands. 2001. Studying the Biology, Ecology, and Distribution of Octopus on Santa Cruz, Galapagos. http://www.darwinfoundation.org/marine/octopus.html Accessed 2001 November 05.
Kazlev, M. Alan. 2000 December 26. Cephalopoda. http://www.kheper.auz.com/gaia/biosphere/molluscs/Cephalopoda.htm Accessed 2001 October 29.
The McGraw-Hill Companies. 1998. Chapter 42: Mollusks and Annelids. http://www.mhhe.com/biosci/genbio/biolink/student/olc2/chap42outline.html Accessed 2001 November 09.
National Resource Center for Cephalopods. 2001 October 17. CephBase. http://www.cephbase.utmb.edu Accessed 2001 November 09.
Smithsonian Institution. 1999. Search For the Giant Squid. http://partners.si.edu/squid/Default.html Accessed 2001 November 05.
University of Michigan Museum of Zoology. 1996 May 13. Class Cephalopoda. http://animaldiversity.ummz.umich.edu/mollusca/cephalopoda.html Accessed 2001 October 27.
University of Texas Medical Branch. National Resource Center for Cephalopods. http://www.nrcc.utmb.edu/ Accessed 2001 October 27.
Whyalla Sports Divers' Club. 2000 October 2. Cuttlefish Protection Proposal. http://www.cuttlefishcapital.com.au/proposalone.htm. Accessed 2001 November 09.
Wood, James B. 2001 October 4. The Cephalopod Page. http://is.dal.ca/~ceph/TCP/index.html Accessed 2001 November 09.
Richard E., Michael Vecchione, and Katharina M. Mangold. 2001 October
31. Cephalopoda Cuvier, 1797. http://phylogeny.arizona.edu/eukaryotes/animals/mollusca/cephalopoda/cephalopoda.html
Accessed 2001 October 28.
McGill, Karli Merkens, Carrie Seltzer
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This website is part of a Biology 26 class project on the conservation of global biodiversity.