Biological Diversity 2001


This image courtesy of CephBase

Kingdom: Animalia
Phylum: Mollusca
Class: Cephalopoda
There are three subclasses of cephalopods: Coleoidea, Nautiloidea, and Ammonoidea, which is extinct.

Our conservation issues focus on the superorders Decapodiformes (squids and cuttlefishes) and Octopodiformes (octopuses), which are part of the subclass Coleoidea.

Subclass: Coleoidea 
 
Superorder:   Octopodiformes

Order: Octopoda


photos curtesy of CephBase

  This 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.



       
            


Order: Vampyromorpha



This image courtesy of the University of Arizona, Tree of Life

   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!

Exciting Cephalopods!

Introduction:
   Known as cephalopods to those of us familiar with names of the classes of animals, this group of mollusks includes squid, octopus, nautilus, and cuttlefish. Cephalopods are part of the phylum mollusca, making their closest relatives snails, slugs, clams, and chitons. In contrast to most mollusks, however, cephalopods have an internal shell or no shell, except the chambered nautilus. There are members of the roughly 650 species of these entirely marine invertebrates in every region of every ocean in the world. Very little is known about cephalopods, however, because of their great variety, because of the increased difficulty of studying marine life, and because there is less funding for the study of invertebrates (Wood 2001).

   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).

Conservation Issues:
   Cephalopods remain, for the most part, elusive creatures of the sea. There are numerous reasons that Cephalopods are rarely listed as threatened or endangered (nationally or internationally). The primary reason squids, octopuses, and cuttlefish have not received much attention for conservation issues is because not enough is known about the species to know whether or not they are threatened. Unlike terrestrial and intertidal mollusks, only recently have humans been able to explore the ocean depths where animals like the giant squid live. For this reason, we have included information about and links to pages addressing research on cephalopods in lieu of information about conservation organizations.

Conservation Status:
   Cephalopods have no conservation status under The United States Endangered Species Act, IUCN, or CITES.

Specific Conservation Issues:
   The California Department of Fish and Game recommended a management plan for the squid fishing industry to the California legislature. Some of the recommendations made to prevent overfishing of squid in the future by limiting the number of squid fishing vessels, limiting the days of the week for squid fishing, researching and monitoring the market squid catch, and exploration of alternative fishing methods (dfg.ca.gov, 2001).
Website: http://www.dfg.ca.gov/mrd/mlma/reports/squid.html

   Whyalla, 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, 2000).
Website: http://www.cuttlefishcapital.com.au


Research on Cephalopods:

   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.

   February 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 habitat—something 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 expedition’s findings. You can, however, read the daily dispatches from 1999.
Website: http://partners.si.edu/squid/Default.html

   In 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 chain—particularly as prey for the flightless cormorant.
Website: http://www.darwinfoundation.org/marine/octopus.html

   The Department of Zoology at the University of Aberdeen, Scotland,
has been collaborating with other European institutions to research
cephalopods, particuluarly those important to the European fishing industry.
In a nutshell, their research includes development, eccology, toxicity,
genetic variation, and population assessment of squids. These issues are
important for establishing a way to estimate the health of the fished squid
populations on a regular basis to prevent overfishing. In that way, this
page touches on conservation issues, but does not directly address squid
conservation. The material on the site consists of information about the
scientists working on the research and summaries of the recent and prior
research projects. The project summaries are written for a scientific
community audience.
Website:
http://www.abdn.ac.uk/%7Enhi104/index.htm

  Superorder:   Decapodiformes


                

   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.

The Cephalopod Page

CephBase

Some Amazing Videos

EuroSquid

M. Alan Kazlev's Cehpalopod Page
(good info, but iffy links)

Literature Cited:

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.

Young, 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.

Authors: Aili McGill, Karli Merkens, Carrie Seltzer
Creation/revision date: 12 November 2001

 

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Subclass: Nautiloidea

 This subclass is made up of pearly nautiluses. These creatures have chambered shells, which they use to control their depth in the water and protect them from predators and water pressure. Nautiluses can be found at depths a much as 300 meters! They can survive in slightly deeper water for short periods, but if they go to 800 meters, their shell implodes!



Acanthaster planci Apis mellifera Capybara Chimpanzee Danaus plexippus Exciting Cephalopods Green Sea Turtle (H-R,K) Green Sea Turtle (B,M,C) Green Serpent Star Holothuroidea Hyenas Latimeria chalumnae Mudpuppy Northern Leopard Frog Pink Seafan Salamanders Scyphozoa Tuatara

This website is part of a Biology 26 class project on the conservation of global biodiversity.


Earlham · Biology Department · Biology 26: Biological Diversity

Copyright ©-2001 Earlham College. Revised 30 October 2001. Send corrections or comments to merkeka@earlham.edu