Virtual Dissection - Squid

External Morphology
1 – This is the squids's dorsal surface. 2 – This is the squids's mantle.
3 – This is the fin portion of the mantle.
4 – This is the collar portion of the mantle.
5 – This is an eye.
6 – This is one of ten arms.
7 – This is one of a pair of tentacles.











1 – This is the squid's lateral surface.
2 – This is the squids's mantle. 3 – This is the fin portion of the mantle.
4 – This is the collar portion of the mantle.
5 – This is an eye.
6 – This is one of ten arms.
7 – This is one of a pair of tentacles.

1 – This is the squid's ventral surface. 2 – This is the squids's mantle.
3 – This is the fin portion of the mantle.
4 – This is the collar portion of the mantle.
5 – This is an eye.
6 – This is one of ten arms.
7 – This is one of a pair of tentacles.
8 – This is the squid's funnel; the equivalent of the clam's excurrent siphon.
9 – This is an incision that was made in preparation for injecting the circulatory system of the squid.

Funnel Area
1 - This is the collar area of the squid's mantle.
2 – This is the squid's funnel.
3 – This is the squid's eye.
4 – The arrows point to the two funnel retractor muscles.
5 – The arrow points to the squid's rectum. The two small flaps are called rectal papillae.
6 – The left arrow points to one of a pair of cartilaginous ridges in the mantle that fits into grooves on the funnel (right arrow).





Buccal Mass
1 – The arrow points to a sucker on one of the squid's arms.
2 – This is a part of the buccal membrane.
3 – This is the buccal mass, a muscular organ with chitinous teeth and a radula for masticating prey to prepare it for digestion.
4 – The arrow points to tissues associated with the squid's salivary glands.
5 – The arrow points to the esophagus. The tissue surrounding the esophagus is associated with the liver.



Malemorphology
1 – This is the funnel area of the head. 2 – The arrow points to the right gill.
3 – The arrow points to the left funnel retractor muscle.
4 – The arrow points to the squid's rectum.
5 – The arrow points to one of the squid's branchial hearts. They receive deoxygenated blood from the precavae and the posterior vena cavae and pump it through the gills.
6 – The arrow points to one of the squid's precavae. These vessels containing the kidneys, receive deoxygenated blood from the head area via the anterior vena cava and direct it to the branchial hearts.
7 – The arrow points to one of the squid's posterior vena cavae. These vessels receive deoxygenated blood from the mantle area and direct it to the branchial hearts.
8 – The arrow points to the squid's caecum, a large chamber receiving masticated food from the stomach. Much of the digestion occurs here.
9 – The arrow points to the squid's single testis. Usually, it is partially covered by the caecum.

Morphology
1 – This is the funnel area of the head. 2 – This is the squid's rectum. It is terminated by two ear-like flaps.
3 – This is the left funnel retractor muscle.
4 – The arrow points to one of the squid's gills.
5 – The arrow points to the ink sac. This melanin-containing sac is dorsal to the intestine an empties into it.
6 – The arrow points to the squid's pair of nidamental glands. They secrete material that becomes the egg casings.
7 – The arrow points to the squid's left branchial heart. They receive blood from the vena cavae and pump it through the gills.
8 – This is the squid's ovary. It occupies much of this part of the mantle cavity and covers the caecum.

StellateGanglion
1 – This is the head area, seen laterally.
2 – This is the dorsal groove in the collar. The cartilaginous ridge in the head fits into it. The groove is supported internally by the pen.
3 – This is the collar.
4 – This is the stellate ganglion, a mass of cell bodies with giant motor axions that innervate the muscles of the mantle for rapid swimming.
5 – This is the squid's left gill. It has been injected with red latex.
6 – This is the left funnel retractor muscle.


Latin.mollis = soft)
This phylum is one of the largest marine groups with over 80 000 species. All comprise of a soft, unsegmented body, consisting of an anterior head, a dorsal visceral mass and a ventral foot.The body is more or less surrounded by a fleshy mantle (an outgrowth of the body wall) and nearly all species in the group secrete a lime shell that covers and protects the body. All, except the class Bivalvia, have a ribbon-like rasping tongue (radula - unique to this phylum) with small chitinous teeth that processes the food. Most mollusks are free living, but slow moving creatures, showing a close association with the substrate. Some attach to rocks or shells, others burrow, others float, octopuses and squids swim freely.
Characteristics:
1. Body usually short and partially or wholy enclosed by a fleshy outgrowth of the body wall called the mantle, which may be variously modified. Between the mantle and the visceral mass is a mantle cavity containing components of several systems (secondarily lost in a few groups).
2. A shell (if present) is secreted by the mantle and consists of one, two or eight parts. the head and the ventral muscular foot are closely allied (the foot being variously modified for burrowing, crawling, swimming, or food capture).
3. The digestive canals are complete and intricate with ciliary canals for the sorting of particles. The mouth with a rudula bearing traverse rows of minute chitinous teeth to rasp food , except in Bivalvia. The anus opening in the mantle cavity. A large digestive gland and often salivary glands are present.
4. The circulatory system is open, except in Cephalopoda and usually includes a dorsal heart with one or two atrias and one ventricle. This is situated in a pericardial cavity. An anterior aorta and other vessels and many blood spaces (hemocoels) exist in the tissues.
5. Respiration occurs via one to many uniquely structured ctenidia (gills) in the mantle cavity (secondarily lost in some), by the mantle cavity, or by the mantle.
6. Excretion by kidneys (nephridia), one or two or six pairs, or only a single one. They usually connect to the pericardial cavity and they exit in the mantle cavity. The coelom is reduced to the cavities of the nephridia, gonads and pericardium.
7. The nervous system is typically a circumesophageal nerve ring with multiple pairs of ganglia and two pairs of nerve cords (one pair innervating the foot and another the visceral mass). Many poses organs for smell, or touch, or taste. Eyespots or complex eyes present. A statocyst for equilibration present.
8. The sexes are usually seperate(some are monoecious, a few are protandric). Gonads add up to four, two or one, all with ducts. Fertilization occurs externally or internally. Most species are oviparous. Egg cleavage determinate, spiral, unequal and total (meroblastic in Cephalopoda). Trochophores and veliger larvae form, or a parasitic stage occurs(Unionidae), or the development is direct (Plumonata, Cephalopoda).
9. Unsegmented (except Monoplasophora). Symmetry bilateral or asymmetrical.


CITE:

Prepared by the BioG 101-104 Course Staff.Comments to Jon C. Glase: jcg6@cornell.eduAll contents © 2000 Cornell University. All rights reserved.Revised: April 5, 2000URL: http://biog-101-104.bio.cornell.edu/
http://library.thinkquest.org/26153/marine/mollusca.htm