Anatomy of Dogfish Shark Flashcards
The dogfish shark is also known as
Spiny dogfish
The dogfish shark belongs to the superclass Piesces because of this 3 characteristics
- Presence of scales
- Presence of gills
- Paired appendages in the form of fins
Its cartilaginous skeleton makes it a member of which class
Chondrichthyes
Animals belonging in class Chondrichthyes
Sharks, skates, rays, chimera
Because its gill slits open separately to the outside it belongs to what subclass?
Elasmobranchii
Adult males of spiny dogfish length
2-3 feet in length
females are slightly larger
some large sharks are more than 30 ft in length
Dogfish shark prefer what temperature
About 10 degrees Centigrade
note: they migrate north in the spring
south in the fall
2 dogfish shark species
Squalus acanthias- found in the North Atlantic coast
Squalus suckleyi- abounds along the Pacific coast
To remember:
Their carnivorous and predacious habits are responsible for the annual destruction of large numbers of commercially valuable fish, they also destroy fishing nets
Their usefulness is for laboratory study
3 reasons why dogfish are studied
- Exhibits the organizational pattern of the vertebrate body in almost a generalized condition
- It is easily dissected because its skeleton is entirely cartilaginous
- Because of its size , this allows as complex structures as the brain , the spinal cord, cranial nerves, inner ear, and the eye muscle to be disclosed with ease
European counterpart
Scyllium
Smooth dogfish
Mustelus
The rough sandpaper quality of the skin surface is due to the presence of ?
Placoid scales embedded on it
Each scale is consists of a diamond- shaped, bony _____
Basal plate
Basal plate is embedded in __
Stratum laxum of the dermis
Projecting caudally above the epidermis surface
Constricted neck and a spine
The base is anchored to the ____
Stratum compactum by fibers
A centrally placed _____ is present within the spine
Pulp cavity
The cavity is contain of
Blood vessels that nourish the dentine that makes up the bulk of the spine
What substance protects the exposed surface of the spine
Enamel-like substance
The skin consists of two major layers
Epidermis (thin outer)
Dermis (thick inner)
The epidermis of what kind of tissue
Stratified epithelium which are flat
The cells of the basal layer is ___
Stratum germinativum - columnar cells - mitotically active - responsible for the formation of the entire epidermis
Numerous unicellular, mucus- secreting cells are distributed along the surface between what elements
Squamous Epithelial elements
Loose connective tissue
Stratum laxum
Denser connective tissue
Stratum compactum
Small pigment cells are called
Melanophores
Responsible for the gray color of the dorsal and lateral surfaces of the dogfish’s body
Melanophores
Note: they are absent from the lighter ventral surfaceand also from localized areas so this results to white spors
Broad and somewhat flattened
Head
Fusiform in shape, in order to facilitate locomotion this gradually tapers posteriorly
Trunk
Compressed laterally and becomes a caudal fin, it is also the principal organ of locomotion
Tail
Five pair of oblique openings, located on the sides of the head, communicates with the pharynx
External gill slits
Means gill plate refers to the plate of skin between external openings of each of the gill slits
elasmobranch
Modified first gill slits located above and behind the eye
spiracle
Serves for water intake, especially when the jaws are grasping food
spiracle
Located laterally near the top of the head, they cannot simultaneously focused on a single object, the eyelids are immovable
Eyes
The linearly arranged series of minute openings, on each side the line extends from a point just behind the spiracle to the tail
Lateral line canal
Thought to serve as a receptor for low-frequency vibrations and hydrostatic pressure changes
Lateral line canal
Pair of flexible appendages located ventrolaterally behind the gill slits, they have short bases and are connected by a ventral cartilaginous bar
Pectoral fins
Pair of flexible appendages located ventrolaterally at the caudal end of the trunk. They are smaller than the pectoral fins
Pelvic fins
Two unpaired appendages located along the dorsomedian line, one somewhat behind the level of the pectoral find, the other somewhat behind the level of the pelvic fin
Dorsal fin
Located at the anterior border of each dorsal fin, they are sharp and posteriorly directed any may be considered modified scales
Fin spines
The presence of fin spines is reflected in the species name
acanthias (Greek akantha, thorn)
Major part of the tail, consisting of a large dorsal lobe and a smaller ventral kive
Caudal fin
This type of tail in which the lobes are unequal in size is called
Heterocercal
Openings situated on the ventral surface of the snout
External nares
Oval and is thought to have an incurrent function
Medial aperture
Round and is presumed to be the excurrent orifice
Lateral aperture
Rather than communicating with the pharynx, the nares end blindly and thus serve only as?
Olfactory organs
Located subterminally, a feature characteristics of elasmobranchs
Mouth
Blind pocket located at each corner of the mouth
Labial pouch
Furrow extending forward from each labial pouch
Labial groove
These structures, thought to be modified placoid scales, are arranged in series of rows paralleling the curvature of the jaws
Teeth
The first two rows of teeth, located on the crest of each jaw
Functional teeth- flat sharped edge and tend to be three pointed- serve to hold and tear food rather than to chew it
Two small openings located on the dorsal surface of the head between the spiracles
Endolymphatic pores
They are the external openings of the endolymphatic ducts which extend up from the internal ear
Endolymphatic pores
Numerous tint pores in the skin of the top and bottom of the head, their presence can be observed by pressing the skin surface and noting the sites from which oozes
Ampullae of Lorenzini
Special endings that serve as thermoreceptors and sometimes mechanoreceptors, these endings are innervated by fibers from the seventh cranial nerves
Ampullae of Lorenzini
Modified copulatory organs located at the median border of each pelvic fin in the adult male of the dogfish
Claspers
Takes form of elongated projections that are indented on one side by a deep groove
Claspers
A region located posteriorly on the ventral surface of the body that serves as a common exit for terminal products of the digestive, urinary and reproductive systems
Cloaca
A cone shaped structure possessing a pore as its apex that projects from the roof of the cloaca
Papilla
Both urine and sperm are emitted through the pore
Urogenital Papilla
The pore is associated with the elimination of urine only
Female urinary papilla
Openings that are located posteriorly on the lateral edge of the cloaca of both sexes and the function is unknown
Abdominal pores