Download Morphologically description of body shape

Morphological and Sectional studies of
Amphioxus & Lamprey
Prepared by : Nada H. Lubbad
Chordata
Protochordata
Urochordate
Cephalochordate
Amphioxus
vertebrata
Hemichordate
Myxini (hagfishes )
Agnatha
Gnathostomata
Cephalospidomorphi
(Lamprey)
 Amphioxus
o Nomenclature:
Common name
Amphioxus= “ pointed on both sides”.
Lancelet =“ Bladelike shape”.
Branchiostoma : Branchio = “ gills” , stoma =“ mouth”
Scientific name
Amphioxus lanceolatus
Subphylum :
Cephalochordate (Notochord length of body)
o Morphologically description of body shape:
1. Slender.
2. 3.5-6.5 cm in length .
3. Translucent.
4. Laterally compressed , pointed at both ends .
5. The anterior two-thirds of the body is roughly triangular in section, and the posterior
third is nearly oval .
6. Metamerism , the body wall shows
metameric segmentation , being made of blocks
of muscles called ( myotomes or myomeres ),
there are about 62 of these on each side .
These myotomes are < shaped.
o
The living form:
1. Shallow waters , it burrows in sand near the shore with greater part of its body
buried and only a fringed anterior oral hood projecting into water.
2. Nocturnal , active at night.
3. World-wide distribution.
o External features:
o
Anatomical features:
Lateral view of anterior end
o Cross sectional studies:
Amphioxus through posterior region of pharynx
T.S of Amphioxus through mid-gut
Dorsal lobe of caudal fin
Caudal artery
Caudal vein
Ventral lobe of caudal fin
T.S of intestinal region
T.S of tail region
 Lamprey
o Nomenclature:
Common name
Scientific name
Sea Lamprey = eel-like
Peteromyzon marinus
Superclass : Agnatha ( Jawless)
Class :Cyclostomata (rounded mouth)
o Morphologically description of body shape:
1. Eel-like body.
2. About 30 cm in length .
3. The skin is smooth and scaleless.
4. No Jaw.
5. No paired fins, but all are medians
6. The body is divided into head, trunk and tail.
• The head region:
1. Buccal funnel , fringed with papillae and lined with yellowish brown
horny teeth.
2. Two eyes , not surrounded by eyelids, but covered by transparent
area of skin.
3. Single nostril on the top of head.
4. Seven small openings , the outer gill slits.
•
The trunk region:
1. Two dorsal fins separated by a notch.
2. The second dorsal fin being continuous with fin around the tail.
3. On the mid-ventral line lies the cloaca from which projects a slender urinogenital
papilla.
•
The tail region:
1. The tail is surrounded by a caudal fin.
2. Fine cartilaginous radials support all median fins , no fin rays such as those found in
fishes.
o
Life process:
Spawning Phase: Spring -early summer
Once sea lampreys have reached sexual maturity, they stop feeding and begin to
congregate off the mouths of streams and rivers in preparation for spawning.
Lampreys construct crescent-shaped nests of small stones and gravel. The female
may lay 30,000 to 100,000 eggs. After spawning, the adults die.
Larval Phase:
Most fertilized eggs settle in amongst the gravel of the nest and hatch in a few
weeks. The young larvae emerge from the nest and then burrow into the stream's
sand and silt bottom. The larvae feed on algae, detritus, and various small
organisms.
Transforming Phase: Late summer- early fall
After three or more years as harmless larvae, they undergo a change called
transformation, where they develop eyes and a sucker-like mouth with sharp teeth.
Parasitic Phase:
Lampreys typically move into the sea to begin a parasitic life, attaching to a fish by their
mouths and feeding on the blood and tissues of the host They can spend 12-18 months in
the parasitic phase until they are sexually mature enough to reproduce.
Diet/Nutrition
- Larva Phase: algae, detritus and various small organisms
- Parasitic Phase: feed off host (fish)
- Spawning phase: No feeding
Lamprey Life cycle
o Cross sectional studies: