Morphological and Sectional studies of Amphioxus & Lamprey Prepared by : Nada H. Lubbad

Chordata Protochordata Cephalochordate Amphioxus Hemichordate Urochordate vertebrata Agnatha Myxini (hagfishes ) Cephalospidomorphi (Lamprey) Gnathostomata

Amphioxus lanceolatus Nomenclature: Common name Scientific name Amphioxus= “ pointed on both sides”. Lancelet =“ Bladelike shape”. Amphioxus lanceolatus Subphylum : Cephalochordate (Notochord length of body) Branchiostoma : Branchio = “ gills” , stoma =“ mouth” Morphologically description of body shape: Slender. 3.5-6.5 cm in length . Translucent. Laterally compressed , pointed at both ends . 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.

The living form: External features: 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. Nocturnal , active at night. World-wide distribution. External features:

Anatomical features:

Lateral view of anterior end

Cross sectional studies: Amphioxus through posterior region of pharynx

T.S of Amphioxus through mid-gut

T.S of intestinal region 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 Nomenclature: Morphologically description of body shape: Common name Scientific name Sea Lamprey = eel-like Peteromyzon marinus Superclass : Agnatha ( Jawless) Class :Cyclostomata (rounded mouth) Morphologically description of body shape: Eel-like body. About 30 cm in length . The skin is smooth and scaleless. No Jaw. No paired fins, but all are medians The body is divided into head, trunk and tail.

The head region: Buccal funnel , fringed with papillae and lined with yellowish brown horny teeth. Two eyes , not surrounded by eyelids, but covered by transparent area of skin. Single nostril on the top of head. Seven small openings , the outer gill slits.

The trunk region: Two dorsal fins separated by a notch. The second dorsal fin being continuous with fin around the tail. On the mid-ventral line lies the cloaca from which projects a slender urinogenital papilla. The tail region: The tail is surrounded by a caudal fin. Fine cartilaginous radials support all median fins , no fin rays such as those found in fishes.

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

Cross sectional studies: