EXTERNAL ANATOMY OF A LAMPREY- CLASS AGNATHA

LAMPREY

FUNCTIONS

• Buccal Funnel - is the beginning of the mouth cavity. It contains the numerous teeth of the adult lamprey. It is surrounded and supported by the oral disc.

• Medial Nostril - The medial nostril is a primitive feature unique to the lamprey. Other vertebrate animals have paired nostrils. The nostril is responsible for detecting scents and leads to a nasal tube in the dorsal region of the head. A lamprey can “smell” by perceiving chemicals in the water.

• Eye - The eye is a sensory organ responsible for receiving visual input. The adult lamprey eye is structurally very similar to the eyes of other vertebrate animals, consisting of a cornea, iris, lens, and retina. There are no eyelids present in the lamprey

• Anterior Dorsal Fin - A fin used to maintain an upright orientation in the water while moving about.

• Posterior Dorsal Fin - This fin has the same function as the anterior dorsal fin.

• Caudal Fin - A powerful fin used to thrust the lamprey’s body through the water

• External Gill Slits - openings that lead to the internal gills that are used to conduct water into as well as out of the pouches thus freeing the buccal funnel for feeding the host.

• Anus - The anus is located immediately anterior to the cloaca. It is an extension of the intestine through which solid waste is expelled from the body

How are Agnathostomes different from Gnathostomes?

Differences:• Agnathostomes are jawless vertebrates with a circular, funnel like mouth while

Gnathostomes are jawed vertebrates.• Agnathans lack paired fins while Gnathostomes have paired fins.

How do parasitic lampreys feed?

• Parasitic lampreys feed by attaching itself to its host through a large buccal cavity funnel lined with horny denticles which helps keep the parasitic adult lamprey attached to its host while a tonguelike cartiligous rod covered with horny teeth rasps the flesh of the victim leaving only skin and skeleton.

What are the similarities and differences between lampreys and

hagfishes?

Similarities• Agnathans; no jaws• No true vertebral column • Have a prominent notochord that serves as the

sole axial skeleton throughout life• No paired fins• No bony skeleton• Slimy skin; no integumentary armor or scales• No bony teeth• Single nostril • Have a buccal funnel

Hagfishes

• Lack rasping dentricles; funnel surrounded by a ring of stubby finger-like papillae

• Chiefly bottom-feeding scavengers• Eyes are vestigial and covered by opaque skin• Do not enter freshwater• 1 semicircular duct• No dorsal fin• No larval stage• Incomplete braincase (skull)

Lampreys

Lampreys• Buccal funnel lined with horny dentricles• Mostly parasitic• Have a dorsal fin• Well developed eyes in adults• Adults live in sea (saltwater), but migrate upstream

(freshwater) to lay eggs• Lamprey eggs develop into sedentary filter-feeding

larvae• Presence of vertebral elements in the trunk• 2 semicircular ducts• Skull is more complex and includes true cartilagenous

braincase

What is the main function of the gill slits of lampreys?

• Seven pairs of gill pouches open separately to the exterior via pore-like gill slits that conduct water into as well as out of the pouches, thus freeing the buccal funnel for feeding on the host.

• Lead to the internal gills that are used to extract oxygen from the water