The document describes the external anatomy and functions of various parts of the lamprey. It discusses the lamprey's buccal funnel containing teeth, medial nostril, eyes without eyelids, dorsal and caudal fins, gill slits, and anus. It compares lampreys to hagfish and gnathostomes, and describes how parasitic lampreys feed by attaching to hosts with their funnel and rasping teeth. The main function of the lamprey's gill slits is to conduct water into and out of the gill pouches, allowing the buccal funnel to be used for feeding.

1. EXTERNAL ANATOMY OF A
LAMPREY- CLASS AGNATHA

2. LAMPREY

3. 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.

4. • 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.

5. • 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

6. • 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

7. • 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.

8. • 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

9. 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.

10. 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.

11. What are the similarities and
differences between lampreys and
hagfishes?

12. 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

13. 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)

14. Lampreys

15. 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

17. 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