What is a Nasohypophyseal opening?
What is a Nasohypophyseal opening?
In galeaspids the nasohypophyseal duct, which is large and either oval or slit-shaped, opens dorsally on top of the head in front of the eyes, and ventrally on the palate (Fig. 5a, b). The nasal sacs and hypophysis open into the duct .
Do lampreys have a hinged jaw?
Together, lampreys and hagfish are usually referred to as the cyclostomes, ‘agnathans’ or jawless vertebrates (see Glossary, Box 1), and, as these names imply, they lack the hinged jaws characteristic of other living vertebrates.
What do lampreys use their pharyngeal slits for?
Pharyngeal slits are filter feeding organs that help the movement of water through the mouth and out of these slits when feeing. During the lamprey’s larval stage they rely on filter feeding as a mechanism for obtaining their food.
Do lampreys have pharyngeal slits?
Their pharynx is perforated by seven round gill slits, which open into muscular pharyngeal pouches. They lack paired fins, but have dorsal, caudal, and anal fins, and some species are quite physically powerful.
Do lampreys have a cranium?
The Agnatha (jawless fishes)—the hagfishes and lampreys—have a distinct cranium and complex sense organs including eyes, that distinguish them from the invertebrate chordates, the urochordates and cephalochordates.
What is vertebrate cranium?
The skull is a bone structure that forms the head in vertebrates. It supports the structures of the face and provides a protective cavity for the brain. The skull is composed of two parts: the cranium and the mandible.
Which organisms do not have hinged jaws?
Both lampreys and hagfishes lack the hinged jaws and paired limbs found in all other vertebrates.
How is the mouth of the lamprey adapted to prey on other fish?
The juvenile sea lamprey uses its suction disk mouth which is filled with small sharp, rasping teeth and a file-like tongue to attach to fish, puncture the skin, and drain the fish’s body fluids. An anticoagulant in their saliva ensures that the blood of the host fish does not clot while the sea lamprey feed.
What is the significance of pharyngeal slits?
Pharyngeal slits are filter-feeding organs found among deuterostomes. Pharyngeal slits are repeated openings that appear along the pharynx caudal to the mouth. With this position, they allow for the movement of water in the mouth and out the pharyngeal slits.
What is buccal funnel of lamprey?
Buccal Funnel: It is actually a downwardly directed depression. The buccal funnel is surrounded by a marginal membrane which is provided with soft small projection called the oral fimbriae or papillae and the longer sensory cirri in between the papilla.
Do lampreys have a jaw?
Lampreys resemble eels in that they have slender, snake-like bodies and smooth, slippery skin. Lampreys do not have jaws, however, but have a sucking disk for a mouth.
Do lampreys have cranium?
Do lampreys have vertebrae?
Unlike hagfishes, with which they were once classified, lampreys have a complete braincase and rudimentary true vertebrae.
What animals have hinged jaws?
Amphibians, reptiles, and birds The jaw articulates via a hinge joint between the quadrate and articular.
Do fish have hinged jaws?
In fact, one of the most significant developments in early vertebrate evolution was the development of the jaw: a hinged structure attached to the cranium that allows an animal to grasp and tear its food. Jaws were probably derived from the first pair of gill arches supporting the gills of jawless fishes.
What adaptations do lampreys have?
They are well-adapted to living in the cold waters of the Arctic. The sharp teeth of the Arctic lamprey aid it in clinging to its host and sucking its blood. They have a rough tongue which helps them to get through the skin of other fish. Their body helps them move in a zigzag pattern thus avoiding predators.
What kind of ventilation does a lamprey use to push water over its gills when it is feeding?
Unlike most fish, which use a buccal pump to gill ventilate, adult lampreys use muscles associated with their gill slits.
What happens to the pharyngeal slits in humans?
All chordates possess a tail and pharyngeal slits at some point in their lives, and humans are no exception. Early on in human development, the embryo has both a tail and pharyngeal slits, both of which are lost during the course of development.
What animals have pharyngeal slits?
In vertebrate fishes, the pharyngeal slits are modified into gill supports, and in jawed fishes, into jaw supports. In tetrapods (amphibians, reptiles, birds, and mammals), the slits are modified into components of the ear and tonsils.
Where does the mouth open in a lamprey?
In the lamprey the funnel shaped oral hood and mouth cavity opens behind into the pharyngeal cavity and opens dorsally into an oesophagus and ventrally into a blind ending respiratory tube.
What is the structure of the respiratory system of lamprey?
6. Respiratory System of Lamprey: In the lamprey the funnel shaped oral hood and mouth cavity opens behind into the pharyngeal cavity and opens dorsally into an oesophagus and ventrally into a blind ending respiratory tube.
What are the accessory olfactory organs in lamprey?
In lamprey the glandular accessory olfactory organ is also present. 5. The Vestibular Organ: The labyrinth develops by an in-pushing of the wall of the head, and later on becomes closed off from the exterior. Internally it is divisible into chambers, which are provided with patches of sensory hairs similar to macula of higher vertebrates.
What is the cleavage of lamprey?
10. Development of Lamprey: The lamprey has telolecithal eggs having large amount of yolk. The cleavage is holoblastic but unequal and results into the formation of blastula having an upper half of micromeres and a lower half of macromeres.