What superclass encompasses lampreys and hagfishes? What trait is used?
Superclass Myxinomorpha, Jawless fishes
Class, order, and family of HAGFISH
Class Myxini
Order Myxiniformes
Family Myxinidae
Class, Order, and Family of LAMPREY
Class Cephalaspidomorpha
Order Petromyzontidiformes
Family Petromyzontidae
Similarities between Myxinidae and Petromyzontidae?
Similarities
No true jaws
Lack scales
No paired fins
Single nasal opening
Large number of paired gill openings (Myxinidae = 1 - 14; Petromyzontidae = 7)
Simple cartilaginous skeletons
Describe Myxinidae skull structure.
Hagfish skulls consists of cartilaginous bars where the brain is mostly surrounded by a fibrous sheath underlaid by the notochord
Describe the Petromyzontidae skull structure.
Family Petromyzontidae
Lamprey skull structure has a more elaborate cartilaginous braincase and comprises a large branchial basket surrounding the gills
What are 9 trait that characterize Myxinidae?
Family Myxinidae, hagfish
- four pairs of tentacles surrounding mouth and opening of nasopharyngeal duct
- the esophagocutaneous duct leads from esophagus to exterior, on left side only, opening behind rearmost gill opening
- 1 to 14 gill openings on each side
- very large slime glands ventrolaterally that produces slime consisting of large thread cells
- dorsal, anal, and caudal fins without fin rays and are thickened skin folds
- exclusively marine, scavengers on dead animals and inverts
- osmotic non-regulators, only vertebrate to do this
- few but large eggs with no larval form
- “breathes” through nose ie nostril is connected to pharynx which is not found in any other fish
What are lampreys characterized(13) by?
Family Petromyzontidae, lampreys
- Internal cartilaginous skeleton no scales
- single dorsal nasal opening not connected to pharynx
- pineal eye
- two semicircular canals (1 in hagfish and 3 in higher verts)
- solid cartilaginous braincase
- cartilaginous branchial basket skeleton with 7 gill pouches that open directly to external
- vertebrae and fin rays present
- osmotic regulators
- fresh water or anadromous
- small eggs ie high fecundity
- ammocete larval stage which metamorphosis into adult
- semelparous
- parasitic adults have toothed tongues while non-parasitic only use adult form for reproduction
What is the buccal funnel?
Hood-shaped structure supported by an internal ring of cartilage that allows for secure attachment to host.
The opening is fringed with numerous finger-like structures – buccal papillae or oral fimbria.
What is the function of oral fimbria/buccal papillae?
Help Petromyzontidae seal itself to prey through suction while teeth help to hold onto prey.
They also serve a tactile and chemosensory function.
Where is the nostril located on Petromyzontidae head and what is it connected to internally?
Nostril is located in the middle dorsal side of the head, in between the eyes, and is connected to the olfactory apparatus.
Are lateral lines present in Petromyzontidae? Myxinidae? What is the lateral line and it’s function?
Found in only Petromyzontidae (lampreys), consisting of groups of pores that sense vibrations and movements in water.
They extend caudally from the top of the lateral eye, dorso-laterally beneath eye and caudally on the ventral surface from the buccal funnel.
What are myomeres?
Segmented body muscle segments connected by myosepta.
How many external gill openings do Petromyzontidae have and where are they located?
7 gill openings located behind the eye on each side of the head.
What and where are the following located: 1) supraoral lamina; 2) infraoral lamina; 3) inner laterals; and 4) outer laterals?
Family Petromyzontidae, lampreys
- supraoral lamina = teeth above toothed tongue
- infraoral lamina = teeth below toothed tongue
- inner laterals = lateral teeth adjacent to both sides of the toothed tongue
- outer laterals = lateral teeth along the exterior of both sides of the toothed tongue, adjacent to the inner laterals
How many gill openings do Myxinidae have?
Family Myxinidae, lampreys
1 to 14 gill opening along both sides of the hagfish
Where are the slime glands located on a Myxinidae?
Smallish holes running along both sides of lower body
What are the functions and location of the external nostril in Myxinidae?
Connects to the pharynx, allowing hagfish (Myxinidae) to “breathe” through nose, bringing water in through the single nostril through to their gills. It is the large opening at the tip if the snout – often hidden – just above the mouth.
When blocked while feeding, Myxinidae breathe through their skin.
Do Myxinidae have eyes?
They have VESTIGIAL EYES which are light sensitive organs only and are not true eyes.
Explain the function and form of the feeding apparatus found in Myxinidae. What is the basal plate?
Family Myxinidae, hagfish
Hagfish feeding apparatus includes a dental plate, structural cartilage, and feeding muscles. The dental plate is the only motile element of the apparatus which is situated above the BASAL PLATE. Function of the basal plate is a series of cartilage that supports the dental plate and muscles pull the dental plate in and out of the oral cavity.
How many barbels are found on Myxinidaes and where are the located?
Hagfish, family Myxinidae, have 4 pairs of barbels located around the mouth and are characteristic of Myxinidae.
Explain the protraction and retraction of the dental plate ITO the retractor and protractor muscles and the basal plate. What are the functions of the barbels at this moment?
hagfish, family Myxinidae
- at rest, the dental plate rests on top of the basal plate
- PROTRACTION: protractor muscle below the basal plate pulls the dental plate along the basal plate out until it protrudes the horny teeth out to grab prey.
- RETRACTION: the retractor muscle located on the dorsal side of the basal plate pulls the dental plate up and back on top of the basal plate.
- barbels are used to sense foodstuff during this feeding
What and where is the posterior cardinal veins?
Located along the length of the lamprey, family Petromyzontidae, the posterior cardinal vein is locate underneath the notochord and is on either side of the dorsal aorta.
What is the notochord and what families is this structures found in?
Found in Myxinidae (hagfish) and Petromyzontidae (lamprey), the notochord is a single, unsegmented rod that supports the body and the body musculature.
