Lamprey Dissection PDF

LAMPREY DISSECTION Petromyzon spp. AKA the Vampire Fish BIO 415L Presented by Dr. Sarah Polekoff  Skeletal elements: Internal anatomy Identify the following structures Annular cartilage Liver...

LAMPREY DISSECTION Petromyzon spp. AKA the Vampire Fish BIO 415L Presented by Dr. Sarah Polekoff  Skeletal elements: Internal anatomy Identify the following structures Annular cartilage Liver of a larval lamprey on the Anterior dorsal cartilage Intestine microscope slide: Posterior dorsal cartilage Follicles Lingual cartilage Ovary Dorsal and ventral fin folds Nasal cartilage Mesentery Myomeres STRUCTURES Auditory capsule Kidney Myoseptum Arcualia Spinal cord Notochord Sagittal section in the text: Notochord Branchial basket Cranial cartilage Dorsal aorta Pericardial cartilage Tongue Gill lamellae LAMPREY Olfactory sac Kidney External structures: Pineal gland Gonad Oral funnel Brain Intestine Naris Intestine Lateral line pores Spinal cord Pineal eye complex Notochord Eye Myomeres External pharyngeal slits Ovary Myomeres Teeth Anterior dorsal fin Buccal papillae Posterior dorsal fin Velum Caudal fin Branchial basket cartilages Tail Dorsal aorta Cloacal apertur Ventral aorta Respiratory tube Heart  The Cyclostomata lineage diverged from other vertebrates over 500 mya  Oldest fossil lamprey is 360 million years old Cyclostomes: Extant Jawless Fish Agnatha (means no jaw)  Hagfish and lampreys  Lack internal ossification  Lack paired fins  Lack scales  Lack jaw  Lack specialized reproductive structures  Single nostril  Velum “pump”  Arcualia = rudimentary vertebral precursors  Single circulation  No stomach acid production  https://www.youtube.com/watch?v=IuCcXto1vPk Lamprey https://www.youtube.com/watch?v=IuCcXto1vPk Background  Earliest vertebrates lacked jaws  Termed “agnathans.”  Petromyzon marinus  Atlantic Ocean and North American Great Lakes,  Most commonly studied cyclostome.  50 species of Petromyzon  Both freshwater and marine  Free-living and parasitic species  Size: 10 cm to 1 m length  Lamprey Background  Habitat: Temperate waters  Lampreys have 7 pairs of gill pouches  Their mouth is located under the oral hood  Larval lampreys  Take water in through their mouths then pump it over their gills (flowthrough ventilation)  Adult lampreys  Use tidal ventilation where water is both drawn in and expelled through their gill openings (pharyngeal slits) Lamprey Background  Larval lampreys use their gills to filter feed Lamprey Background  Most adult lampreys are parasitic  Suction to the body of another vertebrate (usually a fish) and use their tongue to rasp a shallow wound  Don’t kill their host, but leave them weakened with an open wound https://www.youtube.com/watch?v=-SYhOD1Yx10  SKELETAL ELEMENTS “Endochondral” Skeleton  CHONDROCRANIUM: include large cartilages that partially enclose the brain and sense organs (nasal capsule, otic capsule).  Make up the ANTERIOR & POSTERIOR DORSAL CARTILAGE  ANNULAR CARTILAGE: ring-like structure that is the main skeletal element of the oral funnel.  LINGUAL CARTILAGE: supporting the rasping tongue  Extends posteriorly from the annular cartilage >>> ventral to the chondrocranium.  NASAL CARTILAGE or NASAL CAPSULE: sense organs for smell  AUDITORY CAPSULE or OTIC CAPSULE: sense organs for sound SKELETAL ELEMENTS (Cont’d) “Endochondral” Skeleton (endo = within; chondro = cartilaginous)  ARCUALIA: The vertebrae made up of small, cartilaginous structures that lie dorsal to the notochord on either side of the spinal cord.  Embedded in connective tissue. DIFFICULT TO FIND  May occasionally be observed in cross-sections.  NOTOCHORD: axial support of the body.  Elongated rod  Extending from beneath the posterior half of the brain to the tip of the tail SKELETAL ELEMENTS (Cont’d) “Endochondral” Skeleton  BRANCHIAL BASKET: connecting to the chondrocranium is a network of cartilages.  Supports the pharyngeal region  PERICARDIAL CARTILAGE: hemispherical cartilage at the posterior end of the branchial basket.  Lies on the posterior wall of the pericardial cavity  Space that contains the heart.  EXTERNAL STRUCTURES  EYE:  laterally placed, lidless eyes.  Moderately sized and covered by transparent skin.  ORAL FUNNEL:  forms a wide, sucking disk that attaches to the body of the lamprey’s prey (Figures 2.2 and 2.3).  The funnel’s margin bears small, soft projections, the buccal papillae, which are primarily sensory structures.  ORAL DISK:  The interior surface of the funnel  lined with numerous horny teeth, which are cornified epidermal derivatives and thus not homologous with the teeth of more derived vertebrates.  Remove a tooth with forceps to observe a replacement tooth immediately underneath it.  EXTERNAL STRUCTURES (Cont’d)  NARIS: single, median naris lies middorsally between the eyes  LATERAL LINE PORES:  lateral line system, functions in detecting vibrations in the water. Pores for the canals are noticeable in the head.  Arranged in rows.  One occurs just posterior to each eye, and several others may be found between the eye and the anterior end of the oral funnel.  PINEAL EYE COMPLEX: lighter patch of skin immediately posterior to the naris, which lies just below the skin and  functions as a photoreceptor that detects changes in light. EXTERNAL STRUCTURES (Cont’d)  EXTERNAL PHARYNGEAL SLITS:  Subdivided pharynx  Ventral part forms a respiratory tube that can be isolated from the mouth by a valve termed the velum.  This ensures that its liquid diet neither escapes from the pharyngeal slits nor interferes with gas exchange at the gills.  Lamprey continues to ventilate its gills by pumping water in and out of the pharyngeal slits.  EXTERNAL STRUCTURES (Cont’d)  MYOMERES:  lateral surface of the trunk or tail to observe the outline of the segmented series of muscular blocks, the myomeres.  These are composed of longitudinal fibers extending between successive connective tissue partitions, the myosepta.  Contraction of the myomeres on one side of the body flexes the body toward that side  Alternating contraction of the myomeres on opposite sides of the body  Produces the characteristic side-to-side swimming motion of fishes. EXTERNAL STRUCTURES (Cont’d)  FINS: no paired fins, but there are three median fins  The fins are supported by fin rays, which can be seen if the specimen is held up against light 1. ANTERIOR DORSAL FIN 2. POSTERIOR DORSAL FIN 3. CAUDAL FINTAIL  CLOACAL APERTURE: shallow midventral depression. The intestine opens into the cloaca through a slit-like anus.  Anterior to the anus, there is a small urogenital papilla with a terminal urogenital pore through which gametes and excretory products leave the body. INTERNAL STRUCTURES  Gonad may be the first structure visible  Normally moderate size; Large during breeding season  May occupying much of the pleuroperitoneal cavity.  Ovary and testis are SINGLE median structures, supported by a mesentery from the middorsal line lying dorsal to the liver and intestine INTERNAL STRUCTURES  FOLLICLES, OVARY, & TESTIS: ovary and testis are difficult to distinguish from each other. Just before breeding, however, the ovary contains many follicles, giving it a granular appearance compared with the testis.  Genital ducts are absent  Gametes are shed into the coelom (“the body cavity in metazoans, located between the intestinal canal and the body wall” – Oxford Dictionary) INTERNAL STRUCTURES (Cont’d)  LIVER: large, greenish organ at the anterior end of the pleuroperitoneal cavity. If the ovary is very large, it may cover the posterior end of the liver.  INTESTINE: opens into the cloaca through a slit-like anus.  TYPHLOSOLE (aka “spiral valve”): Within intestine. Numerous longitudinal folds are present on its interior surface to increase surface area.  Typhlosole is the largest of these folds INTERNAL STRUCTURES (Cont’d)  MESENTERY: few small mesenteric sheets  Dorsal mesentery, carrying blood vessels to the gut  Present near the posterior end of the intestine.  Spleen is absent  Pancreatic functions:  Tissue performing pancreatic functions is present  Scattered in viscera  Exocrine pancreas: present in parts of the intestinal wall  Islet tissue (endocrine) occurs in the liver  Not visible grossly. INTERNAL STRUCTURES (Cont’d) KIDNEY: long, thin, ribbon-like Lies on either side of the middorsal line Extends for much of the length of the pleuroperitoneal cavity. Archinephric duct: drains the kidney Lies along its free lateral margin SAGITTAL VIEW  SAGITTAL VIEW CRANIAL CARTILAGE or CHONDROCRANIUM TONGUE: Within pit of the funnel lies the rasping tongue Funnel bears horny teeth Not homologous with the structures of the same name in more derived vertebrates. The tongue is used to abrade the skin of prey, so that its blood and body fluids may be ingested.  SAGITTAL VIEW BUCCAL PAPILLAE: small, soft projections, the buccal papillae, which are primarily sensory structures. VELUM: Respiratory valve. Closure + muscular contraction compresses the pharynx and water moves over the gills.  SAGITTAL VIEW OLFACTORY SAC: Dark-walled olfactory sac, directly anterior to the brain. Sac’s interior surface has numerous folds to increase surface area. PINEAL EYE COMPLEX BRAIN INTESTINE SPINAL CORD NOTOCHORD MYOMERES OVARY TEETH SAGITTAL VIEW 1. VENTRAL AORTA: Blood flow > forward from the ventricle through the ventral aorta > seven afferent branchial arteries > capillaries in the septa between the pharyngeal slits. 2. DORSAL AORTA: Blood is recollected > efferent branchial arteries > dorsal aorta > distribution to the body SAGITTAL VIEW RESPIRATORY TUBE: or “pharynx” ventrally. Subdivisions of the embryonic pharynx Not homologous with the esophagus and pharynx of other vertebrates Isolated from the mouth by a valve termed the velum  HEART HEART: Lies in the pericardial cavity Posterior to the respiratory tube. Transverse Septum: Posteriorly separated from the pleuroperitoneal cavity Stiffened by the pericardial cartilage.  HEART 3 Chambers!!! Blood flow > sinus venosus > atrium > ventricle. 1. Sinus venosus is a tubular structure Oriented dorsoventrally Between the atrium and ventricle. Becomes incorporated into r. Atrium in higher-order vertebrae (faber et al., 2019) 2. Atrium Occupies the left side of the pericardial cavity 3. Ventricle Mainly occupies the right side. TRANSVERSE VIEW References Faber, J. W., Boukens, B. J., Oostra, R. J., Moorman, A. F. M., Christoffels, V. M., & Jensen, B. (2019). Sinus venosus incorporation: contentious issues and operational criteria for developmental and evolutionary studies. Journal of anatomy, 234(5), 583–591. https://doi.org/10.1111/joa.12962 Iuliis, G. D., & Pulerà, D. (2019). The Dissection of Vertebrates (3rd Edition). Elsevier S & T. https://bookshelf.vitalsource.com/bo oks/9780124105003