Marine Bio (Exam 3)

Chordata

(Phylum)

Divided into 3 major subphyla

• Urochordata (invertebrate)

• Cephalochordata (invertebrate)

• Vertebrata

Characteristics

• Single hollow, dorsal nerve cord

• Gills or pharyngeal slits

• A notochord (flexible rod between nerve cord and gut)

Urochordata

(Subphylum) → Phylum Chordata

• Includes ascidians, tunicates, salps

• Basic chordate characteristics only present in tadpole-like larva

• Body covered by thick/ or thin tunic/ test made of cellulose-like polysaccharide

(Lec 19)

Cephalochordata

(Subphylum) → Phylum Chordata

• Includes animals like lancelets or amphioxus

• Basic chordate characteristics throughout life

  • ONLY the lack of a backbone separates them from vertebrates

(Lec 19)

Vertebrata

(Subphylum) → Phylum Chordata

• Includes sharks, fish, and mammals

• Backbone, Skull, and Jaws*

*most have jaws

(Lec 19)

Major Clades of Chordates

• Craniata: Chordates w/ a cranium skull

  • hagfishes and vertebrates included

• Vertebrata: Craniates w/ backbones

  • lampreys and gnathostomes

• Gnathostomata: Vertebrates w/ jaws

(Lec 19)

Agnatha

(Clade) → “Jawless fish”

Hagfish “Slime Eels” → Clade: Craniata

• Skull, NO backbone (primitive backbone), NO jaws

• Suction feeding: use muscular mouth/ rows of teeth (scavengers)

• Anguilliform morphology = “eel-like” , no scales

• Produce slime from mucus glands → clogs gills of predators trying to eat

Lampreys → Clade: Vertebrata

• Skull, BACKBONE, NO jaws

• Suction feeding: use muscular mouth/ rows of teeth (often parasitic; suck blood)

• Found in temperate regions; breed in freshwater and move to sea as adults

Chondrichthyes

(Class) “Cartilaginous Fishes” → Major Clade Gnathostomata

2 Subclasses: Elasmobranchii & Holocephali

• Skeleton made of cartilage, more flexible than bone

• Gills → Countercurrent System

• Placoid scales: scales in one direction, opposite direction is rough sandpaper-like

• Myomeres (muscle bands) produces rhythmic contractions for swimming = heavy

  • Large pectoral fins provide lift, heterocercal tail forces head upward + Liver w/ oil

• Ampullae of Lorenzini: sensory organs that can detect movement

• Gill rakers: projections of gill arches for filter feeders

• Eclectic diet (Carnivores): take bites from larger prey

Reproduction: Chondrichthyes

Cartilaginous Fishes

• Fertilization internal: cloaca (female), claspers (male)

  • oviparous: lay eggs in large leathery cases

  • ovoviviparous: egg develops inside and live birth

  • viviparous: no egg, live birth

Respiratory System: Chondrichthyes

Cartilaginous Fishes

• Water must flow over gills for oxygen transfer

• Gills: gill arches (cartilaginous support), gill filaments (increase surface area) with lamellae (higher area)

• Countercurrent System: water and blood flow opposite to each other = maximize O2 enter

  • Obligate ram ventilators: must swim continuously to force water over gills (few shark)

  • Spiracles: opening behind the eye that pumps water over gills (other shark/ rays)

Elasmobranchii

(Subclass) → Class Chondrichthyes

Sharks

• Fusiform body = “streamlined”

• Two Dorsal fins and large paired pectoral fins → pectoral helps w/ stability

• Heterocercal tail (caudal fin): upper lobe longer than lower lobe

• 5 to 7 gill slits behind head, powerful sharp teeth (continually shed)

• Key roles as top predators and scavengers → reflect ecosystem health

Skates & Rays

Stingrays: excavate sediment to expose food

Manta rays: fly through ocean using pectoral fins to filter feed on plankton w/ gill rakers

• Gill slits located ventrally (bottom)

• Pectoral fins fused with head “wing look”

• Whip-like tail (some species have spines)

• Dorsoventrally flattened bodies

Holocephali

(Subclass) → Chondrichthyes

Ratfishes

• Found in deep waters, close to seabed

• 1 pair of gill slits and long, rat-like tail

Osteichthyes

(Class) Bony Fishes

Subclass

• Actinopterygii

• Sarcopterygii (lobe-finned fishes)

Actinopterygii

(Subclass) Ray-finned fishes → Major Clade Osteichythes

• Skeleton made of bone

• Gills use active irrigation → Counter current exchange

• Protrusible jaw: flexible jaw → creates neg pressure and pulls prey in (suction feeding) = carnivores

• Cycloid/ ctenoid scales: thin, flexible, overlapping

• Operculum (gill cover)

• Homocercal tail, with lobes of similar size

• Fin rays: boney rays connected by membranes make fins

• Lateral line: sensory pores on the side to detect predators

• Swim Bladder: keeps them boyant in water

Body Shape and Locomotion: Actinopterygii

• Fast swimmers: fusiform (stream-line body shape)

• Bottom dwellers: dorsoventrally flattened

• Anguilliform: “eel-like” shape for living in vegetation

• Slow swimmer: elongated vertical/ round/ triangle

• Acceleration specialist: Large strong tail (sit/ wait)

• Cruising specialist: stiff body and forked tail

• Maneuvering specialist: disc shapes and large pectoral fins

Reproduction and Behavior: Actinopterygii

• Broadcast spawn and release eggs

• Parental care almost always males

• Nearly all oviparous: lay eggs

• Fishes form schools → well-coordinated units

  • makes fishes a harder target

Mating Systems

• Monogamy: only one partner

• Polygyny: one male w/ many females

• Polyandry: one female w/ many males

• Promiscuity: any number of mates

Sequential Hermaphroditism

• Individual can change sex to another during its lifespan

  • Protogynous: female → male

  • Protandrous: male → female

Simultaneous Hermaphroditism

Male and female at the same time, when mating they play opposite roles

Sarcoterygii

(Subclass) Lobe Finned Fish → Major Clade Osteichythes

• Skeleton made of bone

  • teeth covered w/ true enamel

• Cosmoid scales: bony structure

• Lobed fins → resemble tetrapods limbs

• Diphycercal tail: single tail

Coelacanth

• Thought to be extinct

• Diphycercal tail

• Ovovivparous: eggs hatch in female for live birth

Lungfishes

• Highly specialized respiratory system → max surface area

• Estivation: enter dormant state due to lack of water = survive dry season by burrowing into mud

Tetrapods

Four-limbed vertebrate

• Two major clades split from amphibians → reptiles and mammals

  • Marine Reptiles: Chelonia, Dispsida (Squamata, Archosauria)

Chelonia

• Body enclosed in a carapace (shell) composed of dermal bone

  • can distinguish species by scutes (plates) on shell

• Legs are modified into flippers

• Lungs for O2 → can hold breath for several hrs

• Generally found in tropics/ sub-tropics, can also be found in temperate and Artic waters

• Carnivores or omnivores, exception of adult green sea turtles (herbivores)

• Oviparous: lay eggs

  • Hatchlings have high mortality rate, but if survive can live for 50 - 70 yrs

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