CVA Exam 2

The name Holocephali refers to which of the following traits of chimaeras?

Holostylic suspensorium

The name Elasmobranchii refers to which of the following characteristics of sharks and rays

The gill slits are exposed.

What is the extant (living) diversity of chondrichthyans?

~ 1,400 species

Which of the following traits in not a synapomorphy for chondrichthyans?

Ampullae of Lorenzini

Cookiecutter sharks have ventral light-emitting photophores for deceptively breaking up their silhouettes to predators approaching from below.

True

What is the proportional diversity of Actinopterygii among vertebrates (in species richness)?

50%

The basal (most proximal) mesomere in a lobe-finned 'fish' is called the __________.

humerus

What is the approximate age of sexual maturity for a female Greenland shark?

150 yrs

Which of the following in not a characteristic of bichirs?

Scales thin and cycloid

Which of the following traits best describes sturgeons?

4 sensory barbels on snout

What portion of chondrichthyans are elasmobranchii and holocephali?

Elasmobranchii: ~ 1350

Holocephali: ~ 50

Elasmobranchii consists of _____ and _______.

The only holocephalans are ___.

• Selachii (sharks); Batoidea (skates, rays, sawfish)

• chimaeras (ratfish, ghost sharks)

What are the characteristics of Elasmobranchs?

• 5-7 exposed gill slits

• Euhyostylic: Upper jaw not fused to cranium

• Replaceable rows of teeth

• Placoid scales

• Develop a carilaginous vertebrate

What are the characteristics of Holocephalans?

• 4 gills covered by an opecular fold

• Holostylic: Upper jaw fused to cranium

• Non-replaceable grinding plates for dentition

• Skin mostly smooth (placoid scales mostly lost, except for claspers)

• Retain notochord

What does Suspensorium mean?

Refers to how the jaw is fused/formed

Ex. holostylyic and euhyostylic

What are the 5 synapomorphies of chondrichthyes?

1. Cartilaginous endoskeleton

2. Placoid scales

3. Pelvic claspers

4. Spiral valve intestine

5. Tooth whorl replacement system

6. Liver buoyancy system

7. Ureotolism

What is the tooth whorl replacement system?

Teeth secured to cartilage with ligaments (no bone for sockets) and bone replaced ~ 2-4 weeks

What is the specialized cartilage for chondrichthyans that mostly forms their cartilaginous endoskeleton?

prismatic calcified cartilage

What are the different types of teeth shapes found in chondrichthyans?

• Cladodont

• Serrated triangular (shearing)

• Narrow long (piercing)

• ‘Pavement’-like tooth plate

Teeth well-preserved in fossil record have yielded insight on what?

tropic levels/diet in extinct species

What is the liver buoyancy system?

• There is no swim bladder, which allows for specific buoyancy that is 15% less dense than seawater

  • Deep-sea sharks have massive livers and achieve near-neutral bouyancy; allows energy saving in nutrient-poor environments

  • Benthic sharks and rays have much smaller livers and are negatively buoyant; they sit at the bottom of the sea

• System is dual-purpose - combines floatation and long-term ‘fuel tank’ (stores energy reserves, incompressible)

What is ureotelism?

Retention of urea, allows chondrichthyans to maintain an internal osmotic pressure that is slightly higher than surrounding seawater

How does ureotelism work?

Sharks remain saltier than than the sea which causes small amounts of water to naturally diffuse into their bodies through the gills

Urea is generally toxic, however chondrichthyans produce a chemical that stabilizes proteins and enzymes against the destabilizing effects of both urea and deep-sea pressure. What is this chemical?

trimethylamine N-oxide (TMAO)

True or False:

The ampullae of lorenzini, specialized electroreceptors, are an ancestral gnathostome trait, and not unique to chondrichthyans

True

____ and _____ are absent in chondrichthyans.

Swim bladder; ear bones (otoliths)

What is the shark jaw structure called and describe it.

Holostylic

• Jaw is suspended by the hyomandibula plus ligaments attached to the cranium, which creates a swinging hinge for protruding the jaw away from the snout

What is the ray and skate jaw structure called and describe it.

Euholostyly

• The most extreme suspension; No direct ligament attachment to the front of the jaw and the only support is the hyomandibula

What is winnowing?

A process used by rays and skates that separates food from sediment by repeatedly protruding jaw in a jackhammering motion to sift it for food

What is hydraulic excavation? Who is it used by?

A process used by rays; It is the jetting of water downwards through the mouth or gill slits to dig out feeding depressions in the sand that uncovers buried prey

What is ricochet separation?

Manta rays use this feeding-filtration mechanism that funnels suspended food particles (plankton) into the mouth using specialized cephalic lobes. They are then separated by flap-like filter lobes on the gill rakers; the filter lobes use ricochet separation to bounce food particles into their throat (pharynx) while the water passes over their gills

What do cephalic lobes do?

open up and bring in water

What is another use for the cephalic lobes?

gestural sign language to communicate with other mantas

List the differences in anatomical structure of selachii & batoidea.

The skull of holocephali is ______

holosylic

When did holocephali diverge from elasmobranchs?

~350 mya

~50 species in 3 major groups of holocephali are distinguished by what?

head shape: bulbous, plough-nosed, or long-nosed

• with few exceptions, most are deep sea

The palaquadrate, completely fused to the cranium, describes which jaw suspensorium?

holostylic

What is a unique feature in holocephali males?

Tenacula; special retractable appendages on the forehead (cephalic tenaculum) or in the pelvic region (pre-pelvic tenaculum)

What is cephalic tenaculum (sex forehead)?

• has true teeth, sharing genetic and developmental pathways with oral teeth

• function as a grappling hook to grasp female’s pectoral fin or dorsal fin during copulation

What does durophagous mean?

describes the eating behavior of animals that consume hard-shelled animals

Describe holocephalans unique dental plate

• 3 pairs (2 upper 1 lower) of beak like tooth plates for crushing hard-shelled prey (durophagous)

• Bulk of tooth plates made up of osteodentin, less mineralized version of dentine

What is pleromin?

Mineralized tissue unique to holocephalans that is embedded in osteodentin

• pleromin is mineralized with whilockite, which is different from apatite found in the enamel of the teeth of other vertebrates

Holocephalans:

In two groups the tail is _____, thin and whip-like, edged from above and below by fins of similar size. The remaining group, the caudal fin, is _____ which means larger upper fin lobe with vertrabrate extending into lobe.

leptocercal; hertercercal

What kind of parasites are cookiecutter sharks?

Ectoparasites - lives outside the host

Which of the following class is characterized by a leptocephalus larval stage?

Elopomorpha

Which of the following is not a trait of coelacanths?

Weberian apparatus

Which of the following traits corresponds to Australian lungfish?

Single ventral lung

Which of the following would represent a tetrapodomorph fish?

Tiktaalik

A physoclistous swim bladder has direct ‘duct’ connection to the esophagus

False

More than 35000 species (~95% of all fishes) and more than 50% of vertebrate diversity is consisted of ______.

actinopterygian

96% of actinopterygian are _____

teleost

What are actinopterygians?

ray-finned fish; fin muscle barely extends onto fin (if at all)

How is diversity divided between actinopterygians?

freshwater and marine forms

What are sarcopterygians?

lobe-finned fish/tetrapods; fins monobasal (single humerus present) with internal bony elements (mesomeres) and muscles external to the body wall, creating a cylinder of meat extending away from the body

Both lineages (actinopterygians & sarcopterygians) have fin rays or _____

lepidotrichia; jointed bony fin rays that surround bundles of collagen

How are fin rays supported?

Pterygiophores (skeletal elements)

Which basal actinopterygian lineage consists of bichirs and reedfish (ropefish)?

Cladista (polypteriformes)

Characteristics of Cladistia

• Body highly elongated with a series of 7-18 dorsal finlets

• Thick rhomboid ganoid scales

• Paired ventral lungs

• Spiracular breathing

• Fleshy,lobe-like pectoral fins to ‘walk’ over damp terrain; can survive out of water over extended periods of time

• Ampullae of Lorenzini

• External ‘nasal tentacles’

What are dorsal finlets?

A small series of separate dorsal finlets instead of one long continuous dorsal fin

Describe rhomboid ganoid scales

A multilayered composition consisting of:

• Ganoine (enamel-like substance) outer layer

• Dentin (cosmine or osteodentin), the middle layer

• Basal layer of vascularized cellular bone that happens anchor scale to the dermis

Grow during the life of a fish by adding layers of mineral over time

What are paired ventral lungs?

Respiratory rather than hydrostatic organ, develops as an evagination on the ventral esophagus near the posterior edge of the pharynx

What is spiracular breathing?

Dorsal spiracles behind eyes used to ‘inhale’ air

• Spiracles sealed by hinged dermal ossicles that act as valves, opening briefly during inhalation

External ‘___ _____’ are tube-like nostrils that orient olfactory precision in murky waters

nasal tentacles

Which basal actinopterygian lineage consists of sturgeons and paddlefish?

Chondrostei (acipenseriformes)

Synapomorphies that unite the group Chondrostei

• Palatoquadrate cartilages link at midline to form symphysis (joint); maxilla and premaxilla lost (jaw functions independently of neurocranium)

• Secondary cartilaginous skeleton with persistent notochord and reduced vertebral centra

• Heterocercal tail

• Peroral snout: development of extensive snout located anterior to ventral mouth

• Paired spiracles are present but often vestigial; dorsal swim bladder present

• Physostomous, dorsal swim bladder for buoyancy

Characteristics of the sturgeon (acipenseridae)

• Protrusible, toothless mouth (hyostyly) efficient at suctorial feeding (vacuum prey from riverbed or seafloor)

• 4 sensitive tactile barbels on underside of snout assist in locating prey

• Skin mostly naked except for longitudinal rows of heavy, diamond-shaped bony plates (scutes)

Characteristics of paddlefish (polyodontidae)

• Rostrum (“paddle”) can make up one-third of body length

• Covered in thousands of electroreceptors (ampullary hair cells) that detect electrical signals produced by zooplankton

  • not to be confused with ampullae of Lorenzini, though they do act the same

• Filter feeders that rely on ram feeding and comb-like gill rakers to strain plankton

How are Neopterygii features characterized?

• increased agility

• lighter dermal skeleton (excluding gar)

• more efficient feeding apparatus

What are the skull addictions for neopterygii?

• Symplectic bone - braces the jaw joint and assists in specialized jaw protrusion found in teleosts

• Maxilla freed from preoperculum, allowing it to swing forward when the mouth opens

At the base of the Neopterygii group, ____ is lost but a similar system has evolved in some teleosts.

Ampullae of lorenzini

Holostei includes ___ (semionotiformes) and ___ (amiiformes)

gars; bowfins

Characteristics of Holostei

• Lightly ossified skeleton, reduced vestigial spiracles, paired vomer and more mobile maxilla

• Dorsal, highly vascularized swim bladder, functions to supplement respiration as well as buoyancy

What is the swim bladder helpful for?

Acts as a hydrostatic organ that assists in respiration and buoyancy; it allows survival in hypoxic (low-oxygen) environments

In Holostei as well as Chondrostei, the swim bladder is _____ with direct connection between the foregut and bladder (pneumatic duct) which involved gulping air at the surface

physostomous

True or False.

Both bowfins and gars can breathe air due to their highly vascularized swim bladder

True

What are the characteristics of Seminotiformes?

1. elongated jaws

2. abbreviated heterocercal tail

3. retain heavy ganoid scales

Characteristics of Amiiformes

1. Single extant species: Bowfin (Amia calva) (southeastern North America)

2. Gular plate retained

3. Highly reduced (thin, bony) cycloid scales

4. Internally asymmetrical tail (external appearance appears symmetrical)

What groups are in Neoterygii?

Holostei and Teleost

_____: 96% of all actinopterygians (most successful and diverse vertebrate group

Teleost

What are the several synapomorphies of Teleost?

1. Homocercal tail

2. Scale reduction: Thin cycloid/ctenoid scales (or naked)

   1. Increases swimming efficiency (also present in Amiiformes)

3. Opercular chain mechanism: Mobile/Disconnected premaxilla (Key innovation of Teleost!!)

4. Swim bladder specialization (both physostomous and physoclistous)

5. Weberian apparatus (in clade Ostariophysi)

   1. Weberian only found in this clade!!!

Describe the opercular chain mechanism

• The mechanical link allows Teleost to open its mouth rapidly, using the opercula as a lever

• A disconnected premaxilla, which allows for it to slide forward and downward, creating a circular orifice and a sudden vacuum for inhaling prey

What is a physoclistous bladder?

• A type of fish swim bladder not connected to the gut, so the fish cannot gulp or release air through the mouth.

• Instead, buoyancy is regulated internally by the gas gland, a specialized bundle of capillaries, which secretes gases into the bladder and the oval window for resorption.

  • pneumatic duct lost

Problem: Subject to barrow trauma can’t adjust to pressure from being pulled up and explodes

What is the Weberian apparatus? What class is it found in?

• Found only in the clade Ostariophysi

• A sophisticated middle ear system that consists of four small bones (Weberian ossicles), which are modified versions of the first four vertebrates, and link the swim bladder to the inner ear

  • The swim bladder acts as a drum that vibrates and conducts sound waves to the inner ear sensory receptors

What are the 3 main groups of Teleost to know about?

1. Elopomorpha

2. Ostariophysi

3. Tetraodontiformes

What are the characteristics of Elopomorpha? (tarpons, els, and bonefish)

• Unique leptocephalus larva, transparent, ribbon-like, and leaf-shaped

  • Unique since most fish larva phase called fry

  • Drift passively in ocean currents for months; lack a digestive tract for most of the larval period

• Early diverging Teleost, many of which retain plesiomorphic traits (gular plate, heavy bony scales, phystomous bladder

• Some eels have pharyngeal jaws that shoot forward out of the mouth

Characteristics of Ostariophysi

• Contains 30% of all fish species and ~74% of freshwater species (includes catfish, carp, and minnows)

• Catfish (Siluriformes) have sensory barbels, extremely sensitive Weberian apparatus, locked spines for predator avoidance, and can be smooth-skinned (naked) or encased in heavy, bony plates

  • Frogmouth catfish (Chaca Chaca) has tuberculated skin used for camo

Characteristics of Tetraodontiformes (pufferfish, boxfish, and triggerfish)

• Beak-like fusion of front teeth, fewest vertebrate of any fish (16-18), complete loss of pelvic fins and girdle, opercular reduced to small, hole-like apertures

• Includes the “Mola mola” (Sunfish)- the largest actinopterygian at 5,000 lbs

  • Long pharyngeal teeth shred gelatinous prey before entering the stomach and digestive tracts that are lined with mucus to protect from nematocysts (small harpoons that contain poison) of sea jellies

  

  • Spend long periods thermal basking at the surface to recover metabolism and digest after consuming lots of yummy sea jellies

    

  • Undulating rudder, the clavus, is not a true caudal fin but a fusion of dorsal and anal fins

  • Thick, leathery skin often infested with parasites

Summary comparison of actinopterygian traits

Draw two Actinopterygii trees

One with: Cladista, Chondrostei, Holostei, and Telostri

Other with: Cladista, Actinopteri, Chondrostei, Sturgeons (Acipenseridae), Paddlefish (Polyodontidae), Neopterygii, Holostei, Semionotiformes, Amiiformes, Telostei, Elopomorpha, Ostariophysi, and Tetraodontiformes

Different scales

• Heavy - Ganoid

• Light - Bony dermal scales

  • Ctenoid and Cycloid

Male angler fish attach and live off female angler fish parasitically, this is an example of what?

sexual dimorphism

Different actinopterygian fin muscles and exoskeletons