Download - 3 - Fish
-
7/27/2019 3 - Fish
1/23
Lecture 3 FishAgnatha, Placodermi, Acanthodii, Chondricthyes and Osteichthyes
-
7/27/2019 3 - Fish
2/23
The First Vertebrates: Class Agnatha
the first vertebrates lived about 500 mybp in theCambrian era.
they are placed in the class Agnatha, or jawless
vertebrates
the early agnathans are often referred to as
ostracoderms shell skins in reference to their bony
armour
although ostracoderms have been extinct since about300 mybp, we still have some extant members of the
class Agnatha today
-
7/27/2019 3 - Fish
3/23
Ostracoderm Characteristics
KK Figs. 3.9, 3.10, H&G Figs 3.3, 3.4
no jaws
single nostril onthe top of the head(rather than a pair)
tubular gillopenings
notochord in adults pharyngeal filter
feeding
endostyle organ
few or no paired
fins
-
7/27/2019 3 - Fish
4/23
Modern Agnatha (cyclostomes)
Living Agnatha are
hagfishes (KK Fig.
3.5 a&b) and
lampreys (KK Fig.
3.5 c&d). H&G
Figs. 3.1, 3.2.
-
7/27/2019 3 - Fish
5/23
Modern Agnatha - Hagfish
Hagfish are marinefish that feed ondead fish or marinemammals.
-
7/27/2019 3 - Fish
6/23
Lamprey - mouth showing
teeth
Lampreys are freshwater or anadromous agnathans, many of which are
parasites on other fish as adults.
sea lamprey on lake trout
Modern Agnatha - Lampreys
-
7/27/2019 3 - Fish
7/23
Lamprey larvae - ammocetes
The larval stages of lampreys live in streams, filter-feedwhile mostly buried in the sediment, and bear a
strong similarity to cephalochordates.
Recapitulation?
H&G Fig. 3.2, KK 3.5d
-
7/27/2019 3 - Fish
8/23
Primitive features of cyclostomes
no jaws
single nostril on the top of the head
tubular gill openings no paired fins
notochord persists in adult
pharyngeal filter-feeding in ammocete larvaeThe mysterious conodonts?
-
7/27/2019 3 - Fish
9/23
A Devonian Lamprey
From Gess et al. 2006, Nature 443: 981
Priscomyzon riniensis, from South
Africa 360 mybp
Lampetra fluviatilis, amodern lamprey
-
7/27/2019 3 - Fish
10/23
Fishes with Jaws Fishes with jaws appear in the fossil record about 400 mybp,
or about 100 million years after Agnatha during the Silurianperiod.
By the Devonian age of fishes four classes of fishes with
jaws were diverse and abundant.
Jaws apparently evolved from bones supporting the anteriorgills, and allowed fish to become effective predators rather
than filter feeders (we will return to this later!).
monkfish
-
7/27/2019 3 - Fish
11/23
Classes Placodermi and Acanthodii These two classes are both extinct, but were abundant during the Devonian
(approx. 400 mybp)
Both were heavily armoured, active predators.
Placoderms (KK 3.12, H&G 3.5) Acanthodians(KK 3.14, H&G 3.8)
-
7/27/2019 3 - Fish
12/23
Class Chondricthyes - cartilaginous fishes
Jawed fishes with cartilage rather
than bony skeletons. Most with
unique scales (dermal denticles),
unique teeth, spiracles, and slit-
like gill openings. Known as
fossils since > 400 mybp.
Two subclasses, Elasmobranchii
(sharks and rays) and
Holocephali (ratfishes or
chimaeras)
-
7/27/2019 3 - Fish
13/23
These are mostly active, free-swimming elasmobranchs with
streamlined bodies and large heterocercal tails.
Subclass Elasmobranchii 1 (Sharks)
Streamlined, fusiform,often pelagic.
-
7/27/2019 3 - Fish
14/23
Subclass Elasmobranchii 2 - skates and rays
Dorso-ventrally flattened, many specialized
for bottom feeding.
-
7/27/2019 3 - Fish
15/23
Subclass Holocephalichimaeras or ratfishes
KK 3.13b, H&G Fig. 3.7
Deep-sea chondrichthyans with a fleshy operculum covering the gills.
-
7/27/2019 3 - Fish
16/23
-
7/27/2019 3 - Fish
17/23
Class Osteichthyes - bony fishes
more species than any other class ofvertebrates for the last 150 million years
bony skeletons, scales, operculum
two subclasses:
subclass Actinopterygii
(ray-finned fishes)
subclass Sarcopterygii
(fleshy-finned fishes)
-
7/27/2019 3 - Fish
18/23
Living Actinopterygii with a longhistoryKK 3.17,
H&G 3.9, 3.10
These Actinopterygii go back as fossils for millions of years
and share some primitive traits, including:
- lungs- heterocercal (assymmetric) tails
- bony (ganoid) scales covered with enamel
- notochord in adults
Local fishes
Acipenser= sturgeon
Lepisosteus = gar
Amia = bowfin
-
7/27/2019 3 - Fish
19/23
-soft, flexible (elasmoid) scales
- symmetrical (homocercal) tail
- gas bladder rather than lungs
Atlantic Salmon (Salmo)
KK 3.17
H&G 3.11
Modern Actinopterygii (teleosts)
-
7/27/2019 3 - Fish
20/23
Functional Significance of Tail Shape
KK 1.1
H&G 27.18
-
7/27/2019 3 - Fish
21/23
-
7/27/2019 3 - Fish
22/23
Sarcopterygii - lungfishKK 3.19, H&G 3.12
-
7/27/2019 3 - Fish
23/23
Fish Evolutionary Tree
KK Figs 3.8 and 3.16
5 classes of fish:
Agnatha, Placodermi, Acanthodii,
Chondrichthyes,and Osteichthyes.
Which two are extinct? Which is largest?