OEB 130 Lecture 13+15 (Fish Diversity)

Midterm 2

2 major Otocephala groups

1. Ostariophysi

2. Clupeiformes

Otocephala key trait

ear-head fishes

Ear-swimbladder connection in: clupeomorph fishes

Ear-swimbladder connection in: ostariophysan fishes

Denticeps

a very primitive clupeomorph

Clupeiformes characteristic

• Abdominal scutes

• Schooling behavior; common bait fish

Anadromous vs catadromous

Catadromous: freshwater to the sea to spawn

Anadromous: migrate from the sea to freshwater to reproduce

blueback herring breeding

anadromous fishes, go from sea to freshwater to spawn

acoustico-lateralis system

lateral-line organs and connection to inner ear system

• lateral-line organs that detect vibrations and pressure changes in water

Otic bulla

air-filled sac that contains middle ear bones for hearing

Key traits of otocephela

1. Caudal skeleton anatomy

2. Ear-swimbladder anatomy

Weberian apparatus

a chain of small bones known as ossicles that enhances hearing by connecting the swim bladder to the inner ear, allowing for improved sound perception.

• including the tripus, claustrum, intercalarium, and scaphium.

Ostariophysi traits

1. Swimbladder anatomy “fright cells”, not a great character

2. Webarian apparatus

Alarm substance cells (ASC)

in the epidermis of ostariophysan fishes

• can trigger rapid erratic movement

Water Periodicity

large differences in the depth of water based on wet/dry season

Water periodicity impact on fish

As water rises, it carries debris onto the floodplain floor, providing much new food for young fishes in their nursery grounds.

Two types of fauna in Amazonian fish and their families

Night: Siluriformes (catfishes) and Gymnotiformes (electric knife fishes)

Day: Characiformes (characins)

What does division of the Amazonian fishes into these two “faunas” allow for

allow many species to live together and share resources

What family not in SA but is considered day fauna

Cypriniformes (carps and “minnows”)

Phylogeny and key traits of osteryiophysi

Cypriniformes

carps and minnows

• Specialized premaxillary protrusion mechanism: kinethmoid bone

• Often herbivorous; well-developed pharyngeal jaws, few to no jaw teeth

Gonorynchiformes

milkfishes

• basal branch of osteriophysi

kinethmoid bone

Specialized premaxillary protrusion mechanism in Cypriniformes

Gymnotiformes

electric fishes that are able to generate their own weak electrical fields, and detect them

• 5 families; ~200 species; 1 strongly electric species

  • electric eel

• Lost pelvic girdle and fins; mostly nocturnal

Characiformes

“day fauna” includes:

• vegetarian browsers

• insect eaters

• Pickers of algae and small invertebrates living on plants

• some feed near the surface

• feed in midwater

• and piranhas

Siluriformes

catfishes

• 35 families; 2 marine families; 1 family of strongly electric species

• Some species venomous; popular food fishes; spines on fins