LECTURE 9- Feeding Ecology in Fish

ICHPTHYOLOGY

What bones form the upper jaw in teleosts?

Premaxilla and maxilla, derived from dermal bone.

What is the role of the mandibular and hyoid arches in jaw evolution?

What is the role of the mandibular and hyoid arches in jaw evolution? A: Mandibular arches form biting jaws; hyoid arch suspends the jaws from the cranium.

What is hyostyly and which fish group uses it?

Jaw suspension from the cranium via the hyoid arch; used by chondrichthyans.

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What is the spiracle, and its function?

A modified gill slit between arches; helps ventilate gills, bringing in clean water.

How did jaw mechanics evolve in early teleosts (e.g., salmonids)?

Maxilla became hinged and free-moving, allowing suction feeding.

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What adaptation allows for better suction feeding in teleosts?

Reinforced tube-like mouths and maxillary hinge mechanisms.

How do fish improve suction efficiency when feeding on small prey?

Protrusible jaws minimize water movement, avoiding alerting prey.

What are two key adaptations for jaw protrusion in fish?

: Rostral cartilage (gadoids) and ascending process of the premaxilla (higher teleosts).

What kind of teeth do suction-feeding fish often have?

Cardiform teeth—cone-like, used for gripping slippery prey.

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What are pharyngeal teeth used for?

Grinding tough prey; common in herbivores and some carnivores like moray eels.

How do moray eels handle prey without suction feeding?

Use pharyngeal jaws to grab and pull prey inward.

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What digestive tract adaptations support predatory feeding

: Large, stretchy J- or Y-shaped stomachs and short intestines.

How does intestinal length relate to diet?

Carnivores: short intestines; Herbivores: intestines up to 20× body length.

What are pyloric caecae and their function?

Extensions of the intestine that increase surface area for digestion.

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What do elasmobranchs have instead of pyloric caecae?

Spiral valve intestine for increased surface area and unidirectional flow.

Why is digestion in fish slow

Fish cannot chew; food is ingested in large chunks requiring longer digestion.

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What is a common feature among all elasmobranchs and most teleosts?

Predatory feeding with terminal mouths and well-developed teeth.

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How do ambush predators capture prey?

Use suction feeding and camouflage; often lie in wait and strike quickly.

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What adaptations do ambush predators like anglerfish have?

Modified dorsal fin as lure, large mouth, and camouflage.

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What distinguishes searcher predators?

Actively seek prey; opportunistic; often have streamlined bodies (e.g., tuna).

Why can’t protrusible mouths be used at high speed?

High pressure and water resistance could damage jaw structures.

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What hunting technique do sailfish and thresher sharks use?

Slash and stun prey using bills or caudal fins.

How do archerfish capture prey above water?

Shoot water jets using light refraction to aim accurately.

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What feeding style involves targeting specific prey?

Stalking—relies on specialized hunting strategies and senses.

What sensory systems help stalkers locate prey

Olfaction, chemoreception, and electroreception.

What are grazers and browsers?

Herbivorous fish that feed on algae, plants, or coral.

What feeding behaviors do damselfish exhibit

Defend algae patches; can be territorial and carnivorous (e.g., scale-feeding).

How do filter feeders extract food?

Use gill rakers to strain small prey like plankton or copepods from water.

Name two filter-feeding elasmobranchs.

Whale shark and basking shark—largest fish in the world.

When and why do basking sharks migrate to UK waters?

: During phytoplankton blooms to feed on abundant copepods.

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Why is dentition so diverse in teleosts?

Reflects dietary specialization—gripping, grinding, or suction feeding.