Vertebrate Zoology; Teleosts and Terrestrial Tetrapod Evolution

Introduction to Teleost Evolution

  • Teleosts:
      - Infraclass Teleostei, characterized by significant diversification over evolutionary time.

Key Aspects of Teleost Evolution

  • Key areas of diversification:
      - Jaw structure
      - Locomotion (Movement)
      - Feeding Mode
      - Reproduction

Teleost Reproductive Strategies

A) Non-Guarders

  • Description: Adults leave after spawning; there is ZERO parental care.

  • Types of Non-Guarders:
      1. Broadcast Spawners:
         - Eggs and sperm are released simultaneously in large breeding aggregations, also known as breeding balls.
         - Habitats: Can occur in Pelagic and Benthic habitats, utilizing external fertilization during seasonal mass spawning events.
         - Characteristics include:
           - No mate choice
           - Pelagic example: Snapper
           - Benthic example: Walleye

B) Brood Hiders

  • Description: Fertilized eggs are hidden in nests.

  • Habitats: Commonly found in rivers, streams, and lakes.

  • Examples:
      - Most salmon, trout, and minnows exhibit this strategy.
      - Males typically establish territories for access to mates and nests.
      - Nest construction can be performed by females (e.g., salmonids) or males (e.g., minnows, chubs).

C) Guarders

  • Description: Adults provide definite parental care by guarding eggs and young after spawning.

  • Characteristics:
      - Parental care varies across species, from guarding eggs and embryos to juveniles for up to a year.
      - Territoriality is common to secure nesting sites.
      - Courtship behaviors often include ritualized actions (dancing, movement patterns) and various cues:
        - Olfactory: Pheromones
        - Visual: Males may change color or develop tubercles for signaling.
        - Auditory: Sounds produced during courtship.

Types of Guarders

  1. Substrate Choosers:
       - Males guard eggs laid on chosen substrates (e.g., plants, rocks).
       - Example: Fathead minnow (Pimephales promelas).

  2. Nest Spawners:
       - Adults select and defend nest sites, usually with males constructing nests using substrate materials (sand, stones, etc.).
       - Following spawning, males typically guard both eggs and sometimes the larvae.
       - Examples: Bluegill (Lepomis macrochirus) and Japanese pufferfish.

  3. Cavity Nesters:
       - Examples include Gobies and Sculpins, as well as channel catfish and Stonecat Madtoms.

Bearers

  • Definition: Fish that bear young either viviparously or through mouth or body brooding.

  • Viviparous:
      - Examples: Guppies and mollies, with females bearing independent young.

Examples of Viviparous Fishes

  • Seahorses and Pipefishes:
      - Seahorses exhibit unique copulation where males get pregnant; eggs are fertilized and develop in a brood pouch.
      - Breeding involves male contractions that expel young.

Sarcopterygii

Characteristics of Lobed-Finned Fishes

  • Structure: Lobed fins contain bone and muscle structure outside of body wall.

  • Cosmoid Scales:
      - Multi-layered, consisting of a hard top layer, a middle layer providing strength, and a vascular bone bottom layer.

Groups Within Sarcopterygii

  1. Lungfishes (Dipnoi):
       - Fossil record dates back to 380-400 million years ago.
       - Notably resembles modern lungfish.
       - Six extant species:
         - Neoceratodus forsteri (Australia)
         - Lepidosiren paradoxa (South America)
         - Four Protopterus spp. (Africa)

  2. Rhipidistians:
       - Considered ancestors of tetrapods.
       - Orders: Osteolepiformes and Eotetrapodiformes.

Coelacanths

  • Discovered to still exist in 1938, leading to significant biological insights.

  • Habitat: Deepwater environments, nocturnal behavior, and unique feeding strategies.

  • Conservation Issues: Concern over population recovery rates due to exploitation.

Evolution of Tetrapods

Key Hypotheses

  • Paleontologists once considered Lungfish and Coelacanths as potential ancestors of tetrapods based on limb structure.

  • Rhipidistians identified as the likely ancestors based on shared morphological traits, including homologous limbs, skull structures, and dental patterns.

Transition from Water to Land

  • Factors influencing the transition:
      - Habitat type and availability during the Devonian and Carboniferous periods.
      - Examples include high predator loads in water and abundant food sources on land, with selections favoring terrestrial adaptations.