Swimming, Thermoregulation, Diving(2)

Marine Mammal Biology Overview

  • Instructors: Dr. Jessica Jacob

  • Term: Spring 2025

  • Acknowledgment: © Robin W. Baird

Form Follows Function

  • Structure and function align at all biological levels.

  • Interrelation of morphology, physiology, cell biology, and behavior.

  • Physical laws (mechanical strength, diffusion, heat exchange) constrain body design.

  • Similar designs for similar challenges in biology.

Animal Form and Function

Design Constraints

  • Increasing complexity in large multicellular animals.

  • Specialization of cells and tissues.

  • Development of transport systems (vascular, digestive, urinary, etc.).

  • Coordination systems (neuro, sensory, endocrine) support homeostasis.

Metabolic Rate

  • Energy requirements vary based on size, activity, and environment.

  • Thermoregulation highlights form and function integration for maintaining homeostasis.

Aquatic Anatomy

  • Musculoskeletal anatomy relates to locomotion.

  • Anatomical adaptations facilitate swimming propulsion.

Functional Challenges in Aquatic Environments

  • Modifications to body surface area.

  • Changes in integumentary morphology, vascular mechanisms, musculoskeletal adaptations, metabolic adaptations, and respiratory adaptations.

Aquatic Anatomy: Polar Bears

Adaptive Features

  • Largest bear species.

  • Small ears for cold adaptation.

  • Long neck for swimming; partially webbed forepaws and flat plantigrade feet for drag-based thrust.

  • Crawling strokes for swimming using forelimbs.

Locomotion

Terrestrial

  • Large paws distribute body weight for traction on ice.

  • Soft papillae on foot pads increase grip.

Aquatic

  • Speed can reach 11 m/s when walking.

Aquatic Anatomy: Sea Otters

Anatomical Characteristics

  • Skull: short and robust, blunt rostrum, asymmetric; variable anatomy.

  • Short neck and streamlined body; no clavicle for extreme pectoral mobility.

  • Dense fur coat for insulation, maintained by continuous grooming.

Locomotion

Aquatic

  • Hindlimbs provide propulsion at the surface with pelvic paddling.

  • Vertical undulation of the vertebral column at depth.

Swimming Modes

  1. Ventral surface up for feeding.

  2. Ventral surface down with hind feet propulsion for speed.

  3. Alternating positions for grooming behavior.

Aquatic Anatomy: Pinnipeds

Physical Features

  • Skull structure similar to terrestrial mammals with large eye orbits and short snouts (walrus has distinctive large tusks).

Locomotion

Aquatic Swimming Types

  1. Otariids: pectoral oscillation for propulsion and steering.

  2. Phocids: pelvic oscillation primarily for swimming; forelimbs used for steering.

  3. Walrus: primarily uses pelvic oscillation with forelimbs acting as rudders.

Terrestrial Movement

  1. Otariids walk using all four limbs with extensive head movements.

  2. Phocids shuffle with hind limbs.

  3. Walrus uses a lateral movement, supporting itself on the belly.

Aquatic Anatomy: Sirenians

Feeding Adaptations

  • Herbivorous diet with specialized teeth (molars).

  • Unique skull characteristics: dugong has downturned premaxillae and tusks for digging up sea grasses.

Locomotion

  • Caudal oscillations for propulsion; manatees balance and maneuver with forelimbs.

Aquatic Anatomy: Cetaceans

Odontocetes

  • Telescoped skull with adaptations for underwater breathing (single blowhole, cranial asymmetry).

Mysticetes

  • Large heads with baleen plates for filtering food; two blowholes.

Cetacean Locomotion

  • Swim with vertical fluke movements generating thrust.

  • Allow for efficiently maintained high velocities.

  • Example speeds: bottlenose dolphins reach 40 km/h; killer whales up to 50 km/h.

Diving Mechanics

Challenges Faced

  • Hypoxia and low oxygen supply at depth and during activity.

Physiological Adaptations

  • Cease breathing during dives; adaptations for efficient oxygen use, including bradycardia, vasoconstriction, and metabolic rate reduction.

Respiratory System

  • Active nostrils/blowholes to conserve energy underwater.

  • Flexible chest walls and lung structures facilitating lung collapse at depth.

Breathing Patterns

  • Pinnipeds exhibit vigorous breathing post-dive.

  • Cetaceans breathe single, rapid patterns; lung volume significantly reduced for diving efficiency.

Thermoregulation

Keeping Warm

  • Major concern in the aquatic environment; large body size reduces heat loss.

  • Insulation via blubber or thick fur.

Integumentary System

  • Skin composed of three layers (epidermis, dermis, hypodermis).

  • Hypodermis serves as blubber and insulation.

  • Unique skin features in cetaceans (smooth and rubbery) and differences in thermal regulation among species.

Summary of Diving Behavior

  • Physiological, morphological, and behavioral adaptations enhance diving duration.

  • Different species, like Weddell and elephant seals, show varied dive capabilities and responses.

Homework Assignments

  • Due: January 30, 2025, @ 11:59 PM on Blackboard.

  • Quizzes: Marine Mammal Anatomy on open book/note basis.

  • Guest Lecture: Dr. Iske Larkin on Florida Manatees and Their Conservation.

  • Readings: Chapter 8 from "Introduction to Marine Mammal Biology and Conservation."