MARB 403 Lecture 1
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Class starts at 9:00 AM! WHOOP!
Cetacean Taxonomy and External Morphology
Know species from each family.
Systematics: study of relationships; how many genera are in a particular family?
Marine Mammals of the world
(We're studying Suborder Cetacea)
Sirenia:
- Dugong (Dugong Dugon)
Grouping Pinnipeda: (no longer an appropriate suborder)
- Otariidae (eared seals)
- Odobenidae (Walrus)
- Mustelidae (otters)
- Phocidae (true seals)
Mysticetes (baleen)
Odontocetes (toothed whales)
Order used to be Cetacea, but was recently changed to Order Cetartiodactyla
- Infraorders Mysticeti and Odontoceti
- Closely related enough to Artiodactyls and Ungulates (Pigs, hippos)
Mysticetes
mustached cetaceans
From keratin baleen plates
Ectodermal: hangs on to skin like fingernails, hair
4 families, 14 species
Very symmetrical jaw (c.f. odontocetes)
Smallest: Minke Whales (6 m) Largest: Blue Whale (24 m)
No echolocation
Jaws do not come together (nonsymphyseal)
2 blowholes (nostrils)
Family Balaenidae
- Right and Bowhead whales
- 300 long, thin, fine baleen plates per side (largest amount in all baleen whales)
- Skim feeders 17-ft
- Largest tail-to-body ratio
- Northern Right Whale extremely endangered
Family Neobalaenidae
- 1 Species: Pygmy Right Whale
- 6 m long
- 200 short baleen plates
- According to R. Ewan Fordyce, the pygmy right whale is a cetothere, a grouping of extinct cetaceans
Family Eschrichtiidae
- 1 Species: gray whale
- Bottom-feeder (sucks in water and silt from bottom of ocean)
- Indigenous to north pacific
- scrag whale: used to be whales on both sides of Atlantic, but now only eastern and western
Family Balaenopteridae
- Rorquals: Norwegian for "tubed whale"
- Gular grooves (throat pleats) allow massive amounts of water to be ingested
- Found all over the place
Infraorder Odontocetes
10 families, at least 71 species
Toothed whales
1 blowhole
Jaw is symphyseal
Males larger than females (except in Ziphiidae; beaked whale)
Family Physeteridae
- 1 Species: Sperm whale
- Largest carnivore
- Feed on deep-water squid and fish (> 600m)
Family Kogiidae
- Pygmy and dwarf sperm whales
- 1 genus, 2 species
Family Ziphiidae
- Beaked whale
- 6 genera, 20 species (maybe officially 21 now)
- Largest is bottlenose whale
- 1-2 pairs of (large in male) teeth
Family Platanistidae
- Used to contain all river dolphins, but similarity among river dolphins is result of convergent evolution
- 1 species: Indus (phulan) and Ganges (susu)
- very flexible
- Almost blind
- In a lot of trouble; only a few small populations remain
Family Iniidae
- 1 species: Amazon River Dolphin
- Reduced eyes, but can still see
- excellent echolocation
- also very flexible
- may be monogamous
Family Lipotidae
- 1 species: Baiji River Dolphin
- Essentially extinct
Family Pontoporiidae
- 1 species: Franciscana
- Not freshwater dolphins, but inhabit estuaries and coastal waters in south america
- Not in good shape due to fishing net accidents
Family Monodontidae
- 2 Species: Narwhals and Belugas
- Prominent melon, small beaks
- Male Narwhal's tusk is from left canine tooth
Family Delphinidae
- Largest: 36 species, 17 genera
- 1.5-10m in length
Family Phocoenidae
- True porpoises
- 3 genera, 6 species
- symmetric skull
- simple echolocation
- spade-shaped teeth (c.f. conical delphinid teeth)
- triangular dorsal fin (c.f. recurved "falcate" delphinid)
- No beak/rostrum (c.f. prominent rostrum in other delphinids)
External Anatomy
Mysticetes
Odontocetes
Reproductive Structures
- Females
- one urogenital slit (union with anus)
- 2 mammary glands adjacent to slit
- mammary glands' position near genitals helps infants to slipstream while nursing
- Males
- Two distinct slits; urogenital separate from anus
- internal (retractable) penis
- cetacean penis is muscular (neither blood nor os penis used) and erection is voluntary
Evolution of Cetartiodactyla/Cetacea
- Evolved from land mammal ancestor about 65 Mya
- Ungulates (hippos, pigs) are closest living relatives
Extinct grouping Archaeocetes all have same characteristics
- Remnants of pelvis called anominid [1] bones (attach to penis muscles in males)
- Telescoped skull
- Occipital chondyles (nostrils) moved upwards
- Earbones isolated
- Hyperphalangy (multiple finger bones)
Cetacean-related epochs of Cenozoic Era (from most recent to oldest:
- Pleistocene
- Pliocene
- Miocene
- Oligocene
- Eocene
- Paleocene
Positions of continents has changed, so oceans have also changed (Atlantic ocean is relatively young)
Ancient Mediterranean precursor is origin of all cetaceans and sirens (Tethys sea between Eurasia and Africa)
Evolved from a carnivorous, "racoon-like" ungulate family Raoellidae Indohyus common ancestor in the mid-eocene
Pakicetus [2] was first cetacean
Up-and-down Ungulate undulation is still present
Archaeoceti
Filled niches of extinct large carnivorous marine reptiles
- e.g. Zeuglodons
- reproduced on land
- Had hind limbs
Zeuglodons
Basilosaurs were originally thoght to be dinosaurs
- Small head, loooooong body
Dorudontines
Dolphin-like, no hind limbs
Mysticetes
Toothed, but skull structure was present
First of mysticetes was Mauicetus
Odontocetes
Similar to living dolphins, but had primitive, symmetrical skull
Squalodonts' teeth originally serrated (like shark teeth)
Huge speciation of delphinidae from kentriodontids about 12 Mya
Summary
- Evolved about 65 Mya from early even-toed ungulates
- Baleen and echolocation derived monophyletically
Mating Systems
- monogamy
- one male mates exclusively with one female
- polygamy
- individuals mate with more than one partner
- Polygyny: Some males mate with more than one female
- Polyandry: Some females mmate with more than one male (unusual)
- polygynandry (promiscuity; multi-mate)
- Males mate with more than one female and vice versa (during estris)
Food for thought: why don't males give milk?
Strength of Polygyny
Monogamy → Moderate Polygyny → Strong Polygyny
- Harem Polygyny
- (e.g. elephant seals) breeding females cluster together on beaches; alphamales defend a harem of many females at once.
- lekking polygyny
- males display in particular areas called leks and display for females
- female choice
- often underestimated, but they are usually the ones to raise youngsters
- territorial defense polygyny
- not common among cetaceans (it's a big ocean)
Behavioral Ecology
Addressing functional questions about behavior or how behavior contributes to survival and reproductive success
Ocean has only one "life-giving wall"—the surface
Rivers are fairly enclosed
Niko Tinbergen, The herring Gull's World
Four basic questions of "why?" (e.g. Why does a male humpback male sing?)
- Ultimate: related to reproductive success (attract mate, repel other males)
- Proximate: causitive factor (other males start singing, temperature is just right))
- Ontogenetic: learned behavior (song is learned)
- Phylogenetic: hard-coded in genes (song is evolved)
Scientific Method:
- Observation: look at humpback whales and record songs (Collect starting data; try to understand)
- Hypothesis: use starting data to make educated guesses of why males might sing
- Prediction: If hypothesis is correct, then ...; if hypothesis is incorrect, then ...
- Testing: Collect hypothesis-related data and observe whether 'correct' or 'incorrect' outcome occurred
Group Living
Most cetaceans live in groups (called pods)
Benefits of Group Living
- Reduction of predation (cooperated defense and dilution effect)
- Allocation of time to other activities
- Enhanced detection and capture of prey
- Acquisition or defense of resources
- Improved reproduction
- Learning to old age
- Reduction of mobile parasites
- Physiological, Energetic
Costs of Group Living
- Increased predation (encounter effect)
- Reduced foraging efficiency
- Increased competition for resources
- Increased risk of infection by contagious parasites or diseases
Scientist of the Day
Ewan Fordyce, Evolutionary Biologist
U. of Otago, Dunedin, New Zealand