Lecture Notes Pre-Break

Why study marine vertebrates from an ecological perspective?

They contribute to secondary production, act as nutrient vectors, and exert top-down control on food webs.

What is the "whale pump"?

A process where whales move nutrients between ocean layers by feeding at depth and excreting near the surface.

List commercial reasons for studying marine vertebrates.

Fisheries, whaling, use of fins/skins/pelts, ecotourism.

What is bycatch?

Unintended capture of non-target organisms during fishing.

What makes marine vertebrates sentinels of environmental change?

They reflect shifts in marine ecosystems due to their sensitivity to stressors.

What are the three key features of chordates?

Notochord, dorsal tubular nerve cord, gill slits.

What are the three subphyla of Chordata?

Urochordata, Cephalochordata, Vertebrata.

Name the three main groups of jawed vertebrates.

Chondrichthyes (cartilaginous fish), Osteichthyes (bony fish), Tetrapods (amphibians, reptiles, birds, mammals).

What are the three clades of fish and their buoyancy solutions?

• Agnatha: remain benthic.

• Chondrichthyes: fatty livers, heterocercal tails.

• Osteichthyes: swimbladders.

How do bony fish manage salt balance?

By excreting salt via gills and drinking seawater.

What is the “root effect” in teleosts?

A mechanism to release O2 into the swimbladder via blood acidification and hemoglobin dissociation.

How do fish extract oxygen in water?

Counter-current exchange in gill filaments.

What is unique about crocodile icefish?

They lack hemoglobin due to highly oxygenated cold water.

What sensory system allows fish to detect water motion?

Lateral line system with sensory hair cells.

What adaptations allow fish to detect electric fields?

Specialized electroreceptors for navigation, prey detection, communication.

What is a homology vs. an analogy?

Homology = same origin, different function. Analogy = different origin, similar function.

Define allopatric vs. non-allopatric speciation.

Allopatric = with geographic isolation. Non-allopatric = without it.

What body plan features define vertebrates?

Notochord, dorsal nerve cord, pharyngeal slits, segmented muscles, complete gut.

What was likely the earliest vertebrate?

Amphioxus-like, without bone, jaws, or paired fins.

Define fitness in evolutionary biology.

The reproductive success of a genotype, often measured by surviving offspring.

What are the three major gender systems in fish?

Gonochoristic, simultaneous hermaphrodites, sequential hermaphrodites.

What is protandry and protogyny?

Protandry = male first, female later. Protogyny = female first, male later.

What are the trade-offs in fish reproductive strategies?

Quantity vs. quality of offspring, growth vs. reproduction, care vs. fecundity.

What is adelphophagy?

When shark embryos eat their siblings in utero.

Define Allee effect.

Reproduction fails at low population density due to mating difficulties.

What are the benefits of parental care in fish?

Increased survival due to protection and food access, at a cost to fecundity.

What is buccal fertilization?

Fertilization via sperm swallowing, seen in some catfish.

What is gynogenesis vs. hybridogenesis?

• Gynogenesis: sperm triggers development but is not incorporated.

• Hybridogenesis: male genes used in offspring, but discarded in the next generation.

What is a Newtonian fluid?

A fluid where shear stress is directly proportional to strain rate and viscosity is independent of strain rate (e.g., water, honey).

What is a non-Newtonian fluid?

A fluid where viscosity depends on strain rate or shear (e.g., cornstarch, blood).

What is dynamic viscosity (μ)?

A measure of resistance to shear; used in the equation T = μ (du/dt).

What is kinematic viscosity (v)?

The ratio of dynamic viscosity to density; v = μ/ρ.

What is the Reynolds number (Re)?

A dimensionless number showing the relative importance of inertial to viscous forces; Re = ρuL/μ.

How does body size affect Re?

Larger organisms have higher Reynolds numbers and experience more inertial forces.

What are the two main types of drag?

Form drag (from shape) and friction drag (from surface contact).

What is Bernoulli’s principle in fish?

Pressure differences across body surfaces aid in ram ventilation and filter feeding.

What is thrust in fish locomotion?

The force propelling a fish forward, often generated by the caudal fin.

What is anguilliform swimming?

Snakelike motion involving full-body waves (e.g., eels).

What is carangiform or thunniform swimming?

Wave movement restricted to the back half or tail, reducing drag (e.g., tuna).

What is ostraciform swimming?

Caudal fin sculling without body movement (e.g., boxfish).

What is amiiform swimming?

Medial fin waves with a rigid body (e.g., bowfin, knifefish).

What is labriform swimming?

Pectoral fin rowing (e.g., wrasses), often used for fine maneuvering.

What body form has the lowest drag?

Fusiform (torpedo-shaped) reduces form drag.

How do fish reduce drag?

Streamlined bodies, reduced fin area, mucous layers, and microprojections like denticles.

What are the two major groups of Chondrichthyans?

Elasmobranchs (sharks, rays, skates) and Holocephali (chimaeras).

How are sharks aged?

By counting growth bands on dorsal spines (light bands = summer growth, dark = winter).

Which NZ shark order includes great whites and makos?

Lamniformes (mackerel sharks).

What makes rays and skates different from sharks?

Flattened bodies, gills on the ventral side, different reproductive modes.

How do chimaeras differ from sharks?

Upper jaw fused to skull, 1 gill opening, grinding tooth plates, egg-laying reproduction.

Why are sharks important in ecosystems?

They regulate prey populations via consumptive and non-consumptive effects.

What is a non-consumptive effect of sharks?

Their presence alters prey behavior, reducing overgrazing (e.g., seagrass protection).

What are some NZ protected shark species?

Great white, basking shark, whale shark, oceanic whitetip, and others.

What makes sharks vulnerable to overfishing?

K-selected traits: slow growth, late maturity, few offspring.

What tool helps track shark movements over long distances?

PAT tags (Pop-up Archival Tags).

What is functional ecology?

Study of how environmental factors affect individual organisms’ physiology and behavior.

What is the trophic efficiency between levels?

About 10%, meaning 90% of energy is lost between trophic levels.

Why do marine food webs need biodiversity?

More complexity increases stability and resilience.

What causes fisheries collapse?

Overfishing, increased technology, habitat modification, bycatch, and climate change.

What is the AIS system used for?

Tracking fishing vessels and their activity.

How can kelp forests affect fish productivity?

They provide structure and are highly productive, feeding into the marine food web.

How can isotopes reveal diet in marine species?

Different primary producers leave different 13C/15N isotope ratios in consumers.

How do fish act as ecosystem sentinels?

They record environmental and biological conditions, reflecting ecosystem changes.

What is diel vertical migration (DVM)?

Zooplankton and mesopelagic fish move daily between depths, transporting nutrients.

How do whales affect nutrient cycling?

Through the “whale pump,” recycling nutrients via feces that support phytoplankton.

What is zooarchaeology?

The study of ecological patterns from the past using animal remains, especially useful for understanding long-term fisheries data.

What patterns were observed in Caribbean fisheries over time?

Decline in average fish weight and a shift in both species composition and size of exploited species.

What is a typical signature of overfishing in reef fish populations?

Truncation of larger size classes and a shift toward smaller fish sizes.

Which fish showed size structure changes: obligate or facultative reef fishes?

Obligate reef fishes showed changes; facultative reef fishes did not.

Why didn’t facultative reef fishes show size structure changes?

They spend most time in pelagic zones and are less vulnerable to reef-based fishing.

What does a shift from obligate reef fish to pelagic resources indicate?

A change in the trophic structure and prey base due to the depletion of reef resources.

What archaeological method was used to analyze historical fish remains?

Isotopic analysis of freeze-dried collagen to track changes in carbon and nitrogen cycles.

What does Layman’s statistics reveal about trophic niches over time?

Increased overlap between species and variability within species' trophic positions.

What is mesopredator release?

A rise in mid-level predators when top predators are removed, disrupting trophic balance.

What is the energetic “cost” of mesopredator release?

Higher energy needed to support biomass at higher trophic levels makes fisheries harder to sustain.

What historical pattern was observed in NZ sea lions?

Range contraction due to hunting, with repopulation of the mainland by subantarctic individuals.

What can cause changes in trophic niche?

Competitive release, trophic downgrading, resource limitation, niche expansion/collapse, and spatial/temporal shifts.

What interaction was observed between NZ fur seals and sea lions?

Trophic divergence due to competition; convergence in Otago due to similar resource use.

What classifies an animal as a reptile?

Amniotic egg, scales, and ectothermy.

What are the marine representatives of each reptile order?

Turtles (Testudines), Sea snakes & marine iguana (Squamata), American/saltwater crocodiles (Crocodilia).

What are the two subfamilies of sea snakes?

Hydrophiinae (true sea snakes, viviparous) and Laticaudinae (sea kraits, oviparous).

What are key features of the yellow-bellied sea snake (Hydrophis platurus)?

Pelagic, globally distributed in tropics, highly venomous, passive drifter.

Why is the flat-tailed sea krait (Laticauda schistorhyncha) vulnerable?

It has a very restricted distribution, found only in Niue.

Where are sea snakes found geographically?

Only in the Indian and Pacific Oceans, limited to tropical surface waters.

How do sea snakes move in water?

Lateral undulations with a laterally flattened tail.

How do sea snakes breathe underwater for long durations?

Through cutaneous respiration, supported by low arterial O₂ pressure and vascular networks.

What is unique about sea snake anatomy for diving?

Enlarged right lung with tracheal, bronchial, and saccular regions; staggered paired organs.

How do sea snakes manage osmoregulation?

Salt excretion via sublingual glands; highest NaCl excretion rates among reptiles.

What kind of venom do sea snakes have?

Potent neurotoxins delivered through fixed, frontal fangs (proteroglyphous).

What is the most dangerous sea snake to humans?

Enhydrina schistosa, responsible for ~90% of fatalities.

What are major threats to sea snakes?

Bycatch, habitat loss, coral reef decline, harvesting, and pollution.

What conservation tools help sea snakes?

Turtle exclusion devices (TEDs), Bycatch Reduction Devices (BRDs), MPAs, and fishing restrictions.

Why are sea snake populations declining despite conservation efforts?

Low reproductive rates, high philopatry, and multiple human impacts.

How do sea turtles move through water?

They "fly" through water using their forelimbs like flippers.

What determines sex in sea turtles?

Temperature-dependent sex determination; higher temps (>30°C) produce more females.

What light wavelengths attract hatchlings?

Red, yellow, and green-shifted light (shorter wavelengths).

What challenges do hatchlings face due to artificial lights?

Light pollution disorients them, causing them to move away from the ocean.

How do sea turtles dive so efficiently?

Lungs collapse at 80m, low metabolism, high O₂ binding, and insensitivity to hypoxia.

How does oxygen distribution in leatherbacks differ from mammals?

More oxygen is delivered to blood, less total oxygen stored than in mammals.

Which sea turtle species is the largest?

Leatherback (Dermochelys coriacea), up to 916 kg and 305 cm.

Which turtle has a pliable shell and feeds exclusively on jellyfish?

Leatherback.