Marine Nekton Overview

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

Which of the following characteristics are true for nekton organisms?

They reproduce only through live birth.

They are exclusively vertebrates.

They can move independently of ocean currents. (correct)

They are primarily plankton feeders.

What is the primary role of the swim bladder in fish?

Facilitating breathing through gills.

Maintaining isotonic environment with seawater.

Providing propulsion and balance.

Regulating swimming depth and flotation. (correct)

Which group of nektons is considered the most bio-diverse and abundant?

Invertebrates like squid

Cartilaginous fish

Mammals like whales

Bony fish (correct)

What type of feeders are most abundant among nekton organisms?

Plankton feeders Signup and view all the answers

In terms of size range, which nekton organisms are generally larger?

Sharks and whales Signup and view all the answers

How do nekton organisms primarily reproduce?

Many produce eggs that float in seawater. Signup and view all the answers

Which structure helps nekton organisms sense vibrations in water?

Lateral line Signup and view all the answers

Which of the following statements is true concerning vertebrate nekton?

They possess a vertebral column. Signup and view all the answers

What distinguishes the subclass Holocephali from other classes of fish?

Their upper jaw is fused to the cranium. Signup and view all the answers

Which of the following characteristics is associated with sharks and rays in subclass Elasmobranchii?

Gill clefts opening separately to the exterior. Signup and view all the answers

What is a primary feeding method for lampreys in Class Cephalaspidomorphi?

Suction of live fish blood and juices. Signup and view all the answers

Which of the following statements about marine mammals is correct?

Most are endangered due to hunting and reproduction issues. Signup and view all the answers

Which feature is NOT characteristic of Class Myxini (hagfishes)?

Presence of dermal ossification. Signup and view all the answers

Which adaptation is primarily found in cephalopods like squids?

Siphons used for swimming. Signup and view all the answers

What is a significant environmental impact of squid driftnet fishing?

Results in the death of various non-target species. Signup and view all the answers

Which class of bony fish is known for having fins supported by dermal bones?

Class Actinopterygii. Signup and view all the answers

Which feature is adapted for visibility in the deep sea?

Large eyes Signup and view all the answers

What is the primary function of photophores in deep-sea organisms?

Emit light Signup and view all the answers

What type of organisms primarily make up the base of food webs around hydrothermal vents?

Chemoautotrophic bacteria Signup and view all the answers

How do deep-sea organisms typically adapt to high pressure?

By developing metallic exoskeletons Signup and view all the answers

What primarily causes the natural fluctuations in the abundance of fish in the ocean?

Changes in oceanographic conditions Signup and view all the answers

What occurs during a whale fall?

Whales sink and feed scavengers for months Signup and view all the answers

What type of environment is characterized by cold seeps?

Locations with methane-rich fluids Signup and view all the answers

What biological function do the red body colors of some deep-sea organisms serve?

Camouflage from predators Signup and view all the answers

Study Notes

Marine Nekton

Nekton/swimmers are marine organisms with swimming abilities.
They move independently of currents.
Nekton are heterotrophs.
Nekton have a patchy distribution, dependent on primary production.
Nekton range in size, including fish, squid, octopus, sharks, and mammals.
Nektons are pelagic, found in the epipelagic, mesopelagic, and bathypelagic zones.

Characteristics of Nekton

Nekton have specialized structures for swimming and floating.
Nekton are a diverse group varying in size.
Most nekton are pelagic, but some are bathypelagic.
Nekton are heterotrophic, including herbivores, carnivores, and omnivores.
Nekton maintain osmotic regulation, keeping their bodies isotonic to seawater.
They swim long distances for food.

Reproduction of Nekton

Nekton reproduce by producing eggs or live birth.
Birds and turtles lay shelled eggs on land.
Fish spawn eggs that develop in seawater.
Mammals, such as whales, give birth to live young.
Nekton move via S-shaped contractions (undulations).

Groups of Nekton

Vertebrates are the major group of nekton.
Chordates are part of the vertebrate group.
Invertebrates are the minor group of nekton.
Crustaceans and mollusks are part of the invertebrate group.

Phyla of Nekton

Chordates: fish, sharks, reptiles, turtles, sea snakes, birds (penguins), mammals (whales, dolphins, porpoises).
Mollusks: squid, octopus.
Arthropods: crabs, lobsters.

Fish

Fish are the most bio-diverse and abundant nekton, with over 32,000 species.
Most fish are epipelagic.
Fish are mostly plankton feeders, with high fecundity (herring, sardines, anchovies).
Some deeper water fish are small and use photophores and bioluminescence for locating prey or mates or avoiding predators.

Characteristics of Fish

Fish are ectothermic (cold-blooded), whose temperature depends on the environment.
Fish have a vertebral column.
Fish use fins for propulsion and balance (tail fin, side fins, dorsal fins, and anal fin).
Fish have scales that protect them from injuries and diseases (some fish lack scales).
Fish breathe using gills.
Fish have a swim bladder that regulates swimming depth and buoyancy.
Fish use lateral lines to sense vibrations and detect movement in water.
All fish live in water.

Major Groups of Fish

Jawless fish (superclass Agnatha): e.g., lampreys, hagfishes.
Jawed fish (infraphylum Gnathostomata): cartilaginous fish (class Chondrichthyes) and bony fish (super class Osteichthyes).
- Most abundant and diverse, with over 20,000 species.
- Form profitable marine fisheries.

Jawed Fish (Cartilaginous & Bony Fish)

Chondrichthyes: cartilaginous fish with no true bones, 5-7 gill clefts, rigid dorsal/fin spines, and subclass Elasmobranchii (sharks, rays).
Osteichthyes: bony fish; subclass Holocephali (Chimaeras, upper jaw fused, unmodified branchial arches), superclass Actinopterygii (ray-finned fish); fins supported by dermal bones, scales grow continuously, swim bladder present, and skeleton is well ossified.
Sarcopterygii: fleshy-lobe finned fish (coelacanth and lungfish); cranium not divided.

Squid

Squid are cephalopod mollusks with eight arms and two tentacles.
Tentacles have suckers and hooks.
Squid are active predators.
Many squid are adapted to deep water (Architeuthus, 2cm-20m in size).
Squid lack chambers in active swimmers; using siphons for jet propulsion.
Commercially important.

Squid Driftnet Fishing

Squid driftnet fishing is unselective and negatively impacts marine mammals, seabirds, and turtles.
More selective methods exist but are costly.

Marine Mammals

110 species of marine mammals, including whales, pinnipeds (seals, sea lions, walruses), and sirenians (manatees, dugongs).
Baleen whales are the largest marine mammals.
Marine mammals feed by filtering zooplankton.
Marine mammal populations are decreasing due to high hunting pressure and low reproduction rates.

Taxonomic Groups of Marine Mammals

Cetaceans (whales, dolphins, porpoises)
Pinnipeds (seals, sea lions, walruses) - spend time on land.
Sirenians (manatees, dugongs) - spend time on land.
Fissipeds (polar bears, sea otters) - spend most time on land.

Deep Sea Life

Deep-sea environments, found at the bottom/abyssal regions, are characterized by hostile conditions such as darkness, extreme pressure, and temperature.
Deep-sea organisms include black hagfish, viperfish, and sleeper sharks.

Deep Sea Organisms

Includes a variety of creatures adapted to the deep sea environment.

Food Supply at Deep Sea

Deep-sea food supply relies on marine snow (dead plants, animals, and waste) and scavengers/predators.
Chemoautotrophy is prominent around hydrothermal vents where bacteria use chemical reactions to produce food, forming the base of the food web.

Deep Sea Adaptations

Large eyes are highly sensitive to low light.
Heightened scent and touch senses.
Photophores emit light for prey location, mate attraction, or predator avoidance.
Vertical migration occurs for safety.
Unique body coloration makes them hard for predators to spot.
Adaptations help with pressure (buoyancy adjustment), low temperature (slow movement), and metal protection.

Seafloor Habitats

Abyssal plain: relatively flat with squat lobsters, red prawns, and sea cucumbers.
Whale falls: dead whales provide food sources for scavengers for months.
Hydrothermal vents: volcanic areas with unique ecosystems around hot vents, releasing minerals, heated seawater, and chemotrophic lifeforms.

Brine Lakes

Bodies of highly saline water on the ocean floor, remnants of ancient seas.

Cold Seeps

Hydrocarbons (methane) trapped in Earth percolate up to the seafloor leading to unique marine life like mussels and shrimps.
Occur in canyons, edges, and bottoms of canyons and seamounts.
Seamounts: underwater mountains that affect current flow with unique lifeforms like crabs, corals, anemones, sea stars, and fish.
Deep sea reefs: individual or colonies of diverse species, providing habitats for sea stars and sharks.

Biological Oceanography in Fisheries

Improving understanding of fish abundance fluctuations through data collection on fishing, providing real-time information on fish school locations, and thereby reducing fishing costs.
The study aims at understanding of marine ecosystems and predicting fish stocks from oceanographic data to increase efficiency in the fisheries industry.

Coral Reef Ecology

This section provides notes on Coral Reef Ecology and is designated for an assignment.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Dive into the fascinating world of marine nekton, organisms capable of independent swimming in oceanic environments. From fish and squid to marine mammals, learn about their characteristics, reproductive methods, and the challenges they face in varying oceanic zones. This quiz explores the diverse adaptations and ecological roles of nekton in marine ecosystems.