Invertebrate Zoology Lecture Exam 1

Dr. Cook Tennessee Tech

Lentic

Refers to a standing or still freshwater ecosystem

• Includes ponds, lakes, reservoirs, and some wetlands

• Invertebrates include organisms such as aquatic insects, snails, clams, and crustaceans

Littoral Zone

The shallow area along the shoreline of a lake or other body of water where sunlight reaches the bottom and aquatic plants can generally grow

• Especially important because it tends to have lots of habitat and food, making it highly diverse

Profundal Zone

The deep-water zone of a lake, below the depth where enough light reaches for significant photosynthesis

• Typically inhabited by organisms adapted to low light and low-oxygen conditions

Paleolimnology

The study of ancient lakes and their history, usually by examining lake sediments

• Researchers can use sediment layers to learn about past climate, pollution, vegetation, and environmental changes

Hemocoel

The main body cavity of arthropods and some other invertebrates where hemolymph (blood-like fluid) circulates through the organs

Metamerism

The body is divided into a series of repeated segments (metameres) along the length of the animal

• Ex: annelid (earthworm)

Sternum

A ventral (bottom-side) structure that supports or protects internal organs; in many animals, it is specifically the breastbone

• In arthropods, it is the ventral part of a segment, often associated with the legs

Osmoregulation

The process of maintaining the proper balance of water and dissolved salts (ions) inside an organism

• Aquatic invertebrates constantly exchange water and ions with their environment

• They have to prevent too much water from entering their bodies or too much water from leaving because of osmosis

• Different animals have different strategies (freshwater vs. saltwater, etc. urine)

Nephridium

An excretory and osmoregulatory organ found in many invertebrates

• Kidney-like

Protonephridium

An excretory and osmoregulatory system in invertebrates that is closed at the internal end and opens to the outside of the body

• Typically contains solenocytes or flame bulbs

Solenocyte

A specialized excretory cell found in certain invertebrates that helps with waste removal and osmoregulation

• Protonephridium

• Has a flagellum that beats and helps move fluid through the excretory system

• Like a tiny filter/pump cell

Flame Bulb

A ciliated, bulb-shaped structure found in the excretory system of some invertebrates, especially flatworms

• Protonephridium

• Has cilia that beat like a flickering flame

• Helps remove excess water, with osmoregulation, and moves fluid through the protonephridium

Metanephridium

An excretory organ/system found in many invertebrates, including annelids (earthworms), unlike a protonephridium, it is open to the body cavity (coelom)

• Excretion and osmoregulation

Nephrostome

The funnel-shaped opening of a metanephridium that opens into the body cavity (coelom) that collects fluid from the coelom and directs it into the metanephridium

• Like a funnel

• Often ciliated

Protostomes

Animals in which the blastopore develops into the mouth during embryonic development

• Proto = first, meaning the mouth develops first

• Ex: annelids, mollusks, arthropods

Deuterostomes

Animals in which the blastopore develops into the anus, and the mouth develops second in embryonic development

• Deutero = second, meaning the mouth develops second

• Ex: echinoderms and chordates (including humans)

Determinate Cleavage

A type of embryonic cell division in which the fate of each cell is determined early in development

• Protostomes

• Once the embryo starts dividing, each cell is already committed to becoming a certain type of tissue

• Less ability to compensate for damage or cell loss

  
  

Indeterminate Cleavage

Early embryonic cells remain capable of developing into a complete embryo if separated; the cells' futures are not determined yet

• Deuterostomes

• Allows for possibility of identical twins

Spiral Cleavage

The cells divide at angles, so the cells in one layer sit between the cells of the layer below

• Protostomes

• Often associated with determinate cleavage

Radial Cleavage

The cells divide directly above or below one another, creating rows of cells that line up

• Deuterostomes

• Cells are arranged in a straighter, more straight/aligned pattern

  
  

Archenteron

The primitive digestive cavity that forms during gastrulation in the developing embryo

• Early gut

• The blastopore is the opening into the developing archenteron

Schizocoelous

An animal in which the coelom (body cavity) forms by splitting within the mesoderm

• Protostomes

Pseudocoelomate

An animal that has a pseudocoel, a body cavity that is not completely lined by mesoderm

• “false” body cavity

• Partially lined by mesoderm

Detritivores

Organisms that feed on detritus, which is dead and decaying organic matter

• Ex: earthworms, many insects/arthropods, some crustaceans

• Help break down dead material and recycle nutrients through ecosystems

Shredders

Aquatic detritivores that feed on and physically break apart large pieces of dead organic matter, especially leaves

• Especially important in streams and rivers

• Specific type of detritivore

• Ex: stonefly and caddisfly larvae

Filter Feeders

Animals that obtain food by filtering small particles or organisms out of water

• They typically use specialized structures to trap things like:

  • Plankton

  • Bacteria

  • Detritus

• Ex: some bivalves, sponges, and crustaceans

Exoskeleton

A hard skeleton on the outside of an animal’s body that provides support and protection

• Found especially in arthropods (insects, crustaceans, spiders, etc.)

• Primarily made of chitin

• Because the exoskeleton is rigid, arthropods must molt it to grow

Exopod

The outer branch of a biramous (two-branched) appendage, especially in crustaceans

Arthropoda

A major animal phylum characterized by jointed appendages, a segmented body, and an exoskeleton made primarily of chitin

• Ex: insects, crustaceans, arachnids, myriapods

Decapoda

An order of crustaceans that have five pairs of walking legs = 10 legs

• Ex: crabs, shrimps, lobsters, crayfish

• Crustacean, arthropod, protostome, determinate and spiral cleavage, schizocoelous

Copepoda

A major group/class of small crustaceans, many of which are important members of zooplankton

• They are extremely common in aquatic ecosystems and are an important food source for fish and other animals

Cyclopoida

An order of copepods

• Including many small aquatic zooplankton

Spindacaudata

An order of small freshwater crustaceans commonly called clam shrimp

• They have a bivalved, shell-like carapace that makes them look somewhat like tiny clams

Paleomonidae

A family of shrimps within Decapoda

• Arthropod, protostome, determinate and spiral cleavage, metamerism

Talitridae

A family of amphipod crustaceans

• Ex: beach hopper/sand flea

• Crustacean, arthropod, protostome, determinate and spiral cleavage, schizocoelous

Artemia

A genus of brine shrimp, small crustaceans that commonly live in very salty water

• They are famous for surviving high-salinity environments and are commonly used as food for fish in aquaculture

Juvenile Hormone

A hormone in insects that helps control growth and development, particularly whether an insect remains juvenile or transitions to the adult stage

• Specifically important for arthropods/insects

• High = stay juvenile

• Low = progression towards adulthood

Monoecious

An organism in which one individual has both male and female reproductive organs

• Hermaphroditic?

• One individual has both sexes

Diaptomus

A genus of freshwater copepod

• Commonly found as part of zooplankton in lakes and ponds

• They are an important food source for fish and other aquatic organisms

Ostracoda

A group/class of small crustaceans often called seed shrimp

• Their bodies are enclosed in a two-part, clam-like shell

• Found in both freshwater and marine environments

Cypridae

A family of ostracods

• They are primarily freshwater ostracods

Mysidaceae

A family of small, shrimp-like crustaceans, commonly called mysids or opossum shrimp

• Mostly aquatic and often found in marine environments

Asellidae

A family of freshwater isopods

• They are often found on the bottom of streams, ponds, and lakes, where they feed on decaying organic material

Perinoteum

A thin membrane that lines the body cavity and covers internal organs

• It is associated with the coelom

Blastocoel

The fluid-filled cavity inside the blastula during early embryonic development

• It forms before the archenteron

Epiboly

A type of cell movement during gastrulation where one layer of cells spreads over and around other cells.

Marine to Freshwater

This refers to the evolutionary/ecological transition of organisms

A major challenge is osmoregulation:

• Marine → freshwater means the organism enters a much more dilute environment.

• Water tends to move into the body.

• The organism tends to lose ions/salts.

• It must prevent too much water from accumulating and conserve/replenish ions

Suspension Feeder

An animal that obtains food by filtering suspended particles from the water

• Food can include plankton, bacteria, detritus, and other small particles

• Ex: many bivalves

Bilateral Symmetry

A body plan in which the animal can be divided into two matching halves—a left and right side—by one plane

• Animals have distinct anterior (front) and posterior (back) ends

• Example: humans, earthworms, insects, and most crustaceans

Radial Symmetry

Body parts are arranged around a central point

• The animal can be divided into similar sections by multiple planes passing through the center.

• Ex: jellyfish, sea anemones

Pentaradial Symmetry

A type of radial symmetry with body parts arranged in five sections around a central point

• Characteristic of echinoderms such as sea stars and sea urchins

• Adult echinoderms have pentaradial symmetry, but their larvae are bilaterally symmetrical

Chitin

A strong structural polysaccharide that forms much of the arthropod exoskeleton

• Also found in things like fungal cell walls

Cuticle

A nonliving protective outer layer covering the body of many invertebrates.

• In arthropods, the cuticle forms the exoskeleton and contains chitin

Tergum

The dorsal (top/back) portion of an arthropod body segment

Pleura

The lateral (side) portion of an arthropod body segment

• Think of the three main regions of an arthropod segment:

  • Tergum = top/back

  • Pleura = sides

  • Sternum = bottom/underside

Macromeres

The larger cells produced during early embryonic cleavage

• Usually found toward the vegetal (bottom) pole of the embryo

Cephalized

Having a concentration of sensory organs and nervous tissue at the head/front end of the body

• Common in animals with bilateral symmetry

Metameres

• Repeated body segments that make up a segmented animal

  • Each repeated unit is called a metamere

Arachnoida

A group/class of arachnid arthropods, including spiders, scorpions, ticks, and mites

• Characterized by four pairs of walking legs as adults

Uropod

A paired appendage at the rear end of many crustaceans

• Often helps with swimming, steering, or creating a rapid escape response

Hyalella

A genus of small freshwater amphipod crustaceans

• Commonly found in streams, ponds, and lakes, often associated with vegetation or leaf litter

Serial Homology

When repeated structures within the same organism are derived from the same basic developmental pattern

• Ex: the different pairs of arthropod appendages are serially homologous

Acoelomate

An animal that does not have a coelom (a true body cavity)

• The space between the digestive tract and the body wall is filled with tissue

Eucoelomate

An animal with a true coelom, meaning the body cavity is completely lined with mesoderm

Coelom

A fluid-filled body cavity completely lined with mesoderm

• It provides space for internal organs and allows organs to move/grow independently of the body wall

Ostia

Small openings/pores that allow water to enter the body of a sponge

• Water flows through the ostia into the sponge's internal canal system

Protopod

The basal (proximal) portion of a crustacean appendage from which the branches arise.

• In a typical biramous appendage, the protopod gives rise to the endopod and exopod