Lower Invertebrates (Chapter 8)

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Introduction to Marine Biology, Third Edition by: George Karleskint Jr.; Richard Turner; and James W. Small, Jr.

Invertebrate

animals that lack a vertebral column.

Sponges/Porifera

simple, asymmetric, sessile animals frequently determined by the shape of the bottom sediments or material on which they are growing and by the water currents flowing around them.

Ostia

tiny holes or pores through which large amounts of water circulate.

Osculum

large opening in sponges by which water exits the spongocoel.

Sessile

animals that are permanently attached to a solid surface.

Spongocoel

spacious cavity within sponges.

Collar Cells/Choanocytes

flagellated cells that line the interior of the cylinder, suck water in through the ostia.

Archaeocytes

cells that resemble amoebas in the sense that they can move through the sponge's body; form any of the cell types; transport food; and play an important role in repair and regeneration

Asconoid

simplest sponge body form; small tube shaped sponges; large central cavity = spongocoel; in via ostia; out through osculum.

Leuconoid

sponge body form with the highest degree of folding (allows for sponges to be big); no central cavity; many small interconnected chambers.

Syconoid

sponges that exhibit the first stages of body-wall folding that is lined with collar cells.

Filter Feeder

organism that filters its food from the water

Hermaphrodites

animal that possesses both male and female sex organs

Suspension Feeder

organisms that feed on material that is suspended in sea water (aka filter feeders)

Budding

form of asexual reproduction; group of cells on outer surface of sponge that grows into a tiny new sponge that later drops off

Fragmentation

form of asexual reproduction; production of a new sponge from pieces that are broken off by things such as waves or storms or predators

Desmospongia

largest class of phylum porifera; made of spicules consisting of the protein spongin

Cnidarian

invertebrate animals that have radial symmetry and use stinging cells to capture food and defend itself.

Cnidocyte

stinging cell that all cnidarians possess

Polyp

benthic form of cnidarian; cylindrical body that has an opening at one end (mouth) that is surrounded by a ring of tentacles.

Medusa

free floating stage of cnidarians commonly known as jellyfish

Epidermis

outer layer of cells on all cnidarians (found in both polyp and medusa)

Gastrovascular Cavity

large cavity inside cnidarians lined by a layer of cells called the gastrodermis

Mesoglea

jelly-like substance that lies between the epidermis and the gastrodermis

Cnida

stinging organelle inside the stringing cells of cnidarians

Nematocyst

type of cnidae located within a capsule in the cell; most common type of cnidae

Cnidocil

short, bristle-like structure that extends from one end of the stinging cell and acts as trigger that when touched causes the lid to open and the nematocyst to discharge

Hydrozoan

type of cnidarian; mostly colonial; primarily found in the polyp stage; example is a Portuguese man-of-war

Reproductive Polyp

type of polyp in colonial hydrozoans; specializes in reproduction

Feeding Polyp

type of polyp in colonial hydrozoans; specializes in capturing food and feeding the colony

Scyphozoan

type of cnidarian; "true jellyfish"; have photoreceptors that allow for them to determine if it's dark or light

Cubozoan

type of cnidarian; "box jellys"; found mostly in tropical waters; strong swimmers; usually deadly

Anthozoan

type of cnidarian; only exhibit polyp stage; examples are sea anenomes, soft coral, and coral animals.

Sea Anenome

polyps that are larger, heavier, and more complex than hydrozoan polyps; gastrovascular cavity is divided into compartments; most are sessile and are found attached to things like rocks or shells.

Coral Animal

polyps that secrete a skeleton, which may be hard or soft, around their bodies; generally part of a colony;

Soft Coral

form colonies that look more like plants than animals; have 8 feathery tentacles; body is fleshy; and they are commonly found along Atlantic, Gulf, and southern California coasts

Pedal Laceration

type of asexual reproduction; common in anthozoans; leaving parts of their base behind to grow into new individuals

Planula Larva

planktonic larva that grows in the water column and allows for sessile animals to reproduce by dispersing their young into other areas. generally used in medusa stage of hydrozoans

Ctenophore/Comb Jelly

planktonic, nearly transparent marine animals that are named for their eight rows of comb plates used for locomotion.

Comb Plates/Ctenes

a locomotor organ in ctenophores made of very large cilia

Bilateral Symmetry

body parts of animal are arranged in such a way that only one plane through the midline of the central axis will divide the animal into similar right and left halves; most marine animals exhibit this (NONE OF WHAT WE'RE STUDYING EXHIBITS THIS)

Cephalization

concentration of sensory organs in the head region of an animal

Photoreceptor

sense organs that give the ability to determine if it is dark or light; jellyfish have this

Vertebrate

animal that possesses an internal skeletal rod (backbone)

Tissues

groups of specialized cells that perform a specific function, and organs. sponges lack this

Pinacocytes

layer of cells that provide an outer covering for the sponge. they also line internal chambers that are not lined by collar cells

Spicules

skeletal elements that give support to a sponges body

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