Chapter 13: Class Hydrozoa Flashcards Preview

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Flashcards in Chapter 13: Class Hydrozoa Deck (28):

Most live in a ______ environment and are _________ with both polyps and medusa forms. _____ is not typical.

marine, colonial, hydra


Hydrorhiza? (colonies)

base that colonial hydroids attach to the substratum by.


Hydrocauli (colonies)

stalks that come from root.


Coenosarc? (colonies)

living portion of the hydrocaulus..... aka gastrovascular cavity (coelenteron.) surrounded by three cnidarian layers.


Perisarc? (colonies)

non living chitinous sheath covering the hydrocaulus for protection..



individual polyp animals attached to the hydrocaulus..


Hydranths? (zooid, colonies)

feeding polyp...


Gonangium (polpy, colonies)
L> budding is for?

reproduction!! produces medusa .....
budding is for individual hydroid..


Thecate? (colonies)

perisarc continues as a protective cup around the polyp it can withdraw into for protection...


Athecate? (colonies) withdrawal cup


Velum? (hydroid medusa)

margin of bell projects inward...shelflike....partly closing the open side of the bell and functions in swimming via..msucular pulsations filling and emptying the bel


Manubrium? (medusa)
-gastrovascular system?
-radial canals...ring canal?
lined entirely by gastrodermis

mouth opening at the end of a suspended manibrium leads to the stomach and four radial canals that connect with a ring canal around the margin of the bell and connects with the hollow tentacles..



3rd cellular layer for medusa...smooth and striated muscle..derived from ectoderm...(endoderm, ectoderm, entocodon)


-aboral end?
-oral end?
location of tentacles?

-underside of aquatic leaves and lily, fresh water
-cylindrical tube
-aboral end has a basal or pedal disc
-mouth /oral end on a conical elevation = hypostome
-ring of 6-10 hollow tentacles around mouth


Feeding? (hydra)
-lure in
-gland cells?
-nutritive muscular cells?

prey brush against tentacles and are captured by nematocysts....tentacles move food and engulfed by the mouth which opens to a gastrovascular cavity...
-gland cells discharge enzymes and extracellular digestion occur
-drawn in via pseudopodia nutritive muscular cells in the gastrodermis where intercellular digestion occurs.


Nutritive Muscular Cells?(hydra)
-water influx?
-hydrostatic skeleton?

-tall columnar cells which have laterally extended bases containing -myofibres...running right angles to the body or tentacle axis forming a circular muscle layer....(very weak)
-water comes in through the mouth by beating cilia of the NMC therefore water in the gastrovascular cavity serves as a hydrostatic skeleton


What does the epidermis contain?(6)

epitheliomuscular, interstitial, gland, cnidocyte and sensory and nerve cells.


Epitheliomuscular Cells?(hydra)
-forms most of?
-type of muscle?

forms most of the epidermis and causes muscular contraction (longitudinal muscle) which extend parallel to the tentacle or body axis and contain myofibrils.


Interstitial Cells? (hydra)
-define them
-what do they produce? (4)
- what do they generally not produce

undifferentiated stem cells among the bases of the epitheliomuscular cells.
-produces cnidoblasts, sex cells, buds, nerve cells....not epitheliomuscular cells...they replace themselves.


Gland cells? (hydra)

-tall cells, around the basal disc and mouth
-secrete adhesive substance for attachment and sometimes a gas bubble for floating.


Cnidocytes? (hydra)
-what are the three functional types in hydras?

-penetrants : inject poison
-volvents: recoil and entangle prey
-glutinants: secrete an adhesive substance for locomotion and attatchment


Sensory cells ? (hydra)
-free end?
-other end?
-branches to?

-scattered among epidermal cells, High [ ] around mouth, tentacles and basal disc.
-free end of sensory cell bears flagellum (sensory receptor) for chemical and tactile stimuli
-other end branches into fine processes that synapse with nerve cells.


Nerve Cells? (hydra)
-amount of processes?
-forms synapses with? (4)
-type of synapses/direction?

-multipolar (many processes)
-some they are bipolar (only 2)
-axons form synapses with sensory cell, other nerve cells, epitheliomuscular cells and cnidocytes.
-on-way and two-way synapses with other nerve cells.


Reproduction of Hydra?????

- budding
I> buds appear as outpocketings of the body wall and develop into young hydras that eventually detach from the parent. (think pregnancy but not )


Reproduction for Hydras
-Sexual Reproduction?
- classification
-gonads appear? bc?
-shed via?
-cyst makes?
-hatches when?

-most are dioecious
-temporary gonads appear in autumn, stimulated via low temps or stagnation
-eggs and sperm shed externally
-cyst forms embryo
-encysts form endures the winter and hatches in the spring.


Holoblastic cleavage? (hydra)
-role in reproduction?
-blastula becomes? made up of (3)

zygote undergo form hollow blastula...the inner part forms endoderm and mesoglea is laid down between the endo and ectoderm....cyst forms around the embryo before it breaks loose from the parent.


Other Hydrozoans?????Physalia?

-floating colony
-expanded from the original larval polyp



hydrozoans that secrete calcareous skeletons resembling true corals

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