Scypa – the syconoid sponge
MORPHOLOGI
Scypa (fig.7-4)is a more complex
marine sponge in comparison to leucosolenia. It attaches permanently to rocks
and other solid objects and varies in length between 12mm to almost 25mm. Its
shape resembles a slender vase, bulging slightly in the middle. The osculum is surrounded by a
ring of straight spicules. Smaller spicules protude from other parts of its
body. The body wall isriddled with numerous incurrent pores.
One large central cavity (spongocoel)
leads from the base of the sponge up to the osculum. Aroun the central cavity,
the thick body wall is built of elongated, sac-shapes radial canals. Each canal
lies perpendicular to the central cavity and has a large exhalant opening
(apopyle). undulipodia lining the canal
beat constantly, drawing water into the many inhalant canal chambers.
Partyculary reproductive ones (ova, sperm, gemmules).
The
soft body wall is supported and protected by a skeleton composed of many
calcium carbonate spicules. Four varieties of spicules are present: (1) long,
straight monaxon rods, with guard rods, which guard the osculum; (2) short
straight monaxon rods, surrounding the incurrent pores; (3) triadiate spicules,
embedded in the body wall; and (4) t-shaped spicules, lining the central
cavity.
Physiology
Scypa
lives on fine particles and minute planktonic organisms, drawn into it by the
current created by choanocyte undulipodia. Some digestion occurs within the
choanocytes, but is for the most part carried out by amoebocytes. As in
protozoans, digestion is intracellular; nutriens are diffused through the cells
with the aid of amoeboid archeocytes, which also serve as food-storage sites.
Excretory
matter is discharged through the general body survace, probaly assited amoeboid
wandering cells and possibly choanocytes. Respiration, likewise, takes place
through the cells of the body wall in the absence of any specialized organs.
Sponges
are usually considered to be very quite and sluggish but are actualy among the
most active and energetic of all animals, working night and day to create the
currents of water that bring food and oxygen into the body and carry away
wastes. The amount of water that flows through the body is tremendous; an a
average-size sponge draws about 45 gallons of water through is canal system in
a single day.
True
nerve tissue in sponges has not been demonstrated; single cells, how ever. Do
respons to certain stimuli. A finger placed in the osculum may be forcibly
squeezed due to responsive contractile cells (myocytes) surrounding the
opening.
In many
sponges an individual cut into pieces will grow into several normal sponges,
this process is known as regeneration.
Reproduction
Scypha
reproduces both sexually. Asexual reproduction in volves the formation of buds
near the point of attachment. These eventually break free and take up a
separate existence.
Sexual
reproduction involves the mesenchyme cells. Both eggs and sperm occur in single
individual. The fertilized egg segment by three vertical divitions into a
pyramidal plate of eight cells. A
horizontal divition cuts off a smalls cell from each of the eight, resulting in
a layer of eight large cells crowned by a layer of eight smaller cells. These
arange about a central cavity, producing a blastulalike sphere. The small cells
multiply rapidly and develop undulipodia, while the large cells become
granular, partially growing over the other cells to form an amphiblastula
(fig.7-5). The amphiblastula escapes from the parent as a larva and swims about
for several days until it attaches to a solid object and begins growth as a young sponge.
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