6. Porifera Flashcards
Porifera + Placozoa =
Parazoa
What’s the common name for organisms in phylum Porifera?
sponges
Give the relative species richness of sponges in marine, freshwater, and terrestrial
- marine= 9000 spp
- freshwater= 200 spp
- terrestrial= 0 spp
What’s the approx size range of sponges?
range from a few cm to more than 2m in size
T/F
Porifera show the most cellular differentiation and integration of all Metazoa
False
Porifera show the LEAST cellular differentiation of all Metazoa
Placozoa and Eumetazoa have cross-striated cellular rootlets. Do Porifera have these?
No, Porifera lack these cross-striated cellular rootlets
T/F
All species of sponges are entirely sessile as adults
False
It is true that MOST of them are entirely sessile as adults, but some sponges can move slowly by crawling of their cells (they leave a trail of spicules behind them)
List the 4 classes of sponges in order of most species-rich to least
- Class Demospongiae (7400 spp)
- Class Calcarea (793 spp)
- Class Hexactinellida (682 spp)
- Class Homoscleromorpha (126 spp)
According to the most recent molecular analysis of Porifera, are they most likely monophyletic or paraphyletic?
Monophyletic
- At one point, Homoscleromorpha Class was thought to be more closely related to Eumetazoa than to the rest of the Porifera, which would’ve made Porifera paraphyletic. But this isn’t considered correct anymore
What symmetry are most sponges?
Most show no clear axes of symmetry, though some are almost radially symmetrical
To some extent, sponges are defined based on the absence of typical animal features
List the animal-features that are not present in sponges (
Sponges do not have:
- mouth
- gut
- muscles
- reproductive, digestive, respiratory, nervous, or excretory organs
- true endodermally or ectodermally-derived tissues
T/F
Sponges perhaps have only a single sensory structure
True
(the osculum)
The water-canal system is a feature present in most sponges. Describe it
It has many incurrent pores (ostium), and one or a few large excurrent pores (oscula). There is a spacious spongocoel (a water-filled central cavity- this is not a true coelom)
The movement of water through a sponge’s body is achieved through flagellated ______
choanocytes
- beating of choanocytes= movement
Mesohyl=
mostly non-cellular ‘filler’ material found in sponges
The internal skeleton of sponges is made up of what?
Calcareous or silicious spicules or collagenous spongin (or both)
Cells in sponges are relatively autonomous and show totipotency or pluripotency.
Define autonomous, totipotency, & pluripotency.
autonomous cells= act independently of surrounding cells or tissues
totipotency= cells have the capacity to transform into ALL cell types and perform different tasks
pluripotency= cells have the capacity to transform into MOST cell types and perform different tasks
Sponges have 2 major growth forms:
- upright
- encrusting
Sponge bodies vary from simple to complex. List the 3 main body types and give a feature of each
- Ascon type (= asconoid): single flagellated pumping cavity (spongocoel)
- Sycon type (= syconoid): Many flagellated canals connected to spongocoel
- Leucon type (= leuconoid): Many flagellated chambers connected by non-flagellated canals
*flagellated= lined with choanocytes
T/F
All 3 sponge body plans can be found in all 4 classes
False
All 3 body plants occur in Class Calcaera, but other classes only have Leuconoid
Give the 5 main cell types found in sponges
- Pinacocytes
- Archaeocytes
- Myocytes
- Porocytes
- Choanocytes (collar cells)
Describe pinacocytes
= flat cells that form the outer body covering (called the pinacoderm)
- in some spp, pinacoderm acts like ‘true’ epithelial tissue b/c it can regulate ion levels inside sponge
- in other spp, it lacks a basal lamina, intercellular junctions (cells can pull apart), apical-basal polarity, or ability to regulate ion levels
Describe Archaeocytes
aka “amoebocytes”
= amoeboid cells that can transform into any cell type (= totipotent)
- also make spicules or spongin fibers or transport food
Describe myocytes
= contractile cells
- encircle osculum and flagellated chambers
- can open & close oscula
*myo=muscle
Describe porocytes
= tubular cells (like pieces of macaroni!)
- act as openings to ostia in some groups (can sometimes actually form the ostia)
Describe choanocytes
aka collar cells
(in the choanocyte layer)
- function in pumping & feeding, & also transform into sperm during mating season
What do choanocytes look a lot like?
Choanoflagellate protists
