Intro-Characteristics

Most primitive phylum

No true tissues are present (sometimes considered dynamic tissues because cells can move and change from one form to another)

No organs are present

Cellular independence is characteristics (remember their trick of reorganization after being

pushed through fine mesh cloth into separate cells and then reorganizing into

a whole sponge?)

Mostly marine (150 freshwater spp.)

Require substrate

Usually shallow water (glass sponges at depths)

Capable of indeterminate growth (continues growing throughout lifetime)
 

Thought to be plants until 1765 (water flow observed)
 

Appearance

Erect

Massive

Encrusting

Branching

Coloring

Brightly colored

Green, yellow, orange, red, purple 
 

Basic structure

Unique-water canals (sessile animals that bring their surrounding environment to them)

Basic plan

Ostia – incurrent flow pores or canals which lead to pores

Atrium – spongocoel

Osculum – excurrent flow

from Invertebrate Zoology - Ruppert, Fox and Barnes 7th edition
 

Body wall

Unlike other metazoans – epithelium w/o basement membrane(outer layer but not a true tissue a dynamic tissue)

Pinacocytes – form pinacoderm 

Flat cells – each can contract (thus the animal shrinks)

Porocyte – 

Contains tube

Formed from pinacoderm – perforation or infolding of cell

Mesohyl=mesenchyme is the middle non-cellular layer between inner and outer layers

(remember those layers are not tissue)A protein jelly-like matrixthat contains amoeboid

(motile) cells

    With a skeleton of sorts (made up of spicules)

        Spicule material

Calcareous

Siliceous

Proteinaceous material

Collagen- made up of separate fibers

Spongin- network of fibers (rubbery texture)

Spicule form is a basis for  taxonomy

Shape

MonaxonSingle rodor ray with ends – pointed, knobbed,

hooked

Triaxon – 3 rays

Tetraxons – 4 rays

Hexaxons – 6 rays

Polyaxons – many rays (burr, ray, or star-shaped)

from Invertebrate Zoology - Ruppert, Fox and Barnes 7th edition
 

Size

Megascleres-spicules that provide chief support

Microscleres

                      Spicule Arrangement

Throughout mesohyl & poking through pinacoderm

Interlocking and/or fused

Variably arranged throughout body

   Cell Types

Mesohyl cells ( not a tissue but substance between inner and outer 

walls, but contains amebocytes [mobile cells] orfixed cells)

Archeocytes 

Amoeboid - mobile

Phagocytic -capable of ingesting and digesting particles-a sort of immune system

Totipotent – forms all other types of cells

Collencytes – 

attached by cytoplasmic threads

produce collagen

Lophopcytes

produces collagen

mobile

Sclerocyte

produces spongin or spicules

cells may cluster together and secrete spicule’s centerthey divide & radiate out to 

form ray 

Choanocyte – collar cell

inner layer of body wall lining atrium

collar faces inside of spongeand moves waterusing one

flagellumsurrounded by this

collar of microvilli

    Body Plan

Asconoid form - a simple vase-like radial form with ostia and a single osculum, without folding of the body wall a small spong (volume of atrium vs. volume of water moved limits size)

Syconoid Form

        folding pattern seen in syconoid spongesa solution for increased size

increases surface area

reduces volume of atrium

more efficient water flow

radial symmetry generally (but note below what happens with folding)

invagination of epidermis forms the incurrent canal

pinacoderm layer

  prosopyle = opening into excurrent canal

       evagination forms the excurrent canal (water flows into atrium and from there out through the osculum )

choanocyte layer

prosopyle

radial symmetry lost !

      Leuconoid – most complex water flow & found in most common sponges

Water flow

Dermal pores to subdermal spaces (some as vestibules) to incurrent canals to prosopyles to  flagellated chambers to flagellated canals anastomizng into larger canals to excurrent canal to osculum don’t worry about all of the terminology here but be able to describe the body plan

Up to 30,000 chambers per cubic mm

Appearance

Encrusting, branching, vase-like, tubular (w/ several oscula) 

Internal structure

Bodies solid (canals parallel) 

Hollow (central cavity)
 
 

from Barnes - Invertebrate Zoology - 5th Edition

Physiology

Water flow – substantial amount

Carries food, oxygen, waste, gametes

Choanocytes – spiral movement of flagellae drives water, but this is a  non-synchronous activity

Flow rates & control

Highest at osculum – smallest cross-sectional area

Lowest in flagellated chambers (leuconoid types) – largest overall cross-sectional area

Control

Ostial and oscular openings

Myocytes at the osculum – cf. to smooth muscle but cells unattached to each other

Patternsof water flow

Closed during storms

Some with diurnal flow pattern 

Passive flow occurs in strong current

Feeding – filter feeding mostly

from Invertebrate Zoology - Ruppert, Fox and Barnes 7th edition
 

80% are particles too small to seen with the light microscope/ 20% bacteria & plankton tropical waters have most food in smallest fractionfiltering at dermal pore-prosopyle, by protoplasmic strands in incurrent canals or microvilli of choanocytes.Particles engulfed (taken in by phagocytosis ) (this is performed by all cells – especially pinacocytes and amebocytes-the wandering cellsof the mesenchyme (mesohyl)

digestion occurs in vacuoles inside these cells

Waste, gas exchange, osmoregulation and coordination

ammonia is the principle waste

gas exchange thru direct diffusion

osmoregulation occurs within vacuoles of cells

no nervous system

although messenger chemicals are present in mesohyl

and amebocytes carry these messages around and there is

electrical discharge between adjacent cells (how nerve-

like is this?)

Taxonomy - DISCLAIMER - sponge classification is controversial even at the highest levels (Rupper, Fox, & Barnes)

(Symplasma-subPhylum)– Porifera with syncitial "tissues" 

Class Hexactinellida glass sponges, siliceous lattice,  syconoid forms

Spicules – hexaxons

Lattice – siliceous w/ sieve plate over osculum

Basal spicules w/ tufts for soft sediment

Structure and habitat

    Individualized cup, urns or vase shape

    Body wall- w/out pinacoderm, syncitium externally and internally

Deep water (200 meters-abyss) / Cosmopolitan w/ more in Antarctic

(Cellularia--subPhylum)– Porifera with cellular "tissues" 

Class Calcarea (Calcispongeae)

Spicules - Mon-, tri-, or tetraxon shapes

Calcium carbonate, No spongin

Structure and habitat

    Small (<10 cm)

Occupy shallow water

Cosmopolitan

All 3 body types

    Class Demospongiae – most common form, leuconoid forms

Spicules - Tri- or tetraxon

Along with spongin

Structure and habitat

Brightly colored (amebocytes w/ pigment)

Shape reflects habitat & resources available

Encrusting on vertical surfaces or in crevices

Tubular (w/ branching) on limited substrates (conserves space)

Shallow to deep water

Algal symbionts- non-motile zooxanthella or cyanobacters in mesohyl or amebocytes

Particular examples

                    Boring sponges (Cliona)

Perforates shells or corals (many tunnels)

        Amebocytes excavate chips of material

        Sponge fills tunnels (yellow or red on surface)

        Breaks down shells and corals (pock-marked shells along Atlantic coast)

Spongiidae – 

bath sponges,

no spicules only spongin

Spongillidae – freshwater forms

Clear sections of lakes & streams

Encrusting green forms (zoochlorella in amebocytes)

Class Sclerospongiae – Leuconoid forms, Found in grottos or coral tunnels

Internal siliceous spicules & spngin

External calcareous portion
 
 

A - hexactinellid sponge (spicules fused), B- demospongiae typical leuconoid form, C- sponge on a reef, most likely a leuconoid form, D - another leuconoid form, an encrusting Demospongid, again a leuconoid form (from Barnes, Invertebrate Zoology- 5th Edition)

from Invertebrate Zoology - Ruppert, Fox and Barnes 7th edition
 

Reproduction

Spongillidae – 

Gemmule – asexual reproductive body

Contains inner food-filled amebocytes

Outer hardened amebocytes & spicules

from Invertebrate Zoology - Ruppert, Fox and Barnes 7th edition

Life cycle

Parent disintegrates in fall

Gemmules overwinter

Outer hard cover opens in spring

Adult form develops through summer

Reaggregation

Minimum number of cells required (cf. to gemmule size)

Archeocyte presence required

Pinacocytes link up

Larvae of different species may fuse when settling

sperm

Flagellated chambers (in leuconoid forms) become spermatogonia 

Sperm develops from choanocyte

Sperm released through osculum

Sperm enter through ostia of another sponge

Sperm enter choanocytes

Sperm & choanocyte loose flagella

Both move to egg and fertilize egg

Eggs develop to larvae

Larval development

Ovoviviparous – develop after release

Viviparous – develop inside sponge

Larvae

Parenchymula – solid ball with exterior flagellated cells (except at “posterior”)

Amphiblastula – hollow ball with anterior flagellated cells and posterior larger and nonflagellated cells (megascleres)

Larvae transformed after settling

Some form of gastrulation occurs (much cell movment w/in larva)

flagella lost

Morphogenesis in leuconoid larvae (from asconoid through syconoid to leuconoid forms)

Lifespan 1 to 75 years

Phylogeny

Starts early Paleozooic (Cambrian)

May be pre Cambrian – fossils uncertain

Unique characters of phylum

Water movement

No cephalization

Divergence early-Parazoan vs. Eumetazoan lines