SPONGES

What Phylum are Sponges in?

Porifera “pore-bearing”

What are Homoscleromorpha?

Skeleton absent or of siliceous spicules without an axial filament

What are Calcarea?

Calcium carbonate spicules

What are Demospongiae?

Spicules not with 6 rays, spongin network often present

What are Hexactinellida?

Spicules with 6 rays, syncytial trabecular reticulum

Characteristics of Sponges

Sessile, benthic, suspension feeders

Primarily consume bacteria inside specialized cells

No true tissues (independent but work together)

Cells are not connected

Cells are totipotent (can change form and function)

Intracellular digestion

No nerves or muscles

Skeleton is made of spongin and spicules

What is spongin?

Tough flexible protein fibers

What is spicules?

Hard calcium carbonate (corals) or silicon dioxide (quartz/glass)

What are the parts of a sponge called?

What is the function of choanocytes?

“Collar cell”

Responsible for food uptake

Flagellum draws water into the collar to trap food in mucus

Capture sperm for fertilization

What is the function of amoebocytes?

Motile cell—can transfer food

Totipotent

Involved in feeding, reproduction, and clearing debris

What are the two ways food can enter cells?

Phagocytosis (particles) or pinocytosis (dissolved organic materials)

What are porocytes?

Pore cells

Line the pores (ostia) and channel to spongocoel

What are pinacocytes?

Tablet cells

Form outer epithelium

What is the mesohyl?

Middle layer of sponge

Acellular matrix (gelatinous, nonliving, acellular)

Contains amoebocytes, spicules, and spongin

What are the different body plans of sponges?

Asconoid

Syconoid

Leuconoid

Ecological roles of sponges

Refuge inside sponge (grow much faster than coral)

Many cyanobacteria inside sponge (food)

Filter vast quantities of seawater (maintain water clarity and quality)

Potential use as drugs

Calcareous and siliceous sponges

Bioeroders

What is the difference between DOC and POC?

DOC is 0.45 µm and below

POC is anything above 0.45 µm

What is the sponge loop?

Alternative pathway for transferring DOM to higher trophic levels on coral reefs

Plays a major role in organic matter cycling

What are characteristics of sponge-dominated reefs?

Lower structural complexity

How has the top-down control on sponges in Caribbean reefs changed over time?

Before: more predators —> sponges in refuge habitat

Now: less predators —> more sponges with palatable sponges dominating, sponges are growing larger

What is an effect of overfishing on sponges?

Less sponge-eating fish —> sponges overgrow reef-building corals

What are secondary metabolites?

Responsible for chemical defenses

Important for human health (diabetes, cancer, HIV, antibacterial)

What are palatable species?

Faster rates of growth or reproduction (invest more energy to growth than defense)

What are defended species?

Make metabolically expensive chemical defenses (secondary metabolites)

What is the relationship between palatability and healing rate?

Positive correlation

How would a sponge reef function?

1. Greater abundance of spongivorous fish

2. Greater flux between benthos and water column and higher bacterial abundance

3. Habitat complexity is reduced, primary production increases, bioerosion increase, decrease in accretion

How sponge convert DOC into POC?

1. DOC uptake by sponge cells

2. DOC is metabolized into microbial biomass or used as an energy source and converted into bacterial cells (living biomass)

   1. Sponges shed dead cells, mucus, and symbiotic microbes (POC)

How does higher microbial biomass affect morphology?

Smaller choanocytes

Increased ability to process more DOC

Bacterial symbionts are larger and more abundant

How do sponges reproduce?

Asexually —> budding (newly grown piece)and fragmentation (pieces break off and form a new sponge)

Sexually —> release of sperm and eggs for larval development

How do sponges regenerate lost body parts?

Mitotic cell division (asexual)

What is totipotency?

Cells can become any other cells

Can self-assemble into a sponge

What are colonial organisms?

A separated sponge will re-associate to form another sponge

What are survival pods?

Gemmules (specialized buds)

Contain food, amoebocytes, and a protective covering of spicules

Released when a sponge dies

Resist desiccation

Become adult sponge when conditions become favorable