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  Habitats & ecology
 
 
photograph of spong Adocia sp. competing for space with cup corals and sea anemones

Included in this section is the topic of growth forms, while CHIMNEYS and GLASS-SPONGE REEFS are considered elsewhere.

 

 

 

 

Sponge Adocia sp. competes for space with encrusting coralline algae,
cup corals Balanophyllia elegans, sea anemone Anthopleura elegantissima,
and hydroids. The competition appears to be of the "stand-off" type,
with each participant seeming to respect its neighbours' boundaries. Little
or no work has been done on competitive interactions in west-coast sponges 0.4X

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  Growth forms
 

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Research study 1

 

Field studies on sponge-alga interactions in Tatoosh Island, Washington show that Halichondria panicea does better when it grows in close proximity to the coralline alga Corallina vancouveriensis. If the alga is clipped with scissors and made smaller, percentage cover of the sponge declines. If the clipping is stopped, the sponge rebounds. Other studies show that settlement and metamorphosis of Halichondria larvae in the lab is enhanced when clippings of the alga are placed in the settling dishes. Palumbi 1985 The Amer Nat 126: 267.

NOTE  a group of red algae characterised by large quantities of calcium carbonate in their tissues

 
graph showing effect of clipping of nearby algae on growth of sponge Halichondria panicea
Percentage cover of sponge Halichondria panicea declines when coralline algae growing nearby is clipped. When clipping is stopped at sites in July and September, % cover of sponge increases at those sites
photograph of coralline algae Corallina vancouveriensisCoralline alga Corallina vancouveriensis 0.5X photograph of a sponge Halichondria panicea growing in close associateion with a coralline algaSponge Halichondria panicea growing in association with an unidentified species of coralline alga 0.3X
   
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This is interesting, but what do you think explains the favourable growth of Halichondria in the presence of the alga? Here are some possible answers. Think about them, then CLICK HERE to see an explanation for each answer.

The alga shades the sponge from harsh effects of sunlight.

The alga provides protection from desiccation.

The alga provides protection from nudibranch-predators of the sponge.

 

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Research study 2

 

The demosponge Halichondria panicea has different growth forms depending upon whether it is growing in high- or low-wave-energy areas. In the first, such as in surge channels on the open coast, its texture is stiffer and stronger, “tissue” density greater, spicule content higher, and internal water channels narrower. In the second, such as around pilings or floating docks, its texture is softer and more crumbly.  Palumbi 1986 Ecology 67: 208.

histogram showing effect of waves on tissue mass and spicule content in a sponge Halichondria panicea

photograph of crumbly form of sponge Halichondria panicea courtesy Bill Austin, Victoria
Crumbly form of H. panicea from low-wave-energy dock areas in Barkley Sound, British Columbia. Photo courtesy Bill Austin, Victoria

NOTE this photo may be of H. bowerbanki, a related species with similar growth form to H. panicea

photograph of green form of sponge Halichondria panicea found in wave-exposed areas

Halichondria panicea in protected high-wave-energy area in Barkley Sound, B.C. Halichondria panicea is not found in exposed areas of highest wave action, perhaps because of higher costs of pumping water through a skeletal/body structure that would be strong enough to withstand the severe physical stresses found there 

 

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Research study 3

 

Now, what would happen to a sponge’s stiffness/strength if we were to do reciprocal transplants of Halichondria paniceabetween the two habitats?  In other words, what would be the structure of the new growth in the new habitat in comparison with that of the original sponge? Well, after transplantation from a low- to a high-wave energy area the stiffness/strength of the new growth increases within 4wks and is maintained for at least 1yr at the new high level (Top histogram). 

But, after transplantation from a high- to a low-wave energy area, the stiffness/strength of the new tissue remains unchanged for a time (at least 4wk) and only later does it decrease to a level more characteristic of quiet-water habitats.  Palumbi 1984 Science 225: 1478.

NOTE The author actually separates the 2 components of stiffness and strength in the paper. However, as the trends are the same and for purpose of clarity, they are averaged and presented here as a single value

histograms showing effect on stiffness/strength of sponge Halichondria panicea when reciprocally translocated between calm-water and wave-exposed habitats
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What is the most likely explanation for the results? CLICK HERE for a consideration of each answer.

Different genotypes of sponge respond differently to different habitats. 

Adaptation of a genotype of sponge to a new habitat takes time. 

For whatever reason, it takes the sponge longer to reduce the stiffness/strength of its new growth than to increase it. 

The sponge is exhibiting a sort of “risk-assessment” in its response. 

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Still not clear? If the sponge could talk, its explanation to a group of student sponges might go something like this: 

“Well, when I was moved to the wave-exposed area my loose, crumbly texture was too weak, so my new growth had to be stronger and stiffer even though it took longer to produce and cost more energy to pump water through its smaller-diameter channels.  When I was moved to the calm area, however, my original strong, stiff texture still worked okay, and I just wasn’t confident about making the change to my more crumbly form right away…you never know about these things!”

cartoon of a sponge talking to several smaller sponges
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Research study 4
 

Two species of calcareous sponge Leucoselenia live in different habitats on the west coast and have different growth forms. Leucoselenia nautilia, shown in the photo on the Right, inhabits calm-water areas and has a loosely branching growth form. Leucoselenia eleanor inhabits wave-exposed areas on the open coast and has a tightly anastomosing growth form.

Simple compression tests show how the two forms of Leucoselenia are adapted to compressive stress, as might occur from wave impact. Data and figures courtesy Bill Austin, Victoria

visual comparison of compressive stress tests on two forms of sponges Leucosolenia nautilia and L. eleanor from calm and rough water habitats, respectivelyNot only is the rough-water species more resistant to strain from experimental application of weight, but its recovery is substantially greater than shown by the calm-water species

photograph of Leucoselenia nautiliaLeucoselenia nautilia

drawings showing growth forms of sponges Leucosolenia nautilia and L. eleanor

 

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Research study 5
 

For over a century we have known that the cellular components of sponges can be dissociated. This is easily done by squeezing a bit of sponge, such as Halichondria panicea, through fine-mesh cloth. The resulting cells lose their specialised form and function, and dedifferentiate into a more primitive crawling form. The cells crawl about until they meet up with other cells like themselves, to which they adhere, and within a few days a new sponge has formed, complete with pumping chambers, water channels and chimneys, and possessing all of the diverse cell types of the adult sponge.  If the cells of two different species are dissociated and mixed together, they will crawl by one another to meet up with cells like themselves, and the two species faithfully reconstitute themselves.

NOTE the purple sponge Haliclona sp. also works well

NOTE  in this new form the cells are essentially stem cells, in that they have the potential to develop into any type of specialised cells in the adult body

series of photographs showing dissociation and reassociation of cellular components of a sponge Halichondria Day 0: squeezed through meshDAY 0: Halichondria is squeezed through mesh series of photographs showing dissociation and reassociation of cellular components of a sponge Halichondria Day 2: cells begin to dedifferentialtDAY 2: cells begin to dedifferentiate series of photographs showing dissociation and reassociation of cellular components of a sponge Halichondria Day 4: cells crawl about and begin to reaggregateDAY 4: crawling cells begin to aggregate series of photographs showing dissociation and reassociation of cellular components of a sponge Halichondria Day 5: reaggregating cells are clearly visibleDAY 5: aggregations are easily visible series of photographs showing dissociation and reassociation of cellular components of a sponge Halichondria Day 6: small sponges are formingDAY 6: small sponges are forming throughout the mix
 
Research study 6
 

histogram showing fusion potential between "self" tissues of the sponge Haliclona and tissues from conspecifics at the same and distant sitesphotographs of pre- and post-fusion larvae of the sponge Haliclona sp. courtesy of McGhee 2006 J Exp Mar Biol Ecol 333: 241As described in the foregoing Research Study, sponges are able to distinguish between genetically identical and genetically distinct tissues.  Is this true both during larval and adult stages?  This question is addressed in a laboratory study at the Bamfield Marine Sciences Centre, British Columbia using the sponge Haliclona sp.  Observations on fusion potential indicate that while adults fuse preferentially with self-tissue and therefore exhibit allorecognition (see histogram on Left), the free-swimming larvae fuse equally with sibling and non-sibling larvae, both from nearby and distant sites, indicating an age-activated allorecognition system (see photos above Right). These chimera larvae are capable of successful metamorphosis.  Interestingly, the adults differ significantly in the propensity of their larvae to fuse suggesting variability in parental “strategies”.  The differences manifest in the open-water aggregating propensity of the different larvae and thus in their probability of undergoing chimeric fusion.  The author discusses the significance of this stage-activated allorecognition system; specifically, in possible benefits to larvae and adults in becoming chimeras.  McGhee 2006 J Exp Mar Biol Ecol 333: 241.

NOTE  known as allorecognition (lit. “different recognition”)

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