Overview

Glass sponges are often mistaken for plants because they do not have eyes or a mouth or stomach, but they are in fact living animals. Adult glass sponges are “sessile”, meaning they do not move. They are have a skeleton comprised of millions of fused strands of silica (glass).  Their bodies stretch over the skeleton and have thousands of tiny holes, or pores, through which water constantly flows. They absorb all the food, oxygen, and silica they need straight from the water that surrounds them. They get rid of their waste straight back into the water, which they pump out through their tube-shaped “oscula” with the help of the surrounding water current.

This portion of our website presently concentrates on one group of sponges popularly referred to as glass sponges. They are called Glass Sponges because about 90% of their dry weight is glass or silica (e.g., Dayton et al 1974, Austin 1984). Their scientific name is Hexactinellida (hex = 6; actine = ray) as many components of their skeleton, referred to as spicules, have 6 rays. These rays are aligned along 3 axes at right angles to each other. The number of rays may be reduced in some spicules.

There are some 300 other species of sponges in BC. listed elsewhere on our website and we have colour images for most of them for help in identification.

 
 Mainframe skeleton and examples of spicules from the Cloud Sponge showing the basic 6 rayed form in some and a reduced number of rays in others

Mainframe skeleton and examples of spicules from the Cloud Sponge showing the basic 6 rayed form in some and a reduced number of rays in others

Glass Sponges
(Hexactinellids)

  Glass sponge artwork by Ernst Haeckel, first published in 1904 in his book Art Forms in Nature .

Glass sponge artwork by Ernst Haeckel, first published in 1904 in his book Art Forms in Nature.

The Cloud Sponge Aphrocallistes vastus

At this time our web siteconcentrates on one species, the Cloud Sponge, Aphrocallistes vastus and on those populations occurring in the fjords of British Columbia.

The main skeleton of Cloud Sponges is formed of fused strands of glass. For this reason they are extremely fragile and are at risk of being shattered from human activities such as fishing and diving.

Prior to their discovery in British Columbia, glass sponge reefs were believed to have gone extinct 40 million years ago, in the Jurassic Period.The earliest known hexactinellids are from the earliest Cambrian or late Neoproterozoic. They are fairly common relative to demosponges as fossils, but this is thought to be, at least in part, because their spicules are sturdier than spongin and fossilize better. Like almost all sponges, the hexactinellids draw water in through a series of small pores by the whip like beating of a series of hairs or flagella in chambers which in this group line the sponge wall.

 Diagram of flagellated bodies which line the sponge wall and working together pump water into the sponge (from Reiswig and Mackie, 1983)

Diagram of flagellated bodies which line the sponge wall and working together pump water into the sponge (from Reiswig and Mackie, 1983)

Glass sponges are different from other sponges in a variety of other ways. For example, most of the cytoplasm is not divided into separate cells by walls but forms a syncytium or continuous mass of cytoplasm with many nuclei (e.g., Reiswig and Mackie, 1983).

Like almost all sponges, the hexactinellids draw water in through a series of small pores by the whip like beating of a series of hairs or flagella in chambers which in this group line the sponge wall.

Venus's Flower Basket

Hexactinellids are, typically, limited to the deep sea with the result that few people have seen them or studied them. An exception may be the “Venus’s Flower Basket” A pair of shrimp remain protected together inside. The sponge together with the imprisoned pair of shrimp is often given as a gift at weddings in Japan and the Philippines to signify a long relationship.

 Sponge reef in Hecate Strait east of the Queen Charlotte Islands in British Columbia. 

Sponge reef in Hecate Strait east of the Queen Charlotte Islands in British Columbia. 

venus Flower Basket combo.jpg

where they live

The shallow water occurrence of hexactinellids is rare world wide. In the Antarctic two species occur as shallow as 33 meters under the ice. In the Mediterranean one species occurs as shallow as 18 meters in a cave with deep water upwelling (Boury-Esnault & Vacelet (1994). Another species occurs in shallow water in a southern New Zealand fjord.

Under ice community at McMurdo Sound, Antarctica. Upper area at 15m depth, lower area with glass sponges at 33m depth (from Robilliard, Paine and Dayton. 1974)

Five species occur in depths of 15-35 meters in a range of locations in fjords and in the Strait of Georgia in British Columbia. The shallowest record was communicated to us by Neil McDaniel in 1978. This was a Cloud Sponge at a depth somewhere between 2 and 5.2 meters in depth in Seymour Narrows where current speeds reach 16 knots resulting in major vertical mixing of water. In November 2003 members of the Victoria Dive Club & other divers (Mike Miles, Carole Valkenier Pope and Ian Pope, Mike Kalina, James Dranchuk) surveyed some of the Seymour Narrows area. They found Cloud Sponges at several locations along the SW side of Quadra Island as well as in Seymour Narrows. The shallowest (found by Ian and Carole) was 2.0 meters corrected for tide height in Seymour Narrows. To the best of our knowledge 2 meters is the shallowest record for a hexactinellid sponge since the Cretaceous.

Most of the glass sponges in British Columbia reach sizes of ½ to 3 meters. In northern British Columbia they occur in particularly dense populations which suggested the name “sponge garden".

These sponge reefs were discovered in 1987-1988 by the Geological Survey of Canada at depths of about 220 m. They form mounds up to 18 m high and beds several km in width. Some of these reefs are 8500 to 9000 years old based on core samples (Conway et al 1991). Glass sponge reefs were common during the “Age of Dinosaurs” (e.g. Krautter 1997) but were unknown since that time. Some were being destroyed by trawling. They have recently been designated as no trawling areas by Fisheries and Oceans Canada; but full Marine Protected Area status is needed to ensure that they remain intact.

Click here to see a web site describing these reefs in more detail.

How they grow

Cloud sponges are typically about one meter in size. One individual on Senanus Reef in Saanich Inletmeasured 3.4 meters long by 1.1 meters high by 0.5 meters wide. Many of the cloud sponges in fjords have irregular shapes dominated by broad mittens or “elephant ears”  Note that the broad surface of the mittens tends to be oriented vertically.

What they're made of

Glass sponge tissues contain glass-like structural particles made of silica. The many tiny siliceous elements of a glass sponge's skeleton are called “spicules.” Glass sponges are upright, and possess specialized structures at their bases for holding them to the ocean floor. They are typically cylindrical, but may also be cup-shaped, urn-shaped, or branching. The average height of a hexactinellid is between 10 and 30 cm, but some can grow to be quite large. Hexactinellids possess a cavernous central cavity through which water passes, allowing them to filter food (plankton) and bacteria from the water.

Size & Form

Cloud sponges are typically about one meter in size although one individual on Senanus Reef in Saanich Inlet measured 3.4 meters long by 1.1 meters high by 0.5 meters wide. Many of the cloud sponges in fjords have irregular shapes dominated by vertically oriented, broad mittens or “elephant ears”. Sometimes the cloud sponges have a simpler vase shape but again with vertically oriented mittens while some tubes lack mittens and can be confused with another species of glass sponge. Some of these are likely Cloud Sponges based on retrieval of samples.

  Cloud Sponge on Senanus Reef in Saanich Inlet  which measured 3.4 meters long by 1.1 meters high by 0.5 meters wide.

Cloud Sponge on Senanus Reef in Saanich Inlet  which measured 3.4 meters long by 1.1 meters high by 0.5 meters wide.

  Tubular sponge from Senanus Reef, note the upright tubes with smaller mittens.

Tubular sponge from Senanus Reef, note the upright tubes with smaller mittens.

  This Tubular Cloud Sponge from Jervis Inlet lacks mittens and could be confused with another species of glass sponge.

This Tubular Cloud Sponge from Jervis Inlet lacks mittens and could be confused with another species of glass sponge.