Sponges are one of the most  primitive forms of multicellular animals in our oceans. They are incredibly successful with  over 7.000 known species, but scientists suggest that there are probably 1.000 more which have yet to be discovered . Sponges are sessile invertebrates, living attached to the sea floor for their entire adult life stage.  They are distributed worldwide and are most common in deep waters to the depth of 6.000 m, where they grow attached to hard and soft substrates.

Nevertheless, a rare and ancient species of sponge was discovered to inhabit waters between 200 and 6.000 m. These species, the Glass Sea Sponge, Hexactinellida have been observed from the shallow waters of Mediterranean sea to the coast of British Columbia and Canada , where they form unique sponge reefs. These extraordinarily coloured sponges vary in both shape and colour (Figure 1B,C and D) and, they all possess a very particular silicate triazal spiculer (Figure 1A).

Figure 1. Hexactinellida diversity A. Scanning electron micrograph of microscleres. A/Left a hexaster, the diagnostic spicule type of subclass Hexasterophora. A /Right: an amphidisc, the diagnostic spicule type of subclass Amphidiscophora. B Hyalonema sp., Bahamas; C. Atlantisella sp. Galapagos Islands; D. Lefroyella decora, a (“Hexactinosida”), Bahamas. Image from: The Harbor Branch Oceanographic Institute (Florida , USA).

 

A unique morphology and structure: Their unique characteristic begins with their mineral skeleton that is composed of silica (glass) spicules and continues with their extraordinary capacity to create astonishing glass structures. The morphology displayed by these creatures is also incredibly different from other Porifera due to the structure of their cells and the three-dimensional symmetry (triaxonic symmetry). Their cells are fused together, resulting in one large multi-nucleated cell that is folded around a mineral skeleton. Glass sponges can use this fusion to spread electrical impulses to regulate their filtering actions; this process works in a similar way to the nervous systems in more evolved animals. The triaxonic symmetry is made of three axes that are perpendicular to one another, creating a three dimensional structure. In fact, the name Hexactinellida come from the most common shape of ray: the hecaxtin, which has six developed rays, two per axis. It is not uncommon to find other spicule types, which aid researches with their taxonomy.

They are gaining scientific attention due to the multitude of interesting proprieties they possess such as the ability to be very efficiently transmit light via the use of their spicules. Technologically speaking, their extended spicules are similar in size and material to conventional fiber-optic cables.  Joanna Aizenberg tested glass sponges’s proprieties in a lab and they resulted more valuable and robust than the original cables. Their spicules have an equivalent index of refraction to cables designed by human. In addition, the spicules are strongly resistant and they would reduce telecommunication issues that we are currently experiencing -information displayed in the video below.

 

Account: GeoBeats News

The century of discoveries:  The nineteenth century  saw an increase in deep-sea research when scientists discovered just how densely populated abyssal plains actually were and continue to be to this day. Until 1980, geologists thought that glass sponges went extinct during the Jurassic Era, until they discovered a barrier reef formation off the coast of British Columbia, where the population is still present to this day. In the video below, Dr Jeff Marliave talks about the importance of preserving such incredible creatures, that represent something almost immortal; they are able to cope with thousands of changes to our ecosystem but unable to cope with anthropogenic disturbances.

Account: Ocean Wise

Figure 3: The new MPA lies on a site  designated as a Hope Spot– sites that are internationally recognised for their importance to the global ocean’s (and thus people’s) health.  Image: Sally Leys

Conservation Activities: As previously mentioned by Dr J. Marliave, their ability to form beautiful “glass houses” make them  vulnerable to human impact.  Nowadays, it is also easier to survey anthropogenic disturbances on the sponge population.  Besides, in Canadian waters, where an extended reef of glass sponges formed (Figure 2), it was observed that the population was suffering due to human activities. Half of the extended large reef in the Hecate Strait was destroyed by trawl fishing before fishing restrictions were put in place by the federal government in 2002. The research carried out by Canadian Parks and Wilderness Society (CRAWS) and other NGOs scientist, Sabine Jessen, Sarah McNeil et al, proved how a Marine Protected Area (MPA) was a necessity around such a sensitive environment. The new MPA (Figure 3) is 2140 km² and protects a vast reef made of glass sponges that is 9.000 years old (older than the Pyramids) and more than 8 stories high. Their unique skeletal structure makes the sponge reefs incredibly sensitive to sedimentation and to physical disturbances from trawling. All bottom fishing activities within 200 meters of the sea glass reefs was halted along with trawl fishing restrictions in order to create the MPA.

Figure 2: Glass Sponge reefs in Northern British Columbia. Image: Canadian Parks and Wilderness Society CPAWS

This particular species of Sponge provides a spectacular insight into species which have lived in the oceans for longer than we can imagine. They have highly developed and complex structures that have allowed them to survive for thousands and thousands of years but they cannot evolve fast enough to keep up with increasing anthropogenic activity in the oceans. In order to conserve their beauty and rarity (Figure 4), for the sake of the species itself and for their potential technological importance, it is important to limit activities that might negatively impact the sponges.

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Figure 4:The most common glass house, made by Euplectella aspergillum with a hosted spider inside. Image: NOAA Okeanos Explorer Program

 

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