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 species which have yet to be discovered (reference). Sponges are sessile invertebrates, living attached to the sea floor for their entire adult life stage.  They are distributed worldwide being most common in deep waters  up to 6,000 m, where they grow attached to hard and soft substrates.

This view was radically changed with the discovery of this ancient and beautiful deep-sea species of Glass Sea Sponge (Hexactinellida).

These rare sponges commonly habit deep water from 200 m to 600 m, they have been observed from Mediterranean caves and shallow water to British Columbia and Canada, where they form unique sponge reefs. These extraordinarily colored sponges vary in both shape and colour and, they all posse a very particular silicate triazal spiculer Figure 1.

Fig1. 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 rarity begins with their mineral skeleton that is composed of silica (glass) spicules and continues with their extraordinary capacity to create magic 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. Their skeleton is stealing researchers attention due to the multiple and interesting proprieties which hide behind these animals. It seems like they are very good light-transmitters and there may be a possibility of them using spicules to transmit light, but this is still unknown and requires further research.( explain in the video below) Information  displayed in the video below. 

 

Account: GeoBeats News

The century of discoveries:  The nineteenth century made a positive impact in terms of deep sea research as soon as scientists realized how deeply populated the abyss was. Until 1980, geologists thought that these animals 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. In the video below, Dr Jeff Marliave talks about the importance of preserving such incredible creatures, that represent something almost immortal, able to cope with thousands of changes to our ecosystem but are unable to cope with anthropogenic disturbances.

 

Account: Ocean Wise

Fig3: 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 byDr Jeff Marliave, their ability to form beautiful “glass house” make them incredibly vulnerable to human impact.  It is however easier to survey how humans can affect such an ancient population.  In Canadian waters, where an extended reef of glass sponges formed (Figure 2), half of a 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 CRAWS and other NGOs scientiest 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 amazing glass sponge reefs that are more than 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 fishering restrictions in order to create the MPA.

Fig2: Glass Sponge reefs in Northern British Columbia. Image: CPAWS

These particular species of Sponge are allowing us to admire species which have lived in the oceans for longer than we can imagine. They have a complex and evolved structures that have allowed them to survive for thousands and thousands of years but they are not  specialized in avoiding human disturbance. In order to conserve their beauty and rarity, for the sake of the species itself and for their potential technological importance, is important to limit activities that might negatively impact the sponges. – broader

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Figure 4:Euplectella aspergillum glass house with a hosted spider inside.                              Image: NOAA Okeanos Explorer Program

 

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