…………. a Venus Vase, gift of Peter Dance. Just over a year ago a volunteer from the Sheringham Preservation Society sent me a photo of a bizarre object. It was an exhibit on display in their Shell Gallery and by their kind permission I have included the image in my slideshow. (Personally, I think the single unadorned structure is so beautiful as a simple funnel that it needs no embellishment by being mounted in sextuplicate on a Pecten shell to form a ‘candlelabra’! I was completely foxed and could hardly believe the object was biological in nature (apart from the scallop shell base). I forwarded the photo to Peter who emailed me right back to tell me exactly what the object was, and with the offer to give an example he owned, to me. I accepted with pleasure.
Also known as a Venus’ Flower Basket the object is the skeleton of an Hexactinellid sponge, the skeleton, or test, being made of siliceous spicules (hence their name Glass Sponges). Glass sponges are relatively uncommon and are mostly found at depths from 450 to 900 metres. They are found in all oceans of the world, although they are particularly common in Antarctic waters. They are funnel-shaped animals, ranging from 10 to 30 centimetres in height, with sturdy lattice-like internal skeletons made up of fused spicules of silica. The body is relatively symmetrical, with a large central cavity that, in many species, opens to the outside through a sieve formed from the skeleton.
Being deep water animals relatively few people have seen or studied glass sponges. An exception is the “Venus’s Flower Basket” (Euplectella aspergillum). In some Asian cultures, such as Japan, these sponges are given as marriage good luck charms – rather like horseshoes. Often this species of sponge has two tiny shrimps (always a male and a female) living, symbiotically, inside the sponge’s body cavity. They swim in as larvae and are then trapped and mature inside the sponge’s mesh-like tissues. They would appear to be perfectly happy though, as they feed off the filtered food debris left by the sponge! Any young can escape from the sponge as they are small enough to swim through the mesh of the sponge’s tissue and can move to find their own sponge ‘des res’. If you peer through the mesh on my example, you can see the exoskeletal crustacean debris of its former occupants.
Many people may well have encountered the cleaned and dried skeletons of these sponges in an art class, or seen them in a Victorian glass dome display, as they have always been popular for their delicate beauty. Mine sits alongside other fragile marine curiosities, such as the Paper Nautilus, in a conchological vitrine.