MARINE NATURE NOTES

Otago Daily Times, Issue 21988, 24 June 1933, Page 19

MARINE NATURE NOTES

Written for the Otago Daily Times By David H. Geaham, F.E.S., M.M.8.A., United Kingdom. ' SPONGES. A reader of these notes has made a request for an article on sponges, on how they live and multiply. There is no doubt that the bosom of the sea is full of mysteries, and, among all the animal organisations which live in it, perhaps none is so .little understood as sponges. The average boy or girl that uses sponges in the bath usually expects to find them in the sea ns they are when used in the bath. They would bo more than surprised to know that they would not recognise the sponge in its natural condition. It will then be found to be soft, and to feel not unlike a piece of liver. The outer surface has a coat of jellylike substance, which is susceptible to squeezing and sets up a minute trembling, this being its only symptom of vitality. Although sponges are so numerous and to be found throughout the whole of the temperate and tropical sea and oven in fresh water, very little was known about their real nature and organisation until about 100 years ago. All the naturalists before that time had described them as plants; indeed, a great many people today look on the bath sponge as a plant. Some naturalists even thought they were the houses of worms, in the same way as nests are built by wasps. Since that time, however, many interesting facts have been proved about sponges, and they are now known to bo animals. What we use as sponge in our toilet is nothing but the skeleton of the living animal or, to be correct, animals. For a sponge is nothing but a loosely organised community of living cells, covered with flesh. It may have been yellow, brown or a darkish purple object living at the bottom of a warm, shallow sea. Many sponges smell not unlike garlic, though they are covered with flesh, and they are elastic and slimy to the touch. The sponge that we use may be variously formed, for there are several species of commercial sponges on the market, but us a rule it will be a more or less rounded object and somewhat flattened. At certain seasons of the year the many channels inside a sponge will be found to have their walls studded with yellowish gelatinous granules, which are the germs or young from which the future race of sponges will develop. Cut a living sponge open and you will find these future sponges sprouting from all parts of the skeletons of the canals. These keep tn growing and when they have grown a “ cilia ” or hair-like appendage and are fully formed they soon leave their home walls and are forced through the many canals into the sea of life. Instead of falling to the floor of the ocean, as you would expect a future sponge to do, with a ceaseless vibration of this single hair it propels itself along. Swimming gaily about the sea, or being washed hither and thither, the young sponge begins to become languid and, seeking a suitable rock, shell, or other solid object, it attaches itself and within a remarkably short space of time begins to enlarge its home by forming spicules for a skeleton in which canals are the chief means of development and also of securing food and material for building more cells and walls. From this it will be realised that living sponges are living animals In what we might term developing colonies. As they develop, canals run in all directions both to the interior and to the surface, but the walls are all punctured by Innumerable minute holes each of which leads into a microscopic chamber, usually pear-shaped, aud it by turn opens into a larger port or canal. As the animal growth assumes a larger form, these canals also become larger and all have an outlet.

The pear-shaped chambers are lined with numerous microscopic hairs known to science as cilia, which set up a constant regular beating. This sets up a current of water which enters by the small pores and escapes from the larger outlets or vents. This is the sponge’s method of bringing food and oxygen to all parts. The whole of the sponge is nothing but a labyrinth of passages, while the supporting walls arc a network of branching fibres, but so fine and so delicate that the meshes are barely visible to the naked eye. And what are these fibres but the cleaned bones of a living animal or animals? —-the framework of the future sponge as the public know it. We can truthfully say, therefore, when we have our bath with a genuine sponge, that we have a skeleton to assist iii cleansing our body. Any one who, with a microscope or a good magnifying lens, goes to the shore, obtains a piece of sponge growth, places it in a small glass dish, and covers it with sea water, will in a few minutes behold a wonderful spectacle—a living fountain. The beauty and novelty of 'such, a scene have often arrested my attention, If one can imagine- numerous miniature -volcanoes ail pouring forth water from within, one will understand what the outside of a living sponge is like. The many volcanoes or outlets of the sponge send forth from each cavity an impetuous torrent of fluid, hurling along without stopping. I have often watched this phenomenon for 20 minutes and never have I seen the flow of water diminish or even change its direction, but the stream rolled on with a constant and equal velocity. A further demonstration of these streams issuing from a living sponge can be made more realistic by introducing some powdered chalk and minute pieces of cork to the surface of the water containing the sponge. When the outlets begin vomiting forth their streams of water, the chalk makes the currents of water visible at a greater distance and without a microscope. At a distance of from 7 to 10 feet away the pieces of cork can be seen hurled along by the force of the water issuing from the outlets. The addition of a small quantity of red coloured fluid carmine to the water makes the action of the cilia driving the water in ceaseless torrents all the more remarkable and fascinating. The object of taking in water by the •small canals and forcing it out by the larger is to obtain food for digestion and oxygen. All kinds of solid particles are arrested by the canals and those useful for feeding the cells are retained while the useless are rejected and passed out again. One of the most remarkable features of living sponges is the fact that they can be cut to pieces, broken into fragments as small -as it is possible, and strained through fine mesh and, given the solid on which to attach themselves, they will begin growing again and form new individuals. A sponge is composed of chemical and physical properties related to silk, horn, and ehitin, the Iwit named being the foundation of the shell of crabs and insects. The preparation of sponges for the market is a comparatively simple process. The sponge is first killed; the outer surface and the inner or soft parts must be removed and then macerated to liquify the matter, which is then washed and squeezed out. After boing cleaned they are strung on lines and formed into what is known as wreathes, called “ bunches.” After this they find their way to the primary market, and are sold to dealers who sort them into various sizes. They are then cut and trimmed and sorted into lots designated by the number of pieces required to make a pound weight. As sponges grow at the bottom of the sea various methods of collecting them are in use. The first method Is, of course, that of diving for them, but hooking with a three-curved unbarbed hook, or harpooning with from two to five-pointed tridents are used In the Mediterranean. To-day a great deal of the work is done with machine

diving, and in some parts, where the bottom of the ocean is not too rocky, dredging and trawling are carried out with some success.