MARINE NATURE NOTES

Otago Daily Times, Issue 22326, 28 July 1934, Page 5

MARINE NATURE NOTES

Written for the Otago Daily Times. By David J 3. Gkaham, F.R.M.S. A ROCK POOL. To anyone keen on studying marine life in its many forms, there is nothing more irresistible and attractive than watching the contents of a rock pool. I have had the good fortune to see rock pools in most parts of New Zealand —from Otago in the south to Spirits Bay in the extreme north of the North Auckland province. Prior to coming to Dunedin, I always considered the rock pools on the northern edge of New Zealand tho most picturesque and the most interesting, but, after having explored Seal Point on the east coast of Otago, I have no hesitation in saying that for both nature-study and scientific investigation the latter take pride of place. ' , , , Of all the parts of that wave and wind-beaten shore line, where there are boulders encrusted with green seaweed, runlets in which wrack and seaweed appear as meed forests, corners and holes absolutely infested with Jive winkles, and where there are shingly rifts, no part of Seal Point was nearly so fascinating as the rock pools that lie clear at, say, half low tide. It was in such pools that my mate and I found the hours of daylight go all too quickly. It was also in such pools that we found a - wealth of unusual marine life to carry away for close observations and investigations. As one clambers over the rocks, the first glance of the particular pool which I am going to describe is no different to many others at Seal Point. It docs not reveal anything of interest other than masses of brown and green seaweed, with numerous boulders dotted about. Cracks or fissures are seen on several sides, we stood on the brink of this pool, which ranges from a few inches to three feet in depth, gazing steadily into the clear water, wondering whether to unload onr collecting gear and begin investigations. After a few minutes of watching our eve ß became accustomed to the smaller things at the bottom which we did not see before. My mate observes an enormous five-pointed starfish crawling ever so slowly round for the side of the pool. This decided the issue, and soon our knapsacks, nets, rods, and gear are on the ground. Our first objective was to try to obtain this magnificent starfish. Wading across the pool in my gum boots I caught hold of one of its appendages or fingers to pick it off the rocks. I was able to lift about three or four inches and no more. With its thousands of tube feet on the under surface it held on tightly, and my first efforts failed. My mate' and I found a piece of stick, and, as I lifted, he put the stick under, and by lifting the end of each finger we finally dislodged this magnificent specimen. Once out of the. water the animal was helpless, ns water is absolutely necessary to enable it to use its tube feet. It measured 19J inches from tip to tip. The top surface was of a rugged nature and a somewhat greenish-grey colour, and between the colouring and the ruggedness of its structure it looked very much like its surroundings, and was a splendid camouflage. While we were dislodging this specimen I unknowingly stepped on another one of the same species, hut smaller, measuring 13 inches from tip to tip. The colour of the under surface of these two magnificent specimens was a bright rosy pink with white tube feet. No wonder I found difficulty in removing it, as each of its five fingers possessed more than 400 tube feet, making a total of over 2000. These tube feet are used to grip hold of rocks and to walk about and also to enable the animal to open bivalve shellfish, such as oysters and mussels. , ~,, , . Not far from where we lifted the starfish I found a mussel shell eight inches in length and fastened to the rock by its beard, but without the animal, other than a hard muscle used to keep the valves together. No doubt existed in my mind hut that the starfish had recently used its feet to open it and partake of a meal. lam unable to give my readers a common name for this large starfish, but its scientific name is Sclerastenas mollis. A detailed description of each of the many organisms, vegetable and animal, that was found within the narrow compass of the rock pool would fill a book. The seaweed was wonderful in that it represented many species comorising browns, reds, greens, and intermediate colours. In t such a pool seaweed is not so much torn about as in the open sea, and every species was intact and added much beauty to the pool. ITurthei’aiore, many of the inhabitants had learned to change their outward colours to suit and gave us numerous Surprises. As my mate and I were now lying flat on the edges of the pool, gazing intently into one corner which was more shallow than the rest of the pool, and 1 was turning over small stones and collecting chitons (mail shells), all of a sudden something moved and darted about ine pool. It moved so quickly and stopped so suddenly that neither-of us knew what it was nor could we see it. By zigzagging my hand among the loose stones and weed I made something move, taking a small net and moving it backwards and forwards I caught an unusual fish, one that was new to me, and eventually turned out to be a fish known to science as Bovishtus variegatus, which I named “ Horny,” This fish was so coloured to imitate the surrounding weed and rocks that it was almost impossible to detect it in its natural habitat. We found it possible to look into a shallow pait of the pool and actually look at these fishes and not recognise they were fishes. Hardly credible, but true. . Another interesting fish found in this pool was one known as Taunt aka, which does not exceed 10 inches in length, and is always found ,by turning over stones where it hides by day, coming out to teed after dark. These fish vary a good deal in colour. The adult is usually a brownish olive, which is in some specimens more or less marbled with black and greyish-white.' Not infrequently a white hand is seen from head to ta along the side of the fish. Several small specimens were caught that were - jet black with white tips to. the dorsal spines. They almost deceived us into believing they were a species new to us. These fish show marked parental care, and look after their eggs, which are formed into a hall held together by niim rous fine filaments and weed, even watching over them at the risk of losing their lives. At a later date we found a ball of eggs belonging to one of these fishes in this same pool which had over 30,009 eccs all fastened together. Several species of crabs were found. The common blue crab, often referred to as a poisonous species, was most abundant. Almost every stone that was turned over showed from several to a score of them holding on most tenaciously to the bare rock. A pair of tweezers was used and great care had to bo taken not to catch them by the front claws, for if we did, they would discard one claw after another to escape. This meant that they would be without this member until they changed their coat of armour, when a new leg or claw would be seen in miniature, the common shore crab, reddish in colour, was there in fair numbers. Lmiess caught carefully by the back it would inflict a nasty nip with its front claw. After we had caught a number of interesting forms of life and were busily engaged in looking into the pool, we saw what we thought was a tuft of seaweed on a small stone begin to move across our vision, stop, and start again. On picking it un it proved to be a very fine specimen of those crabs which always ornament and disguise themselves with seaweed and other growth. We always found that nob any of these camouflaged crabs attempted to bite or nip our fingers. They are tiic most inoffensive of all the crabs and no doubt rely on their covering ns a means of defence. They would _ rathoi* roll into a hall than light. This crab made a splendid addition to the aquui'ia ami later on took off nil the present seaweed covering and grew another one from that seaweed, peculiar to the harbour, which wc placed in the tank. A few very large prawns were captured by turning over the stones in the deepest parts and qtiicklv placing one’s hand on them before they had time to jump away to safety. They were nearly four inches in length and of a general olive-green ground colour marbled with brick-red wavy longitudinal lines which gave them a handsome appearance. Besides the crabs and shrimps mentioned, we found a variety of smaller species of crustncea known as nmphipods and isopods, commonly known as. sea slaters and water fleas. The first is related to the land wood-louse or slater of our gardens and hedges. The only difference is that the sea-living ones are green in colour and the terrestrial one brown. We also collected many water fleas or sand hoppers. Strange to say, only one specimen of a hermit-crab was found, this probably being due to the absence of empty shell in this pool.

Of molluscs or shellfish inhabiting this pool we found no fewer than 30 species, all of which were identified later. I think the most numerous were the chitons or mail-shell, which may bo easily recognised by the eight girdles or dorsal plates of which the animal is composed. When pulled olf the rock wall or stones to which they were clinging and brought to the surface the mail-shells curl up into a ball like a land millipede. Above the water wc found numerous specimens and species of the common limpet. The common mussels were also found in clusters holding on by means of their hair-like filaments called the byssus or beard, which is spun by the foot of the animal. They are edible, a valuable source of human food and known to possess a great amount of iodine and therefore useful to those suffering from goitre. Thickly studded in the sheltered parts of the pool were many species of sea anemones, so called from their wonderful resemblance to land flowers. Wc found them in almost every colour and hue from the brightest pink to the dullest green. These animals attach themselves to rocky surfaces by means of the broad base of the column or foot. The top part carries numerous tentacles, never very long, but all armoured with stinging propensities to enable them to catch passing food. Within the radius of the tentacles is a flat surface called the disc, in the centre of which is the mouth. The mouth is really like the opening of a bottomless sack which serves as a stomach into which the digested food falls, while the indigestible portions are rolled up and thrown out by the way they entered.