NATURE NOTES.

Otago Witness, Issue 3196, 16 June 1915, Page 77

NATURE NOTES.

No. XVIJI.—SEASIDE LIFE.

By G. M. Thomson, F.L.S

It is marvellous how many kinds of living treasures can be obtained by dai y walk along any stretch of ocean beach, especially at low tide. The number an condition of the specimens obtained depends a good deal, of course, on the kind of beach. The best collecting ground is a gently sloping sand beach, such as extends from Black Head to Brighton inside the reef of which Green Island is the cap. There are two ways in which the flotsam and jetsam of the _ sea comes ashore —firstly by the force of the waves during a gale, and secondly by the organ isms floating 'close inshore in perfectly calm weather. The latter is by fai the more prolific source of supply. When the surface of the ocean becomes much disturbed by wind, the pelagic or free-swimming organisms sink down below the region of troubled water, and so are safe from harm. Very few such creatures are found on the beaches after a gale On the other hand, when a very heavy swell comes tumbling in to the shore, especially when the tides are very low, one effect is to tear masses of kelp oft the exposed rocks and to throw these up on the beach. Among the firm stems and roots are often to be found many interesting kinds of animals, small fish, and crustaceans, which have taken refuge there. Besides these, various species of fish including conger eels, hagfish, hake, and kingfish are frequently cast ashore; but often in a more -or less bruised and battered condition, and along with them are crabs, shellfish, starfishes, and sea urchins, which are pot always to be met with under normal conditions. For instance, before the days of trawlers the hake was thought to 'be a rare fish, the onlv examples recorded being such as were washed ashore after heavy weather in Cook Strait. It is now known to be fairly common in that region, but confined to somewhat deep water. The lower the tides, the more exposed the usually submerged rocks, and the more mountainous the waves, the greater the chance of getting a good variety of specimens. I cannot remember that I have ever gathered anything new on such occasions, however.^ But a walk along the beach on a winter’s morning after a clear still frosty night, when the surface of the sea scarcely shows a ripple, and the break of the •waves is quite small, frequently rewards the observer with new and interesting forms of life. I have already referred to the frost fish (Lepidopus caudatus), which is usually only taken when it has immolated itself on a flat beach. For it does seem always to come ashore of its own accord, though why it does so is not clear. Sir James Hector thought it pursued its prey too close to the shore, and was left by the long swell during ebb tide. Mr C. H. Eobson, who was formerly a lighthouse-keeper on the coast, and a very intelligent observer, characterised this opinion as incorrect, though very ingenious. He said ; “It is true that the frost fish usually comes on shore during the cold moonlight nights of winter, but it also frequently lands in Clifford Bay, near Cape Campbell, during the daylight, always when it is calm, or with a southerly wind and smooth water. It has been my good fortune to witness several such landings, and though unable to determine the reason of them I can state positively that the fish is not cast up by the sea." but that it deliberately forces itself on shore, selecting a shallow, sandy beach for that purpose. ... On two occasions I stood between a frost fish and the beach, and, as ho came on, turned him with a long stick head to sea, making him swim out; but in a minute or two lie turned again for the shore, going up high and dry as fast as possible, so, ns he°seemed to have set his mind upon landing, I gave up the attempt to influence his*decision, and just took him home for breakfast. All the frost fish which come ashore here are in fine condition; they seem to be in .perfect health, and their landings appear to be deliberate acts of self-immolation. Their, food I believe to be the young of Clupea sagax or Clupea sprattus (sprats or pilchards), but I have found onlv one specimen with food in its gullet sufficiently perfect for McntlficaCion. J Ixave sg©h on© uarrctcoutci lorcmg itself on shore in the same way as the frost fish.” I may say T have also seen barracouta doing this; but they were always fish which bad _ been more or less iniured, or had previously been thrown out of the water and thrown in again. Some authorities have stated that the fish is an abyssal species found _only In extremely deep water, and that in swimming

along a gently ascending sea bottom it gradually reaches a point where the pressure is insufficient owing to the shallowness of the water, and that consequently its swim-bladder bursts, and it cannot sink again. Apart from the improbability of the suggestion, there is no evidence that the swim-bladders of the captured fishes are burst. Here, then, is another problem for our embryo naturalists. Very occasionally a ribbon fish or oar fisdi comes ashore in somewhat similar circumstances. I say very occasionally, for probably not more than two dozen or so have been recorded, and they are so rare and so diverse (though so alike) that we don’t know at all how many species there are, or whether, as some zoologists seem to think, they are all forms of one species. Probably there are several, for apart from their size, which varies from a little over 3ft to as much as 19ft in length, they vary greatly in their relative width. This usually varies from a tenth to a fifteenth of the length; but a small species described somewhat recently by Professor Benham was 45in long, but only fin broad —that is, its length was 60 times greater than its breadth. They are commonly silvery fish, but frequently marked with bars of black across the body, while the fins are usually bright red. The name ribbon fish suggests their shape, while that of oar fish is given on ..account of the longventral fin, which in a specimen caught in Lyttelton Harbour was 3^-ft long. They are deep sea fish, which apparently feed on very minute animal life, for their stomachs are usually nearly or quite empty,'and they have no teeth. Sometimes one picks up a thin glasslike fish like a strip of clear ribbon, about Sin or 9in long, and less than lin in depth. This pretty little object was known to the earlier naturalists of last century as a Leptocephedus, and was classed as the type of a new family. We now r know that it is only a stage —but just exactly what stage I cannot say —in the life-history of some kind of eel. They are beautifully transparent little fish, not much thicker than paper, with backbone or vertebral column made of cartilage only, and they have a remarkably small head, and a relatively large, silvery eye. The life-histories of eels are very difficult things to work out. We think of them as snake-like creatures only found in streams and swamps; but they apparently go to sea, or, at least, to the mouths of rivers, to spawn. Their very young fry are to be met with in small streams and burns, clambering up damp rocks and through little rills; yet at some period or other of their lives they appear to pass through peculiar larval transitions. The Leptoc.ephalus form —a truly marine organism—is apparently one of these. Anyone desirous of studying the smaller forms of animal life cast ashore in calm weather should always be provided with a glass vessel, such as a wide-mouthed bottle, jar, or stout tumbler, in which to place them for examination. Many things which are very beautiful when alive and in the water look shapeless and unlovely when taken out and laid on a firm surface; therefore they should be dropped into a vessel .of clean sea-water, when, if they are alive, they will at once begin to move, any adhering sand will drop off them, and they will appear in all their natural grace and beauty of form and colour. Most of the smaller, free-swim-ming organisms are nearly, or quite, transparent, and their colours when present are usually in bright, but very thin, welldefined bands, streaks, or star-like splashes. The object may be for better protection. Thus I have noticed that the perfectly transparent little jelly-fishes which are such common objects on the surface of the sea, and which are practically invisible till the vessel in which they are floating is held up to the light, appear to have no defensive organs in the shape of urticating cells. On the other hand, the large brown and otherwise conspicuously-marked species are very well provided with such defensive weapons, and can sting the hand or other organ which comes in contact with them. No doubt they are thus protected against fish which might otherwise eat them.

Some half a dozen species of pelagic amphipodous crustaceans are commonly met with on the beaches in still weather. They are all somewhat shrimp-like in general appearance, and are more or less transparent, but prettily marked with colour bands and star-like dots of red or black. The most common and the most distinctive, and one which every beachlover must know quite well, is Phronima novae-zealandhe, a glass-like shrimp which is always found living in what looks like a glass barrel open at both ends. This barrel is the empty test or case of a tunicate mollusc, perhaps a Doliolum, belonging to the Salpidse, or it may be some animal of a lower type. If you find a newly-washed-up specimen and drop it into your glass vessel it will at once commence to move its abdominal joints and swimming legs vigorously', and so nropel its clumsy house through the water. I have never seen a Phronima without a barrel except where it had been washed out by the surf. If one of these liberated animals be placed in the water it swims up to the surface by a series of jerks, and seems to be very helpless without its covering case. We don’t know anything about the life-histories of these animals, and it is quite evident that its development must be very interesting. Most amphipods when hatched from the egg arc in a very advanced state of development, and in form and structure somewhat closely resemble the adults. This is very different from what is common among the Crustacea, most of which arc hatched out in a very rudimentary condition, and go through a series of metamorphoses before they reach the adult form. If Phronima is hatched out in nearly the mature form only differing in size, as is likely, one would like to know when and how it finds a barrel to live in. The case it inhabits belongs to another organism, and the ouestion, Does the young Phronima _ live a free life till it reaches a certain size and age, or does it find sonu* other form of

shelter until it becomes mature? If so, why do we never find the young ones? It is really wonderful how very little we know about these and a thousand other things we meet with in Nature. Their investigation is always interesting, and frequently adds to the sum of human knowledge, which is one of the truest joys in life.

The other pelagic amphipods which get washed ashore, such as Oxycephalus, Erithemisto, and others are also relatively large, some nearly lin long, with rather large eyes, and always more or less of the glassy, transparent appearance of Phronima, but always marked by colour bands and stars.

These are only a few of the things which the sea yields in calm Aveather. They are not really shore animals, but live in the open sea, but are seldom met with there, and our knowledg e of them is mostly derived from specimens picked up on the beaches. I have taken specimens of free-swimming organisms in the tow-net in many parts of New Zealand, from the Bay of Islands down to Port Pegasus, in SteAvart Island, and I have never taken one of the species I have mentioned above. All my specimens have been met with on sandy beaches. I must leave the question of rock-pools and their contents to another paper.