Egg Time

New Zealand Herald, Volume LXXV, Issue 23157, 1 October 1938, Page 10 (Supplement)

Egg Time

By R. A. FALLA, M.A.

THE now life that comes with the spring is now in evidence on all sides; blossoms, buds, and new leaves are contributing to the colour of landscape; spring lambs are everywhere. Although to outward appearance not much changed, the world of life under water is undergoing the same process of multiplication. Whitebaiters know that you can find out something about it by dipping a net into a suitable stream, but any visitor to the seaside during the next few weeks can find out a great deal more by a simple examination of rock pools. Beach Fossicking A few days ago I had the good fortune to go fossicking on the shore with a good-natured professor of biology, who had knocked off work not so much to carry bricks as to turn over boulders. It was the day after the moon had entered on its first quarter and an unusually low tide had laid bare even the hold-fasts and long strands of giant kelp. Although the coast fronted the open sea, a light offshore wind kept it perfectly calm, and for a period of

nearly two hours there seemed to be no appreciable rise of tide. With the additional comfort of warm sunshine the conditions for our quest were ideal. Marine Plants There were seaweeds in profusion. The prevailing colours of green, brown, and red in this group of marine plants have to some extent, in their respective distribution, a relation to the depth at which tho species grow. Many of those near 'high-water mark, exposed to a maximum of light, are green. In the intermediate zone browns predominate, while most of reds inhabit the darker zone near the limits of penetration •of strong light. This rule does not ■ apply so rigidly to the ' caleareous seaweeds. They Include the hard and brittle kinds which-spread mat-like over rocks,''or stand up in clusters and rosettes .like corals rather than plantforms. , , ' ~ Delicate Organisms . : : Swaying on. the fringe, of .weed clusters were other delicate branching organisms looking' more like marine plants '.thahi the. animal forms.vthey really were..lt requires some text-book knowledge, or better still, ■ a g°od pockefeflens, ' to 'recognise Obelia as, ,an animal. Magnification • shows the bell-like-heads and their restlfesS cilia, and in very still water- it-is-sometimes pos-' sible-;;to/ sce'l the young in their freeswimming medusa, stage floating - away from the parent colony. Large 1 Sea-Urchins k So low was the tide th'at the hiding places of, many : large Iseatirchilis. Known also. as. sea-eggs 'from; the shape of 'the shelly husk after all else has decayed these animals in life are much ,mo*-e like hedgehogs, from which resemblance, the namo sea-urchin is derived. The spines which afford them such effective protectibn .are also used as.convenient levers-when,the long tube feet are iri Action and ■ "the creature crawls about. They- are no less efficient

New l3Life Under Water

in helping to wedge the urchin more securely in the hollows and rock pockets into which it retreats. Starfish of three or four kinds were also present, belying their harmless appearance by active movement and most voracious feeding on the smaller organisms. Paua in Abundance One imagines either that this must have been an exceptionally low tide, or that the local human inhabitants were not aware of the culinary possibilities of the paua, for these fleshy molluscs were in abundance. Perhaps the local residents had tried them and found them wanting. But any such decision regarding the paua should be suspended until one has tried the method of P r ®" paration recommended by Mr. Powell in his book on New Zealand shellfish. There were other shellfish in plenty and a student of conchology would have had no difficulty in finding representative species'of three of the five classes of mollusca. A fourth class was represented by some eggs of squid, but we saw nothing of the animals nor of their cousin the octopus. Hermit Crabs V Crustacea were represented by hermit crabs living in the dead shells of molluscs, other crabs with their own protective carapaces,, and more active prawns darting about. There were

numerous barnacles also; indeed, tho list of animals could go on to fill more space than is available for this article. The compiling of a faunal list is a task for a specialist or for someone statistically minded. The simple study of animal and plant associations, however, is one that can. be attempted by any amateur. It is concerned not so much with such relationships as that of the Pinnotheres crab to the mussel iii whose shell it lives, as to the way in which the presence of one organism limits or affects the development of another. Sucker-Fish

Adaptive resistance to wave action as found in the shape or habit of certain organisms such as limpets is another interesting line of study, and so on; the field is practically'unlimited. A study of the reproductive processes of marine organisms would need longer than a casual visit, but at this time of year much may be seen. For example, every little sucker-fish we found was associated with a cluster of eggs sticking to the underside of a stone. Most of them were males guarding eggs which were in process of development; and in a few cases the pocket lens revealed the well-fonnfed eyes and shape of the heads of the young fish' within the eggs.

Spawning Habits Egg-development of fishes living in teeming rock-pools seems to be rapid, but it is • not always so in the sea. Some of the dog-fish and other primitive kinds produce eggs with tough and horny cases.'i Mention of these takes us away from our rock-pools, for they are deposited in deeper water. One such "egg-purse" of a carpet shark recently sent to the Canterbury Museum from 25' fathoms off the mouth, of the Waitaki River contained a lively sharklet swimming round inside with yolk-sac atta'clied. It is indicative of the conservative spawning habits of fish and their dependence on certain conditions that when the eggs of this shark were ■first described by tho late Mr. Edgar Waito thirty years ago the specimens were taken in a trawl at exactly the same place and time of year.