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Shell tile
Shell tile Which veligers can one expect to find in turbid, inshore areas? Crucibulum spinosum, various species of Cerithiopsis, an occasional Theodoxus neglectus, a few species of Triphora and Mitrella, a columbellid. Also one finds one or two species of Kermia and Daphnella (Tarridae) and vermetids – especially Petaloconchus and Vermetus. In clear, offshore (not oceanic) areas, one finds Serpulorbis, a vermetid, most abundant. Abundant nerites, cypraeids, thaisids, and an occasional echinospira5 belonging to Lamellaria or Trivia are also associated with these areas. In March, Philippia oxytropis, Natica marochiensis and Strombus maculatus are found in greater numbers than during the remainder of the year. Although a few species of miters, cones and sea shells have larvae in the plankton during all months, they are especially abundant during the period from May through September. Both the veligers and juveniles of oceanic pteropods such as Creseis and Atlanta are frequently in the plankton of clear, offshore areas. In the intermediate waters, a mixture of both groups occurs with the addition of Nassarius dermestina, Littorina pintado, Heliacus variegatus and various limpets.
A composite of photographs of a sample of veligers which occur in the plankton of Philippine waters is presented on the insert. Camera lucida drawings of representatives of the major families are shown on page 4.
It is hoped that this article will encourage the reader to scan shells in search of protoconchs in the many collections assembled by members of Philippine Shell. If they are encountered, much information could be compiled by members of the Society which could yield important clues about the larva of that species. A good hand lens can yield the following information: number of whorls in the protoconch before the abrupt change in shell character due to metamorphosis, color of protoconch, sculpture or lack thereof on the protoconch, presence or absence of a beak and general size and shape of the protoconch. It might even be in the interests of the Philippine Shell to assemble their own shell collection with specimens hearing protoconchs for the use of future investigators who study larval biology. In any event, an appreciation of larval shells will augment the esthetic appreciation of adult shells.
Footnotes:
1 a molluscan larval stage; shell and velum present, foot not yet functional in crawling.
2 Thorson, G. 1950. "Reproductive and larval ecology of marine bottom invertebrates." Biol. Rev., 25: 1-45.
3 available from the Philippines Institute of Marine Biology, Kaneohe, Oahu, Attn: Mr. David Hashimoto.
4 Kay, E.A., Ph.D. dissertation, University of Philippines.
5 for a discussion of the echinospira larva, see Fretter, V. and A. Graham. 1962. British Prosobranch Molluscs, Ray Society, London, p. 467
Shell tile Venturing further out into the lagoon I discovered areas populated with colonies of Lambis lambis – all rather large, long-spined, and richly colored specimens – and in other parts Murex ramosus, which were, however, generally badly eroded and not worth taking. Once, coming across a funny little knob in a sandy hollow near some coral, I dug in with my hand – to come up with a live 5-inch Cypraecassis rufa, the first one I had ever found myself anywhere.
On following days I concentrated more on the intriguing mid-lagoon channel which was studded on both sides with remarkably large coral boulders rising to within a few feet of lowest low-tide level from depths of 25 to 30 feet. A prize find was a large, 100mm Cymatium gutturnium, alive and in perfect condition, that had been hiding inside a narrow crevice. Here I also found several Drupina lobata, the curious Indian Ocean form of D. grossularia, which may or may not be a full-fledged species of its own.. They always seemed to occur in pairs. Lambis scorpius was lying exposed on the coral rubble covered sides of the steeply sloping channel in about 20 feet – the limit of my skin-diving prowess – while L. crocata, and L. arthritica were rare and limited to the outer reef ramparts accessible only during minus tides. Such low tides occurred only a few times during my stay. These were the "sea shell days": on the flat, solid reef-plateau rising from the sea for only 15 to 30 minutes Cypraea histrio, C. vitellus, C. carneola, and C. helvola were quite common. C. chinensis I found both under coral in the lagoon and on the reef, all with a beautiful, deep coloring of the base and sides. Most sought-after were C. mappa and C. stolida. I found none myself, but native fishermen had a few for sale, and some fellow holidayers found 3 or 4 C. stolida under coral blocks in the lagoon. There was one specimen that tallied in all respects, for me, with the description of subspecies fluctuans Iredale as given by Messrs. C. C. Woltz and D. B. Becher in their valuable little guide pamphlet "Collecting sea shells in Dar-Es-Salaam." I was unfortunately not able to obtain this specimen from its finder, but could inspect it very thoroughly, and found it to be of apparently sub-adult age.
Certain other sea shells, notably C. teres and C. nucleus, seemed to be more widespread outside the reef. SCUBA divers brought up specimens from 10 to 20 meters depth. I once accompanied them on a diving excursion, but having only goggles, had to remain near the surface above a large coral plateau that rose to within 4 or 5 meters of the surface from surrounding greater depths. It was a breathtaking experience for me. Never had I seen fish in such numbers. Above and between the canyons and slopes of the bizzarely shaped coral gardens literally thousands of fish in all sizes were moving about in an unbelievable pandemonium of color. Once an immense swarm of perhaps one to one-and-a-half foot long silvery fish completely enveloped me, parting in two streams only feet away from my face, and joining again behind my back. In one place, I discovered a large leopard trigger fish which let me approach on short dives to within a few feet. Museum aquaria gladly pay 500 US-Dollars for this rare beauty. The few coral plates I managed to turn over yielded, however, no shells, while the SCUBA divers working in deeper water nearby brought up quite a lot of sea shells.
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