Seashells at Cairns 5

Inside of a bivalve seashell tentatively identified as Anadara inaequivalvis (Brugiere)

I seem to remember picking up this shell from the strand-line at Trinity Beach – which is just north along the coast from Cairns in Queensland. I photographed it against an improvised background of my black trousers – first showing the inside and then the outside of the shell. I think it is a shell of Anadara inaequivalvis (Bruguière) (see CIESM The Mediterranean Science Commission Atlas). This species is found along the coast from Northern Territory to central Queensland as well as being an accidentally introduced species in other parts of the world.

Apparently, when the mollusc is younger, the two hinged valves of the shell are different sizes (inequivalve) but as the mollusc matures the shells become equal in size (equivalve). The number of ribs is important for distinguishing between the different species of Anadara. A. inaequivalvis has between 31 and 34 radial ribs (I can count 31 in this particular specimen. A similar species, A. polii (Lamark) has only 26 – 28 radial ribs. The length  of  A. inaequivalvis ranges from 70 – 80 mm in mature specimens with a height of upto 61 mm. Unfortunately, I had no ruler to photograph with the shell to indicate scale but it was a fairly large shell.

Outside of a bivalve seashell tentatively identified as Anadara inaequivalvis (Brugiere)

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Seashells at Cairns 4

Seashell thought to be a Trough Shell on the beach near Cairns

I’m puzzling over this shell at the moment. If I recall correctly, it is a live specimen that rolled up the beach with the tide a bit north of Cairns itself, at Yawarra Beach. It looked fairly ordinary and plain until I turned it round to view the edge and saw beautiful delicate growth rings and lovely purple tinged beaks or umbones. I think it is a Mactra. Possibly Mactra dissimilis Reeve.

This group of shells is fairly large with triangular shells; and the animals live in sand. M. dissimilis is the most common species of this family in northern Queensland. It has a sculpture of concentric growth rings but overall  is generally smooth in appearance. It is white and tinged with purple and is about 50 mm long. It is found from the Northern Territory to northern New South Wales.

Reference

Jansen, P. (1996) Common Seashells of Coastal Northern Queensland, privately published in Townsville, Australia, ISBN 0 646 29824 0.

Seashell thought to be a Trough Shell on the beach near Cairns

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Seashells at Cairns 3

Empty shells of Twisted Ark, Trisidos tortuosa (Linnaeus), at Cairns

The angularity of this bivalved shell made it immediately noticeable on the sandy beach at Cairns. It is called a Twisted Ark because of the strange configuration of the shell which is strongly twisted with a sharp ridge from the top to the margin. The Latin name is Trisidos tortuosa (Linnaeus), formerly Arca tortuosa. It varies from 60 – 100 mm in length and occurs on the Australian coast from the Northern Territory to Queensland.

Reference

Jansen, P. (1996) Common Seashells of Coastal Northern Queensland, privately published in Townsville, Australia, November 1996. ISBN 0 646 29824 0. 

Empty shells of Twisted Ark, Trisidos tortuosa (Linnaeus), at Cairns

Empty shells of Twisted Ark, Trisidos tortuosa (Linnaeus), at Cairns

Empty shells of Twisted Ark, Trisidos tortuosa (Linnaeus), at Cairns

Seashells at Cairns 2

Common Baler, Giant Baler or Melon Shell (Melo amphora)

I only found the one empty beach-worn shell of this Common Baler (Melo amphora Lightfoot) on the beach at Cairns. It is also known as the Giant Baler or Melon Shell. It has spines around the whorls at the anterior end. The pattern on the shell is now indistinct but a fresh shell would have characteristic variable orange-brown zig-zag marks. This species is apparently fairly common in the Indian Ocean, on the Queensland Coast of Western Australia, and off shore New Guinea. The largest recorded size is just under 500 mm in length but this one was only 145 mm. It is quite a heavy shell, and in life it has a thin brown periostracum layer which wears off eventually. The huge curved aperture or mouth of the shell can be used to bale out boats – but has broken on this shell.

Common Baler, Giant Baler or Melon Shell (Melo amphora)

Common Baler, Giant Baler or Melon Shell (Melo amphora)

Common Baler, Giant Baler or Melon Shell (Melo amphora)

Common Baler, Giant Baler or Melon Shell (Melo amphora)

Common Baler, Giant Baler or Melon Shell (Melo amphora)

Common Baler, Giant Baler or Melon Shell (Melo amphora)

Common Baler, Giant Baler or Melon Shell (Melo amphora)

Common Baler, Giant Baler or Melon Shell (Melo amphora)

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Seashells at Cairns 1

An assortment of small seashells lying on the beach at Cairns

Cairns doesn’t have a beach as you would normally understand it. Most of the area offshore is a vast acreage of mudflats on which it is forbidden to walk. However, there is a narrow fringe of sand along the northern part, accessible from the Esplanade that runs along the whole of the seafront. It is here, randomly dispersed, that assorted small seashells lie in natural drifts on the beach at Cairns, Queensland, Australia.

The photographs in this post show how these marine gastropod and bivalve shells look in situ, just as they were found,  on the shore. Identifying them all to species is more problematical – particularly as it is not permitted to collect shells and take them out of the country! I did take lots of pictures while I was there, some in close-up and against the plain background of sand, rock, clothing, or even a plastic dish, so that I could have a go at putting a name to them later. And that is what I am about to do over this series of postings on the seashells I saw in Cairns and other Queensland localities when I was on holiday in 2011.

A handful of assorted small seashells scooped up from the beach at Cairns

An assortment of small seashells lying on the beach at Cairns

An assortment of small seashells lying on the beach at Cairns

An assortment of small seashells lying on the beach at Cairns

An assortment of small seashells lying on the beach at Cairns

An assortment of small seashells lying on the beach at Cairns

An assortment of small seashells lying on the beach at Cairns

An assortment of small seashells lying on the beach at Cairns

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Nerite Shells at Port Douglas

Mostly Nerite Shells (Nerita costata Duclos) in a part-submerged rock crevice at Port Douglas

Nerite Shells are very common inhabitants of rocky shores on the Queensland coast in Australia; and they generally have a wide Indo-Pacific distribution. There are several species but the specimens shown here are Nerita costata Gmelin and were photographed at Port Douglas.

They have a characteristic appearance with thick black rounded ridges spiralling around the shell whorls, with lighter coloured furrows between them. The spire is blunt. The aperture opening is roughly semicircular with a specific arrangement of protruberances or ‘teeth’. The odd-shell-out in pictures 1 and 2 is a Mulberry Shell or Granulated Drupe (Morula granulata Duclos) which has an odd look with spirals of dark rounded bumps vaguely resembling a bunch of grapes or similar.

Mostly Nerite Shells (Nerita costata Duclos) in a part-submerged rock crevice

Dry Nerite Shells in a rock crevice at low tide

Individual Nerite Shell in thin film of water.

Outer surface of Nerita costata

Under surface of Nerita costata showing aperture and operculum

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Mud Creepers

Mud Creepers (1) -  Empty shell of Telescopium telescopium L., Mud Whelk, at Cairns, Queensland, Australia, with remains of an oyster shell and barnacles attached.

Telescopus by Dominic Johns - A sculpture on the esplanade at Cairns, Queensland, Australia. Mud Creepers are a common sight on the tidal mud flats at Cairns in Queensland, Australia. Also called Telescope Shells, Mudwhelks, Telescopic Creepers, or Mangrove Mud Whelk. The Latin name is Telescopium telescopium L. They are so emblematic of the place that they have been glorified by a fantastic piece of sculpture by Dominic Johns on the Esplanade.

The reality, however, is that this large gastropod marine mollusc – living on the glutinous muds exposed by the ebbing tide – is not the most attractive of seashore creatures, in fact, a bit creepy. It is dark in colour, about 6 inches long, and the shell is very thick and heavy, The protruding muscular foot and tubular siphon of the animal are hard to distinguish from the mud itself but I believe the flesh is edible.

Telescopus by Dominic Johns - A sculpture on the esplanade at Cairns, Queensland, Australia.This sea snail seems to struggle as it drags its weighty shell across the mud in strange irregular movements without the supporting medium of water. The furrows incidentally ploughed by the shells leave networks of trails on the mud. In life the shells are often caked with mud but empty shells washed up on the beach show there is actually a great striped pattern.

Mud Creepers (2) - Empty shell of the Mud Whelk or Mud Creeper, Telescopium telescopium L held to show the apertural end at Cairns, Queensland, Australia.

Mud Creepers (3) -  Empty shell of Telescopium telescopium L., Mud Whelk, on the shore at Cairns, Queensland, Australia.

Mud Creepers (4) -  Empty shell of Telescopium telescopium L., Mud Whelk, on the shore at Cairns, Queensland, Australia, with remains of an oyster shell and barnacles attached.

Mud Creepers (5) -  Empty shell of Telescopium telescopium L., Mud Whelk, on the shore at Cairns, Queensland, Australia.

Mud Creepers (6) -  Empty shells of Telescopium telescopium L., Mud Whelk, on the shore at Cairns, Queensland, Australia. One shell has barnacles attached.

Mud Creepers (7) -  Empty shell of Telescopium telescopium L. on the beach at Cairns, Queensland, Australia, with fiddler crabs.

Mud Creepers (8) - Empty shell of Telescopium telescopium L., Mud Whelk, on the shore at Cairns, Queensland, Australia. The shell has barnacles attached.

Mud Creepers (9) - The tidal mudflats at cairns, Queensland, Australia - habitat of Telescopium telescopium L., the Mud Creeper, Mud Whelk, Telescopic Creeper, or Mangrove Mud Whelk.

Mud Creepers (10) - The tidal mudflats at Cairns, Queensland, Australia - habitat of Telescopium telescopium L., the Mud Creeper, Mud Whelk, Telescopic Creeper, or Mangrove Mud Whelk.

Mud Creepers (11) - The tidal mudflats at Cairns, Queensland, Australia - habitat of Telescopium telescopium L., the Mud Creeper, Mud Whelk, Telescopic Creeper, or Mangrove Mud Whelk.

Mud Creepers (12) - Living specimen of Telescopium telescopium L., the Mangrove Mud Whelk, crawling through the glutinous mud at low tide, its heavy shell making a furrow behind it as it is dragged along, Cairns, Queensland, Australia.

Mud Creepers (13) - Trails left in the mud where living Telescopium telescopium Mangrove Mud Whelks have dragged their heavy shells along when the tide is out.

Mud Creepers (14) - Empty shell of Telescopium telescopium L. on the beach at Cairns, Queensland, Australia.

Mud Creepers (15) - Empty shell of Telescopium telescopium L. on the beach at Cairns, Queensland, Australia.

Mud Creepers (16) - Empty shell of Telescopium telescopium L. on the beach at Cairns, Queensland, Australia.

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Trinity Beach-combings

Image

An assortment of seashells and pebbles from the strand-line at Trinity Beach, Queensland, Australia

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A seashell like an ammonite

Empty shell of the marine Cephalopod mollusc Spirula spirula L. - Common Spirula or Ram's Horn, on Myall beach, Cape Tribulation, in Far North Queensland, Australia (1)

Most seashells with a coiled shape are Gastropod molluscs – like the common winkles and whelks. However, the small, loosely-coiled seashell from Myall Beach at Cape Tribulation in Queensland, Australia, shown here belongs to the Cephalopod molluscs.  The most commonly-occurring Cephalopod molluscs at the present time are animals without external shells. Examples of these include the squid, and cuttlefish -  which have a reduced internal skeleton – like the familiar cuttlefish bones found so frequently on beaches. Octopuses are also Cephalods.

We know from the fossil record that, in the distant past, there were many cephalopods with external coiled shells; and these were called ammonites. There are several earlier posts in this blog about fossil ammonites. There is a similar loose coil shaped Cretaceous ammonite called Aegocrioceras quadratum (Crick) found in the UK.

There are a still a few modern Cephalopod species which retain an ancestral-style external coiled shell such as the ones found as Ammonites. These include the Nautilus and and Paper Nautilus group of species. Less commonly known is the single species of the single genus belonging to the family Spirulidae – shown in the photographs here. This is the Common Spirula or Ram’s Horn (Spirula spirula L.). You can see through the fragile translucent shell to the internal septa or partitions that divide the shell up into the compartments that are so familiar from ammonite fossils. The octopus-like animal itself would have in life mainly occupied the outermost compartment, with its swimming tentacles protruding from the circular opening.

Apparently the shell of the Common Spirula is found on beaches all over the world but the living animal is rarely seen because it is a pelagic deep water form. This particular shell specimen has washed ashore with minute goose barnacles or stalked barnacles attached to it. The small balls of sand on the beach with the shell are made by the many burrowing Bubbler Crabs that inhabit this tropical shore.

Empty shell of the marine Cephalopod mollusc Spirula spirula L. - Common Spirula or Ram's Horn, with sand pellets made by the Bubbler Crabs that burrow into the shore, on Myall beach, Cape Tribulation, in Far North Queensland, Australia (2)

Empty shell of the marine Cephalopod mollusc Spirula spirula L. - Common Spirula or Ram's Horn, with sand pellets made by the Bubbler Crabs that burrow into the shore, on Myall beach, Cape Tribulation, in Far North Queensland, Australia (3)

Myall Beach, Cape Tribulation, in Far North Queensland, Australia, where the empty shell of the marine Cephalopod mollusc Spirula spirula L. - Common Spirula or Ram's Horn, was found (4)

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