The Beach Casuarina or Coastal She-oak (Casuarina equisetifolia) is a common plant on Australian tropical beaches. It can occur as a shrub or a tree. It is often the first plant to colonise this basically unfriendly habitat and, although wispy and fairly insubstantial in growth, it provides welcome shade. It looks as if it might be some kind of pine with long drooping needles but in fact the ‘pine needles’ are thin articulated branchlets. In the close-up photographs below you can see that the branchlets resemble the stems of the Horsetail plants (Equisetum spp.) – primitive plants dating back to the Carboniferous Period from which we know them in fossil form in coal measures and similar rocks – they even share similar Latin names.
The leaves of the Beach Casuarina are barely noticeable, being very small indeed and growing with even spacing along the stems from which the branchlets arise. You can see these scale-like leaves if you click to enlarge, for example, the photograph in the gallery below Beach Casuarina 7. The plant has unobtrusive and separate male and female flowers. Male flowers are white at the end of the branchlets while the female flowers are small and red and grow on special side branchlets. The fertilised female flowers develop into small, hard spiky fruits, with some similarity to pine cones [and also strikingly reminiscent in outline shape of the hairstyle favoured by Lisa Simpson and her baby sister Maggie].
These are images of the Mangrove, Nipa, or Nypa palm (Nypa fruticans) which is the only palm thought to be fully adapted to growing in the mangrove biome. It is shown here growing in soft mud under brackish water at the edge of Freshwater Lake (one of the Centenary lakes) at Cairns Botanic Gardens in Queensland, Australia.
These odd objects were found on the beaches at Normanby Island and Cape Tribulation on the Queensland Coast in Australia. They are large woody, angular fruits of the Beach Barringtonia mangrove tree (Barringtonia asiatica). As you can see from the photographs, they get washed up in varying stages of decomposition – anything from the perfect brown box shape with extended corners to a simple mass of fibrous material – sometimes with small sea creatures like colonial Bryozoa or stalked barnacles attached.
This post represents my first visit to the Australian shoreline. Kewarra Beach, just north of Cairns on the Queensland Coast, is fairly typical of the beaches in the area. You can see from the pictures that it was virtually deserted. Even though the temperature was hot, hot, hot, it was also steamy; for the most part, a dull day with rain clouds tumbling down from the mountains.
Rainforest trees come right down to the sand – and as with the mangroves bordering the river, the tangled networks of roots are exposed. Ideal territory for salt water crocodiles – there is even a notice warning of recent sightings. Thinking that one of the dreaded creatures is possibly lurking somewhere – ready to dart out of concealment for a meal – certainly takes the edge off the idea of paddling or exploring the woods by the shore.
The tide had washed in driftwood, dead fish, coconuts, and strange jawbones. Delicate purple-tinged clams rolled on the surf; oysters clustered on rock; and tiny Sand Bubbler Crabs popped in and out of burrows – scattering small balls of sand in linear patterns on the beach. In this paradise, pink Goat’s Foot Morning Glory flowers decorated the grey rip-rap used as a sea defence.
The Cairns Inlet on the Queensland coast is obviously a habitat both rich and diverse. This wonderful natural environment is celebrated by the artist Jennie Scott (2003) in a fabulous and fun ceramic artwork that is embedded in the pavement at Skippers Cafe and Muddy’s Playground (the childrens’ water park) on the Cairns Esplanade. It features examples of all the creatures that live in and on the water just offshore, and that includes fish of all sorts – as you can see from the pictures here.
Maybe this was the fish that got away from the net fisherman shown in the previous post. I guess that it wouldn’t have remained on the beach for long – too many small scavengers like crabs living on the mud flats would have thought it a food bonanza – if one of the local ‘salties’ (crocodiles) didn’t snap it up first as a snack. Visitors to the seashore in Cairns are told not to gut fish on the beach or leave food around after barbecues and picnics because the food attracts crocodiles – which of course is dangerous as they are as likely to eat the people as the discarded fish remains!
I was delighted to see this local fisherman casting his circular net into the shallow waters just off the beach at Cairns. I don’t know whether he was after any particular kind of fish but I know that many fish like to hide amongst the submerged mangrove roots around the shores. Unfortunately, despite repeated attempts, he went home empty-handed on that occasion. I spoke to him and he allowed me to take these pictures and the short video clip of his fishing technique.
TIP – View the following video clip with the sound off because of the noise made by the wind over the microphone.
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.
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.
Jansen, P. (1996) Common Seashells of Coastal Northern Queensland, privately published in Townsville, Australia, ISBN 0 646 29824 0.