Month: November 2015

Sunset on the Fan Shell?

Here lies the remains of the last Fan shell on Deeban Spit.

Possibly.

Over the last two years the number of Fan shells poking out of the sea grass on Deeban Spit at low tide has plummeted. Where once there was a field of a thousand gaping shells, there are now almost none, and those that do remain are empty.

I miss them.

Empty shells on oyster beds

Fan shells are known locally by the more dramatic, but incorrect name of Razor clams. Yet another animal menace just waiting to extract human blood. They are popular in recipes of an Asian flavour, put “razor clam” in your search engine and cooking pops up first, but you will notice that true Razor clams look like old-school cut-throat razors, while our Fan shells look like fans, or perhaps the ear of a donkey. They are all edible regardless of name.

The big shells out on Deeban Spit  are  Pinna bicolour, bivalve molluscs in the genus Pinna, latin for ear. Pinna bicolour is a widely distributed species named for the bright iridescence of the inner shell. It is restricted to the sandy seagrass beds where the larvae are able to settle and feed. Research done in the warm waters of Malasia and the cooler waters of South Australia shows that they grow quickly and reach 20cm in length in the first year. By the second year they reach 26 cm and they are full size in the third year at 35 cm. Lucky Fan shells may go on to live well over a decade, the old ones gather epibiota, just like the hull of a boat.  Eventually they get tired, weighed down and stop moving. Where the seagrass beds remain there is a good chance the Fan Shells will return.

live fan shell survivor
empty fields empty fields

The carnivorous Moon Shell egg mass

Often claimed to be shark poo, these gelatinous croissants made of mucus and a sprinkle of sand are in fact masses of eggs laid by the Moon Shell, a carnivorous snail that feeds on other shelled molluscs. On the sand flats the molluscs include the oysters seen in the photo and the whelks that lie around casually waiting for the returning tide.

If you are a keen observer of sea shells on the sand you will have noticed that some types of empty shells have a tiny neat hole usually drilled at the apex, in the ideal place for threading a necklace. The molluscs that produce these shells have a pair of shells that come together to form a shelter for the soft innards, they are known as bi-valves. The mollusc that made the hole is another type entirely, a gastropod – like the garden snail. The class Gastropoda contains a vast total of named species, second only to the insects in overall number. Moon shell gastropods are able to travel along quite efficiently by extending a big muscular foot. These active mollusc are then able to hunt the less agile bi-valves and anything else that they come across. Moon shells can be carnivorous and they are also known to feed on soldier crabs.

Molluscs have a body plan that  incorporates hardened elements, usually a shell, in the case of an octopus it is a horny beak, while gastropods have a shell and a radula, a tongue structure that looks like a miniature chainsaw composed of many tiny teeth on a band that will easily saw through plant material or drill holes into shells. The moon shell will grab hold of the prey with its foot and locate the precise spot to start drilling with the aid of an acid secretion, the muscle that clamps the two shells together is disabled and the shells can then be prised open and the contents removed.

The moon shell that is commonly found on the Deeban Spit is Polinices (Conuber) sordidus

There is an illegal market for shells collected in Port Hacking with specimens selling for $10 each.

Flannel Flowers

Actinotus hellianthi, the larger of the two Flannel flowers. The larger flowers seem to require more light and are found in exposed positions on rock platforms and on the roadside, while the smaller flowers of Actinotus minor are more common and grow twining through other shrubs and ground cover.

Notice many small black beetles active in the middle of the flowers, probably feeding and acting as pollinators.

Flannel flowers are part of the Apiaceae family and are not daisies, but like daisies the flower structure is not straightforward. In Flannel flowers the centre of the flower is composed of many small florets while the outer rays are actually bracts not petals. The name Actinotus comes from the Greek aktin-/ακτιν, meaning “ray” or “spoke of a wheel” or “sunbeam”.

This group of flowers is growing on the bush track alongside Maianbar Drive overlooking the Basin.

For the big picture click below.

flannekl Flower

Recent Reference Material

Anyone interested in the geography of Port Hacking will enjoy reading this report on disc, available free at the reception desk at Sutherland Shire Council chambers. The disk contains a massive trove of historical photos and views of the natural features of Port Hacking and the catchment area, including the Royal National Park. Of particular interest is the thorough research into the movement of sand and the history of dredging on Deeban Spit.

To see the written section of the report click on this link:

Port Hacking – Past and Present of an Estuarine Environment

The work was released in February 2014 and represents a synthesis of three decades of work by A/Prof Alberto Albani of UNSW and George Cotis, a long time activist and friend of the Hacking. Both authors have extensive experience in the management of coastal regions and  estuaries. Highly recommended.

Snakes and Ladders

The Green Tree Snake is an occasional ground dweller, and when disturbed on the ground it seeks refuge by climbing.  This little snake climbed up a broom handle only to find a dead end.  Now seen back down onto a brick wall and seeking a better  route to the treetops. The Green Tree Snake, Derendrelaphis punctulata,*  is one of four species found in our backyard – all of them are harmless to people.

For the big picture click below.

green tree snake

*Dendra – latin for tree, Elaphe – are another genus of snake, punctulata – fine spotted

http://www.arod.com.au/arod/reptilia/Squamata/Colubridae/Dendrelaphis/punctulatus

Dirty Lizards

There are two distinctly coloured populations of Eastern water dragons living in this corner of Fisherman’s Bay. There are the clean dragons living in the back yard and then there are the dirty dragons that live down by the creek. Clean dragons are grey, flecked with black and white, and dominant males have a distinct red blush on the chest. The rusty dragons live in creek water which carries iron tinged algae. The colour is permanent, but because lizards shed shed their skin a dirty lizard will eventually become clean if it moves away from the creek. The change of colour will take a couple of years to be complete. Some lizards will carry a two-tone appearance for some time.

All dragons like to slumber on a warm patch of their territory. This group of three females and a larger male are taking advantage of a clearing in the ferns where the sun heats the dark soil by the creek. These lizards have been swimming and are now mostly dry, but there is wet patch where one female lizard has been lying on top of the male in the middle. The male can be identified  by his large head. Males wrestle to gain dominance, so there is an advantage to having a large head, or rather, a larger set of jaws.

Which brings us to the latin name of the water dragon; Physignathus lesueurii, where the generic epithet (the first capitalised part of the binomial) refers to a large jaw. The specific epithet refers here to the French artist and naturalist Charles Alexandre Lesueur who traveled with Baudin to Australia in 1801. The Baudin expedition collected over 100000 specimens and many  animals were described from this collection.

Powerful Pellets

Looking up through a skylight I wondered about the large grey sausage adhered to the glass. Some days or perhaps weeks later I went up on the roof and discovered the best part of a small skeleton encased in a tight felt cocoon. On opening the package a pair of mandibles appeared and from the dentition I was able to identify the remains of a brush tail possum. Only one animal will eat a possum and drop the remains in the form of a pellet; the Powerful Owl, Ninox strenua

The pellet is the indigestible portion of a possum meal and it was coughed up from a roost in the Angophora tree that grows over our house. In the following months I found gizzards dropped on the roadway and later the dismembered wings of a fruit bat.

At night in the winter, more often after rain, the Powerful Owl can be heard calling. Locals have different theories about where the owls may nest, roost and hunt. Perhaps they are occasional visitors, perhaps we share a pair with Bundeena.

The powerful owl is listed as a vulnerable species due mainly to habitat clearing. We are fortunate indeed to have them here in Maianbar

To hear a recording of a Powerful Owl calling click on this soundcloud link

The Beginning

This is the first post to the newsfeed. Fresh posts will displace older posts from the top of the page. It is also possible to make the home page static so that the visitor is met with an introduction, but more often this is included in a page titled About because returning visitors would prefer to see something fresh. To keep a post at the top of the page it can be made sticky and it will then cary the Featured title

Scroll down the home page and the posts will appear in sequential order, a quick way for people to catch up on content

To the left hand side are all the widgets and  there are many choose from. I have opted to stack the sidebar with links to static pages – including index of contents and a page introducing myself, and another page for references – Like the posts these pages can have room for comment by visitors, or not. Readers love to leave comments and often the sidebar is used to reward comments by listing latest comments. The engagement of readers is the main way of generating traffic.

All comment can be published immediately, or subject to approval.

The sidebar also include a tag cloud that ranks the tags by size according to the number of entries.

When exploring the site the reader can reset the journey by returning to the top of the home page called up by pressing the title of the sidebar; ecology of MAIANBAR

At the foot of posts are tags and categories, these can be used to draw up all pages on Botany (a category) or more specifically all pages on a particular plant or flower colour (a tag). All content contains  links that may lead to other outside content or to further expansion of text or images, usually such links are underlined, except in the case of an image where a note is given.

Enjoy