Great fleas have little fleas upon their backs to bite 'em,
And little fleas have lesser fleas, and so ad infinitum.
And the great fleas themselves, in turn, have greater fleas to go on;
While these again have greater still, and greater still, and so on.



Augustus De Morgan, A Budget of Paradoxes (1872)

The apparently simple specimen that proved to be a whole community of marine organisms. Photo: B. Baldock.

This small specimen was collected from 21 m deep waters, at St Francis Island, Nuyts Archipelago, South Australia (see also South Australia’s offshore islands, p. 150; 33mb PDF). It was torn from its substrate by the frame of an underwater Baited Remote Underwater Video Station (BRUVS) used to film fish populations as part of the survey of Marine Parks, and was given to the Phycology Unit of the State Herbarium of South Australia in 2015.

LEFT: Remains of the slightly calcified exoskeletons of individual zooids in the bryozoan colonies. RIGHT: Part of the inter-connected chambers of the tree-like sponge, walls stained blue. Photo: B. Baldock.

At first sight I thought the specimen was simply a group of “moss animals” or bryozoans (probably Canda arachnoides Lamouroux, above left).  But closer inspection proved that the bryozoans were growing on a tree-like sponge full of inter-connected chambers (above right).

In addition, under the microscope, I found four algae – a veritable community coating the sponge. Labelled with red numbers 1 to 4 in the images, below.

(1) Dictyopteris gracilis, delicate sporelings attached to a sponge skeleton (top), which is stained blue, and a single flimsy blade (bottom). (2) Lejolisea aegagropila, female structure (top) and stalked sporangia (bottom), stained blue. Photo: B. Baldock.

The largest, a Brown alga, Dictyopteris gracilis Womersley (no. 1), consisted of sporelings “babies”, getting established on a relatively stable, hard substrate, a requirement for most algae to survive.  They could have grown into quite elegant, leaf-like plants some 200 mm tall. Their growing centres (meristems) are found in the notch at the apex of the delicate filmy blades. See the Algae revealed factsheet for the species (420kb PDF).

In addition, there was a tangled set of microscopic pink threads, Lejolisia aegagropila (J. Agardh) J. Agardh (no. 2), easily recognised from its female reproductive structures (procarps and cystocarps) that resemble glass light-bulbs.  Mixed in with the female plants was another stage in the species life cycle – a spore plant with packets of 4 spores (tetrasporangia) on minute stalks.

(3) Acrothamnion preisii, elegant feathery (pinnate) side branches tipped with a glistening gland. (4) Audouinella spongicola, minute threads of the Red alga (arrow), running along the blue-stained walls of the sponge which shows ,also, needle-like skeletal spicules. Photo: B. Baldock.

Perhaps the most striking, however, was the Red alga Acrothamnion preissii (Sonder) Wollaston, with its elegant “feathers”, each ending in a glistening gland (no. 3).

The most unusual alga, although obscure, consisted of lines of elongate red cells (no. 4) running on the surface and around the walls of the inter-connected sponge chambers. These belonged to threads of a very simple Red alga, Audouinella spongicola (Weber van Bosse) Stegenga, which, as its name denotes, specifically lives on sponges.

The common, single-celled foraminiferan Discorbis dimidiatus, its shell punctured with minute pores, lives amongst the algae attached to the sponge. Photo: B. Baldock.

There were other microscopic organisms: shell-like unicellular animals (foraminifera), diatoms with glassy walls; and inevitably, bacteria, but I stopped investigations at the plants and animal described above, thinking I had enough evidence to support the sentiment in the adage at the start of this article.

I hope the BRUVS people can continue to send more, minute but nevertheless interesting marine communities to us at the State Herbarium. You never know what will turn up in the marine world.

Contributed by State Herbarium Hon. Associate Bob Baldock.

Callitris rhomboidea, branch with immature cones. Photo: T. Robinson.

Plant the Month for August is Callitris rhomboidea R.Br. (Oyster Bay pine), which occurs in DEWNR‘s Park of the Month, Onkaparinga River National Park. It is a conifer from the large and cosmopolitan Cypress family (Cupressaceae), which includes many important timber (e.g. Sequoia sp., the Redwoods of North America) and horticultural species (e.g. Cryptomeria, from Japan). Callitris includes approximately 16 species, 13 of which are restricted to Australia. The majority of these occur in heath and woodlands, extending into semi-arid areas. Recent molecular research suggests that Callitris evolved from rainforest ancestors in response to a drying climate over the past 30 million years (Larter et al. 2017) and in contrast to other Australian conifers, they are remarkably drought tolerant, allowing them to thrive in arid conditions.

Callitris rhomboidea, fruiting cone. Photo: T. Robinson.

This species is commonly referred to as the Oyster Bay pine, in reference to its occurrence on the Georges River, in the vicinity of Sydney (also known as Port Jackson pine). Callitris rhomboidea extends from coastal southern Queensland through New South Wales, Victoria and Tasmania. In South Australia, it occurs chiefly on Kangaroo Island and a few scattered localities in the Mount Lofty Ranges, including the Onkaparinga River Gorge, and the Mount Crawford region to the north. While it is widely distributed, Oyster Bay pine is only locally common, occurring on sand dunes and in rocky areas in heath and woodlands. Callitris are intolerant of fire and preferentially grow in areas that are protected by topography or slow rates of fuel accumulation. However, the Oyster Bay pine can readily regenerate from seed, which are held in the thick woody cones that cluster on fruiting branches. Like many plant species of Australia’s fire prone woodlands (for example, Banksia), fire may act as a stimulus for seed release followed by mass germination and generation of dense, even-aged stands.

Callitris rhomboidea in Hale Conservation Park. Photo: T. Robinson.

There are two species of Callitris occurring within the Onkaparinga River National Park. Callitris rhomboidea is perhaps best distinguished from Callitris gracilis (Slender Cypress-pine) by the shape of the cone scales on the female cone, which are rhomboidal (hence the name, rhomboidea) and have a distinct point near the apex.

Callitris rhomboidea is ‘Rare’ within South Australia, and has declined in parts of its range as a consequence of land clearing, grazing and weed competition. While the level of decline is insufficient to warrant listing as ‘Threatened’, factors such as high frequency fires and susceptibility to ‘die-back‘ (caused by the fungal pathogen, Phytophthora cinnamomi) are potential future concerns (IUCN Red List 2017).

Contributed by State Herbarium molecular botanist Ed Biffin.