Abstract
Abstract. Agglutinated foraminifera are marine protists that show apparently complex behaviour in constructing their shells, involving selecting suitable sedimentary grains from their environment, manipulating them in three dimensions, and cementing them precisely into position. Here we illustrate a striking and previously undescribed example of complex organisation in fragments of a tube-like foraminifer (questionably assigned to Rhabdammina) from 1466 m water depth on the northwest Australian margin. The tube is constructed from well-cemented siliciclastic grains which form a matrix into which hundreds of planktonic foraminifer shells are regularly spaced in apparently helical bands. These shells are of a single species, Turborotalita clarkei, which has been selected to the exclusion of all other bioclasts. The majority of shells are set horizontally in the matrix with the umbilical side upward. This mode of construction, as is the case with other agglutinated tests, seems to require either an extraordinarily selective trial-and-error process at the site of cementation or an active sensory and decision-making system within the cell.
Highlights
Agglutinated foraminifera are unicellular organisms that construct their shells from sedimentary grains gathered from the sea-floor environment and cement them together to form what are sometimes intricate three-dimensional constructions (Brady, 1879; Gooday, 1990)
A total of 123 planktonic foraminifer shells are cemented along the tube of the largest fragment, all of which belong to the single species, Turborotalita clarkei (Rögl and Bolli, 1973)
The helical arrangement may reflect the growth sequence, in which generally five or six T. clarkei shells were located around the growing tip, with each new shell being cemented to the left of a pre-existing one
Summary
Agglutinated foraminifera are unicellular organisms that construct their shells from sedimentary grains gathered from the sea-floor environment and cement them together to form what are sometimes intricate three-dimensional constructions (Brady, 1879; Gooday, 1990). Examples of selectivity include foraminifera that gather specific minerals, sometimes heavy ones, such as ilmenite (Makled and Langer, 2010), rutile (Cole and Valentine, 2006) and garnet (Allen et al, 1999), or particular biological clast types such as sponge spicules (Brady, 1879), echinoderm plates (Heron-Allen and Earland, 1909), or coccoliths (Holbourn and Kaminski, 1997; Thomsen and Rasmussen, 2008) It is common for some agglutinated foraminifera to reuse the shells of dead planktonic foraminifera from the surrounding sediment in constructing their tubes (Brady, 1879; Cartwright et al, 1989).
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