Sponges (Porifera) are considered to be the most primitive form of animals. They lack differentiated cells, and can reform if disassociated by (for example) shoving them through a sieve. On the other hand they cannot be considered colonies of single-celled organisms, as they have definite structures, bodies with more-or-less set shapes consisting of networks of pores and channels through which water is pumped; the individual cells feeding separately by filtering food from the water in these channels. They are the only extant group of animals with a fossil record that extends significantly into the Precambrian.
In a paper published in the journal Zootaxa on 25 July 2013, Hans Rapp of the Centre for Geobiology and Department of Biology at the University of Bergen, Christian Göcke of the Forschungsinstitut und Naturmuseum Senckenberg, Ole Tendal of the Zoological Museum of the University of Copenhagen and Dorte Janussen, also of the Forschungsinstitut und Naturmuseum Senckenberg, describe two new species of calcareous Sponge (Calcarea, sponges that have skeletons composed of calcium carbonate), from the Eckström Shelf of the Eastern Weddell Sea, Antarctica.
The first new species is placed in the genus Clathrina and given the specific name brandtae in honour of Angelika Brandt of the University of Hamburg, organizer of two expeditions to the Antarctic. Clathrina brandtae is a yellowish Sponge with a body made up of a loose arrangement of tubes, roughly 1 cm long and 1.5 cm wide. It has a skeleton made up of simple three pointed elements. The Spomge was found at depths of between 118 and 595 m.
The second new species is placed in the genus Leucetta and given the specific name delicata, meaning delicate. Leucetta delicata is a beige sponge with an ovular to cylindrical shape, reaching 2.2 by 1.2 cm. It was found at a single site at a depth of 595 m.
See also A Chambered Glass Sponge from the Early Devonian of northern Spain, A mysterious Glass Sponge from the Early Cambrian of south-east China, New Glass Sponges from the North Atlantic and The oldest animals - Pre-Ediacaran Sponges from Namibia(?)
Clathrina brandtae. (A) Preserved specimen from the Weddell Sea (os = osculum). (B) Spicules, from left: ste = subregular tetractine, rte = regular tetractine, rtri = regular triactine and aa = apical actine of a tetractine. (C) Wall of asconoid tube seen from the interior. Rapp et al. (2013).
The second new species is placed in the genus Leucetta and given the specific name delicata, meaning delicate. Leucetta delicata is a beige sponge with an ovular to cylindrical shape, reaching 2.2 by 1.2 cm. It was found at a single site at a depth of 595 m.
Leucetta delicata. (A) Preserved specimen. os = osculum. (B) Spicules. Bottom left: rte = regular tetractine with very short apical actine. Remaining spicules: rtri = regular triactines of variable size. (C) Cross section of the body wall. cx = cortex. ca = canal. atr = atrium. (D) Cross section of the cortical region. cx = cortex. cch and arrow = choanocyte chamber (scale bar as in E). (E) Cross section of the atrial region. atr = atrium. Rapp et al. (2013).
See also A Chambered Glass Sponge from the Early Devonian of northern Spain, A mysterious Glass Sponge from the Early Cambrian of south-east China, New Glass Sponges from the North Atlantic and The oldest animals - Pre-Ediacaran Sponges from Namibia(?)