Where Topsent went wrong: Aka infesta a.k.a. Aka labyrinthica (Demospongiae: Phloeodictyidae) and implications for other Aka spp.

Early descriptions for species of Aka were poor in detail, and the only spicule type that occurs in this genus does not vary much between species, which led to taxonomic confusion. Moreover, the type specimens of five species of Aka are lost, causing considerable problems. Mediterranean specimens of Aka were identified as Aka labyrinthica (Hancock, 1849) by Topsent (1900), even though this species was originally described from the Indo-Pacific. All following publications on Mediterranean Aka accepted Topsent's decision. We assessed this problem with new samples from the Ionian Sea. Our material consisted of only one specimen of Aka, and we had to rely mainly on spicule characters for comparison with other species. We developed a system for species recognition solely based on spicular characters and biometry, involving a combination of the parameters oxea length, width, tip form and angle of curvature. This approach was surprisingly accurate. Forming ratios of the above parameters was less helpful, but can sometimes provide additional information. We identified our sample as Aka infesta (Johnson, 1899), and describe it as a minute-fistulate species with large, multicamerate erosion traces and stout, smooth oxeas. Our data further imply that A. labyrinthica sensu Hancock has not yet been found in the Mediterranean. Aka labyrinthica sensu Topsent is a collection of different species not including A. labyrinthica sensu Hancock

Cliona minuscula Schönberg, Grass & Heiermann, 2006, sp. nov.

Cliona minuscula, sp. nov. Material examined Two specimens of Cliona minuscula, sp. nov. from Little Pioneer Bay, Orpheus Island, Palm Island Group, Central Great Barrier Reef, Australia (18 40 ’S 146 30 ’E; Fig. 1): Cliona minuscula, sp. nov. holotype: QM G 322595, wet sample in alcohol, original sample number: 5.46, 27.10.2003: in dead, unattached shell of Tridacna crocea in 1.0 m depth on reef crest (Fig. 2 A–B). Cliona minuscula, sp. nov. paratype: QM G 322596, slide preparation, entire specimen was used up for the preparation, original sample number: 2.80, 25.10.2003: in a dead brain coral in 2.2 m depth, from the reef flat. Other species examined: Cliona caesia new comb., various specimens from Little Pioneer Bay, Orpheus Island, Palm Island Group, Central Great Barrier Reef and Heron Island, Capricorn Bunker Group, Southern Great Barrier Reef Australia, wet samples in alcohol, Queensland Museum, spicule preparations in first author’s collection. Cliona patera: MHNG 38767 from the Museum in Geneva, dry specimen, section of a massive sponge. Sample site unknown. Description of the holotype QM G 322595 Live ectosome dark brown, endosome lighter brown to beige. Colour fading when frozen or in alcohol, with endosomal tissue becoming almost transparent. Papillae minute, mean papillar diameter 0.44 mm when contracted (minimum = 0.20 mm, maximum = 0.70 mm, SD = 0.14 mm, N = 25). Form circular in outline, occasionally irregular. Contracted papilla margins flush with surface, but towards centre ‘sunken’ into substrate, latter forming small circular pits around papillae (Fig. 2 C–D). Some of these pits in sample QM G 322595 no longer filled with sponge tissue, but with mud and algae. Papillae evenly dispersed, mean distance from each other 0.40 mm (minimum = 0.16 mm, maximum = 0.80 mm, SD = 0.18 mm, N = 25), fusion rare. Except for small areas opposite shell umbo, tissue not traversing entire width of shell, but penetrating to a depth of 1–2 mm. Sponge tissue emerging on inner side of shell forming net­like pattern (Fig. 2 B). External erosion traces on shell outer surface as papillar pits and shallow grooves that connect papillar pits in close vicinity to each other (Fig. 2 D). Endolithic erosion chambers minute, appearing finely porous, with spherical to oval chambers (Fig. 2 E–F). Under magnification some chambers more irregular in shape as result of merging (Fig. 2 F). Mean chamber diameter 0.59 mm (minimum = 0.2 mm, maximum = 1.3 mm, SD = 0.29, N = 25), mean diameter of canals connecting chambers 0.20 mm (minimum = 0.08 mm, maximum = 0.33 mm, SD = 0.07, N = 10). Endosomal tissue thinly coating chambers and forming fragile membranes. Tylostyles in papillae in loose palisade, spicule points protruding from tissue by about 1 / 3 of spicule length (Fig. 2 G). Tissue with zooxanthellae (dinoflagellate symbionts) concentrated at the sponge surface (Fig. 2 H). Endosomal tylostyles aligned in parallel, forming bundles. Bundles in confused orientation. Skeleton comprised of megascleres only, i.e. of tylostyles (Fig. 3). Mean tylostyle dimensions comparatively small, with shaft length x shaft width x tyle width: 225.3 x 4.5 x 6.8 µm (Tab. 1). Tylostyle width size­frequency distributions skewed to left, indicating very uniform final size. Most tyles oval, slightly elongated (Fig. 3 A–B), but some round (Fig. 3 C–D), rarely with secondary swellings. Shafts predominantly straight (Fig. 3 A–B), neck regions usually subtle, few with sharp creases (Fig. 3 C–D). Axial threads extending about 2 / 3 into tyles. No vesicles observed when using light microscopy, but occasionally striations in tyles (layering of silica). Additional species in the holotype Specimen QM G 322595 contains three other species of bioeroding sponges: Cliona ensifera, Cliona cf. orientalis in ­form and an unidentified species of Aka. Latter two species were only tentatively or incompletely identified, as C. cf. orientalis lacked microscleres and Aka sp. is a small specimen with indistinct fistules. Aka sp. and C. minuscula, sp. nov. occur in two tiers, with C. minuscule, sp. nov. forming the upper layer near the shell surface, being traversed by Aka sp. papillar canals (Fig. 2 E–F). The additional species in QM G 322595 are distinct from C. minuscula, sp. nov. by their spicules (Tab. 2, Fig. 4), papillar size (Tab. 2, Fig. 2 A) and form of erosion chambers (Tab. 2, Fig. 2 B, E–F). Ecology and distribution To date only two specimens of Cliona minuscula, sp. nov. have been found, and only from one sample site at Orpheus Island, Palm Island Group, Central Great Barrier Reef. The sponges were sampled from very shallow depths between 1 and 2 m in unattached rubble (dead clam shell) and in part of the reef framework (dead massive coral). The specimens were from the reef flat, i.e. from the mixed zone (Schönberg 2001), and from the reef crest. Etymology The species name ‘ minuscula ’ was chosen, as compared to other species of Cliona, the new species has minute papillae and erosion chambers and smaller than average tylostyles.Published as part of Schönberg, Christine Hanna Lydia, Grass, Stefanie & Heiermann, Anke Tarja, 2006, Cliona minuscula, sp. nov. (Hadromerida: Clionaidae) and other bioeroding sponges that only contain tylostyles, pp. 1-24 in Zootaxa 1312 on pages 4-6, DOI: 10.5281/zenodo.17388

Cliona celata Grant 1826

Cliona celata Grant, 1826 Diagnosis Clionaidae in, and growth form, with tylostyles as megascleres; microscleres, if present, spirasters or raphides, which may vary in form. Synonymies given by Rützler (2002 b).Published as part of Schönberg, Christine Hanna Lydia, Grass, Stefanie & Heiermann, Anke Tarja, 2006, Cliona minuscula, sp. nov. (Hadromerida: Clionaidae) and other bioeroding sponges that only contain tylostyles, pp. 1-24 in Zootaxa 1312 on page 3, DOI: 10.5281/zenodo.17388

FIGURE 3 in Cliona minuscula, sp. nov. (Hadromerida: Clionaidae) and other bioeroding sponges that only contain tylostyles

FIGURE 3. Cliona minuscula, sp. nov. tylostyles of QM G 322595. A – B—Tylostyles mostly have straight shafts and oval to drop­shaped tyles that are slightly longer than wide. C – D—Occasionally, tylostyles have more spherical tyles with distinct neck areas

Long-term macrobioerosion in the Mediterranean Sea assessed by micro-computed tomography

Biological erosion is a key process for the recycling of carbonate and the formation of calcareous sediments in the oceans. Experimental studies showed that bioerosion is subject to distinct temporal variability, but previous long-term studies were restricted to tropical waters. Here, we present results from a 14-year bioerosion experiment that was carried out along the rocky limestone coast of the island of Rhodes, Greece, in the Eastern Mediterranean Sea, in order to monitor the pace at which bioerosion affects carbonate substrate and the sequence of colonisation by bioeroding organisms. Internal macrobioerosion was visualised and quantified by micro-computed tomography and computer-algorithm-based segmentation procedures. Analysis of internal macrobioerosion traces revealed a dominance of bioeroding sponges producing eight types of characteristic Entobia cavity networks, which were matched to five different clionaid sponges by spicule identification in extracted tissue. The morphology of the entobians strongly varied depending on the species of the producing sponge, its ontogenetic stage, available space, and competition by other bioeroders. An early community developed during the first 5 years of exposure with initially very low macrobioerosion rates and was followed by an intermediate stage when sponges formed large and more diverse entobians and bioerosion rates increased. After 14 years, 30 % of the block volumes were occupied by boring sponges, yielding maximum bioerosion rates of 900 g m−2 yr−1. A high spatial variability in macrobioerosion prohibited clear conclusions about the onset of macrobioerosion equilibrium conditions. This highlights the necessity of even longer experimental exposures and higher replication at various factor levels in order to better understand and quantify temporal patterns of macrobioerosion in marine carbonate environments

Bioerosion rates of the sponge Cliona orientalis Thiele, 1900: Spatial variation over short distances

We studied bioerosion rates and tissue growth of the sponge Cliona orientalis Thiele, 1900. Experimental blocks grafted with sponge tissue were deployed at three sites in Moreton Bay, QLD, Australia, which have different environmental conditions. Bioerosion rates varied between 4, 5, and 10 kg m year when related to final tissue area and between 4, 7, and 16 kg m year when related to initial tissue area of the graft, which supports findings of earlier studies. Comparing results between the sites, eutrophication appeared to have the most stimulating effect and is most likely to have caused the measured differences. However, slight differences between shading and current speeds may also have played a role. Variation may have masked spatial differences of sponge growth, which were insignificant between study sites. Growth and bioerosion nevertheless followed the same trend and were weakly correlated. Habitat quality itself had no influence. Overall, the twofold difference in sponge bioerosion over a distance as short as 10 km suggests that when estimating bioerosion rates, subsamples should be tested at different locations