Spongillida Manconi and Pronzato, 2002

Pronzato, Roberto, Pisera, Andrzej & Manconi, Renata, 2017, Fossil freshwater sponges: Taxonomy, geographic distribution, and critical review, Acta Palaeontologica Polonica 62 (3), pp. 467-495 : 471-473

Order Spongillida Manconi and Pronzato, 2002

Species richness of sponges of the order Spongillida Manconi and Pronzato, 2002 inhabiting continental waters (previous suborder Spongillina Manconi and Pronzato, 2002, and subsequent emendations 2011, 2015) reach 240 valid species (about 3%) of the 8850 species of all extant Porifera ( Hooper et al. 2011; Van Soest et al. 2017). The order Spongillida comprises 48 genera belonging to 6 families i.e., Metaniidae , Spongillidae , Lubomirskiidae , Malawispongiidae , Potamolepidae , and the exclusively fossil Palaeospongillidae . The monophyletic Spongillida ( Manconi and Pronzato 2002, 2015, 2016a, b; Erpenbeck and Wörheide 2007; Cárdenas et al. 2012; Morrow and Cardenas 2015) according to earlier studies, colonized continental water not later than in the Triassic from a hypothetical marine Haplosclerida ancestor Pronzato and Manconi 1994; Manconi and Pronzato 2002, 2015).

Spongillida are widespread on all continents, excluding Antarctica, and several species, possible species complexes, show a wide geographic range ( Manconi and Pronzato 2007, 2008, 2015, 2016a, b). Several studies focus on their occurrence under extremely stressing conditions e.g., temporary water (permafrost) in circumpolar northern regions, temporary water in hot deserts, small temporary ponds in sub arid-arid conditions, and tropical hydrographic basins characterised by flooding and extreme water level variations Manconi and Pronzato 2008, 2015, 2016b).

The abundance of freshwater sponges varies widely from region to region, and in some cases sponge populations are so dense and flourishing that they strongly impact human health and/or productive activities. In the Amazon basin, for example siliceous spicules of sponges are so abundant in the water column, during the raining season, that they are causing permanent eye damage ( Volkmer-Ribeiro et al. 2006) to riverine populations. In the lower Mekong basin Thailand) high biomass of large sponges heavily colonizes fishermen nets, damaging the fishery and aquacul-

ture infrastructures ( Manconi et al. 2013). On the contrary, sponges are very rare or absent in some Mediterranean islands, in the Canary Archipelago, and several Pacific Ocean archipelagos ( Manconi and Pronzato 1994 a, 2009, 2015; Manconi 2008).

Freshwater sponges display highly variable body shape and dimensions, consistency and colour. Specimens range from thin whitish crusts a few mm thick strictly adhering to the substratum, to dark brown massive cushions, and to green branching or erected growth forms. In most species the body consistency is soft and fragile while in other species it is hard with a notably compact texture ( Fig. 1 ). Under unfavourable conditions, such as harsh climate periods, freshwater sponges are reduced, by cryptobiosis, to small spherules known as gemmules (resting bodies) in carpets on the substratum, scattered in the skeletal network, or grouped at the sponge basal portion; but they can be also dispersed in sediments and water column.

The main diagnostic traits that enable us to identify Spongillida are few i.e., skeletal architecture, range of spicule arrangement, geometry, size and shape of spicules, and gemmular traits. Skeletal network is a reticulum of siliceous spicules associated with a notably variable amount of spongin. Spicules, both megascleres ( Fig. 2 ) and microscleres ( Fig. 3 ) are monaxial from smooth i.e., oxeas and strongyles, to spiny i.e., acanthoxeas and acanthostrongyles. Gemmules of freshwater sponges are subspherical to hemispherical (100–1200 μm in diameter, Fig. 4 ), and bear a structured coat of spongin (gemmular theca) variably armed by the spicules (gemmuloscleres) to protect a mass of staminal, totipotent cells contained inside. Morphotraits of this resting stage (i.e., gemmular cage, gemmular theca, gemmular foramen, arrangement of spicules, architecture of spongin structures, together with shape and ornamentations of spicules) are notably diversified and diagnostic at the genus and species level ( Manconi and Pronzato 2002) ( Fig. 4 ). Particularly important, from a taxonomic and phylogenetic point of view, are gemmuloscleres ( Fig. 5 ).

Identification of gemmule-producing sponge species, however, is usually not possible when gemmules are absent from specimens during a phase of their life cycle. Moreover, a number of freshwater sponges, mostly belonging to taxa endemic to ancient lakes, do not produce gemmules. In the palaeontological context, most of the diagnostic traits mentioned above are not useful. Skeletal architecture/network is usually not preserved because spicules joined with spongin become dispersed after its decay. The main character in palaeontological studies is morphology of gemmuloscleres and, to a lesser degree, microscleres, but these are limited only to certain taxa, as indicated above. Megascleres are usually not characteristic enough for generic determination, but some inferences can be made in some cases, e.g., presence of strongyles vs. oxeas.

If the about 240 species of living freshwater sponges are a small minority compared to the marine ones, among the 5000 of all fossil sponge taxa ( Hooper et al. 2011) freshwater species prior to the Quaternary, are, putatively, no more than 16. Their geographic distribution is largely scattered in all continents, except Australia and Antarctica ( Fig. 6 ). Considering the palaeogeography, fossil freshwater sponge taxa seem to have preferred temperate and tropical climates ( Fig. 7).

All discussed here freshwater sponge taxa are Miocene or older in age. Sponges from younger deposits, generally ascribed to extant genera and species, are not included. The sixteen taxa are arranged in chronological order, beginning from the oldest to the most recent. Measurements are reported as length and/or length × thickness.

Institutional abbreviations.—MABA, Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”, Buenos Aires, Argentina; PWL, Naturhistorisches Museum (Palaeontological Collection), Mainz, Germany;SMF, Senckenberg Museum Frankfurt, Germany; TMNH, Toyohashi Museum of Natural History, Japan; USNM, National Museum of Natural History, Smithsonian Institution, Washington D.C., USA (formerly United States National Museum).

Figures

Fig. 1. Growth forms (A–D) and skeletal architecture with variable amount of spongin (E–G) of Recent freshwater sponges of the order Spongillida. A. Oncosclera jewelli (Volkmer-Ribeiro, 1963), Neotropical Region. B. Stratospongilla sp. C. Metania rhodesiana (Burton, 1938), Afrotropical Region. D. Drulia sp. E. Heterorotula capewelli (Bowerbank, 1863), Australasian Region. F. Drulia browni (Bowerbank, 1863), Neotropical Region.G. Uruguayella repens (Hinde, 1888), Neotropical Region. E–G SEM images.

Fig. 2. Morphology of megascleres of Recent freshwater sponges of the order Spongillida. A–F. Oxeas. A. Spongilla lacustris (Linnaeus, 1759), Palaearctic-Nearctic Region, slim smooth oxeas. B. Drulia browni (Bowerbank, 1863), Neotropical Region, stout smooth oxeas. C. Lubomirskia baikalensis (Pallas, 1771), Palaearctic Region, spiny oxeas. D. Makedia tanaensis Manconi, Cubeddu, and Pronzato, 1999, Afrotropical Region, variously spiny slim oxeas. E. Anheteromeyenia argyrosperma(Potts,1880), Nearctic Region, irregularlymicro-spiny oxea.F. Cortispongilla barroisi (Topsent, 1892), Palaearctic Region, irregularly micro-granulated oxea. G–L. Strongyles. G. Potamolepis marshalli Burton, 1938, Afrotropical Region, smooth, stout strongyles with inflated tips. H. Sterrastrolepis brasiliensis Volkmer-Ribeiro and De Rosa Barbosa, 1978, Neotropical Region, smooth strongyles. I. Baikalospongia bacillifera Dybowsky, 1880, Palaearctic Region, strongyloxeas with hooked tips. J. Potamolepis micropora Burton, 1938, Afrotropical Region, strongyles with microspines and inflated tips. K. Swartschewskia papyracea (Dybowsky, 1880), Palaearctic Region, spiny strongyles. L. Nudospongilla cunningtoni (Kirkpatrick, 1906), Afrotropical Region, spiny, slim strongyles. SEM images. Modified from Manconi and Pronzato (2002, 2009).

Fig. 3. Morphology of microscleres of Recent freshwater sponges of the order Spongillida. A–C. Microxeas variously ornate by spines or tubercles. A. Spongilla lacustris (Linnaeus, 1759), Palaearctic-Nearctic Region. B. Sterrastrolepis brasiliensis Volkmer-Ribeiro and De Rosa Barbosa, 1978, Neotropical Region. C. Drulia browni (Bowerbank, 1863), Neotropical Region. D. Microstrongyle with spines of Metania reticulata (Bowerbank, 1863), Neotropical Region. E. Aster-like microscleres with hooks of Dosilia plumosa (Carter, 1849), Oriental Region. F. Pseudomicrobirotules of Corvospongilla burmanica (Kirkpatrick, 1908), Oriental Region. SEM images. Modified from Manconi and Pronzato (2002).

Fig. 4. Gemmule morphology (resting bodies) of Recent freshwater sponges of the order Spongillida. A. Spongilla lacustris (Linnaeus, 1759), Palaearctic-Nearctic Region, subspherical unarmed gemmular theca. B. Metania reticulata (Bowerbank, 1863), Neotropical Region, cage of tangential megascleres around the gemmule.C. M. reticulata, ovoid gemmule (removed from the cage, see B) with radial birotules in the gemmular theca. D. Radiospongilla crateriformis (Potts, 1882), Cosmopolitan, gemmuloscleres radially arranged in the theca (cross section). E. Umborotula bogorensis (Weber, 1890), Palaearctic-Oriental-Australasian Region, subspherical gemmule with distal rotules of gemmuloscleres at the theca surface. F. Stratospongilla bombayensis (Carter, 1882), Oriental-Afrotropical Region, hemispherical gemmule with tangential gemmulosclere at the surface. G. R. crateriformis, gemmular theca with radial gemmuloscleres (close up, cross section). H. U. bogorensis, gemmule surface with distal rotules of birotule gemmuloscleres (close up). I . Oncosclera rousseleti (Kirkpatrick, 1906), Afrotropical Region, gemmule surface with tangential strongyle gemmuloscleres (close up, cross section). SEM images. Modified from Manconi and Pronzato (2002, 2005, 2009).

Fig. 5. Morphology of gemmuloscleres of Recent freshwater sponges of the order Spongillida. A. Cherokeesia armata Copeland, Pronzato, and Manconi, 2015, Nearctic Region, bean-like to ovoid strongyles. B. Potamophloios stendelli (Jaffé, 1916), Afrotropical Region, elongate to ovular strongyles. C. Oncosclera jewelli (Volkmer-Ribeiro, 1963), Neotropical Region, irregularly ovoid strongyles smooth or covered with short spines and tubercles. D. Corvospongilla loricata (Weltner, 1895), Afrotropical Region, slightly curved, stout, spiny strongyles. E. Sanidastra yokotonensis Volkmer-Ribeiro and Watanabe, 1983, Palaearctic Region, oxeas with 2–9 rays rounded to pointed or tricuspidate at tips. F. Spongilla lacustris (Linnaeus, 1759), Nearctic- Palaearctic Region, oxeas strongly bent with large spines.G. Pectispongilla aurea Annandale, 1909, Oriental Region, botryoidal gemmuloscleres with smooth shaft with at the apex polygonal concavities of the botryum. H. Anheteromeyenia argyrosperma (Potts, 1880), Nearctic Region, birotules with spiny shafts and circular rotules with crenulated to indented margins. I. Corvomeyenia everetti (Mills, 1884), Nearctic Region, pseudobirotules with straight, smooth shafts and pseudo-rotules at the apex (up to 10 hooks). J. Acalle recurvata (Bowerbank, 1863), Neotropical Region, pseudobirotules with cylindrical shaft and hooks of umbonate pseudorotules stout and notably recurved bearing microspines at their apices. K. Dosilia plumosa (Carter, 1849), Oriental Region, birotules with large spines on the straight shaft and flat to slightly umbonate rotules with margins bearing small blunt, recurved teeth (spines). L. Racekiela ryderi (Potts, 1882), Nearctic-Neotropical-Palaearctic Region, birotules with smooth shafts and large disk-like rotules with serrated margins and scattered spines or tubercles. M. Ephydatia muelleri (Lieberkühn, 1855), Afrotropical-Nearctic-Palaearctic Region, birotules with smooth, short shaft and rotules with indented margins. N. Trochospongilla horrida (Weltner, 1893), Nearctic-Palaearctic Region, birotules with smooth, short shaft and approximately circular rotules with irregularly thickened margins. O. Acalle recurvata (Bowerbank, 1863), Neotropical Region, tubelliform gemmuloscleres with the proximal large irregularly circular flat rotule with entire margin supporting a smooth shaft decreasing in thickness toward the distal end shaped as umbonate knob-like rotule with a few teeth. P. Drulia browni (Bowerbank, 1863), Neotropical Region, parmuliform gemmuloscleres with the single circular proximal rotule, with lower concave surface, supporting a distal short acute conical stem (shaft). SEM images. Modified from Manconi and Pronzato (2001, 2002) and Copeland et al. (2015).

Fig. 6. Geographic distribution of fossil freshwater sponges (Porifera, Demospongiae, Spongillida).