Phylogeny and evolution of glass sponges (porifera, hexactinellida)

Reconstructing the phylogeny of sponges (Porifera) is one of the remaining challenges to resolve the metazoan Tree of Life and is a prerequisite for understanding early animal evolution. Molecular phylogenetic analyses for two of the three extant classes of the phylum, Demospongiae and Calcarea, are largely incongruent with traditional classifications, most likely because of a paucity of informative morphological characters and high levels of homoplasy. For the third class, Hexactinellida (glass sponges)--predominantly deep-sea inhabitants with unusual morphology and biology--we present the first molecular phylogeny, along with a cladistic analysis of morphological characters. We collected 18S, 28S, and mitochondrial 16S ribosomal DNA sequences of 34 glass sponge species from 27 genera, 9 families, and 3 orders and conducted partitioned Bayesian analyses using RNA secondary structure-specific substitution models (paired-sites models) for stem regions. Bayes factor comparisons of different paired-sites models against each other and conventional (independent-sites) models revealed a significantly better fit of the former but, contrary to previous predictions, the least parameter-rich of the tested paired-sites models provided the best fit to our data. In contrast to Demospongiae and Calcarea, our rDNA phylogeny agrees well with the traditional classification and a previously proposed phylogenetic system, which we ascribe to a more informative morphology in Hexactinellida. We find high support for a close relationship of glass sponges and Demospongiae sensu stricto, though the latter may be paraphyletic with respect to Hexactinellida. Homoscleromorpha appears to be the sister group of Calcarea. Contrary to most previous findings from rDNA, we recover Porifera as monophyletic, although support for this clade is low under paired-sites models.     

The sterols of calcareous sponges (Calcarea, Porifera)

Sponges are sessile suspension-feeding organisms whose internal phylogenetic relationships are still the subject of intense debate. Sterols may have the potential to be used as independent markers to test phylogenetic hypotheses. Twenty representative specimens of calcareous sponges (class Calcarea, phylum Porifera) with a broad coverage within both subclasses Calcinea and Calcaronea were analysed for their sterol content. Two major pseudohomologous series were found, accompanied by some additional sterols. The first series encompassing conventional C(27) to C(29)Delta(5,7,22) sterols represented the major sterols, with ergosterol (ergosta-5,7,22-trien-3beta-ol, C(28)Delta(5,7,22)) being most prominent in many species. The second series consisted of unusual C(27) to C(29)Delta(5,7,9(11),22) sterols. Cholesterol occurred sporadically, mostly in trace amounts. The sterol patterns did not resolve intraclass phylogenetic relationships, namely the distinction between the subclasses, Calcinea and Calcaronea. This pointed towards major calcarean lipid traits being established prior to the separation of subclasses. Furthermore, calcarean sterol patterns clearly differ from those found in Hexactinellida, whereas partial overlap occurred with some Demospongiae. Hence, sterols only partly reflect the phylogenetic separation of Calcarea from both of the other poriferan classes that was proposed by recent molecular work and fatty acid analyses.     

The fatty acids of calcareous sponges (Calcarea, Porifera)

Twenty-nine specimens of calcareous sponges (Class Calcarea, Phylum Porifera), covering thirteen representative species of the families Soleneiscidae, Leucaltidae, Levinellidae, Leucettidae, Clathrinidae, Sycettidae, Grantiidae, Jenkinidae, and Heteropiidae were analysed for their fatty acids. The fatty acids of Calcarea generally comprise saturated and monounsaturated linear (n-), and terminally methylated (iso-, anteiso-) C(14)-C(20) homologues. Furthermore, polyunsaturated C(22) fatty acids and the isoprenoic 4,8,12-trimethyltridecanoic acid were found. The most prominent compounds are n-C(16), iso-C(17), iso-C(18), n-C(18), n-C(20). In addition, a high abundance of the exotic 16-methyloctadecanoic acid (anteiso-C(19)) appears to be a characteristic trait of Calcarea. Long-chain 'demospongic acids', typically found in Demospongiae and Hexactinellida, are absent in Calcarea. The completely different strategy of calcarean fatty acid synthesis supports their phylogenetic distinctiveness from a common Demospongiae/Hexactinellida taxon. Both intraspecific and intraclass patterns of Calcarea showed great similarity, suggesting a conserved fatty acid composition that already existed in the last common ancestor of Calcinea and Calcaronea, i.e. before subclasses diverged.     

Euzkadiella erenoensis n. gen. n. sp. ein stromatopore mit spikulärem skelett aus dem oberapt von ereño (prov. guipuzcoa,nordspanien) und die systematische stellung der stromatoporen

Euzkadiella erenoensis n. gen. n. sp. from the Early Cretaceous of Ereño (Prov. Guipuzcoa, northern Spain) is the first known »stromatoporoid« with a spicular skeleton and a basal skeleton consisting of calcific spherulites. The stromatoporoid sponge shows subtylostyle, oxea and strongyle megascleres. Microscleres are unknown. The sclere arrangement appears as disorganized bundles connected by horizontal sclere bridges. This sclere arrangement is characteristic of the order Haplosclerida (Class Demospongiae, Subclass Ceractinomorpha). The new species is compared with the modern coralline spongesCalcifibrospongia andAstrosclera, and with the Mesozoic stromatoporoids of the families Milleporellidae and Actinostromariidae. In both subclasses of the Demospongiae and within the Class Calcarea stromatoporoid basal skeletons are observed. Therefore the subclass Stromatoporoidea does not exist as a true systematic unit.     

Phylogenetic Position of the Hexactinellida Within the Phylum Porifera Based on the Amino Acid Sequence of the Protein Kinase C from Rhabdocalyptus dawsoni

Recent analyses of genes encoding proteins typical for multicellularity, especially adhesion molecules and receptors, favor the conclusion that all metazoan phyla, including the phylum Porifera (sponges), are of monophyletic origin. However, none of these data includes cDNA encoding a protein from the sponge class Hexactinellida. We have now isolated and characterized the cDNA encoding a protein kinase C, belonging to the C subfamily (cPKC), from the hexactinellid sponge Rhabdocalyptus dawsoni. The two conserved regions, the regulatory part with the pseudosubstrate site, the two zinc fingers, and the C2 domain, as well as the catalytic domain were used for phylogenetic analyses. Sequence alignment and construction of a phylogenetic tree from the catalytic domains revealed that the yeast Saccharomyces cerevisiae and the protozoan Trypanosoma brucei are at the base of the tree, while the hexactinellid R. dawsoni branches off first among the metazoan sequences; the other two classes of the Porifera, the Calcarea (the sequence from Sycon raphanus was used) and the Demospongiae (sequences from Geodia cydonium and Suberites domuncula were used), branch off later. The statistically robust tree also shows that the two cPKC sequences from the higher invertebrates Drosophila melanogaster and Lytechinus pictus are most closely related to the calcareous sponge. This finding was also confirmed by comparing the regulatory part of the kinase gene. We suggest, that (i) within the phylum Porifera, the class Hexactinellida diverged first from a common ancestor to the Calcarea and the Demospongiae, which both appeared later, and (ii) the higher invertebrates are more closely related to the calcareous sponges. Received: 6 August 1997 / Accepted: 24 October 1997     

Non-monophyly of most supraspecific taxa of calcareous sponges (Porifera, Calcarea) revealed by increased taxon sampling and partitioned Bayesian analysis of ribosomal DNA

Calcareous sponges (Porifera, Calcarea) play an important role for our understanding of early metazoan evolution, since several molecular studies suggested their closer relationship to Eumetazoa than to the other two sponge 'classes,' Demospongiae and Hexactinellida. The division of Calcarea into the subtaxa Calcinea and Calcaronea is well established by now, but their internal relationships remain largely unresolved. Here, we estimate phylogenetic relationships within Calcarea in a Bayesian framework, using full-length 18S and partial 28S ribosomal DNA sequences. Both genes were analyzed separately and in combination and were further partitioned by stem and loop regions, the former being modelled to take non-independence of paired sites into account. By substantially increasing taxon sampling, we show that most of the traditionally recognized supraspecific taxa within Calcinea and Calcaronea are not monophyletic, challenging the existing classification system, while monophyly of Calcinea and Calcaronea is again highly supported.     

Sponge paraphyly and the origin of Metazoa

In order to allow critical evaluation of the interrelationships between the three sponge classes, and to resolve the question of mono‐ or paraphyly of sponges (Porifera), we used the polymerase chain reaction (PCR) to amplify almost the entire nucleic acid sequence of the 18S rDNA from several hexactinellid, demosponge and calcareous sponge species. The amplification products were cloned, sequenced and then aligned with previously reported sequences from other sponges and nonsponge metazoans and variously distant outgroups, and trees were constructed using both neighbour‐joining and maximum parsimony methods. Our results suggest that sponges are paraphyletic, the Calcarea being more related to monophyletic Eumetazoa than to the siliceous sponges (Demospongiae, Hexactinellida). These results have important implications for our understanding of metazoan origins, because they suggest that the common ancestor of Metazoa was a sponge. They also have consequences for basal metazoan classification, implying that the phylum Porifera should be abandoned. Our results support the upgrading of the calcareous sponge class to the phylum level.     

Locomotion and contraction in an asconoid calcareous sponge

Various large‐scale behaviors (e.g., locomotion, shape changes, contractions) have been documented numerous times in intact sponges of the class Demospongiae. However, little is known about such motile events in calcareous sponges (Class Calcarea). Here, we report on whole‐sponge behaviors of the calcareous asconoid sponge Leucosolenia botryoides, as revealed by time‐lapse videos. These behaviors included locomotion and contraction. Locomotion in these sponges appeared as an outward movement (25–130 μm h^?1) of the asconoid tubes away from the sponge's center; such translocations were always accompanied by extensive movements of protruding spicules, which appear to act as anchoring hooks for the sponge's translocations. This is the first report of whole‐sponge locomotion in the Calcarea. Contractile waves also were propagated in these sponges at speeds of 50–150 μm h^?1, and they involved systemic contraction, then re‐extension of the asconoid tubes. The observations suggest that, like the more complex demosponges, these simple calcareous sponges are capable of adaptive whole‐animal behaviors (changes in flow, shape, and location), which occur in response to environmental stimuli such as crawling intruders.     

The choanoderm of Sycettusa hastifera (Calcarea,Porifera) is able to generate new individuals

One of the main characteristics of sponges is their capacity for cell dedifferentiation. This capability can allow an impressive amount of asexual reproduction in these animals, because they are able to develop new individuals from just a few somatic cells. Studies of dedifferentiation, however, have focused mainly on sponges of the class Demospongiae. Therefore, we investigated here whether individuals of three different species of Calcarea are able to reconstitute new individuals following artificial fragmentation. We observed that fragmentation releases clumps of choanoderm able to initiate somatic embryogenesis. In Borojevia brasiliensis (asconoid aquiferous system, subclass Calcinea) and Paraleucilla magna (leuconoid aquiferous system, subclass Calcaronea), these clumps started to develop, but they did not pass through the first developmental phases. In Sycettusa hastifera (syconoid aquiferous system, subclass Calcaronea), the choanoderm was reorganized into primmorphs that fused to each other and formed an exopinacoderm. The first primmorphs’ spicules were triactines. Despite a large mortality rate, the primmorphs developed into olynthus stages. The somatic embryogenesis and the metamorphosis of the olynthus were similar to those observed during the sexual development of this and other calcareous sponge species. Our results show that in S. hastifera, and perhaps in other syconoid calcareous sponges, somatic embryogenesis occurs mainly from choanocytes, at least in vitro. However, primmorph development does not follow the same pattern observed in post‐metamorphic sexual development, as in that case diactines are always the first spicules to be synthesized in calcaronean species.     

First evaluation of mitochondrial DNA as a marker for phylogeographic studies of Calcarea: a case study from Leucetta chagosensis

In most animals mitochondrial DNA (mtDNA) evolves much faster than nuclear DNA. Therefore, and because of its shorter coalescent time, mitochondrial (mt) markers provide better resolution to trace more recent evolutionary events compared to nuclear DNA. But in contrast to most other Metazoa, previous studies suggested that in sponges mitochondrial sequence evolution is much slower, making mtDNA less suitable for studies at the intraspecific level. However, these observations were made in the class Demospongiae and so far no data exist for calcareous sponges (Class Calcarea). We here provide the first study that evaluates intraspecific mt sequence variation in Calcarea. We focus on arguably the best-studied species Leucetta chagosensis, for which three nuclear DNA marker datasets existed previously. We here sequenced the partial mitochondrial cytochrome oxidase subunit III gene (cox3). Our analyses reveal an unexpected variability of up to 8.5% in this mitochondrial marker. In contrast to other sponges where this marker evolves considerable slower than the nuclear internal transcribed spacer region (ITS), we found that cox3 in L. chagosensis evolves about five times as fast as ITS. The variability is similar to that of nuclear intron data of the species. The phylogeny inferred with cox3 is congruent with other markers, but separates earlier reported genetic groups much more distinctively than nuclear DNA. This provides further evidence for cryptic speciation in L. chagosensis. All these features make calcarean mtDNA exceptional among sponges and show its suitability for phylogeographic studies and potential as a species-specific (DNA barcoding) marker to distinguish morphologically identical cryptic species.     

Sponge communities of the Antarctic Peninsula: influence of environmental variables on species composition and richness

Sponge communities on the Antarctic continental shelf currently represent one of the most extensive sponge grounds in the world, and all sponge classes are known to occur in the Southern Ocean. Main objectives of this study conducted at the tip of the Antarctic Peninsula were (1) to identify all sampled sponges and (2) to investigate whether the species composition and species richness of Southern Ocean sponge communities in the area of the Antarctic Peninsula are significantly influenced by environmental variables. The studied material originated from 25 AGT catches and was sampled during the expedition ANT-XXIX/3 of RV Polarstern. Samples were collected in three large-scale areas in the vicinity of the Antarctic Peninsula: Bransfield Strait, Drake Passage and Weddell Sea. The following six environmental variables were measured from bottom water samples (except for sea-ice cover): depth (m), light transmission (%), oxygen (µmol/kg), salinity, sea-ice cover (%) and temperature (°C). Two hundred and sixty-three sponge samples were analyzed, and 81 species of 33 genera from all Porifera classes (Calcarea, Demospongiae, Hexactinellida and Homoscleromorpha) were identified. Total numbers of sponge species per sample station ranged from 1 to 29. A detrended correspondence analysis and a backward-stepwise model selection were performed to check whether species composition and richness were significantly influenced by environmental variables. The analyses revealed that none of the measured environmental variables significantly influenced species composition but that species richness was significantly influenced by (1) temperature and (2) the combination of temperature and depth. Results of this study are of crucial importance for development, performance and assessment of future protection strategies in case of ongoing climatic changes at the Antarctic Peninsula.     

ADP-ribosyl cyclase and abscisic acid are involved in the seasonal growth and in post-traumatic tissue regeneration of Mediterranean sponges

In previous papers it has been demonstrated that the plant hormone abscisic acid (ABA) is responsible for the stimulation of water filtration and oxygen consumption elicited by a temperature increase in the Mediterranean demosponge Axinella polypoides. The signal transduction pathway triggered by ABA involves activation of ADP-ribosyl cyclase (ADPRC), leading to an increase of the intracellular concentration of cyclic ADP-ribose (cADPR), a universal and potent intracellular calcium mobilizer. These data prompted us to investigate the possible involvement of the ABA/ADPRC/cADPR system in the sponge life cycle and in post-traumatic tissue regeneration of Mediterranean sponges. ADPRC activity was detected in the cell lysate from several common Mediterranean sponge species, including Calcarea and Demospongiae. Specimens were collected monthly over a 2-year period, from January 2002 to April 2004. All species studied showed a peak of ADPRC activity during July and August 2003, concomitant with an anomalous heat wave that struck the whole Mediterranean basin during these months. In the aquarium, during spontaneous tissue regeneration, an increase of the [ABA]_i and of the ADPRC activity over time zero values was consistently observed. In conclusion, these results indicate that an increase of ABA content and of ADPRC activity correlates with the growth and with post-traumatic tissue regeneration in several Mediterranean sponge species, indicating that the ABA/ADPRC/cADPR system is involved in the response to environmental stress in sponges. Determination of ADPRC activity/ABA content may provide a means to assess metabolic activation of sponge populations under conditions of environmental stress.     

Fatty acid composition and the classification of the Porifera

Investigation of the fatty acid profiles of 55 species of Porifera has confirmed the occurrence of high percentages of both long chain fatty acids (C₂₄-C₃₀) and polyunsaturated acids. These features of the fatty acid profile in conjunction with the content of branched chain acids and the dominance of particular acids in different species allow some systematic discussion. The Dictyoceratida, Clathriidae, Halichondrida, Homoscleromorpha and Calcarea are distinguished by aspects of their fatty acid profiles. The diversity in number and type of sponge fatty acids exceeds that of any other phylum. Environmentally induced variation in fatty acid content is such that percentage compositions alone have little taxonomic informational value.     

Contribution of sponge genes to unravel the genome of the hypothetical ancestor of Metazoa (Urmetazoa)

Recently the term Urmetazoa, as the hypothetical metazoan ancestor, was introduced to highlight the finding that all metazoan phyla including the Porifera (sponges) are derived from one common ancestor. Sponges as the evolutionarily oldest, still extant phylum, are provided with a complex network of structural and functional molecules. Analyses of sponge genomes from Demospongiae (Suberites domuncula and Geodia cydonium), Calcarea (Sycon raphanus) and Hexactinellida (Aphrocallistes vastus) have contributed also to the reconstruction of the evolutionary position of Metazoa with respect to Fungi. Furthermore, these analyses have provided evidence that the characteristic evolutionary novelties of Metazoa, such as the extracellular matrix molecules, the cell surface receptors, the nervous signal transduction molecules as well as the immune molecule existing in Porifera, share high sequence and in some aspects also functional similarities to related polypeptides found in other metazoan phyla. During the transition to Metazoa new domains occurred; as one example, the formation of the death domain from the ankyrin is outlined. In parallel, domanial proteins have been formed, such as the receptor tyrosine kinases. The metazoan essentials have been defined by analyzing and comparing the sponge sequences with the related sequences from the metazoans Homo sapiens, Caenorhabditis elegans and Drosophila melanogaster, the fungus Saccharomyces cerevisiae and the plant Arabidopsis thaliana. The data revealed that those sponge molecules grouped to cell adhesion cell recognition proteins are predominantly found in Protostomia and Deuterostomia while they are missing in Fungi and Viridiplantae. Moreover, evidence is presented allowing the conclusion that the sponge molecules are more closely related to the corresponding molecules from H. sapiens than to those of C. elegans or D. melanogaster. Especially surprising was the finding that the Demospongiae are provided with elements of adaptive immunity.     

Copepods of the genus Asterocheres (Copepoda: Siphonostomatoida) feeding on sponges: behavioral and ecological traits

Abstract. Four copepod species of the genus Asterocheres (A. echinicola, A. latus, A. suberitis and A. complexus ) are recorded for the first time as associated with Mediterranean sponges of the classes Calcarea and Demospongiae (orders Dictyoceratida, Dendroceratida, and Poecilosclerida). Individuals of A. suberitis are described for the first time as inhabiting sponges other than Suberites domuncula . The copepods seemed to use their trunk to suck the material (cuticles or excreted cells) produced at the sponge periphery (ectosome), which indicates that their feeding habits are similar to those observed in species of the same genus that feed on exfoliated tissues of echinoderms. In the laboratory, copepods fed on young sponges (rhagons) of the species Crambe crambe, Cacospongia mollior , and Dysidea avara without reducing the rhagon biomass. In contrast, rhagons of the species Haliclona sp., Hymedesmia spp., and Phorbas tenacior were consumed and their biomass reduced. This may be because the latter group does not produce external proteinaceous material. Copepod offspring were continuously released (∼6 nauplii every 48 h) and the larval stages were capable of limited swimming. We found significantly more copepods over the surface of the sponges than inside them. Copepod abundance was positively correlated with the sponge surface area while not with the sponge biomass. These results indicate that the copepods live preferentially over the sponge surface and that their abundance is surface-area dependent. The behavioral traits described here indicate that the interactions between asterocherid species and sponges are worthy of future study.     

Living on the edge: the sponge fauna of Australia’s southwestern and northwestern deep continental margin

This first assessment of sponges on Australia’s deep western continental margin (100–1,100 m) found that highly species-rich sponge assemblages dominate the megabenthic invertebrate biomass in both southwestern (86%) and northwestern (35%) areas. The demosponge orders Poecilosclerida, Dictyoceratida, Haplosclerida, and Astrophorida are dominant, while the presence of the order Agelasida, lithistid sponges, and the Verongida are noteworthy in providing contrasts to other studies from the deep temperate Australian margin. Most sponge species appeared to be rare as two-thirds were present in only one or two samples—a finding consistent with studies of the shallow Australian sponge fauna. The Demospongiae and Calcarea had similar distribution and abundance patterns being found in the greatest numbers in the south on the outer shelf and shelf edge in hard substrates. In contrast, the Hexactinellida were more abundant at deeper depths and in soft substrates, and were more common in the north. Although the environmental factors that influence sponge distributions on the western margin cannot be completely understood from the physical covariates analyzed in this study, the data suggest depth-related factors, substrate type, and current regimes are the most influential. Incompletely documented historic demersal trawling may partly account for the lower sponge biomass found in the north. The potentially high importance of sponges to benthic ecosystems, as well as the potential for high impacts on sponges by bottom trawling, indicates that maintaining healthy sponge assemblages should be an important consideration for marine conservation planners. Successful management will need to be under-pinned by additional research that better identifies the ecological roles of sponges, and their distributions over local and broad environmental scales.     

Fatty Acids and Other Lipids of Marine Sponges

At the present, the structure of lipids and fatty acids (FA) of almost 250 species of marine sponges has been studied. It was shown that sponges are leaders in FA diversity among aquatic animals. The great majority of the works on research of FA structure in sponges was focused on representatives of the class Demospongiae and was carried out on organisms from tropical and subtropical areas, whereas sponges from the boreal region remain poorly studied.     

An evaluation of support for order-level monophyly and interrelationships within the class Demospongiae using partial data from the large subunit rDNA and cytochrome oxidase subunit I

Large subunit ribosomal DNA (LSU rDNA) sequence data from 120 taxa and cytochrome oxidase subunit 1(COI) sequence data from 27 taxa are analyzed separately and together to estimate the internal phylogeny of the class Demospongiae and to evaluate how consistent these data are with pre-existing hypotheses of relationship concerning order-level monophyly and relationships. The monophyly of Porifera is only slightly inconsistent with LSU data, which do not support the monophyly of the class Demospongiae regardless of the inclusion or exclusion of Homoscleromopha (this result is likely due to the placement of a single hexactinellid taxon within the Demospongiae), however, no LSU support is found for the monophyly of Silicea (Demospongiae+Hexactinellida) unless homoscleromorphs are excluded. Neither the subclasses Ceractinomorpha and Tetractinomorpha, nor the orders Halichondrida, Hadromerida, and Haplosclerida are supported as monophyletic under any data partition. The haplosclerid suborders Haplosclerina and Petrosina are supported as monophyletic to the exclusion of the suborder Spongillina, and the orders Dictyoceratida, Verongida, Poecilosclerida, Astrophorida, Spirophorida, Homosclerophorida, and Agelasida are largely reconstructed as monophyletic, with the exception of few anomalously placed taxa. Few inter-order relationships are strongly supported by any data partition, but there is moderate support for a verongid+chondrosid clade and a tetractinellid+halichondrid clade. Furthermore, LSU data strongly support the existence of two novel clades that do not correspond to the existing classification and that show no morphological uniformity. Finally, every data partition supports the monophyly of a clade that includes the order Agelasida, some members of the genus Axinella, and two taxa tentatively identified as belonging to the orders Hadromerida and Halichondrida.