Living inside a sponge skeleton: the association of a sponge,a macroalga and a diatom

The relationships between sponges and macroalgae have been poorly investigated, especially in temperate waters. This work describes the consortium between the dictyoceratid sponge Dysidea pallescens and the red alga Acrochaetium spongicola permeating spongin fibres in the Mediterranean Sea; moreover, this is the first report of a diatom, Amphora pediculus, living also inside the spongin skeleton. The annual trend of the total algal biomass did not vary over time in relation to the temperature, irradiance and incorporation of foreign bodies. Our analyses, conducted by light and electron microscopy, suggest that both the macroalga and the diatom invade the skeleton of the sponge from the external environment, and that the benthic diatom, epiphyte of the macroalga, is passively carried inside the fibres through the growth of Acrochaetium spongicola. All the examined samples of D. pallescens showed that the macroalga permeated at least some fibres, while the presence of the diatom was occasional. The superficial layer of the sponge, thin and reticulate, likely allows the passage of the light and ensures the algal survival inside the sponge tissue. The high occurrence of the association with A. spongicola, together with the morphological adaptations of the sponge favouring the algal life, suggest that the relationship is mutualistic. The possible benefits for the involved partners are hypothesized. The taxonomy and ecology of endozoic Acrochaetiales are controversial due to the reduced size of thalli, the absence of peculiar diagnostic characters and unknown reproductive structures. Therefore, detailed studies on the relationships between the algae and their hosts will provide helpful information for the algal identification.     

Metagenomic Analysis of Genes Encoding Nutrient Cycling Pathways in the Microbiota of Deep-Sea and Shallow-Water Sponges

Sponges host complex symbiotic communities, but to date, the whole picture of the metabolic potential of sponge microbiota remains unclear, particularly the difference between the shallow-water and deep-sea sponge holobionts. In this study, two completely different sponges, shallow-water sponge Theonella swinhoei from the South China Sea and deep-sea sponge Neamphius huxleyi from the Indian Ocean, were selected to compare their whole symbiotic communities and metabolic potential, particularly in element transformation. Phylogenetically diverse bacteria, archaea, fungi, and algae were detected in both shallow-water sponge T. swinhoei and deep-sea sponge N. huxleyi, and different microbial community structures were indicated between these two sponges. Metagenome-based gene abundance analysis indicated that, though the two sponge microbiota have similar core functions, they showed different potential strategies in detailed metabolic processes, e.g., in the transformation and utilization of carbon, nitrogen, phosphorus, and sulfur by corresponding microbial symbionts. This study provides insight into the putative metabolic potentials of the microbiota associated with the shallow-water and deep-sea sponges at the whole community level, extending our knowledge of the sponge microbiota’s functions, the association of sponge- microbes, as well as the adaption of sponge microbiota to the marine environment.     

Biodiversity of <Emphasis Type="Italic">Spongosorites coralliophaga</Emphasis> (Stephens, 1915) on coral rubble at two contrasting cold-water coral reef settings

Cold-water coral reefs (CWRs) in the northeast Atlantic harbor diverse sponge communities. Knowledge of deep-sea sponge ecology is limited and this leaves us with a fragmented understanding of the ecological roles that sponges play in CWR ecosystems. We present the first study of faunal biodiversity associated with the massive demosponge Spongosorites coralliophaga (Stephens, 1915) that typically colonizes coral debris fields of CWRs. Our study focused on the sessile fauna inhabiting sponges mixed with coral rubble at two contrasting settings in the northeast Atlantic: the shallow inshore (120–190 m water depth) Mingulay Reef Complex (MRC) and the deep offshore (500–1200 m) Logachev Mound (LM) coral province. MRC is dominated by the scleractinian Lophelia pertusa, while LM is dominated by L. pertusa and Madrepora oculata. Nine sponge–coral rubble associations were collected from MRC and four from LM. Measurements of abundance, species richness, diversity, evenness, dry biomass, and composition of sessile fauna on sponge and coral rubble microhabitats were undertaken. Differences in community composition between the two regions were mainly a response to changes in fauna with depth. Fauna composition was also different between sponge and coral rubble within each region. Infauna constituted a minor component of the sponge-associated fauna in MRC but had a higher contribution in LM. Sponge and coral rubble sessile fauna in both regions was mainly composed of cnidarians and molluscs, similarly to some previous studies. Sponges’ outer surfaces at MRC were colonized by a species-rich community with high abundance and biomass suggesting that S. coralliophaga at MRC acts as a settlement surface for various organisms but such a role is not the case at LM. This difference in the role of S. coralliophaga as a biological structure is probably related to differences in fauna composition with depth, bottom current speed, and the quantity/quality of food supplied to the benthos.     

The first case of disease of the sponge <Emphasis Type="Italic">Lubomirskia baicalensis</Emphasis>: Investigation of its microbiome

The first metagenomic analysis of the microbiome of the first sample of diseased endemic sponge Lubomirskia baicalensis (Pallas, 1771) from Lake Baikal and the comparison of the results with data published earlier on the microbiome of healthy sponges were carried out. Essential changes in the composition and structure of the microbial community were detected in the diseased individual possessing an uncharacteristic pink coloring. Cyanobacteria were predominant in the community, the fraction of the representatives of Verrucomicrobia was increased. The diversity and number of eukaryotic algae, as well as of representatives of Bacteroidetes, Proteobacteria, Actinobacteria, and Planctomycetes, were decreased. A wide range of minor phyla were eliminated. The factors affecting the composition of symbiotic communities in sponges were considered. It was supposed that changes in the structure of symbiotic communities resulting in mass disease and death could be caused by an increase in the methane concentration in the water column of Lake Baikal.     

Host location and selection by the symbiotic sargassum crab <Emphasis Type="Italic">Portunus sayi</Emphasis>: the role of chemical,visual and tactile cues

The Sargassum community consists of a unique and diverse assemblage of symbiotic fauna critical to pelagic food chains. Associated symbionts presumably have adaptations to assist in finding Sargassum. In situ scattered Sargassum patches accumulate as they are pushed toward the shoreline (via wind, waves, currents or tides) and are frequently less than 1 m apart and in depths of 10 cm or less as the patches approach the shoreline Crabs, and other symbiotic fauna, must relocate to another patch that is seaward in direction or likely perish as their current patch will likely become beached. This study investigated sensory cues used for host location and selection by the Sargassum crab, Portunus sayi. Chemical detection trials were conducted with a two-chamber choice apparatus with Sargassum spp. and Thalassia testudinum as habitat source odors. Visual detection trials (devoid of chemical cues) and habitat selection trials were conducted in which crabs were given a choice between hosts. Results showed that P. sayi responded to chemicals from Sargassum spp. Crabs visually located host habitats but did not visually distinguish between different hosts. In host selection trials, crabs selected Sargassum spp. over artificial Sargassum and T. testudinum. These results suggest that crabs isolated from Sargassum likely use chemoreception; within visual proximity of a potential patch, crabs likely use both chemical and visual information.     

The potential of azooxanthellate poriferan hosts to assess the fundamental and realized <Emphasis Type="Italic">Symbiodinium</Emphasis> niche: evaluating a novel method to initiate <Emphasis Type="Italic">Symbiodinium</Emphasis> associations

On coral reefs, Symbiodinium spp. are found in most cnidarian species, but reside in only a small number of sponge species. Of the sponges that do harbor Symbiodinium, most are found in the family Clionaidae, which represents a minor fraction of the poriferan diversity on a reef. Our goal was to determine whether Symbiodinium can be taken up by sponge hosts that do not typically harbor these algal symbionts, and then to follow the fate of any Symbiodinium that enter the intracellular space. We used the filter-feeding capacity of sponges to initiate intracellular interactions between sponge-specialist clade G Symbiodinium and six sponge species that do not associate with Symbiodinium. Using a pulse-chase experimental design, we determined that all of the species we examined captured Symbiodinium, and undamaged intracellular algae were found up to 1 h after inoculation. In a longer-term experiment, Symbiodinium populations in Amphimedon erina persisted in sponge cells for at least 5 d post-inoculation. While no evidence of digestion was detected, the population decreased exponentially after inoculation. We contrast these data with the characteristics of symbiont acquisition and establishment in Cliona varians, which normally harbors Symbiodinium. Explants from experimentally derived aposymbiotic sponges were placed in the field where they acquired Symbiodinium from ambient sources (i.e., we did not inoculate them as in the pulse-chase experiments). We began to detect Symbiodinium cells in C. varians after 12 d, and the algal population increased exponentially until densities approached those typically found in this host (after ~128 d). We discuss the implications of this work in light of growing interest in the evolution of specificity between hosts and symbionts, and the fundamental and realized niche of Symbiodinium.     

Upper Triassic (Norian) hypercalcified sponges from the Musandam Peninsula (United Arab Emirates and Oman)

Supercalcified sponges, including sphinctozoans, inozoans, chaetetids, spongiomorphids, occurring in Upper Triassic (Norian-Rhaetian) shallow-marine limestones of Musandam Mountains in United Arab Emirates (UAE), are described. The following taxa were determined: sphinctozoans: Hajarispongia osmani Senowbari-Daryan and Yancey, Nevadathalamia arabica n. sp., Nevadathalamia conica n. sp., Fanthalamia milahaensis n. sp., Iranothalamia incrustans (Boiko), Cinnabaria regularis n. sp.; inozoans: Cavsonella triassica n. sp., Molengraaffia regularis Vinassa de Regny, Peronidella? sp., Circopora cf. caucasica Moiseev, Circopora? sp.; spongiomorphids: Spongiomorpha sp.; chaetetids: Lovcenipora chaetetiformis Vinassa de Regny, Lovcenipora musandamensis n. sp., Lovcenipora sp., chaetetid sponge gen. et sp. indet. The most abundant sponge in the studied material is Nevadathalamia arabica n. sp. The described sponge association of the Arabian shelf (Musandam Mountains) shows close affinity to the sponge association known from age-equivalent terranes in the Panthalassa Ocean (Sonora Mountains in Mexico; Pilot Mountains in Nevada, USA), but is remarkably different from sponge associations in carbonates bordering the Tethys. This difference goes along with the biogeography of wallowaconchid bivalves and is most likely attributed to climatic, palaeogeographic or oceanographic factors.     

Biological Characterisation of <Emphasis Type="Italic">Haliclona</Emphasis> (?<Emphasis Type="Italic">gellius</Emphasis>) sp.: Sponge and Associated Microorganisms

We have characterised the northern Pacific undescribed sponge Haliclona (?gellius) sp. based on rDNA of the sponge and its associated microorganisms. The sponge is closely related to Amphimedon queenslandica from the Great Barrier Reef as the near-complete 18S rDNA sequences of both sponges were identical. The microbial fingerprint of three specimens harvested at different times and of a transplanted specimen was compared to identify stably associated microorganisms. Most bacterial phyla were detected in each sample, but only a few bacterial species were determined to be stably associated with the sponge. A sponge-specific β- and γ-Proteobacterium were abundant clones and both of them were present in three of the four specimens analysed. In addition, a Planctomycete and a Crenarchaea were detected in all sponge individuals. Both were closely related to operational taxonomic units that have been found in other sponges, but not exclusively in sponges. Interestingly, also a number of clones that are closely related to intracellular symbionts from insects and amoeba were detected.     

Microbial community of freshwater sponges in Lake Baikal

The microbial community of Baikal sponges has been studied in five species belonging to the genera Swartschewskia, Baicalospongia, and Lubomirskia of the endemic family Lubomirskiidae. The results show that the total numbers of bacteria and bacterioplankton production have an effect on the growth of L. baicalensis body. Bacteria of the genera Pseudomonas, Bacillus, Micrococcus, Sarcina, Flavobacterium, Arthrobacter, and Acinetobacter living in the sponges are representatives of the Baikal bacterioplankton. Actinomycetes of the genera Streptomyces and Micromonospora are a permanent component of the cultivable sponge microbial community. The numbers and enzyme activities of heterotrophic, oligotrophic, and psychrophilic bacteria isolated from different sponge species and from the ambient water in autumn and in winter have been estimated.     

Screening of the Antarctic marine sponges (Porifera) as a source of bioactive compounds

Sponges (Porifera) currently represent one of the richest sources of natural products and account for almost half of the pharmacologically active compounds of marine origin. However, to date very little is known about the pharmacological potential of the sponges from polar regions. In this work we report on screening of ethanolic extracts from 24 Antarctic marine sponges for different biological activities. The extracts were tested for cytotoxic effects against normal and transformed cell lines, red blood cells, and algae, for modulation of the activities of selected physiologically important enzymes (acetylcholinesterase, butyrylcholinesterase, and α-amylase), and for inhibition of growth of pathogenic and ecologically relevant bacteria and fungi. An extract from Tedania (Tedaniopsis) oxeata was selectively cytotoxic against the cancer cell lines and showed growth inhibition of all of the tested ecologically relevant and potentially pathogenic fungal isolates. The sponge extracts from Isodictya erinacea and Kirkpatrickia variolosa inhibited the activities of the cholinesterase enzymes, while the sponge extracts from Isodictya lankesteri and Inflatella belli reduced the activity of α-amylase. Several sponge extracts inhibited the growth of multiresistant pathogenic bacterial isolates of different origins, including extended-spectrum beta-lactamase and carbapenem-resistant strains, while sponge extracts from K. variolosa and Myxilla (Myxilla) mollis were active against a human methicillin-resistant Staphylococcus aureus strain. We conclude that Antarctic marine sponges represent a valuable source of biologically active compounds with pharmacological potential.     

Metatrancriptomic analysis from the Hepatopancreas of adult white leg shrimp (<Emphasis Type="Italic">Litopenaeus vannamei)</Emphasis>

The amoeba, Mayorella viridis contains several hundred symbiotic green algae in its cytoplasm. Transmission electron microscopy revealed strong resemblance between symbiotic algae from M. viridis the symbiotic Chlorella sp. in the perialgal vacuoles of Paramecium bursaria and other ciliates. Although it is thought that the M. viridis and symbiotic algae could be model organisms for studying endosymbiosis between protists and green algae, few cell biological observations of the endosymbiosis between M. viridis and their symbiotic algae have been published. In this study, we characterized the specificity of endosymbiotic relationships between green algae and their hosts. Initially, we established stable cultures of M. viridis in KCM medium by feeding with Chlorogonium capillatum. Microscopic analyses showed that chloroplasts of symbiotic algae in M. viridis occupy approximately half of the algal cells, whereas those in P. bursaria occupy entire algal cells. The symbiotic algae in P. bursaria contain several small spherical vacuoles. The labeling of actin filaments using Acti-stain? 488 Fluorescent Phalloidin revealed no relationship between host actin filaments and symbiotic algal localization, although the host mitochondria were localized around symbiotic algae. Symbiotic algae from M. viridis could infect algae-free P. bursaria but could not support P. bursaria growth without feeding, whereas the original symbiotic algae of P. bursaria supported its growth without feeding. These data indicated the specificity of endosymbiotic algae relationships in M. viridis and P. bursaria.     

Transformation of Baikal sponges (family Lubomirskiidae) after penetration into the Angara River

Genetic and morphological analysis of endemic sponges of the Lubomirskiidae family from Lake Baikal and the upper reaches of the Angara River was performed. Various sponge species acquired a number of similar morphological traits after the transition from the lake into the river. These traits enabled an increase of sponge skeleton strength under the conditions of elevated hydrodynamic activity. The changes significantly impeded morphology-based species identification of Angara sponges. Phylogenetic analysis of ITS regions and noncoding mitochondrial DNA fragments confirmed that the Angara sponges belonged to the Baikalian Lubomirskiidae family and demonstrated the polyphyletic origin of the sponges. The use of combined molecular and morphological data allowed for the clustering of some sponge samples into groups that corresponded to individual species. The absence of genetic isolation between the Baikalospongia intermedia and Lubomirskia baicalensis species was demonstrated, whereas the B. intermedia profundalis subspecies was well separated from B. intermedia. This finding pointed to the necessity of further studies for the clarification of the taxonomic status of this subspecies.     

The species composition and ecological features of pea crabs of the genus <Emphasis Type="Italic">Pinnixa</Emphasis> White, 1846 (Brachyura: Pinnotheridae) in Peter the Great Bay,the Sea of Japan

This paper provides an overview of pea crabs of the genus Pinnixa White, 1846 (Brachyura: Pinnotheridae) that occur along the Russian coast of the Sea of Japan. Three species of the genus have been recorded for this area: P. tumida Stimpson, 1858, P. rathbuni Sakai, 1934, as well as P. banzu Komai, Nishi & Taru, 2014, which is the first record for the fauna of Russia. All species clearly differ ecologically: P. tumida was found in Posyet Bay in the intestine of the burrowing holothurian Paracaudina chilensis (Müller, 1850); P. rathbuni, in burrows of the echiuroid Urechis unicinctus (von Drasche, 1881); and P. banzu, in tubes of the polychaete Chaetopterus cautus Marenzeller, 1879. The paper also provides a definitive key to Pinnixa species and data on the size, behavior, symbionts, and parasites of P. rathbuni and P. banzu.     

Diversity in symbiont consortia in the pea aphid complex is associated with large phenotypic variation in the insect host

Virtually all eukaryotes host microbial symbionts that influence their phenotype in many ways. In a host population, individuals may differ in their symbiotic complement in terms of symbiont species and strains. Hence, the combined expression of symbiont and host genotypes may generate a range of phenotypic diversity on which selection can operate and influence host population ecology and evolution. Here, we used the pea aphid to examine how the infection with various symbiotic complements contributes to phenotypic diversity of this insect species. The pea aphid hosts an obligate symbiont (Buchnera aphidicola) and several secondary symbionts among which is Hamiltonella defensa. This secondary symbiont confers a protection against parasitoids but can also reduce the host’s longevity and fecundity. These phenotypic effects of H. defensa infection have been described for a small fraction of the pea aphid complex which encompasses multiple plant-specialized biotypes. In this study, we examined phenotypic differences in four pea aphid biotypes where H. defensa occurs at high frequency and sometimes associated with other secondary symbionts. For each biotype, we measured the fecundity, lifespan and level of parasitoid protection in several aphid lineages differing in their symbiotic complement. Our results showed little variation in longevity and fecundity among lineages but strong differences in their protection level. These differences in protective levels largely resulted from the strain type of H. defensa and the symbiotic consortium in the host. This study highlights the important role of symbiotic complement in the emergence of phenotypic divergence among host populations of the same species.     

Nitrification in intertidal sponge <Emphasis Type="Italic">Cinachyrella cavernosa</Emphasis>

The nitrification process in different sections of the sponges remains unresolved, despite several studies on the nitrogen cycling pathways in the tissues of temperate and Arctic sponges. In this study, the abundance, diversity and activity of the associated nitrifying organisms in intracellular, intercellular, extracellular and cortex of a tropical intertidal sponge, Cinachyrella cavernosa, were investigated using most probable number, next-generation sequencing and incubation method, respectively. The nitrification rate and the abundance of nitrifying bacteria showed significant difference among different sections. The nitrification rate in C. cavernosa was 2–12× higher than the reported values in other sponge species from temperate and Arctic regions. Nitrification rate in sponge cortex was 2× higher than in intercellular and extracellular sections. Ammonium and nitrite oxidisers ranged from 10³ to 10⁴ CFU g^?1 in the sponge with a high number of ammonium and nitrite oxidisers in the cortex. Nitrifiers belonging to Nitrosomonas, Nitrospira, Nitrospina, Nitrobacter and Nitrosopumilus were present in different sections of the sponge, with nitrifying archaea dominating the intracellular section and nitrifying bacteria dominating other sections. This study reports for the first time the nitrification inside the sponge cells. The study also suggests that the intertidal sponge, C. cavernosa, harbours metabolically active nitrifiers in different sections of the sponge body with different rates of nitrification. Thus, nitrifiers play an important role in ammonia detoxification within the sponge and also contribute to the nitrogen budget of the coastal ecosystem.     

The Role of Epibionts of Bacteria of the Genus <Emphasis Type="Italic">Pseudoalteromonas</Emphasis> and Cellular Proteasomes in the Adaptive Plasticity of Marine Cold-Water Sponges

It was found that cells of different color morphs of the cold-water marine sponges Halichondria panicea (Pallas, 1766) of the class Demospongiae differ in the content of epibionts of bacteria of the genus Pseudoalteromonas. The sponge cells with elevated levels of epibionts of bacteria of the genus Pseudoalteromonas showed an increased expression of Hsp70 proteins but had a reduced level of the proteasomal catalytic beta 5 subunit, which was accompanied by a change in their activity. Probably, epibionts of bacteria of the genus Pseudoalteromonas may affect the ubiquitin–proteasome system in the cells of cold-water marine sponges and, thereby, ensure their adaptive plasticity.     

Sponges from the Permian of Hambast Mountains,south of Abadeh,central Iran

Upper Permian (Murghabian) sponges from the Surmaq Formation exposed in the Hambast Mountains, south of Abadeh, central Iran are described. The sponge fauna of the Surmaq Formation is composed of at least 26 taxa, including 12 species of sphinctozoans, 12 species of inozoans, one operculospongid, and one lithistid species. The following taxa were determined to genus or species level: Sphinctozoa: Family Sebargasiidae: Amblysiphonella hambastensis n. sp., Discosiphonella iranica n. sp., Family Colospongiidae: Colospongia cortexifera Senowbari-Daryan and Rigby, Exaulipora permica (Senowbari-Daryan), Platythalamiella sp. 1, Platythalamiella? sp. 2, Parauvanella minima Senowbari-Daryan, Colospongia? or Neoguadalupia? sp., Family Guadalupiidae: Cystothalamia surmaqensis n. sp., Imbricatocoelia cf. paucipora Rigby, Fan and Zhang, Family Thaumastocoeliidae: Sollasia ostiolata Steinmann, Family Cryptocoeliidae: Stylocoelia circopora Wu. Inozoa: Family Peronidellidae: Preperonidella cf. Preperonidella recta grossa (Wu), Heptatubispongia symmetrica Rigby and Senowbari-Daryan, Hambastella sincassa n. gen., n. sp., Hambastella cumcassa n. sp., Family Maeandrostiidae: Maeandrostia kansasensis Girty, Maeandrostia? dubia n. sp., Surmaqella pustulata n. gen., n. sp., Family Auriculospongiidae: Pseudopalaeoaplysina huayingensis Wang, Qiang and Zhang, Family Disjectoporidae: Disjectopora beipeiensis Fan, Rigby and Zhang, Lichuanopora cf. bancaoensis Fan, Rigby and Zhang, Family Khmeriidae: Imilce newelli Flügel. Lithistida: Family Astylospongiidae: Raanespongia iranica n. sp. Among the sphinctozoans A. hambastensis n. sp. is an extremely abundant species. Among the inozoans the genus Hambastella n. gen., with both species, is the most abundant genus. The genera Disjectopora, Lichuanopora, and Pseudopaleoaplysina, were described as hydrozoans by early workers, but are assigned to the inozoans in this paper. The Upper Permian sponge fauna, as well as the composition of other reef organisms, from the Hambast Mountains in central Iran is different from that of the assemblage in the Lower Permian reefal limestones of Bagh-e Vang from the Shotori Mountians (northeast Iran).     

Variability in chemical defense across a shallow to mesophotic depth gradient in the Caribbean sponge <Emphasis Type="Italic">Plakortis angulospiculatus</Emphasis>

The transition between shallow and mesophotic coral reef communities in the tropics is characterized by a significant gradient in abiotic and biotic conditions that could result in potential trade-offs in energy allocation. The mesophotic reefs in the Bahamas and the Cayman Islands have a rich sponge fauna with significantly greater percent cover of sponges than in their respective shallow reef communities, but relatively low numbers of spongivores. Plakortis angulospiculatus, a common sponge species that spans the depth gradient from shallow to mesophotic reefs in the Caribbean, regenerates faster following predation and invests more energy in protein synthesis at mesophotic depths compared to shallow reef conspecifics. However, since P. angulospiculatus from mesophotic reefs typically contain lower concentrations of chemical feeding deterrents, they are not able to defend new tissue from predation as efficiently as conspecifics from shallow reefs. Nonetheless, following exposure to predators on shallow reefs, transplanted P. angulospiculatus from mesophotic depths developed chemical deterrence to predatory fishes. A survey of bioactive extracts indicated that a specific defensive metabolite, plakortide F, varied in concentration with depth, producing altered deterrence between shallow and mesophotic reef P. angulospiculatus. Different selective pressures in shallow and mesophotic habitats have resulted in phenotypic plasticity within this sponge species that is manifested in variable chemical defense and tissue regeneration at wound sites.     

Fatty acid composition and antioxidant activity of Antarctic marine sponges of the genus <Emphasis Type="Italic">Latrunculia</Emphasis>

The fatty acid composition of marine cold-water sponges of genus Latrunculia, namely Latrunculia bocagei Ridley and Dendy, 1886, and Latrunculia biformis Kirkpatrick, 1907, for which no fatty acid data had been previously reported, has been examined. High levels of long-chain fatty acids (C_24–30) with high unsaturation levels (mainly polyunsaturation), and high incidence of branched- and odd-chain fatty acids in sponges are suggested to be partially connected with their specific cell membrane requirements to surmount the negative effects of low temperatures and to enable growth in extreme environments. Furthermore, variations in the fatty acid profile at the species level may reflect variations in compositions or quantities of symbiotic microorganisms that commonly represent up to 60 % of the sponge wet weight. The fatty acid compositions of lipid-rich sponge extracts from five Latrunculia specimens dredged from the Bransfield Strait near the Antarctic Peninsula, were obtained using supercritical carbon dioxide and analyzed using gas chromatography–mass spectrometry–flame ionization detection. Furthermore, the antioxidant activities of these extracts were determined using the photochemiluminescent method. Along with common fatty acids, the chemical analyses revealed very long-chain fatty acids (C22, C24). Differences were seen for the fatty acid levels between both species and different specimens of the same species. The observed differences do not seem connected to the habitat depth of the specimen, but rather indicate the variations within the associated microbiome. Furthermore, these sponge extracts showed antioxidant activities, confirming that they contain lipidic compounds that strongly scavenge free radicals.