Harmothöe Hyalonemae SF. NOV. (Polychaeta, Polynoidae), An Exclusive Inhabitant of Different Atlanto-Mediterranean Species of Hyalonema (Porifera, Hexactinellida)

Revision of Iphione Kinberg, 1856 (Annelida, Aphroditiformia, Iphionidae)

The only revision of Iphione was made by Pettibone in 1986, who recognized four species including two newly described in that work: I. muricata (Savigny in Lamarck, 1818) (type species), I. ovata Kinberg, 1856, I. treadwelli Pettibone, 1986, and I. henshawi Pettibone, 1986. She included I. fimbriata de Quatrefages, 1866, I. glabra de Quatrefages, 1866, and I. fustis Hoagland, 1920 within I. muricata, and I. spinosa Kinberg, 1856 and I. hirotai Izuka, 1912 in I. ovata. Three other species were later added to the genus: I. reticulata Amoureux, Rullier & Fishelson, 1978 from the Red Sea, I. coriolis Hanley & Burke, 1991 from the Coral Sea, and I. malifera Piotrowski, 2014 from the Philippines. A recent contribution showed that I. ovata ranges from the Red Sea to the Eastern Pacific and includes I. spinosa and I. reticulata. Our objectives were to revise the genus, evaluating all species and describing new ones by assessing the relevance of morphological features, assisted in part with COI sequence data. We studied the morphology of type and non-type material from 18 institutions and sequenced 52 specimens representing 11 species. We found that the size and position of eyes, the size relationships between cephalic appendages, and the number of rows of macrotubercles in elytra vary with body size. The most relevant diagnostic features for species delineation, confirmed by genetic species delineation, are the type and size relationships of macrotubercles, the presence of fimbriae, the development of the basal tubercle of dorsal cirrophores, the type of neurochaetae (falcate versus acicular), and their tips (uni- vs bidentate; or simple vs hooded). We clarified the type species of the genus as I. ovata, and recognized 17 species, nine previously described and eight new. Our main results include: 1) the restriction of I. muricata; 2) the reinstatement of I. fimbriata including I. fustis; 3) redescriptions of I. coriolis, I. henshawi and I. treadwelli; and 4) the description of eight new species: I. ankeri sp. nov. from Guam, I. corbari sp. nov. from the Saya de Malha Bank, I. harrisae sp. nov. from French Polynesia, I. hourdezi sp. nov. from New Caledonia, I. hyndmani sp. nov. from Hong Kong, I. readi sp. nov. from the Red Sea (including many earlier records of I. muricata), I. richeri sp. nov. from New Caledonia, and I. wilsoni sp. nov. from Australia. Descriptions the eight newly described species include only one based upon a single specimen. Keys are included for the genera in the family, and species of Iphione.

Behavioral traits and territoriality in the symbiotic scaleworm Ophthalmonoe pettiboneae

Among marine invertebrates, polychaete worms form symbiotic associations showing a wide variety of host use patterns. Most commonly, they live solitary on hosts, likely resulting from territorial behavior, yet little is known of the precise nature of the involved interactions. Based on field and laboratory observations, we described the symbiotic association between Ophthalmonoe pettibonae and Chaetopterus cf. appendiculatus from Nhatrang Bay (Vietnam). Then, by experimentally manipulating the competitor-to-resource ratio, we analyzed symbiont behavior and we assessed whether the 1:1 uniform distribution observed in nature could be driven by agonistic territorial behavior. Hosts and symbiont populations had low densities, lacked size relationships and showed higher prevalence when denser. Symbiont behavior included territoriality, expressed through conspecific recognition and intraspecific aggressive interactions (pursuit and escaping, hiding, choosing position, aggressive fighting, and targeting a specific bite zone). Our experiments proved that territoriality led to host monopolization by a single symbiont, provided the first empirical evidence that symbiont body injuries were caused during territorial contests, and allowed us to first suggest that a marine symbiotic invertebrate may control a territory extending beyond its host, even including neighboring hosts. Overall, this is the first report of such a complex symbiotic behavior for an annelid polychaete.

Sleeping with the enemy: unravelling the symbiotic relationships between the scale worm Neopolynoe chondrocladiae (Annelida: Polynoidae) and its carnivorous sponge hosts

The North Atlantic deep-water polynoid worm Neopolynoe chondrocladiae is involved in an exceptional symbiotic relationship with two hosts: the carnivorous sponges Chondrocladia robertballardi and Chondrocladia virgata. While this is an obligate symbiotic relationship, its real nature is unclear. We used a multidisciplinary approach to narrow down the type of symbiotic relationship between symbiont and hosts. Molecular connectivity analyses using COI and 16S suggest that N. chondrocladiae has high potential for dispersal, connecting sites hundreds of kilometres apart, likely aided by oceanographic currents. Microbial analyses on different anatomical parts of five Chondrocladia species suggest that the presence of the worm in C. robertballardi does not affect the microbiome of the sponge. MicroCT analysis on N. chondrocladiae show that it has dorsally oriented parapodia, which might prevent the worm from getting trapped in the sponge. A faecal pellet recovered from the worm suggests that the polynoid feeds on the crustacean prey captured by the sponge, something corroborated by our stable isotope analysis. Light and confocal microscopy images suggest that N. chondrocladiae elytra produce bioluminescence. We propose that the worm might use bioluminescence as a lure for prey (increasing the food available for both the sponge and the polynoid) and thus fuelling a mutualistic relationship.

Interocean patterns in shallow water sponge assemblage structure and function

Sponges are a major component of benthic ecosystems across the world and fulfil a number of important functional roles. However, despite their importance, there have been few attempts to compare sponge assemblage structure and ecological functions across large spatial scales. In this review, we examine commonalities and differences between shallow water (<100 m) sponges at bioregional (15 bioregions) and macroregional (tropical, Mediterranean, temperate, and polar) scales, to provide a more comprehensive understanding of sponge ecology. Patterns of sponge abundance (based on density and area occupied) were highly variable, with an average benthic cover between ~1 and 30%. Sponges were generally found to occupy more space (percentage cover) in the Mediterranean and polar macroregions, compared to temperate and tropical macroregions, although sponge densities (sponges m^-2 ) were highest in temperate bioregions. Mean species richness standardised by sampling area was similar across all bioregions, except for a few locations that supported very high small-scale biodiversity concentrations. Encrusting growth forms were generally the dominant sponge morphology, with the exception of the Tropical West Atlantic, where upright forms dominated. Annelids and Arthropods were the most commonly reported macrofauna associated with sponges across bioregions. With respect to reproduction, there were no patterns in gametic development (hermaphroditism versus gonochorism), although temperate, tropical, and polar macroregions had an increasingly higher percentage of viviparous species, respectively, with viviparity being the sole gamete development mechanism reported for polar sponges to date. Seasonal reproductive timing was the most common in all bioregions, but continuous timing was more common in the Mediterranean and tropical bioregions compared to polar and temperate bioregions. We found little variation across bioregions in larval size, and the dominant larval type across the globe was parenchymella. No pattens among bioregions were found in the limited information available for standardised respiration and pumping rates. Many organisms were found to predate sponges, with the abundance of sponge predators being higher in tropical systems. While there is some evidence to support a higher overall proportion of phototrophic species in the Tropical Austalian bioregion compared to the Western Atlantic, both also have large numbers of heterotrophic species. Sponges are important spatial competitors across all bioregions, most commonly being reported to interact with anthozoans and algae. Even though the available information was limited for many bioregions, our analyses demonstrate some differences in sponge traits and functions among bioregions, and among macroregions. However, we also identified similarities in sponge assemblage structure and function at global scales, likely reflecting a combination of regional- and local-scale biological and physical processes affecting sponge assemblages, along with common ancestry. Finally, we used our analyses to highlight geographic bias in past sponge research, and identify gaps in our understanding of sponge ecology globally. By so doing, we identified key areas for future research on sponge ecology. We hope that our study will help sponge researchers to consider bioregion-specific features of sponge assemblages and key sponge-mediated ecological processes from a global perspective.

Multipartner Symbiosis across Biological Domains: Looking at the Eukaryotic Associations from a Microbial Perspective

Sponges establish tight associations with both micro- and macroorganisms. However, while studies on sponge microbiomes are numerous, nothing is currently known about the microbiomes of sponge-associated polychaetes and their relationships with those of their host sponges. We analyzed the bacterial communities of symbiotic polychaetes (Haplosyllis spp.) and their host sponges (Clathria reinwardti, Amphimedon paraviridis, Neofibularia hartmani, and Aaptos suberitoides) to assess the influence of the sponges on the polychaete microbiomes. We identified both eukaryote partners by molecular (16S and COI genes) and morphological features, and we identified their microbial communities by high-throughput sequencing of the 16S rRNA gene (V4 region). We unravel the existence of six Haplosyllis species (five likely undescribed) associated at very high densities with the study sponge species in Nha Trang Bay (central Vietnam). A single polychaete species inhabited A. paraviridis and was different from the single species that inhabited A. suberitoides Conversely, two different polychaete species were found in C. reinwardti and N. hartmani, depending on the two host locations. Regardless of the host sponge, polychaete microbiomes were species specific, which is a widespread feature in marine invertebrates. More than half of the polychaete bacteria were also found in the host sponge microbiome but at contrasting abundances. Thus, the associated polychaetes seemed to be able to select, incorporate, and enrich part of the sponge microbiome, a selection that appears to be polychaete species specific. Moreover, the bacterial diversity is similar in both eukaryotic partners, which additionally confirms the influence of food (host sponge) on the structure of the polychaete microbiome.IMPORTANCE The symbiotic lifestyle represents a fundamental cryptic contribution to the diversity of marine ecosystems. Sponges are ideal targets to improve understanding the symbiotic relationships from evolutionary and ecological points of view, because they are the most ancient metazoans on earth, are ubiquitous in the marine benthos, and establish complex symbiosis with both prokaryotes and animals, which in turn also harbor their own bacterial communities. Here, we study the microbiomes of sponge-polychaete associations and confirm that polychaetes feed on their host sponges. The study worms select and enrich part of the sponge microbiome to shape their own species-specific bacterial communities. Moreover, worm microbiome diversity runs parallel to that of its food host sponge. Considering our results on symbiotic polychaetes and previous studies on fishes and mammals, diet appears to be an important source of bacteria for animals to shape their species-specific microbiomes.

Brinckmannia hexactinellidophila, n. gen., n. sp.: a hydroid living in tissues of glass sponges of the reefs, fjords, and seamounts of Pacific Canada and Alaska

This paper reports on an intimate association of a cnidarian with glass sponges. Hexactinellid sponges of the genus Heterochone were found to regularly contain numerous tiny hydroids in their tissue. The hydroid belongs to a new genus and species and is here named Brinckmannia hexactinellidophila. Brinckmannia hexactinellidophila is a reduced form, lacking tentacles and gonophores, which certainly is an adaptation to its endobiotic mode of life. The possession of desmonemes allows it to be classified as a member of the suborder Filifera of the order Anthoathecata. The shape of the hydranth reveals some clear affinities with the Proboscidactylidae, a relationship which is also strongly suggested by a comparison of 16S gene sequences. Because a closer relationship to some other families cannot be excluded at this stage, the new genus is nevertheless not assigned to any known family and classified as Filifera incertae sedis.