Temir A. Britayev

New symbiotic associations involving Syllidae (Annelida: Polychaeta), with taxonomic and biological remarks on Pionosyllis magnifica and Syllis cf. armillaris

Several new symbiotic associations involving Syllidae (Annelida: Polychaeta) are reported. The number of known host sponge species infested by Haplosyllis spongicola is updated to 36, with seven hosts being reported for the first time (i.e. Aplysina corrugata, Aplysina sp., Cliona sp., Cliona viridis, Phorbas tenacior, one sponge from Iran, one sponge from Cambodia). Two infestation patterns (a few worms per host cm 3 in temperate waters and 10s or 100s in tropical waters) are identified. The taxonomic and ecological characteristics of the species are discussed. Five associations occurring between four syllid worms and decapod crustaccans are fully reported for the first time. Syllis cf. armillaris, S. ferrani and S. pontxioi occurred inside gastropod shells occupied by hermit crabs as well as Pionosyllis magnifica, which was also found inside the branchial chambers of the giant crab Paralithodes camtschatica. The description of Pionosyllis magnifica is emended on the basis of the new specimens found, while some taxonomic remarks on Syllis cf. armillaris are given. In addition, further evidence of sexual (P. magnifica) and asexual (S. cf. armillaris) reproduction in symbiotic syllids is provided.

Inter-population variability and character description in the sponge-associated Haplosyllis spongicola complex (Polychaeta: Syllidae)

Haplosyllis spongicola is probably the most representative symbiotic syllid harboured by sponges and has been widely reported from tropical, subtropical and temperate seas. Its external morphology seems to be very well adapted for its life-style, with all chaetae being simple and having two small teeth and a large main fang. However, the species has been the subject of a long-lasting taxonomic controversy, which gave rise to more than 15 synonymies, with hundreds of records worldwide. The present paper is based on the study of more than 28 populations obtained from around the world. These populations have been carefully analysed using different approaches (morphometry, morphology and biology). As a consequence, the existence of a pseudo-sibling species-complex within the so-called cosmopolitan H. spongicolahas been revealed. The most relevant characters (as well as their variability) that will allow a future identification of the species involved in the complex are fully described, illustrated and analysed.

Association of the commensal scaleworm Gastrolepidia clavigera (Polychaeta: Polynoidae) with holothurians near the coast of South Vietnam

Abstract The Indo-West Pacific commensal scaleworm Gastrolepidia clavigera Schmarda, 1861 is here recorded for the first time from the waters of Vietnam. It was associated with the sea cucumbers Stichopus chloronotus Brandt, S. variegatus Semper, Holothuria atra Jaeger, H. leucospilota Brandt and Actinopyga echinites (Jaeger). The last two species are reported as hosts for the first time. Each host harboured 1–3 worms. About half of the infested hosts (51.4%) harboured a pair of worms, one male and one female. The frequency of occurrence of G. clavigera on hosts varied from 31.9% on A. echinites to 80.0% on S. variegatus. Infested hosts were larger than non-infested ones. A sexual size dimorphism is characteristic of G. clavigera, with females larger than males. A positive correlation between size of males and females from every pair was found; a correlation between size of holothurian hosts and size of their commensals was not observed. Commensal worms show two main types of trauma, which are described a...

Diet analyses of the scale-worms Lepidonotus squamatus and Harmothoe imbricata (Polychaeta, Polynoidae) in the White Sea

Abstract Under the harsh environmental conditions of the White Sea, the polynoid polychaetes Lepidonotus squamatus and Harmothoe imbricata coexist in the same habitats, often showing recurrent alternations in dominance. The present study focused on their diet and food preferences based on the analyses of gut contents (after dissection of preserved specimens) and faecal pellets (released by selected living specimens). Our results pointed out that the dietary regimes were significantly dependent on the collection site (and the respective dominant prey species) and not on the scale-worm species, suggesting that L. squamatus and H. imbricata are non-selective at the species level. There was also a significant overlap of their dietary regimes and our data support the existence of intra- and inter-specific aggressive behaviour, with H. imbricata being more aggressive than L. squamatus. These findings, combined with their life cycle strategies and other biological and environmental constraints, arose as significant driving forces explaining the population dynamics of the two studied scale-worms in the White Sea.

Description and life-history traits of a new species of Proceraea with larvae infecting Abietinaria turgida (Polychaeta, Syllidae & hydrozoa, sertulariidae)

Abstract A new species of the genus Proceraea (Polychaeta, Syllidae, Autolytinae), P. rzhavskyi, is described. Many specimens of this species at different stages of development were found within the hydrothecae and mucous tubes attached to colonies of the sertulariian hydrozoan Abietinaria turgida (Clark, 1867) at the coast of Mednyy Island, the Commander Islands, Northwest Pacific, 5–12 m depth, in August Larvae and juveniles are present within the hydrothecae from very early stages of development, which appears to be direct. This is the first report of a polychaete with symbiotic larval stages and free-living adults. The smallest specimens have a yolk, a single pair of eyes, and a tuft of short cilia at the apical part of prostomium, but lack setae. As larvae grow, the yolk and the tuft of cilia disappear. Setae and dorsal cirri appear on several anterior segments, the pharynx develops, and juveniles start feeding upon the host. Finally, they occupy the entire cavity of the hydrothecae. A conspicuous tubular addition to the hydrotheca is formed distally as a result of infestation. Upon reaching 10–11 setigers, the juveniles leave the hydrotheca, build mucous tubes attached to the stem or branches of the colony and continue their growth up to the adult stage. The proventriculus and the teeth of the trepan are formed when the worms leave the hydrothecae. Unlike Autolytus all the stages lack ciliary bands on the body. A female stolon (sacconereis) was examined. Proceraea rzhavskyi differs from closely related species, P. okadai and P. mukaishimus, in structure of the trepan and length of head appendages and nuchal epaulettes.

Symbiotic association between Solanderia secunda (Cnidaria, Hydrozoa, Solanderiidae) and Medioantenna variopinta sp. nov. (Annelida, Polychaeta, Polynoidae) from North Sulawesi (Indonesia)

A mimic scale-worm was found associated with the athecate hydroid Solanderia secunda, commonly found on reefs of the NW coast of North Sulawesi, Indonesia. The species resembled Medioantenna clavata Imajima 1997, which was originally described without any reference to a symbiotic mode of life and later reported to be living on a solanderiid hydroid both in Japanese waters. A detailed morphological analysis led us to consider the Indonesian specimens as a new species, namely Medioantenna variopinta sp. nov., which is congeneric with the Japanese species. The new species differs from the type material of M. clavata as it has elytra with one prominent finger-like papilla and all neurochaetae with unidentate tip, instead of an elytral lump and both unidentate and bidentate neurochaetae on segment two. In turn, the Japanese worms associated with Solanderia are here referred to our new species. Two morphological features in M. variopinta sp. nov. are rather unusual among scale-worms. One of them is its extremely high level of bilateral asymmetry and antero-posterior variability in elytral distribution and the other one is its elongated, upwardly directed nephridial papillae. The morphology and geographical distribution of the host together with the known characteristics of the symbiotic association have also been highlighted.

Scale-worms (Polychaeta, Polynoidae) associated with chaetopterid worms (Polychaeta, Chaetopteridae), with description of a new genus and species

Three species of scale‐worms inhabiting chaetopterid tubes have been found during routine studies of benthic communities. Anotochaetonoe michelbhaudi gen. and sp. nov. occurred in the East Atlantic off Congo in association with Spiochaetopterus sp. and Phyllochaetopterus sp. It has a relatively short body (fewer than 50 segments); elytra in posterior part of the body arranged on chaetigers 23, 26, 29, 32, 34, 37, 40, 43, 46, present to posterior end; achaetous notopodia; neuropodia long, with longer subtriangular prechaetal lobes and shorter postchaetal lobes rounded distally; upper neurochaetae unidentate and lower bidentate; globular ciliated papillae present between ventral cirri and ventral basis of neuropodia. Lepidasthenia brunnea occurred in the Mediterranean Sea off the French coast both free‐living and in association with Phyllochaetopterus sp. Ophthalmonoe pettiboneae was found in Vietnam (South China Sea) in association with Chaetopterus sp. This is the second finding of the species. The characteristics of the associations between chaetopterid genera and symbiotic polychaetes are discussed.

Cnidarians and Their Polychaete Symbionts

Cnidarians, especially skeleton-bearing anthozoans and hydrocorals, are known to host abundant and diverse symbiotic fauna encompassing members of the majority of metazoan taxa, ranging from sponges and flat worms to fishes. Members of the class Polychaeta are between the most diverse and perhaps the least studied taxa of coral symbionts. The last revision (Martin and Britayev, Oceanogr Mar Biol 36:217–340, 1998) reckoned about 60 species of symbiotic polychaetes associated with more than 100 species of cnidarian hosts. However, this number is considerably underestimated. Some populations of scleractinians, sea fans and black corals show up to 100 % infestation by symbiotic polychaetes. Close association and inter-relation of highly host-specific symbionts and cnidarian hosts often lead to dramatic changes in the host morphology. At the moment, actual mechanisms of most of mutual relations between host and symbiont in such associations are generally unknown. The objective of the present paper is to summarize data on species composition and ecology of polychaetes associated with cnidarians. In our review, we report 281 species of cnidarian hosts involved in 324 relationships with symbiotic polychaetes. Most polychaete-hosting cnidarians belong to skeleton-bearing taxa, particularly Scleractinia (125 species or 44.48 % of the total cnidarian hosts), Alcyonaria (73 species or 25.97 %) and Hydrozoa (60 species or 21.35 %). About 120 species of symbiotic polychaetes of ten families are reported from cnidarian hosts. Polynoidae include the highest number of cnidarian-associated polychaetes (almost one half of the currently known species), followed by Syllidae and Serpulidae. Host symbiont interrelations, host specificity, location, infestation characteristics and adaptive modifications of symbionts, as well as host reaction on symbionts presence, have been considered. Our review highlights that (1) every group of cnidarians seems to have their own assemblage of symbiotic polychaetes, (2) some deep-sea alcyonaceans and black corals have never been reported without their often undetermined polynoid symbionts so that its presence has been considered as a species-specific, robust taxonomic character, and (3) we certainly expect the polychaete symbionts associated with deep-sea corals to be a hidden hot-spot of diversity, with many species still waiting to be described.

Do syntopic host species harbour similar symbiotic communities? The case of Chaetopterus spp. (Annelida: Chaetopteridae)

To assess whether closely related host species harbour similar symbiotic communities, we studied two polychaetes, Chaetopterus sp. (n = 11) and Chaetopterus cf. appendiculatus (n = 83) living in soft sediments of Nhatrang Bay (South China Sea, Vietnam). The former harboured the porcellanid crabs Polyonyx cf. heok and Polyonyx sp., the pinnotherid crab Tetrias sp. and the tergipedid nudibranch Phestilla sp. The latter harboured the polynoid polychaete Ophthalmonoe pettiboneae, the carapid fish Onuxodon fowleri and the porcellanid crab Eulenaios cometes, all of which, except O. fowleri, seemed to be specialized symbionts. The species richness and mean intensity of the symbionts were higher in Chaetopterus sp. than in C. cf. appendiculatus (1.8 and 1.02 species and 3.0 and 1.05 individuals per host respectively). We suggest that the lower density of Chaetopterus sp. may explain the higher number of associated symbionts observed, as well as the 100% prevalence (69.5% in C. cf. appenciculatus). Most Chaetopterus sp. harboured two symbiotic species, which was extremely rare in C. cf. appendiculatus, suggesting lower interspecific interactions in the former. The crab and nudibranch symbionts of Chaetopterus sp. often shared a host and lived in pairs, thus partitioning resources. This led to the species coexisting in the tubes of Chaetopterus sp., establishing a tightly packed community, indicating high species richness and mean intensity, together with a low species dominance. In contrast, the aggressive, strictly territorial species associated with C. cf. appendiculatus established a symbiotic community strongly dominated by single species and, thus, low species richness and mean intensity. Therefore, we suggest that interspecific interactions are determining species richness, intensity and dominance, while intraspecific interactions are influencing only intensity and abundance. It is possible that species composition may have influenced the differences in community structure observed. We hypothesize that both host species could originally be allopatric. The evolutionary specialization of the symbiotic communities would occur in separated geographical areas, while the posterior disappearance of the existing geographical barriers would lead to the overlapped distribution.

Biodiversity of the community associated with Pocillopora verrucosa (Scleractinia: Pocilloporidae) in the Red Sea

The symbiotic community associated with a scleractinian coral Pocillopora verrucosa has been studied along the Red Sea coast of Saudi Arabia from Al Wajh to the entrance of the Gulf of Aqaba. Forty colonies have been sampled from 2- to 15-m depth in 2 areas, southern and northern. Thirty-six associated species were found, including 15 symbionts and 21 species with uncertain status (SUS). The number of recorded symbiotic species was close to the statistically expected value, while SUS were rare and did not reach the value expected from the Chao 2 model. Species number and abundance positively correlated with the colony volume. Mean abundance of all species and symbionts and the number of SUS per covariate colony volume were higher in the northern area than in the southern area. This may be related to a higher habitat diversity of the surrounding reefs and to the presence of colonies with partially dead tissues in the north. These two factors have a weak impact on symbionts, but strongly affect SUS. The diversity of the pocilloporid-associated communities range from 36 to 127 species along the Indo-Pacific and Tropical East Pacific, with 9 to 19 of them being symbionts. The total species diversity varies owing to the SUS number, while the core of true symbionts includes much fewer species and is less variable. The diversity of Pocillopora symbionts in the Saudi Arabian coast (15 species) is among the highest for the studied areas in the Indo-Pacific.