Submarine Caves Research Articles

The fauna of decapod crustaceans in submarine caves of the Ryukyu Islands, with special reference to environmental factors in the caves

The fauna of decapod crustaceans in submarine caves of the Ryukyu Islands, with special reference to environmental factors in the caves

Recent progress and future potential in faunal studies of the submarine caves in the Ryukyu Islands

Recent progress and future potential in faunal studies of the submarine caves in the Ryukyu Islands

A new tardigrade species of the genus Neostygarctus Grimaldi de Zio et al., 1982 (Tardigrada, Arthrotardigrada) from the Great Meteor Seamount, Northeast Atlantic

A new species of Neostygarctus Grimaldi de Zio et al., 1982 is described from the Great Meteor Seamount summit plateau in the Northeast Atlantic. Neostygarctus grossmeteori sp. nov. is characterized by the number and position of dorsomedian spines (five spines on the cephalic plate and each body plate and on the caudal plate, the spines decreasing in length backwards); the presence of eyes and of one or two pairs of ventral cervical spines; a transversal row of two to five short but strong spikes on the ventral side of the lateral body processes; only the internal claws of each leg provided with a normal accessory spine. The new species is related to N. acanthophorus Grimaldi de Zio et al., 1982 but differs by details of the dorsal body spines and the sculptures, the presence of ventral neck spines and ventral spikes on lateral body projections. Neostygarctus grossmeteori sp. nov. differs from two other known species of Neostygarctus, N. oceanopolis Kristensen et al., 2015 (Condor Seamont, NE Atlantic) and N. lovedeluxe Fujimoto & Miyazaki, 2013 (submarine cave NW Pacific), even more obviously by the number and position of dorsal body spines.

New sciaphilic plakinids (Porifera, Homoscleromorpha) from the Central-Western Pacific

The sponge class Homoscleromorpha is a key model for the evolutionary biology of the Metazoa but its diversity remains poorly known. Here we describe six new species of the homoscleromorph family Plakinidae found in shaded habitats (submarine caves, tunnels and overhangs) of New Caledonia and Marquesas Islands, Central-Western Pacific. The new species belong to four genera: Corticium (Corticium vaceleti sp. nov.), Plakina (Plakina finispinata sp. nov.), Plakinastrella (Plakinastrella osculifera sp. nov., Plakinastrella nicoleae sp. nov. and Plakinastrella pseudolopha sp. nov.), and Plakortis (Plakortis ruetzleri sp. nov.). Plakinastrella pseudolopha sp. nov. has a novel spicule type called here 'pseudolophose spicules'. The diversity of Homoscleromorpha is raised to 50 species in the Pacific Ocean and 120 spp. worldwide.

A new species of the stenopodidean shrimp genus Odontozona Holthuis, 1946 (Crustacea: Decapoda: Stenopodidea: Stenopodidae) from the Ryukyu Islands, Indo-West Pacific.

A new species of the stenopodidean shrimp genus Odontozona Holthuis, 1946 is described and illustrated on the basis of 3 specimens recently collected from submarine caves of Okinawa-jima and Ie-jima Islands, the Ryukyu Islands, southwestern Japan, Indo-West Pacific. Odontozona okunoi sp. nov. closely resembles O. anaphorae Manning Chace, 1990 described from Ascension Island, South Atlantic Ocean, but differs from it by a combination of morphological characters, including the large cardiac spine on the carapace, the spines on the pleural surface, the posterior tooth of the telson, the irregular row of small spines on the dorsomesial surface of the third pereopod chela, as well as the length ratio of the third pereopod chela against carpus and merus. This study increases the total number of species described in the genus Odontozona to 21, nine of which occur the Indo-West Pacific.

Descriptions of new sponge species and genus, including aspiculate Plakinidae, overturn the Homoscleromorpha classification

Among the Porifera, the taxonomy and systematics of Homoscleromorpha is one of the most challenging. Over the last two decades, this class and its single order Homosclerophorida have seen a high rate of new descriptions and phylogenetic investigations which have led to the resurrection of two well-supported families, defined as the `spiculate' Plakinidae and the `aspiculate' Oscarellidae. In recent years, the development of an integrative taxonomic approach and the exploration of new marine ecosystems have revealed an even higher diversity of Homoscleromorpha and highlighted the importance of complementary datasets (cytological, biochemical and molecular) to better explain the phylogenetic classification. Using this integrative approach, we here describe two new species of Plakinidae from submarine caves in the Caribbean Sea: Plakina arletensis sp. nov. and Aspiculophora madinina gen. nov. sp. nov., the latter being aspiculate with an unusually well-developed collagen layer in its mesohyl and an abundant and diverse prokaryote community. The recently described Oscarella nathaliae was reassigned to Plakina on the basis of new molecular data and a careful re-examination of morphological characters. Thus, Plakina nathaliae comb. nov. and A. madinina are the first aspiculate representatives of Plakinidae and indicate the need for a detailed re-examination of Homoscleromorpha using this integrative taxonomic approach. (C) 2017 The Linnean Society of London, Zoological Journal of the Linnean Society, 2017

Foraminiferal ecozones in two submarine caves of the Orosei Gulf (Sardinia, Italy)

Because submarine caves are affected by wide spatial and temporal environmental variability, they are ideal environments for studying the effects of environmental changes on ecological indicators. Benthic foraminifera are protozoa living in marine and transitional habitats, developing typical assemblages as a response to different environmental conditions. For this, they have been increasingly used as ecological indicators for environmental characterization and monitoring. This study was the first one aimed to compare benthic foraminiferal fauna of two different submarine caves of temperate areas, Bel Torrente and Bue Marino, in the Orosei Gulf (Sardinia, Italy). It resumes the main results obtained in Bel Torrente cave by a previous research, implemented by new data acquired by the study of Bue Marino cave. The caves were surveyed and sampled by GUE (Global Underwater Explorers) divers for the first 450 m to recognize distinct ecozones, their ecological significance, and to compare them as regards species composition and extent. The succession of Marine, Entrance and Transitional Ecozones was recognized in both the caves. While the Marine Ecozone pointed out environmental conditions very similar to those of shallow water marine environment, the Entrance and Transitional Ecozones indicated increasing environmental stress. In the Entrance Ecozone, the dominance of tolerant species was probably due to the high environmental variability for the episodic high energy floods and, locally, reduced oxygenation events. In the Transitional Ecozone, the decrease of seawater salinity and temperature, especially after rainy periods, probably encouraged the prevalence of agglutinated taxa, which are normally rare in Mediterranean shallow water marine environment, while they are common in high latitude basins.

Taxonomy of Plakina (Porifera: Homoscleromorpha) from Aegean submarine caves, with descriptions of three new species and new characters for the genus

Sponges of the Class Homoscleromorpha, despite their high evolutionary significance, are still poorly known due to their small size and cryptic habit. In this study, we describe five species of the homoscleromorph genus Plakina from submarine caves in the Aegean Sea (Lesvos Island, Greece): Plakina bowerbanki, P. trilopha, P. anisoactina sp. nov., P. anomala sp. nov., and P. hellenica sp. nov. Plakina anomala sp. nov. is the first species of the genus with papillae and the first Homoscleromorpha with a microcavity-filling habit. Plakina bowerbanki, P. anomala sp. nov. and P. anisoactina sp. nov. present exceptionally stout, annulated lophose spicules with highly variable ramification patterns, including some original types. The high diversity of Plakina in the two caves of Lesvos Island is similar to that of northwestern Mediterranean caves. Despite being much less studied, the Aegean Sea now equals the Western Mediterranean as the two ecoregions of the Mediterranean with the highest diversity of Plakina, with eight species each. The Aegean Sea encompasses a huge number of submarine caves, and therefore it has great potential for the discovery of new species of Homoscleromorpha.

Bryozoan assemblages from two submarine caves in the Aegean Sea (Eastern Mediterranean)

Although bryozoans are one of the dominant sessile phyla in Mediterranean marine caves, little information is available on the bryozoan diversity of this habitat in the eastern basin. In this study, bryozoan assemblages of two Aegean marine caves located at different depths and characterised by different morphology were studied. The examination of 30 quadrats (20 × 20 cm) scraped from the vertical walls and cave ceilings, at increasing distances from the entrances, yielded 74 taxa (67 living and 47 dead), half of which were shared by both caves. Cheilostomes largely prevailed (59 taxa) over cyclostomes and ctenostomes (14 and 1 species, respectively). Nodular to fungiform bioconstructions were formed by species with multilayered colonies in both caves. Differences in the taxonomic structure of bryozoan assemblages between the two caves as well as on the spatial variability of diversity, abundance and growth morphologies within each cave seem to be linked to the different cave morphology and associated environmental conditions. Moreover, a considerable number of taxa were reported for the first time from the Eastern Mediterranean and the marine cave habitat, supporting the idea that knowledge of their bryozoan diversity is far from being considered complete.

First finding of anchialine and submarine cave dwelling brittle stars from the Pacific Ocean, with descriptions of new species of Ophiolepis and Ophiozonella (Echinodermata: Ophiuroidea: Amphilepidida).

Two new species, Ophiolepis cavitata n. sp. and Ophiozonella cavernalis n. sp., are described from the specimens collected in shallow water submarine caves in the Ryukyu Islands, southwestern Japan. Ophiolepis cavitata n. sp. is distinguished from the other congeners in having prominent tubercle-shaped knobs on dorsal arm plates; two sizes of disc scales on the aboral disc, the larger surrounded by 3-8 times smaller disc scales; larger scales concave; radial shields wider than long; a trio of distinct scales present distal to each pair of radial shields; oral shields partly concave; 3 arm spines on proximal portion of the arms. Ophiozonella cavernalis n. sp. is distinguished from the other congeners in having polygonal, uniform size disc scales; oral shields almost as long as wide, shallow concave proximal sides that end in a fairly sharp point medially; arms about 9 times longer than disc diameter; 3 cylindrical arm spines, of which the oral most one is slightly larger than other 2 spines. Ophiozonella cavernalis n. sp. is the second finding of an anchialine-endemic ophiuroid and the first finding from the Pacific Ocean.

Description of the first Caribbean Oscarellidae (Porifera: Homoscleromorpha)

The sponge class Homoscleromorpha has a challenging taxonomy and its systematics is still a matter of debate. A significant effort has recently been deployed to better evaluate the diversity of these sponges, and each new exploration of cryptic habitats reveals new species. Although several undescribed or wrongly determined Oscarella-like sponges have been reported by different authors, the Oscarellidae family still lacks description of its true Caribbean representatives. The exploration of various submarine caves in the Lesser Antilles has allowed us to find and to formally describe the first two Oscarellidae of the Caribbean Sea, Oscarella filipoi sp. nov. and Oscarella zoranja sp. nov. Both new species are quite common in semi-dark habitats throughout the Lesser Antilles. Moreover, O. filipoi sp. nov. is the largest Oscarellidae ever observed world-wide. Both species harbor a sylleibid aquiferous system and a high density of ovoid to spherical choanocyte chambers. The molecular taxonomy clearly shows their affiliation to the Oscarella clade containing the type species of the Oscarellidae family. In addition to their growth forms, these two species differ in the shape of their mesohylar cells, and in the degree of development of their basal region. This latter trait is particularly remarkable in large specimens of O. filipoi which can have a very thick ectosome.

A new species ofOphioconis(Echinodermata: Ophiuroidea) from Ryukyu Islands, southwestern Japan

Ophioconis claviculata sp. nov. is described on the basis of three specimens collected from Ryukyu Islands, southwestern, Japan. The new species is distinct in having: disc covered by granules; four, sometimes five flat, polygonal oral papillae on each side of jaw; broad and flat teeth with hyaline distal end; spiniform and conical arm spines, two times longer than the corresponding arm segment at the maximum length; oralmost arm spines on proximal portion of arms flattened and clavate; four tentacle scales on third tentacle pore; and ventral arm plate longer than wide, with concentrate lamellar striations. The new species was found under rocks of open water as well as in a dark and medium to low salinity (28 ppt) environment of submarine cave, suggesting that this species tolerate this specific condition.

Current situation of decapod crustacean researches in anchialine and submarine caves of the Ryukyu Islands

Current situation of decapod crustacean researches in anchialine and submarine caves of the Ryukyu Islands

The distribution of benthic foraminifera in Bel Torrente submarine cave (Sardinia, Italy) and their environmental significance

The use of benthic foraminifera as ecological indicators in submarine caves of temperate seas have never been studied before and it represents a new approach, verified by this research. The Bel Torrente submarine cave (Gulf of Orosei, Sardinia, Italy) was surveyed by GUE (Global Underwater Explorers) scuba divers in order to georeferencing the cave before positioning the sampling stations, from the entrance to 430 m inside the cave. A total of 15 water samples were collected to investigate abiotic parameters (temperature, salinity, pH) while 15 sediment samples were collected to analyze grain size and benthic foraminifera. Benthic foraminifera, investigated for the first time in a submarine cave of temperate areas, were exclusively found from the entrance to 300 m inside the cave. Species distribution and assemblage diversity have been found to be correlated to the environmental gradient towards the inner cave, mainly due to the decreasing of temperature and salinity and the increasing of the flow energy. Water acidification seems responsible for the transition from a calcareous hyaline-dominated assemblage to an agglutinant-dominated one, occurring between 120 and 150 m from the entrance. Common taxa of the Sardinian coastal marine area are present only close to the entrance of the cave, while species found in the inner part are nearly exclusively epifaunal clinging/attached or infaunal taxa, with tolerance for wide variability of environmental parameters, such as Gavelinopsis praegeri, and opportunist infaunal taxa such as Eggerella advena. The agglutinant taxa found in the cave are conversely very rare in coastal marine assemblages of the area. This suggests a very efficient dispersal mechanism for the colonization of the caves, involving probably juvenile foraminifera at a “propagule” stage.

Halosbaena okinawaensis, a new species of Thermosbaenacea (Crustacea) from submarine cave on Okinawa Island, Ryukyu Islands, southwestern Japan

A new thermosbaenacean, Halosbaena okinawaensis sp. nov. is described from a submarine cave in Okinawa Island, Ryukyu Islands, southwestern Japan. The species differs from its congeners in having a subtrapezoidal exopod segment 1 of pereiopods 2–6, a curved penial lobe, and a telson with a pair of simple macrosetae subdistally on dorsal surface.

Cryptic serpulid-microbialite bioconstructions in the Kakoskali submarine cave (Cyprus, Eastern Mediterranean)

The biostalactites from the Kakoskali cave in Cyprus represent a new example of the complex biotic relationships between skeletal organisms and microbial communities in building bioconstructions of cryptic marine environments. Biostalactites are mainly constituted of polychaetes of the family Serpulidae and, to a lesser degree, foraminifers and bryozoans. Within the skeletal framework of these organisms, two types of microcrystalline calcite (micrite) have been recognized: autochthonous and detrital micrite. The autochthonous fraction is syndepositionally lithified and occurs as clotted peloidal and, subordinately, aphanitic (structureless) textures, suggesting the presence of heterotrophic microbial activities thriving on decaying metazoan organic matter. This fraction is limited to the protected portions of the bioconstructions, especially in the inner and lower parts. The presence of iron and manganesiferous oxidizing bacteria is suggested by the deposition of ferromanganesiferous crusts and Frutexites-like structures. These microbial-induced biomineralizations are the main evidence of carbonatogenetic and Fe–Mn, autotrophic and chemoheterotrophic, bacterial activities. The Kakoskali cave is frequently visited by divers who, during their immersions, resuspend the fine bottom sediment, which later covers the surface of the bioconstructions, disturbing the delicate equilibrium of the biotic association. This perturbation, which is also caused by strong waves and currents, during winter months, reflects on the bioconstruction morphologies, community composition, and colonization pattern. Bioconstructions exhibit an upper smooth surface, produced by few taxa (e.g., polychaetes, foraminifers), hosting a low number of living individuals, and a lower comparably rough surface, colonized by a more abundant community showing a higher species richness. The ratio surface roughness/smoothness is related to micrite sediment type: the upper part is mainly characterized by loose detrital micrite while the internal and lower parts by syndepositional cemented autochthonous micrite.

Microbial Biomineralization in Biotic Crusts from a Pleistocene Marine Cave (NW Sicily, Italy)

ABSTRACTBiotic crusts occurring in the Early Pleistocene Rumena Cave, in NW Sicily, have been analyzed from a geomicrobiological point of view. The crusts consist largely of scleractinians and of subordinate bryozoans and serpuloideans, all typical of submarine cave biota. Encrustations document a blind cave in a shadowed setting, or possibly below the fair weather swell zone. Autochthonous and, subordinately, detrital fractions were observed within the skeletal framework of biotic crusts. The syndepositional lithified fraction occurs mainly as very fine-grained laminations. Clotted peloidal and aphanitic (structureless) textures occur in the micrites as well. Autochthonous micrite is always associated with a significant amount of organic matter remains. In caves from the Plemmirio area in SE Sicily, the autochthonous microbial micrite, occurring in the bioconstructions, contains bacterial lipid biomarkers, including abundant compounds derived from sulfate-reducing bacteria. It is likely that a similar microbial mediation was involved in the formation of the autochthonous micrite present in the biotic crusts of the Rumena Cave.

Response of subtropical submarine-cave ecosystem to Holocene cave development and Asian monsoon variability

AbstractA submarine cave is a unique environment that is dark, food limited, semi-isolated from the outside, and sheltered from wave action. However, our knowledge of the long-term change in submarine-cave ecosystems remains limited. We document here the community-scale responses toward long-term change in a submarine cave, Daidokutsu in Okinawa in southern Japan. Using both metazoans (ostracods and bivalves) and protozoans (larger benthic foraminiferans) in two sediment cores obtained from the cave, we reconstruct the faunal and diversity changes of the past 7 Kyr. All taxonomic groups showed long-term, gradual linear change of faunal composition from predominantly open-water taxa to predominantly cave taxa, and ostracods showed short-term variability of species diversity. The long-term faunal trend probably reflects gradual isolation of the cave ecosystem due to coral reef development (i.e., development of the cave ceiling) during periods of the Holocene transgression and subsequent sea-level highstand. The short-term diversity changes show substantial similarity to centennial- to millennial-scale Holocene Asian monsoon variability. Ostracod species diversity peaks tend to correspond with periods of strong East Asian winter monsoons. The results indicate that limestone submarine-cave ecosystems, an important cryptic habitat, developed gradually during the Holocene and may be sensitive to rapid climate changes.

How a collaborative integrated taxonomic effort has trained new spongiologists and improved knowledge of Martinique Island (French Antilles, eastern Caribbean Sea) marine biodiversity.

Although sponges are important components of benthic ecosystems of the Caribbean Sea, their diversity remained poorly investigated in the Lesser Antilles. By organizing a training course in Martinique, we wanted both to promote taxonomy and to provide a first inventory of the sponge diversity on this island. The course was like a naturalist expedition, with a field laboratory and a classroom nearby. Early-career scientists and environmental managers were trained in sponge taxonomy. We gathered unpublished data and conducted an inventory at 13 coastal sites. We explored only shallow water habitats (0–30 m), such as mangroves, reefs or rocky bottoms and underwater caves. According to this study, the sponge fauna of Martinique is currently represented by a minimum of 191 species, 134 of which we could assign species names. One third of the remaining non-identified sponge species we consider to be new to science. Martinique appears very remarkable because of its littoral marine fauna harboring sponge aggregations with high biomass and species diversity dominating over coral species. In mangroves, sponges cover about 10% of the surface of subtidal roots. Several submarine caves are true reservoirs of hidden and insufficiently described sponge diversity. Thanks to this new collaborative effort, the Eastern Caribbean has gained a significant increase of knowledge, with sponge diversity of this area potentially representing 40% of the total in the Caribbean Sea. We thus demonstrated the importance of developing exploratory and educational research in areas historically devoid of biodiversity inventories and systematics studies. Finally, we believe in the necessity to consider not only the number of species but their distribution in space to evaluate their putative contribution to ecosystem services and our willingness to preserve them.

First description of the female ofHeteromysoides simplexHanamura & Kase, 2001 (Mysidacea: Mysidae) collected from a submarine cave on Ie-jima Island, Ryukyu Islands, southwestern Japan

Abstract The female of Heteromysoides simplex Hanamura & Kase, 2001 is described for the first time based on material collected from a submarine cave on Ie-jima Island, Ryukyu Islands, southwestern Japan. Morphological descriptions and illustrations of this specimen are given.