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Telestula ridgensis sp. nov. is a deep-sea octocoral species collected from the Central Indian Ridges (CIR) seamount. The megabenthic communities were sampled from the depths between 1917 and 2053 m using a benthic sledge. It forms part of a baseline environmental and benthic ecological assessment. All these data will be functional in assessing the impact of future massive sulfide mining in the Indian Ocean. We describe a new octocoral species based on integrative taxonomic methods through morphological comparison and molecular phylogenetics. The sclerome of the new species consists of short, stellate plates, crosses, and irregularly shaped and branching forms with dense tubercular ornamentation. The polyp sclerites are arranged in longitudinal rows underneath the tentacles. Two mitochondrial DNA genes (mtMutS and COI) and one ribosomal nuclear DNA gene (28S rRNA) were sequenced to separate the new species. The phylogenetic analyses strongly support the placement of new species in the genus Telestula clade.

The high diversity and endemism of benthic species on seamounts are extensively documented. Although the number of squat lobster species from seamount habitats has increased, species from the Central Indian Ridge (CIR) and Southwest Indian Ridge (SWIR) systems remain largely unknown. The hydrothermally active Indian Ridge system harbours potential sites for future Seafloor Massive Sulphides (SMS) mining. Since seabed mining may create a long-lasting impact on the deep-sea ecosystems, it could harm the unique deep-sea life associated with mineral deposits. This study identified two undescribed squat lobster specimens: one from the genus Munidopsis Whiteaves, 1874 from the CIR system in water depths ranging from 1981 to 2033 m, and one from the genus Typhlonida Macpherson & Baba in Machordom, Ahyong, Andreakis, Baba, Buckley, Garcia-Jimenez, McCallum, Rodriguez-Flores & Macpherson, 2022 from the SWIR system in depths ranging from 2070 to 2404 m. Both new species may be distinguished morphologically and genetically based on the partial mitochondrial (mtCOI) gene. To generate baseline environmental and biodiversity data, efforts for accurate sampling and correct identification of biological species are required

The sponge-associated benthic shrimp Spongicoloides weijiaensis Xu, Zhou & Wang, 2017 is reported for the first time from the Southwest Indian Ridge (SWIR). A single female specimen of S.weijiaensis was associated with the hexactinellid sponge belonging to Dictyaulus sp. that was collected using a benthic sledge from the southwest Indian Ridge at a water depth of 2358 m. The spongicolid shrimp is reported using both classical taxonomic and molecular tools (cytochrome c oxidase subunit 1—COI). The S. weijiaensis specimen from the SWIR appears to represent a morphological variant that has pigmented eyes, telson with thirteen spines, and a broadly rounded setiferous posterior margin. This new report at a latitude of nearly 26° South on the seamount provides the first Mid Ocean Ridge sector record for stenopodidean shrimp known to date.

The topographic fabric of the rift valley floor has been analyzed using the multibeam echosounder data obtained by the autonomous underwater vehicle (AUV) Abyss at two locations over a short segment of the slow-spreading Central Indian Ridge between 10°18′ and 10°57′S. The region is influenced by hydrothermal venting in the near vicinity. Two AUV dives D51 and D52 were performed over this segment at two locations that are 30 km apart and covered 5 km2 and 8 km2 seafloor area, respectively. The dive D51 covered the off-axis part of the rift valley floor in the middle part of the segment, and the dive D52 is located near to the non-transform discontinuity that covered the terminal part of an oceanic core complex (OCC). High-resolution seafloor topography as revealed by the AUV-mounted multibeam echosounder system brought out several micro-bathymetric fabric features such as a lava lake, a cratered volcano, an OCC, and the foot wall volcanic complex at the distal part of the OCC. The valley floor imaged in the D51 is marked by a lava flow encompassing an area of 1 km2 and a volcano in the NE corner. The volcano has a diameter of about 800 m with an elevation of about 200 m from the adjacent seafloor, and the partially mapped volcano crater has a relief of about 60 m. A prominent linear fissure running parallel to the ridge axis has been identified; this feature joins with the volcano. Analysis of AUV-mounted CTD data indicated three distinct temperature spikes ranging 0.009 to 0.013 °C in the region of dive D51. The observed temperature spikes appear to be related to the linear fissure on the seafloor and probably represent leaky venting of fluids from the fissure. With respect to the dive D52, the foot wall volcanic features associated with the OCC are prominent. The volcanic seafloor feature covered an area of 3.45 km2 and is conspicuous with rugged topographic fabric at the base of the OCC. These inferences and the morphotectonics of the rift valley floor as revealed by the AUV data suggest moderate hydrothermal venting in this segment of the slow-spreading Central Indian Ridge.

Iron is a limiting nutrient in the marine biogeochemical cycle, and hydrothermal processes at mid-ocean ridges are well-known as one of its sources to the water column. However, a major portion of the hydrothermal iron is precipitated near the source and plays an essential role in oceanic elemental cycling. Here, we carried out a detailed study on the geochemical characteristics of Fe, using a sequential chemical extraction protocol, in a short sediment core collected from the eastern Southwest Indian Ridge (SWIR) to understand the iron association in individual mineral phases. Major and trace and rare-earth element concentrations, positive europium anomaly, and rare-earth fractionation show that the source components in the sediment core are composed of biogenic, local mafic, ultramafic, and hydrothermal origin. Solid-phase Fe speciation results indicate that >60% of Fe is associated with the Fe-oxides phase and indicate the hydrothermal plume particulates settled from the water column. A relatively low concentration of Fe associated with the pyrite and silicate (FeRes) phase suggests an erosion of sulphide and silicate minerals from the nearby vent field. The down-core variation reflects the transformation of primary ferrihydrite to more stable oxide mineral goethite/hematite and, to some extent, the formation of silicate minerals.

Congenital absence of the inferior vena cava (IVC) triggers collateral vessel growth to drain the peripheries and abdominal organs. This causes venous stasis and increases the risk of deep vein thrombosis (DVT) and pulmonary embolism. Typically, patients with absent IVCs present before 30 years of age, with bilateral DVT symptoms triggered by intense exercise. The abnormality can remain undetected as computed tomography imaging is not usually performed. Due to the increased risk of clotting, these patients should be on life-long anticoagulation. Raising clinical awareness of this condition, to ensure appropriate investigations and treatment, is important.

Spongicoloides weijiaensis Xu, Zhou & Wang, 2017 (Fig. 1–6) Spongicoloides weijiaensis — Xu, Zhou & Wang 2017: 11, Figs. 2–5.— Kou et al. 2018: 100.— Bochini et al. 2020: 712. — Schnabel et al. 2021: 32. Spongicoloides novaezelandiae — Goy 2015: 310, Figs. 9 –11 (in part). Material examined: 1 female, 35.1 mm TL, NCPOR /HYD-IO/0018, Southwest Indian Ocean Ridge, Indian Ocean, R / V ‘MGS Sagar’ cruise MGS–26 (station: MGS 26C BD–15), 12 May 2019, 26° 28′ 10″ S, 67° 26′ 21″ E, 2358 m, benthic sledge, Coll. Baban Ingole, samples in 90% ethanol. Measurements (mm): Female, PCL: 12.2, RCL: 15.4, TL: 35.1. Description: Rostrum nearly horizontal, slightly overreaching basal article of antennular peduncle; rostral base triangular in dorsal view, armed with 9 dorsal, 2 ventral spines. Carapace with distinct cervical groove, anterolateral margin with scattered small spines; branchiostegal and pterygostomial regions smooth, and several spinules situated posterior to them, postorbital region armed with one short longitudinal row of spinules, groups of similar spinules also present on a posterior portion of cervical groove and rostrum. Antennal spine blunt. Eye s well developed, moderate in size; cornea globular, dark pigmented, broader than eyestalk, eyestalk armed with minute spines. Color in life: Body whitish, translucent; some intrathoracic organs visible. Antennular peduncle reaches mid-length of antennal scale, the first article distinctly longer than both distal articles combined, with a blunt spine distolaterally, stylocerite small, subacutely pointed, second article longer than the distal article, bearing a single distal spinule on inner margin, distal article unarmed. Antenna has stout basicerite, bearing four (right) or three (left) large spines at a distolateral angle, an additional four (right) or three (left) small spines on the ventrodistal margin, and two (right) or three (left) small spines on ventral surface proximally. Carpocerite overreaching first article of antennular peduncle. Antennal scale broad; twice as long as rostrum, 2.7 times as long as wide; lateral margin slightly concave, not setiferous, with ten (right) or twelve (left) spines; distolateral bifid spine slightly falling short of or just reaching rounded distal margin of lamella; inner margin convex; both inner and distal margins with long plumose setae; dorsal surface with single longitudinal carina. Basal article of antennal peduncle armed with three (right) or two (left) terminal spines laterally. Mandible strong, with well-developed 3-jointed palp; distal article densely setose on the margin, oval, subequal in length to intermediate article; molar and incisor processes separate. Molar surface smooth, tooth absent, incisor bearing with 2 strong stout distal teeth followed by 8 small sharp teeth on the mesial margin. Maxillule has simple palp bearing a pair of terminal setae; distal endite broad, its mesial margin straight or truncates with simple setae and 10 stout spines; proximal endite suboval, narrowing or tapering distally. Maxilla has palp stout distally, tapering, bearing simple setae; distal and proximal endites bilobed; scaphognathite well developed with plumose setae. The branchial formula is summarized in Table 1. First maxilliped has bi-jointed palp; distal article with one prominent spine; proximal article broad, 1.5 times of distal article in length; distal endite large, rounded anteriorly, proximal endite bilobed; exopod well developed; epipod large, subequally bilobed. Second maxilliped having endopod composed of seven articles; dactylus triangular, ~ 1.5 times as long as broad; propodus is subquadrate ~ 2 times of dactylus in length; carpus short, distally widening 0.5 times as long as propodus; long merus, 3 times as long as carpus; ischium not fused with basis with 0.2 times as long as merus; epipod oval, with rudimentary podobranch; exopod absent. Third maxilliped with 7-jointed endopod, slender, slightly overreaching mid-length of antennal scale in full extension; dactylus tapering distally; propodus 1.8 times as long as dactylus; carpus 1.1 times of propodal length; merus 1.7 times of carpal length; ischium subequal to merus; basis shortest, approximately 0.2 times length of ischium; coxa with tiny epipod; exopod absent. First pereiopod is reaching distal margin of antennal scale; dactylus half as long as palm; subcylindrical palm, with some grooming setae; carpus longest, nearly 2.4 times as long as palm, distal part of flexor margin of carpus with a tuft of grooming setae, merus 0.7 times as long as carpus; ischium 0.5 times as long as merus; coxa and basis short, unarmed. Second pereiopod is similar in shape to the first pereiopod, longer, overreaching distal margin of antennal scale by the length of chela; dactylus 0.4 times as long as palm; carpus 1.9 times as long as palm; merus 0.8 times as long as carpus; ischium 0.4 times as long as merus; coxa and basis short, unarmed. Third pereiopod is the strongest and longest, overreaching distal margin of the antennal scale by the length of the chela; fingers terminating each in strongly curved, corneous claw, tips crossing, fixed finger with deep longitudinal concavity proximally, bearing single rounded tooth at nearly mid-length of cutting edge and with a short row of small teeth on the proximal cutting edge, distoventral margin without a row of teeth; dactylus 0.6 times of palm length, protruded at proximal 0.4 of length, with concavity on distal half portion; palm almost equal to merus in length, subcylindrical; propodus with some minute teeth present on distal half of flexor margin; carpus widening distally, nearly half as long as palm; merus of right third pereiopod unarmed, merus of left third pereiopod bearing minute tooth at approximately distal 0.2 of its length on flexor margin; ischium 0.9 times as long as carpus, flexor margin entirely smooth, distolateral margin also with similar teeth; basis and coxa short, unarmed. Fourth pereiopod is overreaching distal margin of antennal scale by the length of dactylus and propodus, dactylus short, compressed laterally, biunguiculate, ventral unguis shorter than dorsal unguis, both demarcated, with some much smaller accessory teeth arising from bases of both ventral and dorsal ungues; propodus approximately 0.4 times length of carpus, armed with a single row of 11 or 12 movable spines on flexor margin; carpus longest; merus 0.8 times length of the carpus, ischium half-length of merus, unarmed; coxa and basis short and stout. Fifth pereiopod is overreaching distal margin of antennal scale by dactylus and half-length of propodus. Sixth thoracic sternite with paired triangular plates, the ventral surface curved in. Seventh and eighth sternites with bilobed prominences. Pleomeres glabrous. First somite short, uniramous, divided into two sections by distinct transverse carina, posterior section of pleuron rounded. Second to fourth pleura each bearing one articular knob; first to the third pleura broadly rounded ventrally, unarmed, and setose on ventral margin; fourth to sixth pleura each with several small posteroventral teeth. First pleopod uniramous. Second to fifth pleopods biramous. Uropod with stout protopod, lateral margin terminating in two spines. Endopod and exopod each with a single weak dorsal carina. The lateral margin of the exopod is slightly convex with a row of 15 (left) or 16 (right) acute teeth, excluding a broad trilobed tooth on the distolateral angle. Endopod ovate, falling short of posterior margin of telson. Telson quadrangular, almost twice as long as broad, slightly constricted near the base, with two dorsolateral carinae prominent, lateral margin armed bearing 10 (right) or 12 (left) posteriorly directed spines; constricted part of each lateral margin with a single proximal submarginal spine, lateral marginal spines distinct. Setiferous posterior margin broadly rounded, with 13 spines. Molecular data: A COI gene sequence of S. weijiaensis from the SWIOR has been deposited in Genbank (NCBI accession number MT806161). The pairwise genetic distances within species of Spongicoloides weijiaensis ranged from 0.02 to 0.03. Distribution: The distribution of S. weijiaensis now extends from the North West Pacific, Madagascar, Indian Ocean (off Northern Australia), New Zealand, New Caledonia, Fiji, Tasmania (349–2380 m) to the seamount in the Mid Ocean Ridge sector of the Southwest Indian Ocean (2358 m). Remarks: Throughout the species’ range, S. weijiensis has been found at depths of 349 to 2380 m; with 2380 m being the deepest record for any stenopodidean. Specimens from New Caledonia and Madagascar were identified as S. novaezelandiae but were shown to belong to S. weijiaensis (Schnabel et al. 2021). The Spongicoloides weijiaensis of Southwest Indian Ocean Ridge is morphologically similar to S. weijiaensis Xu, Zhou & Wang, 2017 and S. corbitellus Kou, Li & Gong, 2018. Both specimens match the type description in nearly all aspects. Slight variation in the pigmented eyes, distal and proximal endites both bilobed compared to the original description is an additional large postorbital carapace spine, the first pleonite being more distinctly ridged (Figure 4A). A recent paper on New Zealand stenopodideans covers the differences between S. novaezelandiae and other species of Spongicoloides (Schnabel et al. 2021). Both our SWIR specimen and S. weijiaensis were found in the Euplectella sponge, S. corbitellus was collected from another euplectellid sponge of the genus Corbitellus (Kou et al. 2018). Even though our specimen of Spongicoloides weijiaensis from SWIR is similar to S. iheyaensis Saito, Tsuchida & Yamamoto, 2006, S. corbitellus, S. zhoui Zhao, Xu, Yang & Qiu, 2021 all from the Western Pacific Ocean, is distinguished by the differences in spination of carapace, sixth pleonal somite, and third pereiopod (Figures 2 & 4)., Published as part of Rengaiyan, Periasamy, Palayil, John Kurian & Ingole, Baban, 2022, A new report on the deep-sea sponge-associated Spongicoloides weijiaensis Xu Zhou & Wang, 2017 (Decapoda: Spongicolidae) from the Southwest Indian Ocean Ridge, pp. 267-277 in Zootaxa 5195 (3) on pages 269-272, DOI: 10.11646/zootaxa.5195.3.5, http://zenodo.org/record/7187865, {"references":["Xu, P., Zhou, Y. & Wang, C. (2017) A new species of deep-sea sponge-associated shrimp from the North-West Pacific (Decapoda, Stenopodidea, Spongicolidae). Zookeys, 685, 1 - 14. https: // doi. org / 10.3897 / zookeys. 685.11341","Kou, Q., Gong, L. & Li, X. (2018) A new species of the deep-sea spongicolid genus Spongicoloides (Crustacea, Decapoda, Stenopodidea) and a new species of the glass sponge genus Corbitella (Hexactinellida, Lyssacinosida, Euplectellidae) from a seamount near the Mariana Trench, with a novel commensal relationship between the two genera. Deep Sea Research Part I: Oceanographic Research Papers, 135, 88 - 107. https: // doi. org / 10.1016 / j. dsr. 2018.03.006","Bochini, G. L., Cunha, A. M., Terossi, M. & Almeida, A. O. (2020) A new genus and species from Brazil of the resurrected family Macromaxillocarididae Alvarez, Iliffe & Villalobos, 2006 and a worldwide list of Stenopodidea (Decapoda). Journal of Crustacean Biology, 40, 704 - 714. https: // doi. org / 10.1093 / jcbiol / ruaa 064.","Schnabel, K. E., Kou, Q. & Xu, P. (2021) Integrative Taxonomy of New Zealand Stenopodidea (Crustacea: Decapoda) with New Species and Records for the Region. Diversity, 13, 343. https: // doi. org / 10.3390 / d 13080343","Goy, J. W. (2015) Stenopodidean shrimps (Crustacea: Decapoda) from New Caledonian waters. Zootaxa, 4044 (3), 301 - 344. https: // doi. org / 10.11646 / zootaxa. 4044.3.1","Saito, T, Tsuchida, S. & Yamamoto, T. (2006) Spongicoloides iheyaensis, a new species of deep-sea sponge-associated shrimp from the Iheya Ridge, Ryukyu Islands, southern Japan (Decapoda: Stenopodidea: Spongicolidae). Journal of Crustacean Biology, 26, 224 - 233. https: // doi. org / 10.1651 / C- 2650.1","Zhao, Y. U., Xu, T., Yang, W. & Qiu, J. W. (2021) A new species of the deep-sea shrimp genus Spongicoloides (Decapoda: Spongicolidae) from the South China Sea. Zootaxa, 5005 (3), 276 - 290. https: // doi. org / 10.11646 / zootaxa. 5005.3.3"]}

Rengaiyan, Periasamy, Palayil, John Kurian, Ingole, Baban (2022): A new report on the deep-sea sponge-associated Spongicoloides weijiaensis Xu Zhou & Wang, 2017 (Decapoda: Spongicolidae) from the Southwest Indian Ocean Ridge. Zootaxa 5195 (3): 267-277, DOI: https://doi.org/10.11646/zootaxa.5195.3.5

We describe a new deep-sea sponge species, Fibulia occiensis sp. nov., from the Central Indian Ocean Ridge (CIOR) at Rodrigues Triple Junction (RTJ), of the family Dendoricellidae Hentschel, 1923. Two sponge specimens were collected between 1982–2079 m depth using a benthic sledge in the 25° South Oceanic Core Complex (OCC) region. The megabenthic fauna was collected to establish a baseline of environmental and benthic ecological data. This data will be handy in assessing the impact of sulfide mining in the near future. Fibulia occiensis sp. nov. is fragile and stalked, has a single type of oxea, and no sigma. The new species is different from the congeneric Fibulia species by its larger oxeas and the strongly curved isochelae.

Genus Fibulia Carter, 1886 “ Fibulia is defined by having a plumose or confused choanosomal skeleton of multispicular tracts; microscleres arcuate or reduced isochelae and the presence of only a single size category of oxeas” (taken from Van Soest 2002)., Published as part of Rengaiyan, Periasamy, Palayil, John Kurian & Ingole, Baban, 2022, A new deep-sea sponge Fibulia occiensis sp. nov. (Poecilosclerida: Dendoricellidae) from the 25 ° South Oceanic Core Complex in the Central Indian Ocean Ridge, pp. 87-96 in Zootaxa 5162 (1) on page 89, DOI: 10.11646/zootaxa.5162.1.6, http://zenodo.org/record/6796860, {"references":["Carter, H. J. (1886) Descriptions of Sponges from the Neighbourhood of Port Phillip Heads, South Australia, continued. Annals and Magazine of Natural History, Series 5, 18, 34 - 55 + 126 - 149. https: // doi. org / 10.1080 / 00222938609460122","Van Soest, R. W. (2002) Family Dendoricellidae Hentschel, 1923. In: Hooper, J. N. A. & Van Soest, R. W. M. (Eds.), Systema Porifera. A guide to the classification of sponges. Kluwer Academic / Plenum, Publishers, New York, New York, pp. 567 - 571. https: // doi. org / 10.1007 / 978 - 1 - 4615 - 0747 - 5 _ 60"]}

In globally distributed deep-sea hydrothermal vent plumes, microbiomes are shaped by the redox energy landscapes created by reduced hydrothermal vent fluids mixing with oxidized seawater. Plumes can disperse over thousands of kilometers and are complex. Their characteristics are determined by geochemical sources from hydrothermal vents, e.g., hydrothermal inputs, nutrients, and trace metals. However, the impacts of plume biogeochemistry on the oceans are poorly constrained due to a lack of integrated understanding of microbiomes, population genetics, and geochemistry. Here, we use microbial genomes to understand links between biogeography, evolution, and metabolic connectivity, and elucidate their impacts on biogeochemical cycling in the deep sea. Using data from 37 diverse plumes from 8 ocean basins, we show that sulfur metabolism defines the core microbiome of plumes and drives metabolic connectivity. Amongst all microbial metabolisms, sulfur transformations had the highest MW-score, a measure of metabolic connectivity in microbial communities. Our findings provide the ecological and evolutionary basis of change in sulfur-driven microbial communities and their population genetics in adaptation to changing geochemical gradients in the oceans.

In the prediction of accurate wave force, the consideration of short-crested wave is important in representing the actual ocean condition. Owing that, nonlinear wave characteristics are expected to change the flow properties when the wave passes the structures, which showing these characteristics are crucial to be accounted. However, literature reported that the overestimation on the design of marine structures has shown a lower reliability in the wave force prediction considering long-crested wave. Further in detail, the effect of wave directionality and directional spreading angle from the actual sea conditions, i.e. the short-crested waves, have been neglected in a way. To prove the validity of this statement, an experimental investigation was conducted to quantify the effects of wave directionality on the wave forces and to propose the hydrodynamic coefficients incorporated the effect of directional spreading angles. The wave directionality in term of directional spreading angles were considered, ranging from 5 to 45°. Then, the measured wave surface elevation and wave forces were processed using least square method to compute the hydrodynamic coefficients and to evaluate the wave forces. To quantify the effect, force ratio factor was adopted. Based on the finding, short-crested waves led to 20 % force reduction as compared to the long-crested. On top of that, a reduction of 1.12 % of wave force has also been observed for every one-degree incremental of the directional spreading angle. As conclusion, the wave directionality was found contributing to the reduction of wave force which may provide new improvement on the accuracy of wave force formulation for the design of lean marine structures.