New Taxa and Occurrences of Mesophotic and Deep-sea Goniasteridae (Valvatida, Asteroidea) from Okinawa and adjacent regions.

Thirteen new records of Goniasteridae showing mesophotic occurrence are presented, including a new species of Pseudoceramaster doto n. sp. from southern Japan and a new genus and species, Churaumiastra hoshi nov. gen. nov. sp. which occurs in southern Japan, the Philippines and Western Australia.

Exploring the trends of adaptation and evolution of sclerites with regards to habitat depth in sea pens.

Octocorals possess sclerites, small elements comprised of calcium carbonate (CaCO3) that are important diagnostic characters in octocoral taxonomy. Among octocorals, sea pens comprise a unique order (Pennatulacea) that live in a wide range of depths. Habitat depth is considered to be important in the diversification of octocoral species, but a lack of information on sea pens has limited studies on their adaptation and evolution across depth. Here, we aimed to reveal trends of adaptation and evolution of sclerite shapes in sea pens with regards to habitat depth via phylogenetic analyses and ancestral reconstruction analyses. Colony form of sea pens is suggested to have undergone convergent evolution and the loss of axis has occurred independently across the evolution of sea pens. Divergences of sea pen taxa and of sclerite forms are suggested to depend on habitat depths. In addition, their sclerite forms may be related to evolutionary history of the sclerite and the surrounding chemical environment as well as water temperature. Three-flanged sclerites may possess the tolerance towards the environment of the deep sea, while plate sclerites are suggested to be adapted towards shallower waters, and have evolved independently multiple times. The common ancestor form of sea pens was predicted to be deep-sea and similar to family Pseudumbellulidae in form, possessing sclerites intermediate in form to those of alcyonaceans and modern sea pens such as spindles, rods with spines, and three-flanged sclerites with serrated edges sclerites, as well as having an axis and bilateral traits.

Redescription of Synactinernus flavus for the First Time after a Century and Description of Synactinernus churaumi sp. nov. (Cnidaria: Anthozoa: Actiniaria).

Two species of Synactinernus sea anemones were found in Japanese waters. Synactinernus flavus Carlgren, 1918, the only described species of this genus, is rediscovered from off the Goto Islands a century after the original description. Synactinernus flavus was once synonymized with Isactinernus quadrilobatus Carlgren, 1918; however, we show that, based on morphological (including examination of type specimens) and molecular (using nuclear 18S rDNA) evidence, these species are completely different. The other species, Synactinernus churaumi sp. nov., was found off Ishigaki Island and Okinawa Island by a remotely operated vehicle (ROV), and had been kept for 15 years in a tank at the Okinawa Churaumi Aquarium. There are clear differences between these two species; therefore, we describe the second species and revise the diagnosis of Synactinernus.

First record of Larsonella pumilus (Teleostei: Gobiidae) from Japan, with phylogenetic placement of the genus Larsonella.

During a survey of deep-sea fauna, using a Remotely Operated Vehicle, a single specimen (21.6 mm in standard length) of Larsonella pumilus (Larson Hoese, 1980) was collected at a depth of 214 m off the coast of Okinawa Island, Japan. It represents the first record of this species from Japan. The collection site was far deeper than previous reports for this species. This suggests that the main habitat of L. pumilus is deeper than previously recognized and it may explain the paucity of records of this species. As the previously available morphological description of L. pumilus was based on only a single specimen (holotype), this new specimen is described herein. Its morphology corresponds closely to the original description of the holotype, except that faint melanophores are arranged radially around the eyes and scattered on the trunk and the fins. Mitochondrial genome sequences of L. pumilus and 19 related species demonstrate close relationships between L. pumilus and the genus Priolepis. These data also indicate that the genus Priolepis is not monophyletic.

Two large squat lobsters of the superfamily Chirostyloidea (Crustacea: Decapoda: Anomura) from the Ryukyu Islands, southwestern Japan, with description of a new species of the genus Eumunida Smith, 1883.

Two species of the chirostyloid families Sternostylidae and Eumunididae, Sternostylus investigatoris (Alcock Anderson, 1899) and Eumunida balteipes n. sp., are reported on the basis of material collected from deep waters off Kume Island, Ryukyu Islands, southwestern Japan. Sternostylus investigatoris is recorded for the first time and is the second species of the genus from Japanese waters. Eumunida balteipes n. sp. is morphologically closest to E. sternomaculata de Saint Laurent Macpherson, 1990, but the armature of the thoracic sternite 3 and P1 palm distinguishes the two species.

Direct Growth Measurements of Two Deep-sea Scalpellid Barnacles, Scalpellum stearnsii and Graviscalpellum pedunculatum.

Yoichi Yusa, Natsumi Yasuda, Tomoko Yamamoto, Hiromi Kayama Watanabe, Takuo Higashiji, Atsushi Kaneko, Kazuki Nishida, and Jens T. Høeg (2018) Little is known about the growth rates of invertebrates living in ordinary deep-sea habitats such as continental slopes. Thus, the growth rates of two species of the deep-sea scalpellid barnacles, Scalpellum stearnsii and Graviscalpellum pedunculatum, were studied in two aquaria (at Nara and Okinawa Churaumi, Japan). In addition, growth of an S. stearnsii individual after 1 year of deployment was measured in the field. Overall, adult individuals of both species showed slow growths over 8 months (at Nara) and 2 years (at Okinawa) of rearing (e.g., at Nara: 2.0 ± 3.6 µm d-1 for S. stearnsii and 5.9 ± 2.7 µm d-1 for G. pedunculatum; mean ± SD). In contrast, growth rates of juvenile S. stearnsii at Nara were greater (15 ± 7.7 µm d-1). The in situ growth rate of the adult S. stearnsii (3.4 µm d-1) was greater than the average, but within the range of the rates of similar-sized individuals recorded in aquaria. Compared with other pedunculate barnacles, both species show small growth rates typical for deep-sea animals.

New records of the squat lobster genus Munida Leach, 1820 (Crustacea: Decapoda: Anomura: Munididae) from deep-water off Okinawa Islands, Ryukyu Islands, Japan, with description of a new species.

Two species of the squat lobster genus Munida Leach, 1820, M. pollioculus n. sp. and M. zebra Macpherson, 1994, are recorded from deep-waters off Okinawa Islands, the Ryukyu Islands, at depths of 1000 m and 495 m, respectively. The new species closely resembles M. clevai Macpherson, 1999 and M. microps Alcock, 1894, but it differs from the latter two in the absence of a proximal spine on the mesial margin of the cheliped dactylus and the more stout dactylus of the second pereopod. Munida zebra is first recorded from the Northwest Pacific, as well as Japanese waters, with its geographical range extended to the north from the previously known southwestern Pacific localities.