Osteodiscus abyssicola, a new snailfish (Cottoidei: Liparidae) collected off the Pacific coast of northern Japan.

The snailfish Osteodiscus abyssicola sp. nov. is described from a single specimen collected off the Pacific coast of Hokkaido, northern Japan, at a depth of 4,6714,744 m. It is distinguished from all currently recognized congeners by the following combination of characters: vertebrae 49; dorsal-fin rays 44; anal-fin rays 39; principal caudal-fin rays 8; pyloric caeca 5; mouth horizontal; teeth on both jaws simple and sharp, without cusps; upper and lower jaw symphyses without diastema; cephalic pore sizes moderate, similar to or slightly larger than nostril; gill slit extending ventrally to 2nd pectoral-fin ray base; pectoral fin notched; mandibular symphysis to center of anus 101.6% head length (HL); posterior edge of pelvic disk to center of anus 15.5% HL; epural 1, reduced; epipleural ribs absent. An emended diagnosis and key to the species of Osteodiscus are provided.

Etmopterus lantern sharks use coelenterazine as the substrate for their luciferin-luciferase bioluminescence system.

The lantern shark genus Etmopterus contains approximately 40 species of deep-sea bioluminescent cartilaginous fishes. They emit blue light mainly from the ventral body surface. The biological functions of this bioluminescence have been discussed based on the luminescence patterns, but the bioluminescence mechanism remains uncertain. In this study, we detected both coelenterazine and coelenterazine-dependent luciferase activity in the ventral photophore tissue of Etmopterus molleri. The results suggested that bioluminescence in lantern sharks is produced using coelenterazine as the substrate for the luciferin-luciferase reaction, as some luminous bony fishes.

Two new species of snailfishes of the genus emCareproctus/em (Cottoidei: Liparidae) from the western North Pacific Ocean with a range extension of emCareproctus brevipectoralis/em.

Three snailfish species of Careproctus (Cottoidei: Liparidae), including two new species, are described from the deep Pacific Ocean off northern Honshu Island, Japan. Careproctus cyanogladius sp. nov., collected from the depths of 2,698-3,223 m, can be distinguished from congeneric species by having the following combination of characters: vertebrae 63; dorsal-fin rays 57-58; anal-fin rays 50; principal caudal rays 7; pectoral-fin rays 29-31; pectoral fin without a notch; uppermost pectoral-fin base below a horizontal through posterior margin of maxillary; pelvic disk oval; chin pores well separated; teeth simple; pyloric caeca 6-10; body pale blue or gray when fresh. The other new species, Careproctus orri sp. nov., collected from depths of 640-808 m, can be distinguished from congeneric species by having the following combination of characters: vertebrae 58-60; dorsal-fin rays 52-53; anal-fin rays 47-49; pectoral-fin rays 34-35; pectoral fin with a distinct notch; cephalic pores 2-6-7-2, chin pores single, unpaired; gill slit extending ventrally to 5th or 6th pectoral-fin ray; teeth strongly trilobed; peritoneum dark, stomach white. In addition, one specimen of Careproctus brevipectoralis Chernova, Thiel Eidus, 2020 was newly collected from Japan, and is redescribed here in detail with comments on intraspecific variations.

Bathyraja (Arctoraja) sexoculata sp. nov., a new softnose skate (Rajiformes: Arhynchobatidae) from Simushir Island, Kuril Islands (western North Pacific), with special reference to geographic variations in Bathyraja (Arctoraja) smirnovi.

A new species of softnose skate (Arhynchobatidae), Bathyraja sexoculata Misawa, Orlov, Orlova, Gordeev and Ishihara is described on the basis of five specimens collected from off the east coast of Simushir Island, Kuril Islands, located in the western North Pacific. The specimens conformed to the genus Bathyraja by having the anteriormost pectoral-fin skeleton almost reaching the snout tip, and a slender unsegmented rostral cartilage. Within Bathyraja, the new species belongs to the subgenus Arctoraja (currently with four valid species) due to the relatively short tail (79-86% of disc width), high count of predorsal caudal vertebrae (more than 86), and large strong nuchal and scapular thorns. It is most similar to Bathyraja (Arctoraja) smirnovi, distributed in the Seas of Japan and Okhotsk, in having tail thorns not extending to the nuchal area, median thorns discontinuous from the nape to the tail, and no mid-dorsal thorns. However, B. sexoculata can be distinguished from B. smirnovi by the following characters: three pairs of white blotches on the dorsal disc surface (vs. blotches absent, or a pair of white or dark blotches in B. smirnovi), dark blotch around cloaca, dark bands along mid ventral line of tail (vs. dark blotch and band usually absent ventral disc surface in B. smirnovi), 86-93 predorsal caudal vertebrae (vs. 80-87 in B. smirnovi), and a unique mitochondrial DNA cytochrome c oxidase subunit I sequence. Proportional measurements, including disc width, disc length, head length, preoral length, prenarial length, internarial distance, eye diameter, and tail length, also differ between the two species. For the referential purpose, geographical variations of B. smirnovi distributed in the Seas of Japan and Okhotsk are analyzed and clarified based on morphological and genetic data. Significant morphological and genetic differences were found between local populations in the Seas of Japan and Okhotsk.

A new species of the codlet genus Bregmaceros from the western Pacific Ocean (Gadiformes: Bregmacerotidae).

Bregmaceros retrodorsalis sp. nov., a new codlet species is described based on specimens from shallow to deep waters off Japan and Melanesia. It differs from all congeners by having the origin of second dorsal-fin well posterior, above bases of 5th to 7th anal-fin rays and combination of the following characters: a pointed snout distinctly longer than eye diameter; upper lobe of opercle branched distally; body relatively slender, its depth 10.0‒13.0% SL; 13 principal caudal-fin rays (middle 11 branched); 52‒57 second dorsal-fin rays; 58‒63 anal-fin rays; 16‒18 transverse scale rows below dorsal-fin origin; 86‒93 longitudinal scale rows along body axis; vertebrae 55‒58; entire body evenly covered with melanophores, those on lateral sides forming regular longitudinal rows, one melanophores per scale; head and isthmus entirely, but loosely, covered with variably sized melanophores.

Bregmaceros anchovia sp. nov., a new codlet species from the western Pacific Ocean (Gadiformes: Bregmacerotidae).

A new codlet species is described from Japan, Taiwan, Indonesia and Australia. It is distinguished from its congeners by having a pointed snout extending beyond jaws, a stripe of black dots above anal-fin base, a black vertical band on caudal-fin base, and the following combination of characters: ventral surface of head and abdomen devoid of melanophores; ventral portion of abdominal vertebrae with a pointed parapophysis and a blunt ventral post-zygapophysis; peritoneum, pyloric caeca, and intestine pale; dorsal-fin rays 46-52; anal-fin rays 47-55; pectoral-fin rays 15-17; principal caudal-fin rays 12‒14; caudal vertebrae 35‒39; total vertebrae 50-54. Furthermore, as a result of this study, Bregmaceros pescadorus Shen described from southwestern Taiwan is herein recognized as a junior synonym of Bregmaceros nectabanus Whitley.

End-to-end test to evaluate the comprehensive geometric accuracy of a proton rotating gantry using a cone-shaped scintillator screen detector.

In this study, we aim to evaluate the comprehensive geometric accuracy of proton rotating gantries by performing an end-to-end test using a cone-shaped scintillator screen detector, known as XRV-124. The XRV-124 comprises a cone-shaped sheet-like scintillator and charge-coupled device camera that detects the scintillation light. First, the results of the Winston-Lutz and end-to-end XRV-124 tests performed on a conventional linear accelerator were compared to confirm the reliability of the XRV-124, and the snout position dependency of the geometric accuracy was evaluated for the proton rotating gantry as a pre-verification process. Thereafter, an end-to-end test including computed tomography imaging and irradiation in 30° steps from 0° to 330° for two proton rotating gantries, which have the same specifications, was performed. The results of the pre-verification indicated that sufficient accuracy was obtained for the end-to-end test of the proton rotating gantry. The end-to-end test results showed a peak-to-peak deviation of up to 2 mm for some of the coordinate axes. The two gantries exhibited almost similar results in terms of the absolute quantity; however, a few trends were different. Thus, the beam axis deviations were confirmed to be within the safety margin, as expected in clinical practice. Based on the results of this study, the XRV-124 can be used as a comprehensive end-to-end constancy test tool, as it enables a comparative verification of multiple rotating gantries and geometric accuracy verification of different treatment modalities.

[Influence and Countermeasure of Respiratory Motion on Matchline Profile of Field Matching Technique in Passive Scattering Proton Therapy for Esophageal Cancer].

This study aimed to evaluate the influence of change in respiratory motion on matchline (ML) and reduction of the effect by increasing ML levels of field matching technique in passive scattering proton therapy for esophageal cancer. To evaluate the influence of respiratory motion in terms of stability, we measured relative dose around ML using a respiratory motion phantom. The relative error was -0.5% when the respiratory motion phantom worked stable, whereas there was obvious change that the relative error was -25.5% when the difference of amplitude between upper field and lower field was one side 3 mm on each cranially and caudally direction. In clinical case of the seven esophageal cancer patients simulated by the treatment planning system, assuming the difference of amplitude was 3 mm, the relative error of maximum (minimum) dose in clinical target volume around ML against the original treatment plan were 5.8±1.2% (-6.0±2.7%), 3.3±0.9% (-3.8±1.0%), and 2.4±0.5% (2.6±0.8%) on average (±SD) when ML levels were 2, 4, and 6, respectively. Increasing ML levels can reduce the influence of respiratory motion.

Branchiostegus biendong, a New Tilefish from Vietnam (Perciformes: Branchiostegidae).

A new tilefish, Branchiostegus biendong, is described on the basis of three specimens (181-209 mm in standard length [SL]) collected from a local fish market of Quy Nhon on the South China Sea coast of central Vietnam. It can be distinguished from 17 congeners in having the following combination of characters: six diagonal scale rows exposed on cheek; cheek scales moderately large (diameter 2.2-2.5% SL); predorsal ridge black; cheek almost silver with an oval-shaped, yellow blotch along ventral margin of eye; dorsal fin translucent yellowish with narrow black margin overlapping stronger yellowish coloration dorsally; upper lobe of caudal fin with 5-6 yellow stripes and tip with black blotch; and lower lobe of caudal fin navy blue. A key to five species of Branchiostegus from Vietnamese waters is provided.

Glossanodon macrocephalus, a new argentine fish (Argentinidae) from the Arabian Sea.

A new species of argentinid fish, Glossanodon macrocephalus Bineesh Endo, from the Arabian Sea, off the southwestern coast of India, is described on the basis of four specimens (129-164 mm SL). The new species clearly differs from its congeners in the following combination of characters: dorsal-fin rays 10-11; pectoral-fin rays 21-23; anal-fin rays 12-13; pelvic-fin rays 11-12; branchiostegal rays 5; gill rakers on first arch 30-36; vertebrae 47-48; a patch of small conical teeth on middle of lower jaws; predorsal 49-51% SL; prepectoral 36-39% SL; prepelvic 57-58% SL; distance from pelvic to anal-fin origin 26-28% SL; head length 35-39% SL; eye diameter 22-26% HL; snout length 28-30% HL; location of anus immediately anterior to anal-fin origin; broad longitudinal black stripe above lateral line; dark spot on the base to half of pectoral fin; and no teeth on tongue. The new species is a benthopelagic dweller on muddy bottoms in depths of around 300-600 m.

Feasibility of CBCT-based proton dose calculation using a histogram-matching algorithm in proton beam therapy.

The aim of this study was to confirm On-Board Imager cone-beam computed tomography (CBCT) using the histogram-matching algorithm as a useful method for proton dose calculation. We studied one head and neck phantom, one pelvic phantom, and ten patients with head and neck cancer treated using intensity-modulated radiation therapy (IMRT) and proton beam therapy. We modified Hounsfield unit (HU) values of CBCT and generated two modified CBCTs (mCBCT-RR, mCBCT-DIR) using the histogram-matching algorithm: modified CBCT with rigid registration (mCBCT-RR) and that with deformable image registration (mCBCT-DIR). Rigid and deformable image registration were applied to match the CBCT to planning CT. To evaluate the accuracy of the proton dose calculation, we compared dose differences in the dosimetric parameters (D2% and D98%) for clinical target volume (CTV) and planning target volume (PTV). We also evaluated the accuracy of the dosimetric parameters (Dmean and D2%) for some organs at risk, and compared the proton ranges (PR) between planning CT (reference) and CBCT or mCBCTs, and the gamma passing rates of CBCT and mCBCTs. For patients, the average dose and PR differences of mCBCTs were smaller than those of CBCT. Additionally, the average gamma passing rates of mCBCTs were larger than those of CBCT (e.g., 94.1±3.5% in mCBCT-DIR vs. 87.8±7.4% in CBCT). We evaluated the accuracy of the proton dose calculation in CBCT and mCBCTs for two phantoms and ten patients. Our results showed that HU modification using the histogram-matching algorithm could improve the accuracy of the proton dose calculation.

Phylogenetic diversity and cosymbiosis in the bioluminescent symbioses of "Photobacterium mandapamensis".

"Photobacterium mandapamensis" (proposed name) and Photobacterium leiognathi are closely related, phenotypically similar marine bacteria that form bioluminescent symbioses with marine animals. Despite their similarity, however, these bacteria can be distinguished phylogenetically by sequence divergence of their luminescence genes, luxCDAB(F)E, by the presence (P. mandapamensis) or the absence (P. leiognathi) of luxF and, as shown here, by the sequence divergence of genes involved in the synthesis of riboflavin, ribBHA. To gain insight into the possibility that P. mandapamensis and P. leiognathi are ecologically distinct, we used these phylogenetic criteria to determine the incidence of P. mandapamensis as a bioluminescent symbiont of marine animals. Five fish species, Acropoma japonicum (Perciformes, Acropomatidae), Photopectoralis panayensis and Photopectoralis bindus (Perciformes, Leiognathidae), Siphamia versicolor (Perciformes, Apogonidae), and Gadella jordani (Gadiformes, Moridae), were found to harbor P. mandapamensis in their light organs. Specimens of A. japonicus, P. panayensis, and P. bindus harbored P. mandapamensis and P. leiognathi together as cosymbionts of the same light organ. Regardless of cosymbiosis, P. mandapamensis was the predominant symbiont of A. japonicum, and it was the apparently exclusive symbiont of S. versicolor and G. jordani. In contrast, P. leiognathi was found to be the predominant symbiont of P. panayensis and P. bindus, and it appears to be the exclusive symbiont of other leiognathid fishes and a loliginid squid. A phylogenetic test for cospeciation revealed no evidence of codivergence between P. mandapamensis and its host fishes, indicating that coevolution apparently is not the basis for this bacterium's host preferences. These results, which are the first report of bacterial cosymbiosis in fish light organs and the first demonstration that P. leiognathi is not the exclusive light organ symbiont of leiognathid fishes, demonstrate that the host species ranges of P. mandapamensis and P. leiognathi are substantially distinct. The host range difference underscores possible differences in the environmental distributions and physiologies of these two bacterial species.

Round and pointed-head grenadier fishes (Actinopterygii: Gadiformes) represent a single sister group: evidence from the complete mitochondrial genome sequences.

The gene order of mitochondrial genomes (mitogenomes) has been employed as a useful phylogenetic marker in various metazoan animals, because it may represent uniquely derived characters shared by members of monophyletic groups. During the course of molecular phylogenetic studies of the order Gadiformes (cods and their relatives) based on whole mitogenome sequences, we found that two deep-sea grenadiers (Squalogadus modificatus and Trachyrincus murrayi: family Macrouridae) revealed a unusually identical gene order (translocation of the tRNA(Leu (UUR))). Both are members of the same family, although their external morphologies differed so greatly (e.g., round vs. pointed head) that they have been placed in different subfamilies Macrouroidinae and Trachyrincinae, respectively. Additionally, we determined the whole mitogenome sequences of two other species, Bathygadus antrodes and Ventrifossa garmani, representing a total of four subfamilies currently recognized within Macrouridae. The latter two species also exhibited gene rearrangements, resulting in a total of three different patterns of unique gene order being observed in the four subfamilies. Partitioned Bayesian analysis was conducted using available whole mitogenome sequences from five macrourids plus five outgroups. The resultant trees clearly indicated that S. modificatus and T. murrayi formed a monophyletic group, having a sister relationship to other macrourids. Thus, monophyly of the two species with disparate head morphologies was corroborated by two different lines of evidence (nucleotide sequences and gene order). The overall topology of the present tree differed from any of the previously proposed, morphology-based phylogenetic hypotheses.

Major patterns of higher teleostean phylogenies: a new perspective based on 100 complete mitochondrial DNA sequences.

A recent preliminary study using complete mitochondrial DNA sequences from 48 species of teleosts has suggested that higher teleostean phylogenies should be reinvestigated on the basis of more intensive taxonomic sampling. As a second step towards the resolution of higher teleostean phylogenies, which have been described as the "(unresolved) bush at the top of the tree," we reanalyzed their relationships using mitogenomic data from 100 purposefully chosen species that fully represented all of the higher teleostean orders, except for the Batrachoidiformes. Unweighted and weighted maximum parsimony analyses were conducted with the data set that comprised concatenated nucleotide sequences from 12 protein-coding genes (excluding 3rd codon positions) and 21 transfer RNA (tRNA) genes (stem regions only) from each species. The resultant trees were well resolved and largely congruent, with most internal branches being supported by high statistical values. All major, comprehensive groups above ordinal level as currently defined in higher teleosts (with the exception of the Neoteleostei and several monotypic groups), such as the Eurypterygii, Ctenosquamata, Acanthomorpha, Paracanthopterygii, Acanthopterygii, and Percomorpha, appeared to be nonmonophyletic in the present tree. Such incongruities largely resulted from differences in the placement and/or limits of the orders Ateleopodiformes, Lampridiformes, Polymixiiformes, Ophidiiformes, Lophiiformes, Beryciformes, Stephanoberyciformes, and Zeiformes, long-standing problematic taxa in systematic ichthyology. Of these, the resulting phylogenetic positions of the Ophidiiformes and Lophiiformes were totally unexpected, because, although they have consistently been considered relatively primitive groups within higher teleosts (Paracanthopterygii), they were confidently placed within a crown group of teleosts, herein called the Percomorpha. It should be noted that many unexpected, but highly supported relationships were found within the Percomorpha, being highly promising for the next investigative step towards resolution of this remarkably diversified group of teleosts.