Hiromitsu Endo

Phylogenetic analysis of host–symbiont specificity and codivergence in bioluminescent symbioses

Several groups of marine fishes and squids form mutualistic bioluminescent symbioses with luminous bacteria. The dependence of the animal on its symbiont for light production, the animals specialized anatomical adaptations for harboring bacteria and controlling light emission, and the host family bacterial species specificity characteristic of these associations suggest that bioluminescent symbioses are tightly coupled associations that might involve coevolutionary interactions. Consistent with this possibility, evidence of parallel cladogenesis has been reported for squid–bacterial associations. However, genetic adaptations in the bacteria necessary for and specific to symbiosis have not been identified, and unlike obligate endosymbiotic associations in which the bacteria are transferred vertically, bacterially bioluminescent hosts acquire their light‐organ symbionts from the environment with each new host generation. These contrasting observations led us to test the hypotheses of species specificity and codivergence in bioluminescent symbioses, using an extensive sampling of naturally formed associations. Thirty‐five species of fish in seven teleost families (Chlorophthalmidae, Macrouridae, Moridae, Trachichthyidae, Monocentridae, Acropomatidae, Leiognathidae) and their light‐organ bacteria were examined. Phylogenetic analysis of a taxonomically broad sampling of associations was based on mitochondrial 16S rRNA and cytochrome oxidase I gene sequences for the fish and on recA, gyrB and luxA sequences for bacteria isolated from the light organs of these specimens. In a fine‐scale test focused on Leiognathidae, phylogenetic analysis was based also on histone H3 subunit and 28S rRNA gene sequences for the fish and on gyrB, luxA, luxB, luxF and luxE sequences for the bacteria. Deep divergences were revealed among the fishes, and clear resolution was obtained between clades of the bacteria. In several associations, bacterial species identities contradicted strict host family bacterial species specificity. Furthermore, the fish and bacterial phylogenies exhibited no meaningful topological congruence; evolutionary divergence of host fishes was not matched by a similar pattern of diversification in the symbiotic bacteria. Re‐analysis of data reported for squids and their luminous bacteria also revealed no convincing evidence of codivergence. These results refute the hypothesis of strict host family bacterial species specificity and the hypothesis of codivergence in bioluminescent symbioses.

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

ABSTRACT “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 bacteriums 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.

A new batfish,Coelophrys bradburyae (Lophiiformes: Ogcocephalidae) from Japan, with comments on the evolutionary relationships of the genus

A new ogcocephalid batfish,Coelophrys bradburyae, is described on the basis of a single specimen collected from the Pacific coast off Aomori, Japan, at a depth between 557–595 m. The species differs from others of the genus by having a small eye (7.1 in head length), short upper jaw (3.7 in head length), short pectoral and pelvic fins (length 3.0 and 9.6 in head length, respectively), small illicial cavity (width 5.3 in head length), and no bifurcated tubercles on the lateral surface of the body. A key to the species ofCoelophrys is given and the evolutionary relationships of the genus discussed based on cladistic analyses: the sister relationship withHalieutopsis was confirmed and possible paedomorphic states, including the globose body, proposed as having evolved secondarily from a flat-bodied ogcocephalid ancestor.

Notes on a specimen of the deep-sea pelagic fishBrotulotaenia nielseni from the South China Sea (Ophidiidae)

T he deep-sea ophidiid subfamily Brotulotaeniinae includes only one genus, Bvotulotaen&, and four nominal species (Cohen, 1974): B. nigm Parr, 1933, B. crassa Parr, 1934, B. nielseni Cohen, 1974 and B. brevicauda Cohen, 1974. Cohen (1974) and Machida (t990), however, have suggested that B. crassa is a junior synonym of B. nigr~l. Although rarely encountered, members of the genus are widely distributed in tropical and subtropical mesoand bathypelagic waters (Cohen, 1974). Of the four species, B. nielseni has previously been recorded from the Pacific off the western coasts of North and Middle America (,Cohen, 1974), the Banda Sea (Cohen, 1974) and the western Pacific north of New Guinea (Parin et al., 1977), as well as the Arabian Sea (Kashkin, 1978) and the tropical western Indian Ocean (Shcherbachev, 1980). In 1982, the R/V No. 704 Nanfeng, Nanhai Fisheries Research Institute, Peoples Republic of China, collected a single specimen of Bromlotaenia nielseni by trawl from the northern South China Sea (Fig. 1). The genus, previously unknown from this area, was not included among the 118 deep-water pelagic fish species of the South China Sea listed by Yang et al. (1996). The present specimen represents the third record of the species from the Pacific, differing from published data for the species in having more dorsal and anal fin rays, and vertebrae. Because dorsal and anal fin ray and vertebral counts are thought to be diagnostic for each nominal species (Cohen, 1974; Shcherbachev, 1980), the present specimen is herein described in some detail. All measurements were straight-line measurements. Counts of vertebrae and vertical fin rays were taken from radiographs. Terminology for the cephalic sensory pores follows Cohen (1974). Standard length is abbreviated as SL. The specimen is deposited in the Laboratory of Fishes, Shanghai Fisheries University (SFC).

A new species of Trichonotus (Perciformes: Trichonotidae) from Somalia and redescription of Trichonotus cyclograptus (Alcock, 1890) with designation of a lectotype

A new sand diver Trichonotus somaliensis n. sp. (Trichonotidae) is described on the basis of 13 specimens collected off the coast of Somalia at a depth of 38−78m. The new species is most similar to T. arabicus and T. cyclograptus in lacking elongated anterior dorsal-fin spines and having dark markings on the lateral body surface in males. However, the new species differs from the others in having the following characters: lateral-line scales 54−57; gill rakers on first arch 5−6+18−24; 12–14 blotches on upper half of body in both sexes; first dorsal-fin soft ray length in males 19–28% of standard length; and no free dorsal pterygiophores. Trichonotus cyclograptus, a poorly known species, is redescribed on the basis of the newly-designated lectotype and paralectotypes.

Redescription and designation of a neotype for Aphthalmichthys kuro Kuroda 1947, and its placement in Callechelys (Anguilliformes: Ophichthidae)

Aphthalmichthys kuro, described by Kuroda (1947) based on a specimen from Suruga Bay, Japan, is referred to Callechelys (family Ophichthidae, subfamily Ophichthinae). It differs from its congeners in its vertebral number (142–146), tail length (2.0–2.1 in TL), and coloration (brownish black). The holotype is lost; we herein designate a neotype and redescribe and illustrate the species based on 5 specimens from Japan and 2 from Taiwan.

Redescription of a rare deep-sea batfish, Halieutopsis bathyoreos (Lophiiformes: Ogcocephalidae)

Halieutopsis bathyoreos Bradbury, 1988 (Lophiiformes: Ogcocephalidae), previously described only on the basis of the holotype (62.6 mm in standard length) from the central North Pacific, is redescribed on the basis of the holotype and six additional specimens (41.2–68.7 mm in standard length) collected from the western South Pacific, off Papua New Guinea, and the western North Pacific, including the Japanese Archipelago. Halieutopsis bathyoreos is distinguished from its congeners by having a shelflike rostrum extending anteriorly well beyond the mouth, a dorsal escal lobe slightly bisected ventrally, an illicial cavity square in outline and completely visible in ventral view, and lacking tubercles on the ventral surface of the disk. The following characters are newly added to the diagnoses of this species: rostrum width 21–29% of head length, tubercles on the dorsal surface of the disk about half the diameter of those on the lateral margin, and 13–15 large lateral-line scales on the tail.

Mesovagus , a replacement name for the grenadier genus Mesobius Hubbs and Iwamoto 1977 (Actinopterygii: Gadiformes: Macrouridae), a junior homonym of Mesobius Chamberlin 1951 (Chilopoda: Lithobiomorpha: Lithobiidae)

A replacement name, Mesovagusnom. nov., is proposed for the grenadier genus Mesobius Hubbs and Iwamoto 1977, which is preoccupied by Mesobius Chamberlin 1951 in lithobiid centipedes (Chilopoda: Lithobiomorpha).

Redescription of Nezumia infranudis (Gilbert & Hubbs, 1920), with the first record of the species from the Eastern Indian Ocean (Actinopterygii: Gadiformes: Macrouridae)

Abstract Nezumia infranudis is redescribed from the holotype and an additional specimen collected from the Timor Sea at a depth of 610–690 m. It belongs to the Nezumia spinosa group (herein defined) and is most similar to the Indo-West Pacific N. spinosa. Nezumia infranudis is distinguished from other congeners by the following combination of features: pelvic-fin rays 11; body scales covered with long, reclined, needle-like spinules densely scattered over exposed portion; underside of head almost completely naked, with prominent sensory pores; teeth in broad bands in both jaws; snout long (31–32% of head length (HL)), protruding well beyond upper jaw; second spinous ray of first dorsal fin greatly elongated (height of first dorsal fin 158–166% HL); no prominent dark band encircling trunk; first dorsal fin almost uniformly blackish. The first report of N. infranudis in the Indian Ocean represents the only confirmed record of the species since its original description. A key to species of the N. spinosa group is provided.

Genetic divergence between two forms of a tongue sole Cynoglossus interruptus

Genetic differences between trilinear and dilinear forms of a tongue sole, Cynoglossus interruptus, were examined by use of isozymes. Unequivocal differences were detected between the two forms, including complete replacement of alleles at the FBALD-2*, MDH-3*, PROT-1*, and SOD-1* loci, almost complete replacement at the AAT-3*, AH-1*, AH-2*, EST-3*, G3PDH-3*, GPI-2*, IDHP-1*, and MDH-1* loci, and extreme differences in allelic frequencies at the GPI-1* and PGDH* loci. The genetic distances (D values) between the two forms were 0.4207–0.4353, figures predicatively significant at the specific level. The considerable genetic differences strongly suggested that the two forms represent distinct species.