Mamoru Yabe

Evolutionary history of anglerfishes (Teleostei: Lophiiformes): a mitogenomic perspective

BackgroundThe teleost order Lophiiformes, commonly known as the anglerfishes, contains a diverse array of marine fishes, ranging from benthic shallow-water dwellers to highly modified deep-sea midwater species. They comprise 321 living species placed in 68 genera, 18 families and 5 suborders, but approximately half of the species diversity is occupied by deep-sea ceratioids distributed among 11 families. The evolutionary origins of such remarkable habitat and species diversity, however, remain elusive because of the lack of fresh material for a majority of the deep-sea ceratioids and incompleteness of the fossil record across all of the Lophiiformes. To obtain a comprehensive picture of the phylogeny and evolutionary history of the anglerfishes, we assembled whole mitochondrial genome (mitogenome) sequences from 39 lophiiforms (33 newly determined during this study) representing all five suborders and 17 of the 18 families. Sequences of 77 higher teleosts including the 39 lophiiform sequences were unambiguously aligned and subjected to phylogenetic analysis and divergence time estimation.ResultsPartitioned maximum likelihood analysis confidently recovered monophyly for all of the higher taxa (including the order itself) with the exception of the Thaumatichthyidae (Lasiognathus was deeply nested within the Oneirodidae). The mitogenomic trees strongly support the most basal and an apical position of the Lophioidei and a clade comprising Chaunacoidei + Ceratioidei, respectively, although alternative phylogenetic positions of the remaining two suborders (Antennarioidei and Ogcocephaloidei) with respect to the above two lineages are statistically indistinguishable. While morphology-based intra-subordinal relationships for relatively shallow, benthic dwellers (Lophioidei, Antennarioidei, Ogcocephaloidei, Chaunacoidei) are either congruent with or statistically indistinguishable from the present mitogenomic tree, those of the principally deep-sea midwater dwellers (Ceratioidei) cannot be reconciled with the molecular phylogeny. A relaxed molecular-clock Bayesian analysis of the divergence times suggests that all of the subordinal diversifications have occurred during a relatively short time period between 100 and 130 Myr ago (early to mid Cretaceous).ConclusionsThe mitogenomic analyses revealed previously unappreciated phylogenetic relationships among the lophiiform suborders and ceratioid familes. Although the latter relationships cannot be reconciled with the earlier hypotheses based on morphology, we found that simple exclusion of the reductive or simplified characters can alleviate some of the conflict. The acquisition of novel features, such as male dwarfism, bioluminescent lures, and unique reproductive modes allowed the deep-sea ceratioids to diversify rapidly in a largely unexploited, food-poor bathypelagic zone (200-2000 m depth) relative to the other lophiiforms occurring in shallow coastal areas.

Phylogenetic position of the family Trichodontidae (Teleostei: Perciformes), with a revised classification of the perciform suborder Cottoidei

The phylogenetic relationships of the family Trichodontidae and suborder Cottoidei (and zoarcoid Bathymasteridae) are reconstructed morphologically. The monophyly of the Trichodontidae, Cottoidei, and Zoarcoidei is unambiguously supported by 14 synapomorphies, including 1 newly recognized (and also 4 synapomorphies when ACCTRAN is accepted). It is assumed that the Trichodontidae is deeply nested within the Cottoidei, and the family and Cottoidea plus Cyclopteroidea have a sister relationship, supporting a previously inferred molecular phylogenetic hypothesis. We propose that the Trichodontidae is placed into the cottoid superfamily Trichodontoidea.

A new cottid species, Icelus sekii (Perciformes: Cottoidei), from Hokkaido, Japan

A new cottid species, Icelus sekii, is described on the basis of six specimens collected from off Rausu and Urakawa, Hokkaido Island, Japan. This species is distinguished from its congeners by the following combination of characters: supraocular and parietal spines absent; nuchal spine obscure; uppermost preopercular spine unbranched; no scales between dorsal scale row and lateral line scale row, and no scales below lateral line scale row; supraocular, parietal, and nuchal cirri present; five dark brown saddles dorsolaterally; anal fin rays 13; pectoral fin rays 15; vertebrae 12 + 24–25 = 36–37. Icelus sekii can be mature at the smallest size among the species of Icelus. As a secondary sexual character, the male holotype has unique ensiform flaps on the distal tips of the first dorsal fin.

Systematics of sculpins of the genus Radulinopsis (Scorpaeniformes: Cottidae), with the description of a new species from northern Japan and the Russian Far East

Abstract The cottid genus Radulinopsis Soldatov and Lindberg is recognized as a valid taxon including two species, R. derjavini Soldatov and Lindberg and R. taranetzi sp. nov., both distributed in shallow waters around Hokkaido, Japan, and the Russian Far East. Radulinopsis taranetzi differs from R. derjavini in having an almost naked body, teeth on the prevomer, and higher meristic counts. Radulinopsis derjugini Soldatov is synonymized with R. derjavini. A key to species of Radulinopsis and related genera is given. Based on a cladistic analysis of 18 morphological characters, Radulinopsis is the sister group of the Japanese genus Astrocottus, and the monophyletic eastern North Pacific group comprising Radulinus plus Asemichthys is the sister group of the western North Pacific group of Radulinopsis plus Astrocottus. Triglops, having a wide distribution throughout the North Pacific and North Atlantic, is putatively the sister group of a monophyletic group including these four genera. Bolins genus Radulinus (including Radulinopsis as a subgenus) and Taranetzs subfamily Radulinae (including only Radulinus and Radulinopsis) are polyphyletic and therefore invalid.

Barbels and related muscles in Mullidae (Perciformes) and Polymixiidae (Polymixiiformes)

Abstract Barbels of the Mullidae and Polymixiidae were observed osteologically and myologically. They were considered to be derived from branchiostegal rays. Four muscles, the extensor tentaculi, retractor tentaculi, and two sections of rotator tentaculi, were related to the barbels in both families. These muscles originate from almost all the hyoid bones in mullids, whereas they originate only from the ventral hypohyal and fifth branchiostegal ray in polymixiids. In addition, each muscle related to the barbel of the former is independent from others, but that of the latter is interconnected. These muscular differences indicate that the barbels occurring in the two families are nonhomologous.

Icelinus pietschi sp. nov. and a rare species, Sigmistes smithi, from the southern Kuril Archipelago (Scorpaeniformes: Cottidae)

Abstract A new cottid, Icelinus pietschi sp. nov., and a rare species, Sigmistes smithi Schultz, were collected from intertidal zones in the southern Kuril Archipelago. Icelinus pietschi, represented by five specimens (34.8–42.2 mm SL) from Iturup Island, is distinguished from other species of Icelinus by having the dorsal scale rows terminating before the posteriormost base of the second dorsal fin, spines absent on the dorsal surface of the head, a single common opening of the terminal pores of the mandibular canal, a cirrus on the base of the nasal spine, and a slightly bifid uppermost preopercular spine without denticles dorsally. Six examples (36.8–42.9 mm SL) from Urup Island of Sigmistes smithi, previously known only rarely from the middle of the Aleutian Archipelago, constitute the first record of the species from the western North Pacific.

Osteological development of the lumpfish,inimicus japonicus (pisces: Synanceiidae)

The osteological development of the synanceiidInimicus japonicus, was described on the basis of five larvae and four juveniles (4.2–10.1 mm BL) reared in the laboratory, and two wild adult specimens. All bones, except for the basisphenoid, were formed in all larvae and juveniles, but fusions between the uppermost actinost and scapula, upper caudal plate and urostyle, and third preural centrum and hemal spine were not completed by 10.1 mm BL. Following comparison with the adult condition, a rod-like ossified bone without a tooth plate on the upper branchial arch of larvae and juveniles was considered homologous with the second pharyngobranchial. The number of epurals and length of the neural spine on the second preural centrum varied (unrelated to growth) and it is inferred thatJ. japonicus shows intraspecific variations in these bones.

A new species of sculpin,Icelus ecornis (Scorpaeniformes: Cottidae) from the southwestern Okhotsk Sea

A new cottid species,Icelus ecornis, is described on the basis of 31 specimens collected from 159–226 m in the southwestern Okhotsk Sea off Hokkaido, Japan. It is distinguished from all other members of the genusIcelus by the following combination of characters: no supraocular and parietal spines; short blunt nuchal spine; cirri absent from head and body, except for supraocular, parietal and nuchal regions; platelike scales of dorsal row bearing 6–10 long uniform spinules; tubular lateral line scales bearing small spines on dorsal and posterior margins; large oval black spot on first dorsal fin; 16–20 anal fin rays.

Juvenile development of a flathead,Suggrundus meerdervoortii (Scorpaeniformes: Platycephalidae)

Juvenile development ofSuggrundus meerdervoortii was described, based on twelve specimens (12.9–43.8 mm SL) collected from off Yamagata Prefecture, Japan Sea. Two exterior openings in the lateral line scales were completed at ca. 35 mm SL, with the interopercular flap and iris lappet being visible at ca. 44 mm SL, these all being useful taxonomic characters. In juveniles and additional young and adult specimens (ca. 70–191 mm SL), the proportions of head length, snout length, orbital diameter, caudal peduncle depth and caudal fin length decreased with growth; interorbital width decreased rapidly until ca. 70 mm SL, but more or less stabilised thereafter (70–191 mm SL).

A new cottid species,Porocottus coronatus, from the Pacific coast of Hokkaido, Japan

A new cottid species,Porocottus coronatus, is described on the basis of nine specimens from the Pacific coast of eastern Hokkaido, Japan. It differs from other species of this genus by having a group of finger-like cirri on the dorsal midline of the head, long uppermost preopercular spine, 15–16 anal fin rays and well developed cephalic sensory system with many small pores.