Bregmaceros moseri Harold & Baltzegar, 2023

Harold, Antony S. & Baltzegar, D. Andrew, 2023, A new species of Bregmaceros (Gadiformes: Bregmacerotidae) from the eastern Pacific Ocean, with comments on B. atlanticus and B. japonicus, Zootaxa 5352 (2), pp. 266-278 : 268-275

publication ID	https://doi.org/ 10.11646/zootaxa.5352.2.7
publication LSID	lsid:zoobank.org:pub:E6414078-CEA2-4B86-9230-38EA2A7BFB0C
DOI	https://doi.org/10.5281/zenodo.8432500
persistent identifier	https://treatment.plazi.org/id/03B887CE-FFAA-FFFE-C198-8C688225D69A
treatment provided by	Plazi
scientific name	Bregmaceros moseri Harold & Baltzegar
status	sp. nov.

Treatment

Bregmaceros moseri Harold & Baltzegar , sp. nov.

(New common name: Gyre codlet)

( Figs. 1–6 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 ; Table 1 View TABLE 1 )

urn:lsid:zoobank.org:pub:AB0CD178-905B-4C86-84E8-45A7A94D0206

Bregmaceros sp. : Stevens & Moser, 1996: 480–481, fig. Bregmacerotidae View in CoL 2 (California Current and vicinity, early stages 2.2– 14.0 mm).

Bregmaceros japonicus View in CoL (non Tanaka): Świdnicki, 1991: 130 (description of osteology; specimens collected at or near type locality of B. moseri , 21°N, 158°20′W, Oahu , Hawaii, p. 146, 16 precaudal vertebrae) GoogleMaps .

Holotype. USNM 325144 About USNM (1 of 11 in lot originally, 44.2 mm), 21°00′N, 158°20′W (southwest of Oahu Is. ), R / V El Pescadero IV, Field No. 71-6-24, 0049–0253 h, 17 Jun. 1971. GoogleMaps

Paratypes. SIO 96-42 About SIO (2, 45.5–50.5 mm), 15°17′S, 112°00′W (southeast Pacific ), EASTROPAC Expedition Sta. 75.133, 08 Mar. 1968 GoogleMaps . SIO 97-98 About SIO (4, 39.9–48.7 mm), 24°N, 139°W GoogleMaps , R / V David Starr Jordan Cruise 7210, Sta. 24.139, 29 Oct. 1972 . USNM 466574 About USNM (3, 22.3–~ 40 mm), 0–270 m, 01°03′ to 01°07′S, 158°00′W (south of the Line Islands ), NORPAX-79 Expedition GoogleMaps , R / V Gyre Sta. 79-5-10, 19 May 1979 . USNM 466575 About USNM (8, 23.6–47.6 mm), 21°20′ to 21°30′N, 158°20′ to 158°30′W (off Oahu Is. ), 0–80 m, coll GoogleMaps . T. A. Clarke, Field No. 71-9-1, 1958–2135 h, 17 Sep. 1971 . USNM 466576 About USNM (11, 32.2–43.2 mm; 2 C&S, 40.2–44.8 mm), collected with the holotype . USNM 466573 About USNM (3, 20.4–41.0 mm), 0–320 m, 01°52′ to 01°58′S, 153°08′ to 153°09′W, NORPAX-79 Expedition GoogleMaps , R / V Wecoma Sta. 79-9-1, 0400–0558 h, 02 Sep. 1979 .

Non-types. SIO 73-17 About SIO (1, 45.6 mm), 09°52.8′N, 113°50′W GoogleMaps , R / V Aries I, 19 Nov. 1970 . SIO 75-130 About SIO (6, 25.4– 41.9 mm), 12°32′N, 118°54′W, Field No. J57-019, 26 Apr. 1990 GoogleMaps . SIO 92-57 About SIO (2, 43.2–48.2 mm), 06°06′N, 104°29′W, EASTROPAC Expedition Sta. 30.183, 14–15 Jul. 1967 GoogleMaps . SIO 97-112 About SIO (2, 44.7–47.9 mm), 21°45′N, 118°00′W GoogleMaps , R / V David Starr Jordan Cruise 7210, Sta. 140.120, 0202 h, 08 Nov. 1972 .

Diagnosis. A species of Bregmaceros Thompson with high precaudal vertebral counts (15 or 16), as compared with typically 13 or 14 (but 15 in B. anchovia , 14–16 in B. neonectabanus , and 14 or 15 in B. retrodorsalis ), high longitudinal and predorsal scale counts (89–91 and 21–26, respectively), and concentrated dark pigment along dorsum with ventral portion of head unpigmented, especially cheek, jaws, throat, operculum, and ventral of nares. Dentary teeth caniniform, greatest tooth length two to three times greater than that of premaxillary teeth. Premaxillary postmaxillary process absent.

Description. Description based on 26 specimens. Morphometric and meristic characters summarized in Table 1 View TABLE 1 . Body shape and general arrangement and shapes of fins typical of species of Bregmaceros .

Maximum observed adult body size 50.5 mm SL. Body elongate anteriorly relative to other Bregmaceros species (predorsal length 38.2–44.4 % SL), compared with generally less than 40% in similar species, e.g., B. atlanticus ( Fig. 2 View FIGURE 2 ); particularly apparent in large number of small scales: longitudinal scales 89–91 (holotype, 91) and predorsal scales 21–26 (25). Precaudal vertebrae 15 or 16 (16). Slightly compressed. Maximum body depth located at about origin of D2. Dorsal profile of body horizontal from occiput to just anterior to D2, and slightly inflected at D2 origin; profile straight from that point posteriorly to posterior lobe of D2 where it is slightly convex. Ventral body profile slightly sinuous, with bases of anterior and posterior lobes of anal fin convex. Anteriormost well-developed anal-fin pterygiophore bilaterally divergent, as in B. atlanticus and B. japonicus . Caudal fin slightly emarginate with 14 principal fin rays; dorsal and ventral procurrent fin rays each 11 to 13. Total caudal-fin rays 34–37.

Head small, 14.2–17.7 % SL. Snout slightly rounded and short, approximately equal in length to that of orbit. Adipose eyelid narrow, covering posterodorsal one quarter of eye. Nares located at level of dorsal half of orbit, separated from orbit by large lachrymal dorsal process. Upper jaw slightly shorter than lower; posterior tip of maxilla ventral to posterior 2/3 of eye. Premaxillary ascending process broad and lacking postmaxillary process (see description and figures for B. japonicus, Świdnicki, 1991: 139–140 , fig. 8B); premaxillary teeth biserial, outer-row teeth larger than inner, continuous along premaxilla and with 34 to 38 conical teeth in series. Maxillary teeth absent. Dentary teeth biserial: outer-row teeth 20 to 27, conical, slightly shorter than those of premaxilla; inner-row teeth 12 to 14, recurved, about 2 to 3 times larger than outer-row teeth and those of premaxilla. Vomer with oblique row of 2 or 3 conical teeth on lateral processes. Palatine teeth absent. Photographs of cleared and stained specimen (USNM 466576, 40.2 mm) depict positions of modified opercular structure ( Fig. 3A View FIGURE 3 ) and that of modified anal-fin pterygiophores ( Fig. 3B View FIGURE 3 ) as described and illustrated below. Opercle elongate ventrally and broadly pointed, anterior margin broadly convex, posterior margin concave and bearing elongate posterodorsal spine or rod-like process with single termination (not branched as in B. mcclellandi sensu stricto, Torii et al., 2003a; B. anchovia, Ho et al., 2020b ) ( Fig. 4A View FIGURE 4 ). Gill rakers reduced, as small dentigerous plates. Prehaemal anal-fin pterygiophore modifications: in specimen 4 (USNM 466576, 44.8 mm), second anal-fin pterygiophore (i.e., first well-developed anal-fin pterygiophore) proximally divergent as broadly triangular transverse blade, first (anteriormost) anal-fin pterygiophore with similar albeit much smaller transverse blade with horizontal dorsal margin adhering via connective tissue to central portion of second ( Fig. 4B View FIGURE 4 ). In the other cleared and stained specimen (40.2 mm), which has three prehaemal anal-fin pterygiophores, anteriormost and shortest is somewhat unmodified, but second and third have transverse blade-like processes. Remaining proximal anal-fin pteryiophores lack such bilateral modification.

Color in Preservative.—Dorsum, including dorsal portion of head, covered by diffuse moderately dark brown ground pigment ( Fig. 5A, B View FIGURE 5 ) with scattered larger, dark chromatophores posterior to head and over dorsal half of body. Dorsal surface of head covered by scattered dark chromatophores except above eye and over pineal window where pigment cells are much more broadly scattered. Dark pigment also located directly posterior to eye but most of operculum, cheek, jaws, and ventral surfaces of head nearly unpigmented ( Fig. 5C View FIGURE 5 ); approximately 10 to 20 widely scattered small dark chromatophores on lower part of cheek or on upper jaw in some specimens ( Fig. 5A View FIGURE 5 ). Lateral portion of snout directly below nares unpigmented. Ventral half of body over abdomen and posterior to caudal-fin base covered with numerous, minute dot-like chromatophores. Dorsal and ventral margins of scale pockets along upper half of body darkly pigmented, giving overall appearance of reticulation ( Fig. 5D, E View FIGURE 5 ). Minute dot-like chromatophores present from below second lobe of dorsal fin to caudal-fin base ( Fig. 5F View FIGURE 5 ), and in some specimens longitudinal alignment of that pigment producing three or four fine parallel lines.

Anterior lobe of dorsal fin with large, dark brown chromatophores scattered over basal two thirds, remainder of fin unpigmented. Anal and pelvic fins unpigmented. Pectoral fin with large, dark brown chromatophores along medial and lateral portions of its base, and associated with basal one half of most rays; lateral three or four rays unpigmented. Diffuse, dark pigmentation present in recess medial to pectoral-fin base. Caudal fin with diffuse, dark brown pigment confined to basal one half of principal rays; procurrent rays unpigmented. Internal pigmentation not apparent in cleared specimens.

Juveniles as small as 22 mm SL examined had general pigmentation pattern similar to that described above but lack delineation of scales. Flanks largely unpigmented except for series of stellate chromatophores scattered over abdomen. A 14.0 mm juvenile illustrated by Stevens & Moser (1996: fig. Bregmacerotidae 2) likely to represent B. moseri shows uniform covering of dark chromatophores, including caudal peduncle.

Distribution.—Known only from the east central to eastern Pacific, including as far west as the Hawaiian Islands, to the south near the Line Islands, and eastward to the vicinity of the California Current ( Fig. 6 View FIGURE 6 ). There is little information available relating to the vertical distribution of B. moseri , but it is probably upper mesopelagic: maximum tow depths 80 m (1958–2135 h), 270 m (times not available), and 320 m (0400–0558 h).

Etymology.—The specific epithet moseri is based on the late H. Geoffrey Moser, who contributed hugely to our understanding of the biodiversity of mid-water fishes. In the Early Stages of Fishes in the California Current Region, Stevens & Moser (1996) referred to larval and post-metamorphic juveniles that, based on the data provided, are probably early stages of B. moseri .

Remarks and Discussion.— Bregmaceros moseri is most similar to B. atlanticus , B. japonicus , and another widely distributed undescribed form. That undescribed species (“ Bregmaceros sp. 5 ” herein), with higher anal-fin ray counts (59–67) than other species of Bregmaceros , has been frequently misidentified as B. mcclellandi , in particular D’Ancona & Cavinato (1965), who took a rather expansive view of the variation in that species. These species are all rather darkly pigmented in comparison with most others in Bregmaceros . In particular, the dorsum pigment is rather dark and usually exhibits a reticulate appearance due to the delineation of the exposed margins of scales by small dark chromatophores. The new species is distinguished from B. atlanticus and B. japonicus by the high longitudinal scale counts in B. moseri (87–91) compared with 71–87 in B. japonicus ( Nakabo, 2002) and 71–81 in B. atlanticus (present study), its high precaudal/prehaemal vertebral counts (15 or 16 in B. moseri versus typically 14 and occasionally 15 in B. atlanticus and 14 in B. japonicus ), and the generally unpigmented lower lateral and ventral surfaces of the head in B. moseri versus the presence of widespread dark chromatophores in those areas of B. atlanticus and B. japonicus .

These three species all have an opercle bearing an unbranched elongate posterior rod-like process, a feature also present in B. cayorum and B. rarisquamosus , according to Torii et al., (2003c), B. bathymaster and B. houdei , as described and illustrated by Świdnicki (1991), and also in B. cantori and B. neonectabanus , based on original data. The remaining species of Bregmaceros have a branched opercular termination. The three putatively related species, B atlanticus , B. japonicus , and B. moseri , also have bilaterally divergent prehaemal anal-fin pterygiophores that, together with associated body-wall musculature and connective tissue, represent a unique structural complex situated immediately posterior to the coelomic cavity.According to Świdnicki’s (1991: 155) description, the anterior/ prehaemal pterygiophores (“radials”) have a convex anterior margin and the upper (i.e., proximal) end is widened laterally, but it is not specified which of the species he examined in making that description nor did he report an anatomical dichotomy in anterior pterygiophore structure within the genus. Apart from B. atlanticus , B. japonicus (s. str.), and B. moseri , all other species of Bregmaceros have unmodified equivalent pterygiophores (e.g., B. houdei in Świdnicki, 1991: fig. 17C) and also elongate posterior branches of the coelomic cavity extending posteriorly on either side of the anal-fin proximal pterygiophores, which are observed to bear posterior portions of the gonads in some species. The posterior portion of the left ovary is apparently observable in B. anchovia through the body wall ( Ho et al. 2020b: fig. 3E), an observation that is consistent with our own of other species of Bregmaceros we have dissected (e.g., B. bathymaster , B. cantori , B. lanceolatus , and B. pseudolanceolatus ). We infer the presence of the divergent anal-fin proximal pterygiophore feature, based upon outgroup comparison to an array of gadiforms, to be a likely synapomorphy of a clade within Bregmaceros containing B. atlanticus , B. japonicus , B. moseri , and a number of other undescribed species bearing this feature (e.g., “ Bregmaceros sp. 5 ”). Other gadiforms examined include Euclichthys polynemus McCulloch (Euclichthyidae) , Microgadus proximus (Girard) and Pollachius virens (Linnaeus) (Gadidae) , Nezumia bairdii (Goode & Bean) (Macrouridae) , Merluccius bilinearis (Mitchill) (Merlucciidae) , Muraenolepis marmorata Günther (Muraenolepididae) , Phycis chesteri (Goode & Bean) and Urophycis regia (Walbaum) (Phycidae) , Raniceps raninus (Linnaeus) (Ranicipitidae) , and Steindachneria argentea Goode & Bean (Steindachneriidae) . Of these gadiforms, Steindachneria argentea also has a bilaterally expanded anterior anal-fin pterygiophore but it differs in anatomical details from that of Bregmaceros species. Also, based on published phylogenetic studies of the Gadiformes (e.g., Markle, 1989; Howes, 1991; Roa-Varón et al., 2021), Steindachneria is not closely related to the Bregmacerotidae and therefore the anatomical similarity is likely to be non-homologous.

Among these related species, B. moseri is most similar to B. atlanticus and B. japonicus , especially with the pigmentation pattern described above and meristic values that include anal-fin ray counts fewer than 60. Nevertheless, neither of those two species have precaudal vertebral counts of 15 or 16 or dark pigment on the head restricted for the most part to the dorsal/dorsolateral surfaces and with largely unpigmented snout, cheek, and lower part of the operculum. Bregmaceros atlanticus and B. japonicus both exhibit more general and diffuse head pigmentation dorsally and laterally without a marked ventral border. Belyanina (1974) set B. japonicus as a junior synonym of B. atlanticus and reported records of the species from the eastern Pacific. Some of those records may represent B. moseri , but the characteristic features of the new species, such as head pigmentation pattern and high precaudal vertebral counts, were not reported.

The osteological description of “ B. japonicus ” provided by Świdnicki (1991) is based on material from off Hawaii which is evidently the new species, B. moseri . Świdnicki’s (1991) descriptions and illustrations of the osteology are a most valuable source of information on the new species. His B. “ japonicus ” exhibits the rather high precaudal vertebral count and lack of a premaxillary postmaxillar process, both of which confirm our conclusion. The latitude and longitude (21°N, 158°20′W) at which his “ B. japonicus ” material was collected (NMNH No. 71-6- 36, inferred to be an El Pescadero IV station number) is the same (verbatim but rounded off) as the type locality of B. moseri (El Pescadero IV field number 71-6-24), although apparently from a different station.

Stevens & Moser (1996: 480, fig. Bregmacerotidae 2) described and illustrated larvae and juveniles of an undescribed species (also referenced by Hare et al., 2006: 583) from the California Current. They were unable to identify these early stages (up to postflexion, 6.2–14.0 mm) by comparison to known valid species in this genus and referred them to Bregmaceros sp. It was one of two species of Bregmaceros from the California Current for which they reported early stages, the other being B. bathymaster . Their specimens do not compare well with those reported for other species and, based on their geographical occurrence, general pigmentation pattern, and meristic values, they are likely to be early stages of the species described here as new, however, we have not examined any material from the California Current. Although the nearest of our records are from further south at 12° 32′N, 118° 54′W (SIO 75-130) or to the west of the CalCOFI (California Cooperative Oceanic Fisheries Investigations) survey area, larvae and later stages are probably transported extensively within the eastern portion of the North Pacific Gyre and the Equatorial Current systems.

No species barcode sequences from verifiable conspecifics are currently available. A population/specieslevel phylogenetic study (A. Roa-Varón & A.S. Harold, unpubl.) will likely reveal molecular data that will further characterize the new species and contribute to an understanding of its phylogenetic position within the genus.