Higher Gill Raker Counts Research Articles

Stolephorus acinaces, a new anchovy from northern Borneo, and redescription of Stolephorus andhraensis Babu Rao, 1966 (Clupeiformes: Engraulidae)

Stolephorus acinaces sp. nov. is described from 14 specimens from the northern coast of Borneo, Malaysia. The new species is closely related to Stolephorus andhraensis Babu Rao, 1966, which is redescribed, both species having a long upper jaw with the posterior tip beyond the posterior margin of the preopercle, no predorsal scutes, the posterior preopercular margin indented and concave, the posterior tip of the depressed pelvic fin not reaching to a vertical through the dorsal-fin origin, no dark lines on the dorsum, and no black spots below the eye. However, the former is distinguished from S. andhraensis in having higher gill raker counts on the first and second gill arches (14–16 + 21–23 = 36–38 and 9–11 + 18–20 = 27–31, respectively vs. 14–16 + 19–21 = 33–37 and 8–11 + 16–19 = 26–29, respectively in S. andhraensis), a longer caudal peduncle (19.7–21.9% SL vs. 16.9–19.9%), longer pectoral fin (14.3–15.2% SL vs. 12.8–14.4%), and shorter pelvic fin (6.7–7.6% SL vs. 7.4–8.9%). A molecular analysis showed that S. acinaces sp. nov. is the sister group of the clade (S. andhraensis, Stolephorus tamilensis Gangan, Pavan-Kumar, Jahageerdar & Jaiswar, 2020, and S. acinaces sp. nov. has about 7% mean p-distance divergence in the mitochondrial cytochrome oxidase I (COI) gene with each of the two species of this clade.

Redescriptions of Dussumieria acuta Valenciennes 1847 and Dussumieria albulina (Fowler 1934), two valid species of rainbow sardines (Clupeiformes: Dussumieriidae)

Dussumieria albulina (Fowler 1934), formerly regarded as a junior synonym of Dussumieria acuta Valenciennes 1847, is shown to be a valid species and is redescribed on the basis of 29 specimens, including the holotype. Although the two species resemble each other morphologically, sharing body scales with numerous longitudinal striae posteriorly, a deep body, 26 or fewer lower gill rakers on the first gill arch, and 15 or fewer branchiostegal rays, the former is distinguished by lacking parasphenoid teeth (vs. distinct conical teeth on parasphenoid in D. acuta), higher gill raker counts (total gill rakers on first gill arch 33–41 vs. 30–38), a rather slender body (20.6–24.4% SL vs. 23.4–28.2% SL in individuals of D. acuta > 75 mm SL), and melanophores scattered on the 3rd to 9th (vs. 1st to 5th) pectoral-fin rays from the uppermost ray. Analysis of the mitochondrial cytochrome oxidase I (COI) gene in both species showed them to be separated by 12% mean p-distance. A redescription of D. acuta is also provided.

Stolephorus babarani, a new species of anchovy (Teleostei: Clupeiformes: Engraulidae) from Panay Island, central Philippines.

The new anchovy Stolephorus babarani n. sp. is described on the basis of 26 specimens collected from Panay Island, central Philippines. The new species closely resembles Stolephorus bataviensis Hardenberg 1933 and Stolephorus baweanensis Hardenberg 1933, all these species having a long upper jaw (posterior tip extending beyond posterior margin of preopercle), and numerous dusky spots on the suborbital area (in adults), snout and lower jaw tip. However, the new species differs from S. bataviensis by usually having the posterior tip of the depressed pelvic fin not reaching to vertical through the dorsal-fin origin (vs. extending beyond vertical through dorsal-fin origin), a shorter head (23.9-25.5% of standard length vs. 25.3-28.0%), and a greater distance between the dorsal-fin origin and pectoral-fin insertion (D-P1; 133.9-151.8% of head length vs. 109.9-136.3%). Stolephorus babarani is distinguished from S. baweanensis by having a shorter snout (3.6-3.9% of standard length vs. 3.8-4.6%). Moreover, the new species can be distinguished from S. bataviensis and S. baweanensis by higher gill raker counts on the first and second gill arches (16-18 + 21-23 and 10-13 + 18-21, respectively, vs. 14-17 + 19-22 and 9-12 + 17-20 in S. bataviensis and 14-17 + 19-22 and 9-12 + 17-21 in S. baweanensis). Stolephorus babarani is separated by 5.3% and 10.7% mean p-distances in the mitochondrial COI from S. baweanensis and S. bataviensis, respectively.

A new goatfish of the genus Upeneus (Mullidae) from Lombok, Indonesia and first verified record of U. asymmetricus for the Indian Ocean.

Upeneus lombok n. sp. is described from two specimens collected off Lombok, Indonesia, at depths of 54-76 m, and one subadult specimen from the local fish market at Tanjung Luar, Lombok. Four specimens of U. asymmetricus were collected at the same fish market representing the first record of the species since its description from two Philippine Islands in 1954. These two species are compared in detail and with five congeneric species that all share a 7-spined dorsal fin and a high gill-raker count. Upeneus lombok n. sp. differs from all other congeners in having a short snout (snout length 9.0-9.6% SL) combined with a low anal fin (anal-fin height 12-13% SL in adults, 15% in single subadult). The newly recorded U. asymmetricus specimens differ from their types only slightly and all eight specimens together differ from all congeneric species in the combination of 7 dorsal spines, 12-14 pectoral fin rays, 26-28 total gill rakers, short pectoral fins (pectoral-fin length 18-21% SL) and short jaws (upper jaw length 8.7-11% SL). In both species the caudal-fin colour patterns of fresh fish are of diagnostic significance, the only exception being a close similarity between Upeneus lombok n.sp., U. saiab, and U. seychellensis. Additional comparisons with 14 Upeneus species which overlap in distribution or occur in nearby areas are also made. Needs for further taxonomic exploration of the Indonesian-Philippine region and for enhanced attention to the economic and ecological importance of Upeneus species are discussed.

Coexistence and origin of trophic ecotypes of pygmy whitefish,Prosopium coulterii, in a south‐westernAlaskan lake

Ecologically, morphologically and genetically distinct populations within single taxa often coexist in postglacial lakes and have provided important model systems with which to investigate ecological and evolutionary processes such as niche partitioning and ecological speciation. Within the Salmonidae, these species complexes have been well studied, particularly within the Coregonus clupeaformis-C. laveratus (lake and European whitefish, respectively) group, but the phenomenon has been less well documented in the other whitefish genera, Prosopium and Stenodus. Here, we examined the morphology, feeding biology and genetic structure of three putative forms of the pygmy whitefish, Prosopium coulterii (Eigenmann & Eigenmann, 1892), first reported from Chignik Lake, south-western Alaska, over 40 years ago. Field collections and morphological analyses resolved a shallow water (< 5 m depth) low gill raker count form (< 15 first arch gill rakers), a deepwater (> 30 m), low gill raker form and a deepwater, high gill raker count (> 15 gill rakers) form. The two low gill raker count forms fed almost exclusively on benthic invertebrates (mostly chironomids), while the deepwater, high gill raker count form fed almost exclusively on zooplankton; differences in diet were also reflected in differences both in δ(13) C and δ(15) N stable isotopes. All three forms were characterized by the same major mitochondrial DNA clade that has been associated with persistence in, and postglacial dispersal from, a Beringian glacial refugium. Analysis of variation at nine microsatellite DNA loci indicated low, but significant differentiation among forms, especially between the two low gill raker count forms and the high gill raker count form. The extent of differentiation along phenotypic (considerable) and genetic (subtle) axes among the Chignik Lake forms is similar to that found among distinct taxa of Prosopium found in pre-glacial Bear Lake (Utah-Idaho, USA) which is probably at least ten times older than Chignik Lake. Our analyses illustrate the potential for the postglacial differentiation in traits subject to divergent natural selection across variable environments.

Astyanax cocibolca, a new characid (Pisces: Ostariophysi) from Lake Nicaragua, Central America

Astyanax cocibolca, a small filter-feeding species is a new characid species endemic to Lake Nicaragua. It is distinguished from the syntopic Astyanax aeneus by its high gill raker count, slender body, upturned snout, long maxillary bones, conical outer premaxillary teeth, lower number of scales above lateral line, more intense black lateral band, smaller size, and trophic niche partitioning. At present the new species utilizes the open-water habitat at least as a nursery where young can feed on the rich plankton population. Adults feed on copepoda, cladocera, fruits, seeds and algae. The bulk of the adult population presumably resides inshore.

Revision of the snailfish genus Allocareproctus Pitruk &amp;amp; Fedorov (Teleostei: Liparidae), with descriptions of four new species from the Aleutian Islands

Liparid fishes of the genus Allocareproctus Pitruk &amp; Fedorov were collected throughout the Aleutian Islands during surveys conducted by the Alaska Fisheries Science Center, U.S. National Marine Fisheries Service, and represent the first documented records of this genus in North America. Based on this material, we revised the genus and recognized four new species described herein. Allocareproctus is distinguished from all other liparid genera by the following characters: anterior 4–8 dorsal-fin rays with tips exserted from the fin membrane, papillae associated with some pores of the cephalic lateralis system, and symplectic extending to the medial aspects of thequadrate and metapterygoid. Allocareproctus jordani (Burke), the type species of the genus, is uniformly pink-red in coloration, with a dark peritoneum, simple teeth, a pigmented nasal papilla, and a single lobe on the orobuccal valve. It ranges from Sagami Bay, the type locality, north through the Kuril Islands, and east to Umnak Island of the Aleutian Islands, at depths of 75 to 495 m. Allocareproctus ungak n. sp. is most similar to A. jordani, differing in having trilobed teeth, an unpigmented nasal papilla, and higher counts of median-fin rays and vertebrae. It is found only between Seguam Pass and Samalga Pass in the east-central Aleutian Islands at depths of 318 to 461 m. Allocareproctus kallaion n. sp. is also known only from Seguam Pass and Samalga Pass at depths of 278 to 450 m and is distinguished from all other species of Allocareproctus by its blotchy red body color in life and dusky head coloration in life and in preservation, high gill raker count, high precaudal vertebrae count, and comb-like orobuccal valve. Allocareproctus tanix n. sp. is most similar to A. unangas n. sp. and is distinguished by its orange-peach coloration, pale peritoneum, absence of an interorbital papilla, and greater body depth. It is found only in the central Aleutians at depths of 104 to 650 m. Allocareproctus unangas n. sp. is also found only in the central Aleutians at similar depths of 210 to 465 m and is distinguished by its trilobed teeth, absence of a nasal papilla, and dark peritoneum. Based on our examination of holotypes, Careproctus pycnosoma Gilbert &amp; Burke and C. curilanus Gilbert &amp; Burke are valid species and not synonymous with A. jordani.

A new cryptic species of Sorubim Cuvier (Siluriformes: Pimelodidae) from the upper and middle Amazon Basin

Sorubim maniradii, a new species, is described on the basis of 29 specimens from the middle and upper Amazon River Basin of Bolivia, Brazil, Ecuador, and Peru. This species is similar in morphology to S. lima and S. elongatus, but is distinguished from all congeners by its diffuse (versus conspicuously black) lateral stripe and high gill raker count (31–37 versus 13–23). It occurs sympatrically and syntopically with S. lima and S. elongatus.Species nova—Sorubim maniradii.

New Species ofGerresfrom the Southern Malay Peninsula, Belonging to theGerres setiferComplex (Perciformes: Gerreidae)

Gerres silaceus n. sp. is described from the holotype and two paratypes from the southern Malay Peninsula. The species is included as the fourth species in the “G. setifer complex” [G. chrysops Iwatsuki, Kimura and Yoshino, G. decacanthus (Bleeker), G. setifer (Hamilton), G. silaceus n. sp.], differing from all other congeners from the Indo-Pacific in having two supraneural bones and small size (less than 100 mm in standard length vs three supraneural bones and adults > 100 mm SL). The new species is further characterized by presence of IX, 10 dorsal fin rays, 34 or 35 lateral line scales, 3.5 scales between the 5th dorsal fin spine base and lateral line, caudal fin short (mean 29% of SL), slender second anal fin spine, pelvic fin ray with a wide white margin posteriorly, and a uniformly silvery ocher body. Gerres silaceus differs from G. setifer and G. decacanthus in body color, the last dorsal fin spine slightly shorter or similar length to the penultimate spine, higher gillraker counts and broadly rounded caudal fin lobes; it differs from G. chrysops in higher gillraker counts, rounded caudal fin lobe posterior margin and body color. The four species are generally distributed allopatically in the Indo-western Pacific.

Four new species of the lanternfish genusDiaphus(Myctophidae) from the Indo‐Pacific

Abstract Four new species of the genus Diaphus are described. Three of these are in the subgeneric group with a suborbital luminous organ and are members of the D. fulgens species group with a raised AOa1 photophore. D. impostor sp. nov. from the Indo‐West Pacific is most similar to D. aliciae, differing in lower gill raker count and smaller size. D. wisneri sp. nov. from north of Hawaii and south Pacific lacks a luminous scale at the PLO and has a lower gill raker count than similar species. D. kora sp. nov. from north‐east of New Zealand has a large luminous scale at the PLO, and a longer Vn and lower gill raker counts than similar species. D. kapalae sp. nov. from the south‐western Pacific is most similar to D. splendidus and D. antonbruuni, from which it differs by the presence of an Ant, higher gill raker counts, and position of the VLO photophore.

A New Species of Indo-West Pacific Etelis (Pisces: Lutjanidae), with Comments on Other Species of the Genus

A new species of the percoid fish genus Etelis, Lutjanidae, characterized by high gillraker count, is described and illustrated; the new species is known from specimens collected off Sri Lanka (Ceylon) and Papua, New Guinea. Eteliscus marshi is shown to be a junior synonym of Etelis carbunculus. Etelis evurus, frequently considered as a junior synonym of Etelis carbunculus, is demonstrated to be distinct from the latter species and to be a junior synonym ofEtelis coruscans. Etelis coruscans is closely related to Etelis oculatus, the only Atlantic member of the genus. A key to the species of Etelis is provided.

Sympatric Occurrence of Two Species of Humpback Whitefish in Squanga Lake, Yukon Territory

Squanga Lake in the Canadian headwaters of the Yukon River contains two species of humpback whitefish, characterized by modal first arch gill raker counts of 23 and 28 but with overlap in the range of counts. The species can be separated more sharply by raker counts of the second arch, also with modes of 23 and 28. Seven other morphometric characters not correlated with gill raker count each have significantly different means, but some overlap, between the species.In June the species with high raker count mainly occupies the pelagic zone, while the low count species occupies the bottom layers at all depths. The high count species feeds mainly on plankton, the low count species on bottom organisms. The high count species spawns in inlet and outlet streams in November and December. Gonad development in June suggests that the low count form spawns later, in localities unknown. Samples from early winter spawning runs contained exclusively high count individuals. A few fish, probably hybrids, had raker count corresponding to one species and most other morphological characters corresponding to the other. Tentative names for the species are Coregonus clupeaformis (high gill raker count) and Coregonus pidschian.