Gill Rakers Research Articles

Etelis boweni sp. nov., a new cryptic deepwater eteline snapper from the Indo-Pacific (Perciformes: Lutjanidae).

A new species of Etelis is described based on 16 specimens collected from the Red Sea and Western Australia, with confirmed genetic records throughout the Indo-West Pacific. It is similar to and was often misidentified as Etelis carbunculus Cuvier, with both species sharing the diagnostic character of low number of developed gill rakers. Nonetheless, the two species are genetically divergent and differ morphologically in adult body length; proportions of eye, snout, cheek and caudal fin; shape of head, opercular spine and sagittal otolith; and coloration of the tip of the upper caudal fin. Etelis boweni has a wide Indo-west Pacific distribution that largely overlaps with E. carbunculus, and the two species are often caught on the same fishing line.

EmGarra/em emorontesi/em, a new species from the Orontes River drainage (Teleostei: Cyprinidae).

Garra orontesi, new species, is described from the Orontes River drainage in the eastern Mediterranean Sea basin in Turkey and Syria. It is distinguished from its congeners in the Mediterranean Sea basin and adjacent Mesopotamia by possessing 17-21 gill rakers on the lower part of the first gill arch, the pelvic-fin origin usually below the second branched dorsal-fin ray, 8½ branched dorsal-fin rays, usually 2-3 scales between the tip of the pectoral and pelvic-fin origins, and no tubercles behind the upper posterior eye margin. It is also distinguished by a minimum K2P distance of 2.7% in its COI barcode region against G. rufa, and 3.9% against the geographically adjacent G. turcica.

Re-Description of Sillago malabarica, Silver Whiting from Southern Indian Waters

Sillaginids possess similar taxonomic characters, which make the specific identification difficult, and many true species may be hidden in the synonymy of wide-ranging species. There are currently 36 valid species of sand whitings in the family Sillaginidae. Thirteen valid species are reported from Indian waters and six species are reported from the Arabian Sea. Investigations into the sillaginid diversity off the west coast of India revealed the presence of a species from the Arabian seawhich, on examination, proved to be very similar to the types of Sciaena malabarica. Based on conventional taxonomic analysis and DNA barcoding, we therefore raise Sillago malabarica (new combination) from the synonymy of S. sihama and re-describe it here. Distinctive characteristics of the species include XI-XII spines in the first dorsal fin; I, 21–24 rays in the 2nd dorsal fin; 3–4/7–8 gill rakers on 1st gill arch, Head length 25.2–30.4; Snout length 39.4%–46.8% HL; post-orbital length 34%–37.5% HL, 34 total vertebrae (abdominal: 13, haemal: 4 and caudal: 17); single sharp spine on the opercular edge; swim-bladder with eight or nine lateral processes extending from entire lateral surface of main body of swim bladder; golden silvery body, dorsal and anal fins hyaline, with yellow tips and the absence of a mid-lateral streak or dark bands. Apart from re described species S. malabarica, original S. sihama is also recorded from Indian waters, in our studies.

Chondrostoma smyrnae, a new nase from the Tahtalı reservoir drainage in the Aegean Sea basin (Teleostei, Leuciscidae)

Chondrostoma smyrnae, a new species, from the Tahtalı reservoir drainage is distinguished by having a slightly arched lower jaw with a well-developed keratinised edge, a deep and cylindric body, a complete lateral line with 47–52+1 total scales, 8–9 scale rows between the lateral line and the dorsal-fin origin, 4 scale rows between the lateral line and the pelvic fin-origin, and 19–23 gill rakers on the first gill arch. Moreover, molecular analyses using full cyt b (1141 bp) and partial coI (652 bp) sequences of the mitochondrial genome from specimens of the new species, C. smyrnae and specimens belonging to other Chondrostoma species from central and western Anatolia demonstrated that the C. smyrnae is easily differentiated by their high pairwise genetic distances of cyt b and coI data set (>2.20 and 1.03%, respectively) and by their position in the phylogenetic trees obtained through Maximum Likelihood (ML) methodology.

Comparison of morphological characteristics of the river puffer, <i>Takifugu obscurus</i>, the tiger puffer, <i>T. rubripes</i>, their hybrids, and their triploid hybrids

Various biometric and geometric measures were used to discriminate between the morphologically similar river puffer, Takifugu obscurus, tiger puffer, T. rubripes, their hybrids, and their triploid hybrids. The hybrids and triploid hybrids had greater anal fin width, nostril width, and snout length than the parental species (p<0.05). However, they had less caudal peduncle depth, inter-orbital width, head length, and head width (p<0.05). The morphometric and meristic characteristics of the hybrids and triploid hybrids were either intermediate between the parental species or more similar to those of one parental species. However, the external morphology of the hybrids and triploid hybrids was predominantly maternal. The triploid hybrids had asymmetry in the fin rays and gill raker numbers. This study identified phenotypic characteristics by distinguishing the morphological variables of river puffer, tiger puffer, their hybrids, and their triploid hybrids.

A new species of Thrissina from Pakistan (Arabian Sea), with redescription of Thrissina whiteheadi (Wongratana 1983) (Clupeiformes: Engraulidae)

Thrissina supra sp. nov. is described based on 15 specimens collected from Sindh, Pakistan. The new species is closely related to Thrissina whiteheadi (Wongratana 1983), which is herein redescribed, both species having a relatively long upper jaw with the posterior tip slightly beyond the opercle posterior margin, the snout tip above the eye center level, similar numbers of gill rakers, ventral scutes, and fin rays, and the first supramaxilla absent. However, the former is characterized by higher counts of longitudinal scale rows (45–47 vs. 40–42 in T. whiteheadi), transverse scales (12 or 13 vs. 10 or 11), total gill rakers on the first, second, third, and fourth gill arches [35–39, 33–37, 22–24, and 18–22, respectively vs. 30–34 (rarely 36), 29–32 (34), 19–21 (23), and 15–18 (14, 19), respectively], and branched anal-fin rays [42–45 (rarely 40) vs. 39–42 (43)], a longer snout (3.7–4.1% SL vs. 3.1–3.6%), pelvic fin (9.0–10.4% SL vs. 7.7–9.0%), and mandible (17.3–18.3% SL vs. 15.4–17.2%), a shorter pelvic-fin insertion to anal-fin origin distance (17.0–18.8% SL vs. 19.1–24.2%), and distinct paired dark lines along the dorsum from the occiput to the caudal-fin base (vs. uniformly distributed dorsal melanophores).

Description of two new species of Bassozetus (Ophidiiformes: Ophidiidae) and a redescription of Bassozetus robustus Smith and Radcliffe 1913

Two new deepwater assfish species, Bassozetus trachibranchus and Bassozetus squamosus, are described from the 29 western Atlantic and four western Indian and western South Pacific specimens, respectively. In addition, a redescription of Bassozetus robustus Smith and Radcliffe in Radcliffe 1913, with which both of the above two new species have been previously confused, is provided on the basis of 14 specimens and its distributional range is revised to the western Pacific Ocean. The three species are separable from the 13 known congeners by the following combination of characters: dorsal-fin rays (116–126), anal-fin rays (95–103), oblique scale rows (30–47), pelvic-fin length (14.3–21.7% SL), a single well-developed median bashibranchial tooth patch, and one or two deep indentations on the sagitta dorsal margin, plus long gill rakers (10–14 in B. robustus) and head, predorsal and prepelvic lengths (20.5–22.8% SL, 19.4–21.1% SL and 15.3–18.1% SL, respectively, in B. robustus). Additionally, B. trachibranchus, B. squamosus and B. robustus are distinguishable from each other as follows: oblique scale rows (39–45 in B. trachibranchus, 44–47 in B. squamosus, and 30–36 in B. robustus), eye diameter to head length ratio (greater in B. squamosus than in similarly sized specimens of the other species), pelvic fin length/distance between pelvic and anal fins ratio (smaller in B. robustus than in similarly sized specimens of the other species), and 2nd to 4th lower limb morphology (many small tooth patches arranged along the outer ridges in B. trachibranchus, absent or a few only in the other species).

Oligocene basking sharks (Lamniformes, Cetorhinidae) of the Carpathian Basin with a reconsideration of the role of gill rakers in species diagnostics

ABSTRACT Basking sharks are presented in the modern fauna by a single species (Cetorhinus maximus), although they have been much more diverse in the past. This group of sharks first appeared in the fossil record in the middle Eocene of the Antarctic and the U.S.A., but most of the described extinct taxa are known from the Oligocene and lower Miocene of Europe. Gill rakers are the most abundant among basking shark remains and their morphological details play an important role in species diagnostics. The shape of isolated gill rakers from 16 Oligocene localities of Poland was analyzed using various morphological approaches, including geometric morphometrics. Results indicate that descriptive characters have a wide range of variation and low diagnostic value, and they are associated directly with the position of gill rakers on the gill arch. Morphological indices describe proportions by discrete structures and could be effective only in the identification of the stratigraphically most distant taxa. Geometric morphometrics revealed significant differences between all of the species designated earlier except for †Caucasochasma zherikhini and †Keasius parvus. At the same time, considering the obtained results on morphology along with the geographic distance, Oligocene basking sharks from Poland should be assigned to †K. parvus. Geometric morphometrics of gill rakers supports the taxonomic distinctness of both †K. rhenanus and †K. septemtrionalis. Study results indicate that reliable taxonomic attribution of extinct basking sharks by the shape of gill rakers, in the absence of other skeletal elements (teeth and/or vertebrae), should be sample-based using multivariate approaches.

Three new goatfishes of the genus Upeneus from the Eastern Indian Ocean and Western Pacific, with an updated taxonomic account for U. itoui &lt;br /&gt;(Mullidae: japonicus-species group)

Coastal marine fish diversity from E India and Indonesia to S Japan is still insufficiently investigated. Of the 42 species of goatfishes (Mullidae) recorded from this area, 12 were described only since 2010 and ten of those belong to the genus Upeneus. During a recent review of species of Upeneus of the so-called japonicus-species group (characterized by seven dorsal-fin spines), 13 specimens that had been previously identified as U. guttatus from Indonesia and Vietnam were found to be distinct, representing possibly two undescribed species. These specimens were studied together with 20 U. itoui from S Japan, a rather similar species, and a yet unidentified congeneric from S Japan. In total 41 morphometric, 10 meristic and several colour characters were examined and detailed comparisons with a large data set from all 14 japonicus-group species conducted. Three new species, U. dimipavlov n. sp. from Nha Trang, S-central Vietnam, U. elongatus n. sp. from Tanega-shima Island, Kagoshima, S Japan and U. willwhite n. sp. from Lombok, S Indonesia are described and an updated account for U. itoui is provided. Among these four featured species, U. elongatus is the most different, having more gill rakers, the shallowest head and body and distinct colour patterns on caudal and dorsal fins. Upeneus dimipavlov differs from the remaining two species in having a more rounded and less laterally compressed body with a wider caudal peduncle and no conspicuous mid-lateral body stripe in fresh fish. Upeneus willwhite differs from U. itoui in deeper head, larger eyes, longer upper jaw and barbels and oblique bars on the lower caudal-fin lobe which do not cross the entire lobe. Additional comparisons of each of the four featured species with all other japonicus-group species and U. heterospinus were conducted providing evidence for distinction and differential diagnosis. Unvouchered in-situ photographs of four goatfish specimens from the Central Philippines that resemble U. elongatus in caudal- and dorsal-fin colour patterns are presented. The need for further sampling and associated taxonomic investigations as prerequisites for appropriate assessment of ecological and conservation parameters such as diversity, distribution and rarity is emphasized in the discussion.

Acropoma musorstom, a new lanternbelly (Acropomatidae) from the South Pacific and the first record of Acropoma splendens from the Andaman Sea off southwestern Thailand

A new species of the genus Acropoma, A. musorstom sp. nov. is described based on four specimens (126.3–143.0 mm in standard length: SL) collected from Vanuatu and the Molucca Islands, Indonesia. The present species is distinguished from other congeners by a combination of the following characters: luminous gland short, U-shaped around anus; luminous-gland length 10.3–13.7% SL; symphysis of lower jaw not protruded; proximal radial of first anal-fin pterygiophore with concavity on anterior surface; anus situated closer to pelvic-fin insertion than to origin of anal fin; weakly ctenoid scales on lateral side of body; vertical line on cheek absent; scales between first dorsal-fin base and lateral line 4; pectoral-fin rays 16–17; and gill rakers 20–21. Acropoma splendens (Lloyd 1909) collected from off Phuket, it represents the first record of this species from the Andaman Sea off southwestern Thailand. A key to the species of Acropoma currently known from the Indo-Pacific is provided.

Epinephelus insularis, a new species of grouper from the western Pacific Ocean, and validity of E. japonicus (Temminck and Schlegel 1843), a senior synonym of Serranus reevesii Richardson 1846 and E. tankahkeei Wu et al. 2020 (Perciformes: Epinephelidae)

A new species of grouper, Epinephelus insularis is described based on 12 specimens (271.6–528.0 mm standard length: SL) from the western Pacific Ocean. The new species, previously confused with Epinephelus chlorostigma (Valenciennes in Cuvier and Valenciennes 1828), is distinguished from all congeners by the following combination of characters: dorsal-fin rays XI, 16 (rarely XI, 17); longitudinal scale series 114–132; total gill rakers 21–24; posterior margin of anal fin rounded; caudal fin truncate, its posterior margin with a narrow white line; head, body, and all fins with small polygonal brown spots (expanded on head and body undersurface) on a pale background, forming a reticulate pattern; and pectoral fin brownish. In addition, Serranus areolatus japonicus Temminck and Schlegel 1843, which has been regarded as a junior synonym of E. chlorostigma, is redescribed as a valid senior synonym of Serranus reevesii Richardson 1846 and Epinephelus tankahkeei Wu, Qu, Lin, Tang and Ding 2020. Epinephelus japonicus is characterized as follows: dorsal-fin rays XI, 17; longitudinal scale series 101–119; total gill rakers 23–26; posterior margin of anal fin rounded; caudal fin convex, without white lines; head, body (lateral surface only), dorsal, pelvic, anal, and caudal fins with small polygonal brown spots forming a pale reticulate pattern; and pectoral fin yellowish.

Four new species of Serranochromis (Teleostei: Cichlidae) from the Cuanza and Okavango river systems in Angola, including a preliminary key for the genus.

The present study describes Serranochromis alvum n. sp., Serranochromis swartzi n. sp., Serranochromis cuanza n. sp., and Serranochromis cacuchi n. sp. from Angolan tributaries of the Cuanza and Okavango systems in Angola. The presence of four or five scale rows between the posterior margin of the orbit and the ascending arm of the preoperculum, the presence of widely set unicuspid teeth on the jaws, widely separated gill rakers, and anal fins with egg ocelli place these four species in Serranochromis. The Serranochromis described herein are distinguishable based on a combination of morphological and meristic characters, as well as pigmentation patterns. The interorbital width (14.3-15.9 % HL) of S. alvum is narrower than that of S. swartzi (17.6-19.8), S. cuanza (16.3-18.0), and S. cacuchi (20.0-21.7). Moreover, the interorbital width of S. cacuchi is greater than the other three described species. Serranochromis swartzi has a smaller preorbital depth (16.2-18.9 % HL) and snout length (29.6-31.9 % HL) than Serranochromis cuanza (PD 19.1-22.2, SNL 35.2-39.6 % HL). Serranochromis alvum is known only from the type locality at Cuito-Cuanavale at the junction of the Cuito and Cuanavale rivers, tributary to the Okavango River in Angola. Serranochromis swartzi is known only from the type locality in the Cuanza River, Angola. Serranochromis cuanza is restricted to the Cuanza River, below Capanda Dam, Angola, while S. cacuchi is known only from the Cacuchi River, a tributary of the Cuchi-Cubango River in Angola. The limited distribution of all four species and the absence of many congeners suggest, that in addition to previous studies that invoked a lacustrine speciation model, vicariance through drainage isolation seems to have played an important role in driving speciation in this group. The minimum polygon clusters that are formed when the first principal components of the meristic data are plotted against the second sheared principal components of the morphometric data show separation of the four new species.

Morphometric and meristic characteristics of Mugil cephalus (grey mullet) from wetland of Ogun water-side Local Government Area

Investigations on the morphometric and meristic characteristics were conducted on grey mullet, Mugil cephalus collected from wetland of Ogun waterside Local government Area, Ogun state, Nigeria. A total number of ninety-one live specimens were caught from the wetland of Ogun waterside Local government Area, for a period of March to June 2012. The fish were immediately preserved on ice in order to slow down rate of decomposition and their total length (TL) (cm), standard length (SL) (cm), head length (HL) (cm), body width (BW) (cm) and body weight (g), were measured fresh within 24 hours. Its sex was also determined by dissecting out the gonads to reveal eggs or testes. The mean values of total length TL, standard length SL, head length HL, body width and body weight for both male and female of M. cephalus for the month of March to June were 18.0±1.1 and for male and 18.6±0.9 for female (M/F), 14.7±1.0 and 14.7±0.6 (M/F), 3.3±0.2 and 3.2±0.1 (M/F), 3.8±0.2 and 3.0±0.5 (M/F), and 52.3±5.5 and 66.7±1.1 (M/F). Gill raker of M. cephalus gave a different result as there was difference between male and female,108 – 138 (male), and 104 and 148 (female).The growth pattern for male species were near isometric with b = 2.53, female species was negative allometric (b = 2.88) and combined sexes was isometric (b = 2.80). Information obtained from the study will contribute to the baseline data for carrying future studies on its ecology and conservation and development.

OSTEOLOGY OF PARABROTULA PLAGIOPHTHALMUS (OPHIDIIFORMES: BYTHITOIDEI: BYTHITIDAE)

Parabrotula (Zugmayer 1911a), included in the family Bythitidae (Ophidiiformes), is a genus of small viviparous mesopelagic fishes with two valid species. Parabrotula plagiophthalmus is known from collections made worldwide except in the eastern Indian, eastern Pacific, and western South Atlantic Oceans; most specimens are from the North Atlantic Ocean. Most anatomical data for P. plagiophthalmus are limited to aspects of external anatomy, the reproductive system, and meristic data that can be gathered through radiographs; virtually no data on other aspects of the osteology of P. plagiophthalmus are available. In this study, we describe the skeleton of P. plagiophthalmus from cleared and stained specimens and computed tomography data. Many aspects of the skeleton of P. plagiophthalmus are reduced (subopercle; ceratobranchial 5; gill rakers; gill filaments; distal radials of median pterygiophores; caudal skeleton; posttemporal; supracleithrum; scapula; distal pectoral radials; pelvic girdle and fins; scales) or absent (mesethmoid; nasal; pterosphenoid; intercalar; infraorbital bones; endopterygoid; coronomeckelian; supramaxilla; pharyngeal toothplates). All bones of the skull are extremely thin dermal or perichondral ossifications, with little to no endochondral components. The vomer supports a variable number of teeth (0–3). The pars autopalatina and its ossification are separated from the pars metapterygoidea and pars quadrata and their ossifications; the thin ectopterygoid bridges these elements of the suspensorium. The lower jaw is very large compared with all other elements of the viscerocranium. The pectoral radial plate was never observed to be divided into separate radial elements. We discuss the skeleton of Parabrotula in the context of other taxa but call attention to the need for further comparative studies of the anatomy of ophidiiform fishes.

Ontogenic Development Of Gills In Pre To Post-Flexion Stages Larvae Of Himalayan Snow Trout Schizothorax Plagiostomus (Heckel)

The ontogenic development of gills, including gill arch, gill filaments, and gill rakers in pre to postflexion stages larvae of Himalayan Snow Trout Schizothorax plagiostomus were studied with the objectives that this study could serve as a base for further studies about the early embryonic development and organogenesis in various fish species inhabiting hill stream environments. To obtain the pre to post-flexion stages larvae, an artificial breeding experiment was conducted during September- October on the bank of snow-fed river Alaknanda by stripping method. Further, the development of the gill apparatus was studied histologically, using light microscopy. Hatchling takes place 124-130 hours after fertilization at the incubation temperature of 19-200C. On second dph (day post-hatching), gill arches, gill filaments, and branchiostegal membrane began to differentiate. By the third dph, blood channels were observed in gill filaments as well as in pseudobranch. Formation of secondary lamellae, branchial arteries, elongation of the gill cover, cartilaginous rod formation in the gill arch, and the branchiostegal membrane was discernible by fourth-fifth dph. Pillar cells and afferent and efferent arteries with RBCs in primary and secondary lamellae were observed on the seventh dph. Around the onset of exclusive exogenous feeding (twelfth dph), gill rakers and a group of pillar cells with blood channels were recognizable. Well-organized and functional gill structures with increased number and size of secondary gill lamellae were present among the fifteenth-seventeenth dph larvae. The general pattern of structural and functional development of both the natural site and laboratory-reared larvae was similar, except a large amount of mucous and clustered epithelial cells among the laboratory-reared larvae, which may be due to the physiological as well as environmental stress posed by the adverse physicochemical conditions.

A New Species of the Anchovy Genus Stolephorus Lacepède 1803 from North Sumatra, Indonesia, and Redescriptions of Stolephorus pacificus Baldwin 1984 and Stolephorus teguhi Kimura, Hori and Shibukawa 2009 (Teleostei: Clupeiformes: Engraulidae).

Stolephorus leopardus sp. nov. is described here, and Stolephorus pacificus and Stolephorus teguhi are redescribed. Those three species are distinguished among congeners by the presence of more than 30 gill rakers on the lower limb of the first gill arch and a short maxilla, posteriorly just reaching the anterior border of the preopercle. Stolephorus pacificus and S. teguhi have rarely been reported since they were originally described, and therefore detailed morphological data and further diagnostic characters are provided. Stolephorus leopardus, in turn, is described based on four specimens collected on Nias Island, North Sumatra Province, Indonesia. The new species can be distinguished from S. pacificus and S. teguhi by a shorter pectoral fin (15.6-16.3% of standard length vs. longer than 16.5%), a longer snout (4.7-4.8% of standard length vs. < 4.5%), and an intermediate number of total gill rakers on the first gill arch (63-68 in S. leopardus vs. 57-63 in S. pacificus and 72-82 in S. teguhi). In addition, the new species differs from S. pacificus in having a dark line on the dorsum (vs. line absent), numerous melanophores laterally on the head (vs. a few melanophores on the snout and mandible tips), and higher counts of branched anal-fin rays [19-21(modally 19) vs. 17-19 (18)]. Stolephorus leopardus is further distinguished from S. teguhi by a shorter anal-fin base (22.4-22.5% of standard length vs. 22.7-25.3%).

Does ecological release from distantly related species affect phenotypic divergence in brook charr?

Ecological opportunity occurs when a resource becomes available through a decrease of interspecific competition and another species colonizes the vacant niche through phenotypic plasticity and intraspecific competition. Brook charr exhibit a resource polymorphism in some Canadian Shield lakes, where a littoral ecotype feeds mainly on zoobenthos and a pelagic ecotype feeds mostly on zooplankton. The objectives of this study were to test that (i) resource polymorphism is common in these brook charr populations, (ii) the presence creek chub and white sucker, two introduced species competing with brook charr for littoral resources, will decrease the phenotypic divergence between the two brook charr ecotypes, and (iii) the ecological release from introduced species will increase population and/or individual niche widths in brook charr. The study was based on 27 lakes and five indicators of resource use (stomach content, liver δ13C, muscle astaxanthin concentration, pyloric caecum length, and gill raker length). Our results indicate that within-lake differences in resource use by both ecotypes are common and stable through time. When facing interspecific competition, both littoral and pelagic brook charr incorporated more pelagic prey into their diet but maintained the amplitude of their differences in resource use, which contradicts our second prediction. Finally, we did not find any significant effect of introduced species on population and individual niche widths of brook charr. We suggest that the difference in feeding mode among distantly related competitors could prevent the complete exclusion of a species from a given niche and explain the lack of response to the ecological release.

Histopathological Effect of the Different Concentration of Crude Oil and Its Products on the Gill Apparatus of Catfish (&amp;lt;i&amp;gt;Heterobranchus bidorsalis&amp;lt;/i&amp;gt;)

This project is aimed at assessing the Histopathological effect of the different concentration of crude oil and its products on the gill apparatus of catfish (<i>Heterobranchus bidorsalis</i>). Three concentrations (1.0, 3.0 and 5.0 M/L) of the petroleum products Premium Motor Spirit (PMS), Dual Purpose Kerosene (DPK) and Bonny-Light Crude oil (BLCO) were made. To each concentration, three adults of <i>H. bidorsalis</i> were incubated for 1, 24 and 96 hours. Triplicate values of samples were recorded in each of the different concentration of petroleum products. Three plastic containers containing three fishes each were not contaminated with petroleum product and was left as control (0.0 M/L) for the experimental work. Histology of the gill was used to determine the pathology of petroleum products on the gills. Histopathological examination following exposure to petroleum products showed elongation of gill lamellae, hyperplasia of lamellae, fusion of lamellae tips, separation of respiratory epithelium with underlying supporting tissue and altered gill rakers. Microscopical observation showed a significant difference (P<0.05) in hyperplasia and elongated gill lamellae. There were no significant difference (P>0.05) in heartbeats, weight and underlying supporting tissue in the different concentration of petroleum products. The various biological responses and changes observed with such histological alterations can be used as a tool to detect toxic effects of pollutants in the organs of living organism making it a good environmental stressor indicator for bioassay.

Revision of the Genus Scopelogadus (Melamphaidae). 3. S. bispinosus and S. perplexus sp. n.

Scopelogadus bispinosus has been redescribed, its species status has been restored. It has long been considered a subspecies of S. mizolepis. The species inhabits mainly the tropical and subtropical zones of the central and eastern parts of the Pacific Ocean; in the northeastern Pacific Ocean, it is found in temperate waters. A new species S. perplexus sp. n. has been described from the tropical waters of the Pacific Ocean. The new species is characterized by the presence of a large number filaments of pseudobranch (10–11), the largest of the two branchial lobes opposite the angular gill raker is relatively short; the color of the stomach surface is uniformly dark, without noticeable darkening in the back.

Morphological divergences as drivers of diet segregation between two sympatric species of Serrapinnus (Characidae: Cheirodontinae) in macrophyte stands in a neotropical floodplain lake

Abstract Diet and morphology of Serrapinnus notomelas and Serrapinnus sp.1 were investigated across ontogeny, as a way to elucidate the key elements linked to the resource partitioning (a main driver for species coexistence). Fish sampling was conducted monthly between October 2010 and March 2012. Individuals were captured, identified, and classified into juvenile or adult. Our results show ontogenetic and interspecific differences in feeding abilities and morphological traits. Differences in body shape (relative area of the dorsal fin, length of head, height of the caudal peduncle, the aspect ratio of the pectoral and pelvic fin) favored divergent swimming performances (more maneuverability in S. notomelas and continuous swimming to Serrapinnus sp.1). We also observed divergences in trophic apparatus traits and correlations with different diets. In this context, it is highlighted that understanding the relationship between morphology and diet can assist in elucidating the processes that permeate the coexistence between sympatric species, and between ontogenetic periods. Besides, the relevant contribution of the measures of the trophic apparatus (gill raker length, the number of teeth cuspids, and intestinal coefficient) in trophic segregation seems to be a strong evidence in favor of the proposed discriminatory and predictive capacities of these traits.