Gill Rakers Research Articles

Benthic–limnetic morphological variation in fishes: Dissolved organic carbon concentration produces unexpected patterns

AbstractVariation in traits related to foraging and locomotion in benthic and limnetic habitats has been observed in many fishes. Benthic and limnetic food chain productivity in lakes is strongly influenced by the concentration of dissolved organic carbon (DOC) in the water, suggesting that DOC might indirectly impose selection on these traits and lead to classic benthic forms at low DOC concentrations and limnetic forms at high DOC concentrations. We tested this hypothesis via geometric morphometric and meristic analyses of bluegill sunfish (Lepomis macrochirus, Centrarchidae) from 14 lakes with DOC concentrations ranging from 4 to 24 mg/L. These lakes, located in close proximity to each other, straddle the drainage divide between the Mississippi River and Laurentian Great Lakes basins in northern Wisconsin, USA. Bluegill morphology was consistently related to lake DOC concentration in both drainage basins, despite differences in morphology between basins. Fish from higher DOC lakes had deeper bodies and smaller heads, among other differences, though the proportion of shape variation described by DOC was low. Gill raker length and inter‐raker spacing were positively related to DOC concentration. Although some traits were thus related to DOC concentration, the directions of these relationships did not match the predicted benthic–limnetic patterns. Further, no relationships were evident between DOC and gill raker number, eye width, pectoral fin dimensions, or pectoral fin insertion angle in univariate analyses. These variable outcomes suggest that selection linked to DOC does not map neatly onto the classic benthic–limnetic axis, that high DOC favors a benthic–limnetic generalist rather than a limnetic specialist, or that the benthic–limnetic morphological dichotomy is less clear and universal than is often suggested.

Morphometric and meristic characteristics of the first record Fistularia petimba (Lacepède, 1803) and Fistularia commersonii (Rüppell, 1838) (Piscès: Fistulariidae) from the Egyptian Mediterranean waters (West Alexandria)

In the present study, morphometric and meristic characteristics of the cornetfishes, Fistularia spp., from the Egyptian Mediterranean coast were described. The linear length-length relationships and the allometric growth pattern were also investigated. Specimens were sampled from October 2017 to March 2019, by trawling in the marine area along the west of Alexandria City. The data analysis showed that the red cornetfish, Fistularia petimba (Lacepède, 1803), which is one of the IUCN Red List, was observed in this zone for the first time. Fistularia petimba dorsal, anal, pectoral, ventral, and caudal fins formulas were defined as follows: D 15; A 15; P (I + 14); V (i + 5); and C 18. This fish species was characterized by, elongated bony plates that were present anteriorly and posteriorly to the dorsal fin with a number of 23 bony plates anterior to the dorsal fin with the absence of gill rakers. Arched lateral line and sharp spines were on the posterior ossifications. The body color was orange–brown on the upper side and white on the bottom with transparent fins and a touch of orange color on the tips. The bluespotted cornetfish, Fistularia commersonii (Rüppell, 1838) reached 107.5 cm in total length. Its fins formulas were as follows: D (13–17); A (12 – 18); P (I + 13) – (I + 15); V (i + 5); and C 18. The vertebrae count was between 84 and 88, including the urostyle that had the first 4 vertebrae fused and without bony plate or gill rakers. Arched lateral line and rows of blue spots or line appeared on the back. The body color varied from brownish to olive on the upper side and white on the bottom with transparent fins and a touch of rosy pink color on the tips. The linear regression equations for the different morphometric characters of F. commersonii were highly correlated (R2 > 0.90). The allometric coefficients (b) of the various morphometric characters of F. commersonii were also studied. Further studies on the biological and fisheries parameters are recommended for F. commersonii as well as following the presence and establishment of F. petimba in the Egyptian waters.

Occurrence of microplastics in gastrointestinal tracts of planktivorous fish from the Thoothukudi region.

Planktivorous fish are easily susceptible to passive microplastic ingestion during their feeding behaviour and may be transferred along with the marine food web. Hence, the present study was conducted to assess the microplastics prevalence in the planktivorous fish (677 individuals) collected from 2 landing centres in the Thoothukudi, Gulf of Mannar region, South Tamil Nadu, India. The prevalence of microplastics was detected in 118 out of 677 individuals, with a mean abundance and percent occurrence of 1.22 ± 0.47 items/individual and 17%, respectively. The ingestion of microplastics in planktivorous fish was primarily due to their feeding habitat, in which they were prone to the accidental or passive intake of microplastics regardless of the fish's length and body weight. The microplastics abundance was significantly higher in Sardinella gibbosa (1.34 ± 0.56 items/individual), which might be due to their pelagic and planktivorous feeding habitat, highest filtration capacity, presence of closed gill rakers, and also due to the passive ingestion of microplastics as food items. Fibres, blue, and 1 to 2mmsized microplastics were predominant in the guts of Sardinella gibbosa, accounting for 95.74, 47.87, and 46.80%, respectively, whereas in Leiognathus lineolatus, fragments, black, and 1 to 2mmsized microplastics were highly prevalent with 62.96, 72.22, and 79.62%, respectively. The predominance of various shapes (fragments, fibres), sizes (1-2mm), and colours (blue and black) of microplastics in the guts of fish was influenced by their passive ingestion, ingestion of contaminated planktonic prey, lack of selectivity of prey particles and their resemblance to plankton species. Polypropylene polymers predominated (96.77% and 95.23%) in both fish, followed by polystyrene (3.22% and 4.76%). Furthermore, this study provides baseline data and insists that there is a need for continuous monitoring of the distribution of microplastics.

Small Differences in Diet Facilitate the Coexistence of Three Forage Fish Species in an Inshore Northern Patagonian Habitat

Forage fish play the crucial role of transferring energy from lower to upper trophic levels. These small pelagic fish feed on plankton and can compete with each other for food, leading to potentially complex interactions. Three forage fish species (Sprattus fuegensis, Strangomera bentincki, and Engraulis ringens) are commonly found in the inshore waters of Northern Chilean Patagonia, a region with large spatial variability in oceanographic conditions and in the zooplankton community. To better understand what factors may explain coexistence among these three forage fish species, we examined differences in resource availability (zooplankton community and abundances) in three locations (Chiloé, Cordillera, and Aysén regions) within Northern Patagonia. We compared the diet of the three fish species using both stable isotope and stomach content analyses, and we measured their gill rakers. S. fuegensis, the only species found in all three regions, had flexible diets which lent it greater success than the other two species at foraging in waters with fewer prey. We found little diet differentiation among the three species in the copepod-rich Cordillera region, but the diverging diets of S. bentincki and S. fuegensis in the copepod-poor Chiloé region suggest that diet partitioning in areas with fewer resources is due to competition. The small differences in diet facilitates coexistence among the three species, which may help explain the lack of correlation between the three species’ population abundances in the Cordillera region over the past 6 years. Finally, our results show that the high degree of oceanographic heterogeneity in Northern Patagonia may encourage species separation based on their specific environmental requirements.

Description of a new species of queenfish, Scomberoides pelagicus from Indian seas

Aim: The study was carried out to ascertain whether morphotype of Scomberoides commersonnianus (Talang queenfish) existing along the Indian coast is a new species or not. Methodology: Talang queenfish and the morphotype were tested for their uniqueness using systematic and molecular tools. The morphometric and meristic details including otolith morphometry were analysed and compared for taxonomic divergence and Cytochrome Oxidase I and Cytochrome b gene sequences for quantifying genetic divergences. Results: The systematic analysis indicated significant morphometric differences between both. The otolith morphometry and phylogeny also confirmed the divergence between them, and qualified the morphotype as an independent species status and named Scomberoides pelagicus sp. nov. Interpretation: The new species is distinct by deep ovate body, concave dorsal head profile, anal fin origin anterior to second dorsal fin and pelvic to pectoral fin, helical arrangement of body scale and stout and less numerous gill rakers on the first gill arch. The phylogeny as on Cytochrome b and Cytochrome Oxidase 1 sequences are very distinct, with 11.2% and 2.0% divergence respectively. Their known distributional range are peninsular region of Indian coast, Malaysian region of the South China Sea and Manila Bay, Philippines.

Morphological investigation of the gills of the dusky grouper Epinephelus marginatus (Lowe 1834) using gross anatomy and scanning electron microscopy.

The current study has designed to investigate the morphological characteristics of the gills of the dusky grouper (Epinephelus marginatus) by gross morphology, scanning electron microscopy, and morphometric analysis. The study was carried out on 10 fresh fish. The fish has four-gill arches on each side. The lengths of the first-, second-, third-, and fourth-gill arches were 5.27, 4.2, 3.2, and 2.8cm. The gill arches carried a longitudinal band, the bases of the gill filaments, and gill rakers that varied from rectangular to circular shapes. Each gill arch had two main lateral and medial rows and two accessory rows of gill rakers in an alternative manner with each other. The dusky grouper fish had long rakers, whereas the longest one was the lateral rakers of the first arch, which were 467 and 1271.9μm in width and length. Three types of spines appeared on the gill arches and rakers. The long spine had detected on the apex of the short rakers. Each gill arch carried on its ventral side two rows of gill filaments. The long filaments were at the middle of the gill arch, while the short ones were at the rostral end of the gill arch. The study has demonstrated the taste buds, mucous, chloride cells, and significant features of the epithelial covering of the gill arches and rakers. The morphology of the gills of the dusky grouper indicates the adaptation to their marine environment.

A New Species of the Bengal Spined Anchovy Stolephorus from the Eastern Indian Ocean and Redescription of Stolephorus dubiosus Wongratana, 1983, with Comments on the Evolution of Prepelvic Scute Numbers within Stolephorus (Clupeiformes: Engraulidae).

The Bengal Spined Anchovy, Stolephorus taurus sp. nov. is described from 21 specimens from the northern Bay of Bengal. The new species closely resembles Stolephorus dubiosus Wongratana, 1983, which is redescribed. Both species have a predorsal scute, spine on the pelvic scute, long maxilla posteriorly slightly short of or just reaching the posterior margin of the opercle, 25 or more gill rakers on the lower limb of the first gill arch, and double black lines on the dorsum posterior to the dorsal fin. However, the new species differs from S. dubiosus in having a longer pelvic fin with the posterior tip of the depressed fin beyond vertical through the dorsal-fin origin (vs. usually not reaching to vertical through dorsal-fin origin), longer pectoral fin, second dorsal-and third dorsal-fin rays, second anal-and third anal-fin rays, and greater interorbital width. Stolephorus taurus sp. nov. is closely related to Stolephorus baganensis Delsman, 1931 and S. dubiosus, although at least 2% mean p-distance divergence in the mitochondrial cytochrome c oxidase subunit I (COI) gene separates each of the three species. A phylogenetic reconstruction of the evolution of the number of prepelvic scutes within Stolephorus indicated that having six scutes was the most likely ancestral condition in the genus, and was later reduced in the evolution of Stolephorus to five or four scutes. One such reduction occurred recently in the lineage of Stolephorus taurus sp. nov.

Stolephorus lotus, a New Anchovy (Teleostei: Clupeiformes: Engraulidae) from the Northern Territory, Australia.

A new anchovy Stolephorus lotus sp. nov., is described based on 30 specimens collected from Van Diemen Gulf, Northern Territory, Australia. The species closely resembles Stolephorus acinaces Hata, Lavoué and Motomura, 2020 and Stolephorus andhraensis Babu Rao, 1966, in having a long maxilla (posterior tip just reaching or extending slightly beyond the posterior margin of the opercle), indented posterior preopercular margin, anal fin with 16-18 branched fin rays, and 21-23 lower gill rakers, and lacking a predorsal scute and pelvic scute spine. However, the new species differs from the other two species in having higher counts of longitudinal series of scale rows and predorsal scales (37-39 and 20 or 21, respectively vs. 35-38 and 17-19 in the other two) and a more anteriorly located anal-fin origin (below bases of sixth to eighth dorsal-fin rays vs. eighth to tenth dorsal-fin rays).

Development of gill rakers may influence the prey choice in Chinese perch (Siniperca chuatsi) larvae

Chinese perch (Siniperca chuatsi) larvae prey on other fish species larvae at the beginning of exogenous feeding but do not eat any zooplankton in natural conditions, the mechanism behind this special feeding habit is unclear at present. This study aimed to visualize the development of gill rakers in Chinese perch larvae and observe the ingestion of larvae to different size Artemia in low salinity (5 g/L) water. Our results indicated that Chinese perch larvae demonstrated a slow development in gill rakers, larvae only had some buds from hatching to 7 days post hatching (dph), and the first and second real gill raker was observed at 9 dph and 12 dph respectively. The edar gene expression also consisted with development of gill rakers. Meanwhile, the results of ingestion showed larvae preferred to feed large size Artemia, and larvae fed the large size Artemia also had a higher npy gene expression. Compared with the larvae fed small size Artemia, the larvae which fed the large size Artemia had a higher survival rate. These data inform hypotheses development of gill rakers may influence the prey choice in Chinese perch larvae, no real gill rakers may cause the larvae can not to forage small size zooplankton at first-feeding stage and, thus, the Chinese perch larvae form the special feeding habit.

Heteropneustes fuscus (Siluriformes: Heteropneustidae), a new catfish species from Kerala, India

Abstract. Plamoottil M. 2021. Heteropneustes fuscus (Siluriformes: Heteropneustidae), a new catfish species from Kerala, India. Biodiversitas 22: 87-98. Heteropneustes fuscus, a new catfish species, is described from Kerala, India; it is a close congener of Heteropneustes fossilis (Bloch, 1794) described from Tranquebar in Tamil Nadu. Heteropneustes fuscus has been misidentified as H. fossilis until now, but it differs from Bloch's species in color and many other rigid taxonomic variables. The new species can be distinguished from its relative species in the following combination of characters: deep black body and fins, 4-5 branched dorsal-fin soft rays, 72-75 anal fin rays, 58-60 total vertebrae, 26-32 total gill rakers; deeper and wider body; deeper caudal peduncle; greater pre occipital and post occipital distances and longer anal fin. The new fish is edible and found in freshwater rivers, streams, ponds and paddy fields in Kerala. It is also cultivated in some artificial impoundments. Heteropneustes fuscus is compared with its congeners, scientifically named and taxonomically described.

On the Taxonomic Status of the Red Icefish Channichthys rugosus (Notothenioidei: Channichthyidae) from the Kerguelen Islands (South Ocean)

The presented work is the final part of the taxonomic revision of the Antarctic icefishes of the genus Channichthys Richardson, 1844 (Notothenioidei: Channichthyidae) from the Kerguelen Islands, the species composition of which was discussed until recently. Based on the morphological study of all available specimens from the ZIN and BMNH collections (including the holotype), a comprehensive redescription of the Red icefish Channichthys rugosus Regan, 1913 from the waters of the Kerguelen islands (South Ocean) was carried out, including external morphology, seismosensory system, gill apparatus, and axial skeleton. As a result, new diagnostic features of Red icefish were discovered and previously known ones were clarified, which made it possible to confirm the species validity. Comparison with other valid species icefishes was done. Channichthys rugosus differs from Ch. rhinoceratus Richardson, 1844 by a high anterior dorsal fin, the fin membrane of which reaches the apexes of its longest rays (does not reach in Ch. rhinoceratus), as well as a narrow and concave interorbital space (compared to the wider and flat one), by stronger granulation and a uniform reddish body color (dark spotted-marble in Ch. rhinoceratus). Channichthys rugosus differs from Ch. velifer Meissner, 1972 by the number of rays in the first dorsal fin (7–9 versus 9–12) and pectoral fin (18–20 versus 20–21), the presence of bone plaques in the proximal part of the medial lateral line (absent in Ch. velifer), and monochromatic reddish body coloration (spotted in Ch. velifer). Channichthys rugosus differs from Ch. panticapaei Shandikov, 1995 by the presence of only 1 row of gill rakers on the first gill arch (2 rows in Ch. panticapaei) and by light coloration (brownish-black in Ch. panticapaei).

Comparative Study of Hematological and Histopathological Alterations in Oreochromis niloticus and Clarias gariepinus Exposed to Industrial Waste Effluents

In recent decades the level of foreign compounds in aquatic ecosystems such as heavy metals, pesticides and other persistent organic pollutants has increased alarmingly as a result of domestic, industrial and agricultural effluent. This research therefore examined the histopathological and haematological effects of industrial effluent on Orechromis niloticus and Clarias gariepinus. The histopathology and haematology parameters of the fishes exposed to graded doses of the effluent were assessed using conventional techniques. The results of the haematological assessment of the fishes shows a steady and significant (P < 0.05) reduction in the PCV of the tilapia from 23% (control) to 10% and 25% (control) to 18% in catfish exposed to 6.25 ml/L of the effluent, the RBC count reduced with increase in the concentration of the effluent from 2.60 x 106/L (control) to 1.15 x 106/L (tilapia) and from 2.80 to 1.72 x 106/L (catfish) in the sample exposed to 6.25 ml/L of the effluent. Also, the values of Hb concentration reduced from 7.73 g/dL to 3.10 g/dL (tilapia) and from 8.33 to 5.17 g/dL (catfish). However, the WBC count increased from 4800.33 x 103/L to 9500.30 x 103/L (tilapia) and from 5300.30 x 103/L to 7800.50 x 103/L (catfish) in those exposed to 6.25 ml/L of the effluent. In the histological assessment of the gills of the fishes, the tilapia fish exposed to 6.25ml/L of the effluent recorded an extensive damage, distortion and thickening of the tilapia fish gill lamellae. Also, there was loss of secondary lamellae and loss of gill raker filaments of the catfish. The liver cells of tilapia had many monocytes (kuppfer cells) while there were mild increase in the number of kuppfer cells of the catfish. The kidney artery of tilapia was filled with leucocytes while there were cellular proliferation (hyperplasia) and less of melanin deposits in the kiney cells of catfish. These are indications that the industrial effluent contain toxicants that are dangerous to the fish health.

Testing the “young-species” hypothesis for Alburnus heckeli Battalgil 1944 (Teleostei: Leuciscidae) inhabiting Lake Hazar, Turkey

Alburnus heckeli Battalgil 1944 is endemic to Lake Hazar in the Euphrates-Tigris River system (Persian Gulf basin) and shares morphological and molecular characters with the widespread species A. sellal Heckel 1843, except putatively for the number of gill rakers. This study compared morphometric and meristic data for A. heckeli with lentic and lotic populations of A. sellal. The only significant difference was in the number of gill rakers in lotic populations of A. sellal (10–25) vs. lentic populations of A. sellal (26–35) and A. heckeli (28–35). Although our results are consistent with the interpretation of A. heckeli and A. sellal as “young species”, the amiguity of available morphological and molecular sequence data suggest that A. heckeli is best treated as a junior synonym of A. sellal until reliable differences are found.

Сиг — пыжьян Coregonus lavaretus pidschian (Gmelin, 1788) бассейна реки Хатанги

The paper presents the results of a morphological and ecological study of three sympatric forms of the Humpback whitefish from the Khatanga River basin, Taimyr Peninsula, Krasnoyarsk krai territory. Statistically significant differences in plastic and meristic features between all compared formswere revealed.The most significant values of meristic features were found by the number of gill rakers (between riverine form and lacustrine-riverine form tₛₜ = 3.55), riverine form and lacustrine form (tₛₜ = 8.92), lacustrine-riverineform and lacustrine form (tₛₜ = 6.72). Significant differences were found in the number of scales in the lateral line when comparing riverine and lacustrine-riverine forms (tₛₜ = 3.16), riverine and lacustrine forms (tₛₜ = 2.85). Significant differences were noted in the plastic characters between riverine and lacustrineforms of Humpback whitefish: in the length of the head (between riverine and lacustrine-riverinetst = 5.49, riverine and lacustrinetst = 5.49); by antedorsal distance: riverine and lacustrine-riverine (tₛₜ = 2.67), riverine and lacustrine (tₛₜ = 4.40); in eye diameter between lacustrine-riverine and lacustrine (tₛₜ = 6.89), riverine and lacustrine (tₛₜ = 9.42).A comparison of the morphological features of lacustrine, lacustrine-riverine and riverine forms of whitefish in the Khatanga River basin with those forms from other water bodies in northern Siberia is carried out.Differences in meristic and plastic features are shown.The age range of riverine whitefish in catches is represented by 9 age groups (4+ - 12+), lacustrineriverine - 13 (6+ - 18+), lacustrine - 4 (13+ - 17+).The distribution and migration of allHumpback whitefish forms in the river basin are presented on the basis of our own observations and literary sources.The nutrition of individual forms has been studied, the basis of the Humpback whitefish diet is made up of benthic organisms: caddisflies, chironomids, mollusks and amphipods. English version of the article is available at URL: https://panor.ru/articles/siberian-whitefish-coregonus-lavaretus-pidschian-gmelin-1788-khatanga-river-basin/77293.html

Comparative morphological characteristics of spawning populations of Baikal omul (Coregonus migratorius, G.) in the Posolsky Sor, Selenga and Barguzin rivers

The morphological structure, size-age variability and dynamics of age-related fertility of producers of Baikal omul of pelagic, near-bottom and coastal morpho-ecological groups during the depressive state of the population were studied. There is an improvement in the indicators of the growth rate of fish, maturation and an increase in absolute individual fertility against the background of the dilution of the population and the release of the feeding area. A comparative characteristic of some morphological features of fish among morphological-ecological groups is given. The number of gill rakers on the first gill arch significantly distinguishes different morpho-ecological groups and ranges from 36 to 43 pieces for the near-bottom, from 40 to 46 pieces for the coastal and from 44 to 53 pieces for the pelagic morpho-ecological groups. It is noted that the spawning populations of the coastal and pelagic groups are mainly represented by young individuals. With age, the proportion of females increases in all groups. The largest indices of the pectoral, abdominal and anal fins, responsible for movement in the vertical plane, rotation and stop, are noted in the near-bottom group.

Experimental Induction of Tenacibaculosis in Atlantic Salmon (Salmo salar L.) Using Tenacibaculum maritimum, T. dicentrarchi, and T. finnmarkense.

There is a limited understanding of the pathogenesis of tenacibaculosis in Atlantic salmon (Salmo salar L.) and there are few reproducible exposure models for comparison. Atlantic salmon were exposed via bath to Tenacibaculum maritimum, T. dicentrarchi, or T. finnmarkense, and were then grouped with naïve cohabitants. Mortalities had exaggerated clinical signs of mouthrot, a presentation of tenacibaculosis characterized by epidermal ulceration and yellow plaques, on the mouth and less frequently on other tissues. Histopathology showed tissue spongiosis, erosion, ulceration, and necrosis ranging from mild to marked, locally to regionally extensive with mats of intralesional bacteria on the rostrum, vomer, gill rakers, gill filaments, and body surface. Exposure to T. maritimum resulted in less than a 0.4 probability of survival for both exposed and cohabitants until Day 21. Exposures to T. dicentrarchi resulted in 0 and 0.55 (exposed), and 0.8 and 0.9 (cohabitant) probability of survival to Day 12 post-exposure, while T. finnmarkense had a 0.9 probability of survival to Day 12 for all groups. This experimental infection model will be useful to further investigate the pathogenesis of tenacibaculosis, its treatment, and immunity to Tenacibaculum species.

Two new species of Myxobolus Bütschli, 1882 (Cnidaria: Bivalvulida: Myxobolidae) infecting the gill of the black redhorse, Moxostoma duquesnei (Lesueur) (Cypriniformes: Catostomidae) in the Little Tennessee River Basin, North Carolina.

Two new species of Myxobolus Bütschli, 1882 (Bivalvulida: Myxobolidae) are described from the gill of the black redhorse (Moxostoma duquesnei [Leueur][Cypriniformes: Catostomidae]) from the Little Tennessee River Basin, North Carolina, United States. Myxobolus branchiofilum n. sp. infects lumen of the lamellar arterioles and Myxobolus branchiopecten n. sp. infects the bone and cartilage at the tip of the gill rakers. They differ from all congeners by a combination of myxospore dimensions and the presence or absence of an iodinophilic vacuole in the sporoplasm, mucous envelope, intercapsular process, and sutural markings. A phylogenetic analysis of the small subunit ribosomal DNA recovered M. branchiopectin sister to Myxobolus sp. (AF378343) in a clade composed of 6 species of Myxobolus, which infect predominately cypriniform intermediate hosts. Myxobolus branchiofilum was recovered sister to Myxobolus ictiobus Rosser, Griffin, Quiniou, Alberson, Woodyard, Mischker, Greenway, Wise & Pote, 2016 in a clade composed of 8 species of Myxobolus, which predominately infect catostomid intermediate hosts. Histological sections of infected gill revealed intra-lamellar plasmodia of M. branchiofilum in the lumen of the lamellar arterioles and foci of M. branchiopecten developing in the bone and cartilage of the gill raker tip. These are the first myxozoans reported from the black redhorse. Given that these two new species are morphologically congeneric but recovered in distantly related clades, we discuss the persistent issue of myxobolid genera paraphyly/polyphyly.

Revalidation and redescription of Serranus knysnaensis Gilchrist, 1904, (Perciformes: Serranidae) with a new distribution record.

A southwestern Indian Ocean (SWIO) percoid fish Serranus knysnaensis Gilchrist, 1904, was long synonymised with the comber, Serranus cabrilla (Linnaeus, 1758), from the eastern Atlantic Ocean, Mediterranean and Black Sea. However, when the species was brought out of synonymy by Heemstra Heemstra (2004), reasons for this decision were not given. This study aims to revalidate the present taxonomic status of S. knysnaensis using morphological and molecular assessments. The two species are distinguished by the number of circumpeduncular scales (2634 in S. knysnaensis versus 3438 in S. cabrilla) and total gill rakers (1822 versus 2224). Serranus knysnaensis is also distinct from S. novemcinctus Kner, 1864, the other SWIO species of Serranus, based on total gill raker counts (1822 versus 3135). Genetic analysis of mitochondrial DNA barcode (COI) sequences for 17 Serranus species revealed three closely-related monophyletic clusters corresponding to S. cabrilla, S. novemcinctus and S. knysnaensis that were supported (P 0.001) by species delimitation methods. Even though the genetic distances among the three species were the lowest in the genus (1.60-1.99%), these species may be ecomorphs or lineages that have only recently diverged from each other. These three species also have allopatric distributions and our morphological and molecular data thus confirm that S. knysnaensis is a valid species.

Description of a new codling species of Physiculus from Taiwan (Gadiformes: Moridae).

A new species of codling Physiculus megastomus sp. nov. is described based on the holotype and a subadult paratype collected from northern and eastern Taiwan. The new species is classified in Physiculus by the presence of a ventral light organ on the abdomen and a chin barbel, and the absence of vomerine teeth. It is distinguished from congeners in having a large mouth with the posterior end of the maxilla extending well behind the level of the posterior margin of the orbit, its length 57.8‒60.7% in head length (HL) and the combination of the following characters: both jaws bearing caniniform teeth; snout, suborbital area, and gular region fully scaled; ventral light organ small, its length 5.5‒6.7% of distance from the interventral line to the origin of the anal fin (InV-af), located approximately at the mid-point of InV-af; five gill rakers on the upper limb of the first gill arch. DNA barcoding supported the establishment of the new species.

Gross morphological and surface ultrastructural investigation on the gills of the European barracuda Sphyraena sphyraena.

The present work examined 10 gill systems of European barracuda grossly and by scanning electron microscopy (SEM). Grossly, there were four pairs of the gill arches. The convex border of the gill arch carried the gills filaments, but there were abundance of spines near to its concave border and the gill rakers were absent. Laterally near to the convex border of the gill arch, SEM observations revealed that the first gill arch carried small elliptical, oval, cuboidal, and triangular groups of two shapes of spines; spearhead-like spines and canine-like spines, but the other three gill arches carried larger groups of the same shaped spines with the appearance of waterfalls. Medially near to the convex border of the first gill arch, the canine-like spines were observed only in the form of vertical rectangular groups that adhered in some areas. Laterally near to the concave border, the two shapes of spines were present in the form of longitudinal groups separated by spaces at the first gill arch, but these spaces were absent in the other three gill arches. Medially near to the concave border of the first gill arch, the two shapes of spines were presented in oval groups, while the other three gill arches were covered entirely by cuboidal groups of the two shapes of spines. The absence of the gill rakers in conjunction with an abundance of spines helps the European barracuda to control the food particles from escaping to the gill filaments to prevent its suffocation.