Gill Rakers Research Articles

Cryptic persistence and loss of local endemism in Lake Constance charr subject to anthropogenic disturbance.

In the welcome circumstance that species believed extinct are rediscovered, it is often the case that biological knowledge acquired before the presumed extinction is limited. Efforts to address these knowledge gaps, in particular to assess the taxonomic integrity and conservation status of such species, can be hampered by a lack of genetic data and scarcity of samples in museum collections. Here, we present a proof-of-concept case study based on a multidisciplinary data evaluation approach to tackle such problems. The approach was developed after the rediscovery, 40 years after its presumed extinction, of the enigmatic Lake Constance deep-water charr Salvelinus profundus. Targeted surveys led to the capture of further species and additional sympatric normal charr, Salvelinus cf. umbla. Since the lake had been subject to massive stocking in the past, an evaluation of the genetic integrity of both extant forms was called for in order to assess possible introgression. A two-step genomic approach was developed based on restriction site associated DNA (RAD). Diagnostic population genomic (single nucleotide polymorphism [SNP]) data were harvested from contemporary samples and used for RNA bait design to perform target capture in DNA libraries of archival scale material, enabling a comparison between extant and historic samples. Furthermore, life history traits and morphological data for both extant forms were gathered and compared with historical data from the past 60-120 years. While extant deep-water charr matched historical deep-water specimens in body shape, gill raker count, and growth rates, significant differences were discovered between historical and extant normal charr. These resulted were supported by genomic analyses of contemporary samples, revealing the two extant forms to be highly divergent. The results of population assignment tests suggest that the endemic deep-water charr persisted in Lake Constance during the eutrophic phase, but not one of the historical genomic samples could be assigned to the extant normal charr taxon. Stocking with non-endemic charr seems to be the most likely reason for these changes. This proof-of-concept study presents a multidisciplinary data evaluation approach that simultaneously tests population genomic integrity and addresses some of the conservation issues arising from rediscovery of a species characterized by limited data availability.

A New Species of Lycodapus from the Emperor Seamount Chain, Northwestern Pacific Ocean (Teleostei: Zoarcidae)

A new species, Lycodapus imperatorius, is described from the seamounts of the Emperor Ridge, North Pacific Ocean. The new species can be identified by its stout gill rakers, single interorbital pore, four preopercular and four mandibular pores, 95–99 vertebrae, numerous vomerine and palatine teeth, and COI mtDNA sequences. Although the new species is most similar to L. endemoscotus and L. antarcticus in morphology, the closest match to already published sequences was Lycodapus fierasfer, which is fairly different from the new species in terms of morphology. The incongruence between molecular and morphological inferences might be explained by the homoplastic nature of the morphological characteristics used for species delimitation in Lycodapus. The percent of genetic identity between the closest species of Lycodapus ranges from 95.4 to 98.6% in comparison with 99.5–100.0% between individuals of the same valid species. A key of the genus is amended to include the new species.

Description of a new Pangasius (Valenciennes, 1840) species, from the Cauvery River extends distribution range of the genus up to South Western Ghats in peninsular India.

A new species of the genus Pangasius, is described based on 17 specimens collected from the Cauvery River, India. It can be distinguished from its sister species from South and Southeast Asia, by its widely placed, small and rounded vomerine and palatine tooth plates, longer maxillary and mandibular barbels, greater vertebrae count 50 (vs. 44-48), and smaller caudal peduncle depth (6.5-8.2% SL vs. 9.89-13.09% SL). The tooth plates of the new species closely resembles that of Pangasius macronema but can be clearly distinguished from the latter by having lesser gill rakers (16-19 vs. 36-45); a smaller eye (2.4-4.4% SL vs. 5.2-9.6% SL); and larger adipose-fin base (1.5-2.9% SL vs. 0.1-1.2% SL). The mitochondrial cytochrome c oxidase (COI) gene sequence of the new species shows the genetic divergence of 3.5% and 5.1% from P. pangasius and P. silasi respectively, the two sister species found in South Asia and India. The species delimitation approaches, Poisson Tree Processes (PTP) and assemble species by automatic partitioning (ASAP) clearly resolved that the P. icaria is distinct from its sister species. Phylogenetic position of the species with its sister species was evaluated using maximum likelihood and Bayesian analysis. The discovery of this previously unknown species of genus Pangasius from the Cauvery River of peninsular India indicates important biogeographical insight that this genus migrated till the southern division of Western Ghats.

Morphological comparison of the detailed structure of gill rakers from three different feeding habits of marine fish species

The feeding habits and habitat of different fish species influence the morphology and functions of their gill rakers. This study used gross anatomy and scanning electron microscopy to investigate the morphological features of the gill rakers in Siganus luridus, Boops boops, and Pagrus pagrus. The gill rakers appeared as medial and lateral rows in all studied fishes. Except for Pagrus pagrus, which had a unique gill rakers arrangement in which the medial row of the 4th gill arch had the most gill rakers, the longest and most gill rakers were on the 1st gill arch in all studied fishes. The gill rakers of Siganus luridus were smooth, with various spine-like shapes, such as spine-like gill rakers, which were bifid or trifid spines, or duck toe-shaped gill rakers. According to SEM of the Siganus luridus' gill rakers, the trifid end gill rakers resembled caterpillars, and the duck toe-like gill rakers had three or four finger-like spines connected by inter-spine tissue. The Boops boops had long conical gill rakers with pointed ends on the lateral sides of the 1st gill arch, and the remaining rows had short gill rakers. According to SEM of the Boops boops' gill rakers, the long gill rakers were semi-conical and only had needle-like spines on the medial surface. The short gill rakers were projected as a boat and had three different shapes based on spine distributions. Gill rakers include those with a median crest and long spine laterals, those with only lateral spines, those with usually dorsal spines, and those with long wedge-shaped spines. Pagrus pagrus’ gill rakers were short, with fine-needle spines covering their tops. By SEM of the Pagrus pagrus' gill rakers, they appeared as a cylindrical elevation with spines on top. The spines were conical in shape with pointed curved or straight ends. The maximum value of the gill rakers’ lengths was discovered in the lateral row of the 1st gill arch, while the minimum value was in the medial row of the 4th gill arch. As a result, this is the first study of the three fish species' gill rakers. In the studied fishes, the morphological characteristics of gill rakers demonstrated unique structural specifications in feeding behavior.

FEEDING HABITS OF SOLDIER CROAKER Dendrophysa russelii (Cuvier, 1829) DISTRIBUTED IN COASTAL AREAS OF THE MEKONG DELTA, VIETNAM

This study researched the feeding habits of soldier croaker Dendrophysa russelii (Cuvier,1829) distributed in coastal areas of the Mekong Delta from May to December, 2021. Fish samples were randomly collected in different sizes by trawl-net. Fish stomachs were fixed in a 4% formalin solution to prevent contents in the stomach from being digested. The results showed that soldier croaker had a small mouth, the teeth on the jaw were short and pointed with no canine tooth, the gill rakers were sparse, the stomach was pouch-shaped, the caeca have 4-8 tubes, and the intestine was short. Relative between gut length and body length (RLG) < 1 indicated that soldier croaker is a carnivorous fish. The food spectrum of immature fish was narrower thanthat of mature fish. However, the feed ingredient was shrimp which always accounts for the highestpercentage in the two fish size groups, followed by fish and other foods that accounted for a low proportion.

Four new species of the frogmouth genus Chaunax (Lophiiformes: Chaunacidae) from Taiwan and the Philippines

Four new species of the genus Chaunax found in Taiwan and the Philippines are described. Chaunax albatrossae sp. nov. belongs to the C. abei species group and is distinct from its congeners in having a dark gray mouth cavity, a dark brown to black gill chamber and gill rakers and skin covered with only short, simple spinules. Three new species belong to the C. fimbriatus species group: Chaunax erythraeus sp. nov. is distinct in having a uniformly pinkish-red body and an entirely black gill chamber; Chaunax obscurus sp. nov. is distinct in having a dark gray mouth cavity and orange-red marbling on the dorsal surface that fades after fixation; and Chaunax viridiretis sp. nov. is distinguished by its green reticulate pattern with some small, bright-white patches on the dorsal surface. The diagnostic characters used to identify the chaunacids are summarized and a key to all Chaunax species found in Taiwan and adjacent waters is provided.

Genetic correlations between harvest weight and secondary traits in a silver carp (Hypophthalmichthys molitrix) genetic improvement program

In 2017, the base population of a family-based silver carp (Hypophthalmichthys molitrix) genetic improvement program was spawned in Bangladesh. This program aims to improve the growth rate of silver carp under polyculture production systems, through direct selection on the primary trait of harvest-age weight. The objective of this study was to quantify genetic variation in, and genetic correlations between, harvest-age weight (assessed on 8012 fish from 184 families) and a set of secondary traits (assessed on 1603 fish from 175 families). Secondary traits examined included feeding and digestive system traits (i.e. gill raker sponginess and gut length as a ratio of standard length), a morphometric trait (i.e. extent of overlap of pectoral and pelvic fins) and health traits (i.e. presence of Lernaea and prevalence of red spots — sites of inflammation/haemorrhaging). Despite not being under direct selection, genetic change in secondary traits is possible across generations in closed genetic improvement populations as a result of a correlated response to selection for the primary trait (i.e. indirect selection), adaptation to culture conditions, inbreeding and/or genetic drift. It was found that the additive genetic variance within genetic groups was significantly different from zero for all but the studied health traits. Heritability estimates for harvest-age weight and pectoral/pelvic fin overlap were moderate (0.24 and 0.22, respectively) but were low for gill raker score and relative gut length (0.12 and 0.09, respectively). Genetic correlations between harvest-age weight and secondary traits were not significantly different from zero, indicating that selection for harvest-age weight will not result in a correlated response to selection in the studied secondary traits.

Redescriptions of Dussumieria elopsoides Bleeker, 1849 and related nominal species led to the revalidation of Dussumieria hasseltii Bleeker, 1851 and Dussumieria productissima Chabanaud, 1933 (Clupeiformes: Dussumieriidae)

Numerous rainbow sardine specimens, previously identified as Dussumieria elopsoides Bleeker, 1849, due to their elongate body, scales without posterior striae, and numerous gill rakers and branchiostegal rays, were examined and confirmed as representing four valid species: true D. elopsoides (restricted to Indonesia), Dussumieria hasseltii Bleeker, 1851 (previously regarded as a junior synonym of D. elopsoides; Arabian Sea to Philippines and Indonesia), Dussumieria modakandai Singh, Jayakumar, Kumar, Murali, Mishra, Singh and Lal, 2021 (Arabian Sea to Ryukyu Islands), and Dussumieria productissima Chabanaud, 1933 (previously regarded as a junior synonym of D. elopsoides; Gulf of Aden, Red Sea and eastern Mediterranean). Each species is redescribed in detail and a key based on morphological characters provided. The phylogenetic relationships among seven species of Dussumieria (including three of the species examined in the present study) were reconstructed from the cytochrome oxidase I (COI) gene, the genetic distinctiveness of each species being indicated by at least 4.1% mean p-distance divergence from the others.

A new species of deep-water Lethrinops (Cichlidae) from Lake Malawi.

A new species of cichlid fish, Lethrinops atrilabris is described from specimens collected by trawling at a depth of around 90 m off Monkey Bay, southern Lake Malawi. It is assigned to the genus Lethrinops on the basis of its vertical flank barring, lack of enlarged cephalic lateral line canal pores and the form of the lower jaw dental arcade. It can be distinguished from congeneric species by its male breeding dress of contrasting flank barring and dark ventral surface, most strikingly on the lips, throat and chest, its relatively small known maximum size [<75 mm standard length (SL)], large eyes (38%-41% head length), laterally compressed body (depth 2.5-2.7 times max head width) and lower gill raker count (13-14).

Description of three new species previously identified as Stolephorusbengalensis (Dutt & Babu Rao, 1959) or Stolephorusinsularis Hardenberg, 1933 and a re-description of S.bengalensis (Chordata, Osteichthyes, Clupeiformes, Engraulidae).

Examination of numerous specimens characterised by predorsal scute, long maxilla, indented preopercle and pelvic scute lacking a spine and previously identified as Stolephorusbengalensis (Dutt & Babu Rao, 1959) or Stolephorusinsularis Hardenberg, 1933, revealed four distinct species, true S.bengalensis (distributed from the Bay of Bengal to Pakistan) and three new species, viz., Stolephoruseldorado sp. nov. (Taiwan to Java, Indonesia), Stolephorusdiabolus sp. nov. (Strait of Malacca, from Penang , Malaysia, to Singapore) and Stolephoruseclipsis sp. nov. (Bintan Island, Riau Archipelago, Indonesia). Characters separating the four species include numbers of gill rakers on each gill arch and vertebrae and pelvic fin and dorsal-fin ray lengths. Two molecular markers (mitochondrial cytochrome b and cytochrome oxidase I genes) demonstrated the distinction of three of the species examined morphologically and enabled a reconstruction of their phylogenetic relationships. Each species was genetically divergent from the others by 3.5%-7.7% mean uncorrected distance in the mitochondrial cytochrome oxidase I gene.

Toxic Effects of Arsenic in Commercially Important Fish Rohu Carp, Labeo rohita of Bangladesh

This study was designed to elucidate the effects of arsenic (As) on the morpho-behavior, growth development and molecular mechanisms of a commercially important fish, rohu carp, Labeo rohita, in Bangladesh. Fish fry with an average weight of 387.5 ± 169.25 mg and an average length of 3.35 ± 0.37 cm were collected from a local hatchery in Mymensingh, Bangladesh and acclimatized for a week in the Department of Fisheries, University of Dhaka before starting the exposure with arsenic. Fishes were exposed for a period of 14 days with three treatments of NaAsO2, namely treatment 1(T1)—2.5 mg/L; treatment 2 (T2)—15 mg/L; and treatment 3 (T3)—30 mg/L, along with a control (C)—0.0 mg/L, with three replicates. These concentrations were determined based on the LC50 value for 96 h measured for this experiment. This study revealed remarkable morphological abnormalities and deformities in arsenic-exposed rohu carp. In fish exposed to 30 mg/L, caudal fin erosion was a frequent deformity. There was no significant difference in RNA:DNA ratio among the treatments. The overall weight of fish was decreased as the concentration of arsenic was increased. The T3 fish had a statistically significant negative weight gain (−0.05 ± 0.07 g), but the other treatments (T1 and T2) and control fish had no significant weight gain. Different types of histopathological changes were observed in the gills and intestines of arsenic-treated fish. Necrosis and severe damages were found in the secondary lamellae of gills at the highest arsenic concentration (30 mg/L). Epithelial lifting, irregular shape and damages in the gill raker were also observed in the primary lamellae of the gills for the same treatment. In this study, the expression of heat shock protein (HSP 60) and metallothionein (MT) genes was assessed by qPCR, and these genes were upregulated in different treatments compared to controls. The findings of the present study suggest that arsenic pollution significantly changes the morphology, behavior, growth, development, histopathology and molecular mechanisms of this economically important fish, rohu carp, in Bangladesh.

Comparative morphology of gill apparatus of common carp (&lt;em&gt;Cyprinus carpio&lt;/em&gt;) and African catfish (&lt;em&gt;Clarias gariepinus&lt;/em&gt;)

Common carp and African catfish belong to the Cyprinidae (Cypriniformes) and Catfish (Siluriformes) orders, respectively. They are characterized by a different habitat, as a result of which the structure of the gill apparatus has a number of features [3]. The article describes the macroscopic and microscopic morphology of the gills of the represented fish species. Each of them had four complete pairs of gills, and the fifth was rudimentary without gill filaments. The gill rakers of carp tended to be short and widely spaced compared to the long and thin rakers of catfish. The gill filaments of the carp were longer than those of the African catfish, indicating a larger area of the gill surface in the former species. All gill regions, as seen from light microscopy, are covered with mucous epithelium.

Hoplostethus roseus, a new roughy fish from the western Pacific based on morphology and DNA barcoding (family Trachichthyidae).

A new species of the roughy fish genus Hoplostethus is described from 11 types and a non-type specimen collected from Taiwanese waters. It can be distinguished from its congeners by a combination of characters: pectoral-fin rays 14-17 (modally 15-16); pyloric caeca 65-84; total gill rakers 19-20; predorsal scales 18-22; oral cavity, branchial chamber, top and underside of tongue, and peritoneum uniformly black; distal margin of membrane between dorsal-fin spines black; caudal fin without a black margin; caudal-fin base brownish. Comparisons of the new species with similar species are provided. DNA barcoding supports the monophyly of the new species, which appears to be closely related to Hoplostethus japonicus [average cytochrome c oxidase subunit I Kimura-2-parameter (COI K2P) distance of 4.1%].

Silurichthys exortivus, a new catfish (Teleostei: Siluridae) from eastern Borneo, Indonesia.

Silurichthys exortivus, a new species of silurid catfish, is described from the Mahakam River drainage in eastern Borneo. The new species can be distinguished from congeners in lacking a dorsal fin, having 4 (vs. 67) principal rays on the upper caudal-fin lobe and a combination of: body depth at anus 14.0% SL, caudal peduncle depth 5.1% SL, pelvic fins absent, 54 anal-fin rays, caudal fin with asymmetrical lobes (upper lobe 1.1 times longer than lower), 48 vertebrae, 1 gill raker on the first branchial arch, and a mottled brown body. Based on the reduced number of principal caudal-fin rays, S. exortivus, S. ligneolus and S. sanguineus are hypothesized to form an exclusively Bornean clade.

Descriptions of Two New Species, Sillago muktijoddhai sp. nov. and Sillago mengjialensis sp. nov. (Perciformes: Sillaginidae) from the Bay of Bengal, Bangladesh

Due to difficulty in recognition, many true species have been covered under the synonyms of wide-spread species. To justify the identification of a widely distributed species, Sillago sihama from the Bay of Bengal, Bangladesh, an integrated approach including morphology and DNA barcoding was used. Two unrecognized species of Sillago, i.e., Sillagomuktijoddhai sp. nov. and S. mengjialensis sp. nov., were identified from the coastal area of Bangladesh. S. muktijoddhai sp. nov. has marked differences in the body color, anal fin color, number of gill rakers, snout length, and swimbladder. S. mengjialensis sp. nov. has notable differences in the anal fin color, snout length, and swimbladder and is distinguished from S. muktijoddhai sp. nov. by the body color and swimbladder. The morphological characters of 14 documented Sillago species with two posterior extensions of the swimbladder were referenced and distinguished to accredit the two new species. Genetic analyses of partial mitochondrial cytochrome oxidase subunit I and 16S ribosomal RNA also supported the validity of the new species. This study has increased the number of recognized species of Sillago in the world and confirmed the prevailing misidentification of these two new species in Bangladesh as so-called S. sihama. Moreover, the study confirmed the misidentification of S. mengjialensis sp. nov. in Indonesia as S. sihama and the identification of unknown Sillago sp.1 in India.

Biometric characteristic of the common goldfish Carassius auratus auratus (Linneaus, 1758) in Basra freshwater systems

About 110 specimens of the goldfish Carassius auratus auratus (Linneaus, 1758) were obtained from the Department of Fisheries and Marine Resources Laboratory College of Agriculture and the Marine Sciences Center, University of Basrah. Morphometric and merestics characteristics were measured, total and standard length ranged between 90-150 mm and between 70-110 mm, respectively. Number of scales in the lateral line ranged from 25 to 27. Number of dorsal branched rays ranged from 14 to 15, gill rakers from 42 to 44. Total vertebrae fin count was 25-27. There were five rays with the branchuiostegal rays.&#x0D;

Morphology and Anatomy of Endemic Fish Leptobarbus melanopterus (Cyprinidae) in Danau Sentarum National Park Kapuas Hulu Regency

One of the endemic freshwater fishes in Danau Sentarum National Park (DSNP) is Leptobarbus melanopterus which has high economic value for both commercial and collection purpose. However, the overfishing of L. melanopterus running over decades with harmful catch tools is worried could contribute to the population decline in the future. At the same time, this species has never been cultured and fishermen catch directly in the habitat on a daily basis. This research was aimed to identify the morphological and anatomical characters of L. melanopterus. All samples were collected from three different sites in DSNP and measured its morphological and anatomical sizes manually. The results showed that the length of mandibula barbel was the distinguishing character between females and males, with loading score of 0.81. Most meristic variables showed no difference between two sexes. In terms of anatomical measurements, L. melanopterus females had larger gill sizes than males, including gill raker, gill arch and fill filament. Our findings signify the thorough morphological and anatomical sizes of L. melanopterus which are important in identifying fish stock, growth pattern and sexual dimorphism for future culture management.

Trophic Relations between Native Salvelinus malma Walb. and Introduced Oncorhynchus nerka Walb. in the Landlocked Lake Sevo, Kamchatka

Fish introductions are known to be dangerous due to the unexpected spread of diseases and disorganization of the food web. In 1986, the resident sockeye salmon Oncorhynchus nerka from Kronotskoye Lake was introduced into an isolated lake in Kamchatka inhabited by the native lacustrine Dolly Varden charr Salvelinus malma. Thirty years later, we analyzed the stomach content, stable isotope ratio and lipid fractions in muscles, as well as the parasite fauna of fish to assess the trophic relationships between the two species. It has been found that the sockeye salmon has occupied the planktivorous niche; no diversification into trophic forms depending on the number of gill rakers, like in the ancestral population, was detected. The indigenous benthivorous S. malma is represented by three trophic groups. Mature dwarf individuals, as well as the juveniles, mainly consume insect larvae on the lake slope; large fish feed on amphipods in the same habitats; and 10% of the large Dolly Varden switches to facultative piscivory. Predators die as a result of Diphyllobothrium sp. hyper invasion, which infects fish when feeding on the sockeye salmon. The diversity of parasite fauna is 3/4 poorer in the introduced sockeye in comparison with the donor population; part of the parasite species is obtained by the sockeye from the Dolly Varden.

Johnius sasakii, a new species of croaker (Perciformes: Sciaenidae) with a key to Johnius from East Malaysia, Borneo.

A new sciaenid fish, Johnius sasakii sp. nov. from the East Malaysian coastal waters of Sabah and Sarawak, Borneo is described herein. Johnius sasakii sp. nov. can be separated from the close congeners, Johnius heterolepis and Johnius carouna by having less gill rakers on the lower limb of the first gill arch (mode number 9 vs. 10 for J. heterolepis; 11 for J. carouna). It can be distinguished from J. heterolepis with the higher modal number of gill rakers on the upper limb of first gill arch (5 vs. 4), shorter anal-fin base length (9% vs. 10% of SL) and first anal-fin ray length (1012% vs. 1213% of SL) respectively. Furthermore, J. sasakii sp. nov. can be further differentiated from J. carouna by its shorter second anal-fin spine length 710% SL (usually 810%) vs. 1114% SL (usually 1112%) and slightly deeper body depth 2529% SL (usually 2628%) vs. 2328% SL (usually 2426%). Meanwhile, J. sasakii sp. nov. can be easily differentiated from J. macrorhynus by a present of molariform teeth on inner rows of jaws and stumpy gill rakers. Johnius (Johnius) sasakii sp. nov. can be clearly distinguished from species of the subgenus J. (Johnieops) by the lack of enlarged outer row teeth on upper jaw. A Kimura 2-parameter genetic distance comparison of 450 bp sequences of mitochondrial 16S rRNA and 488 bp nuclear gene S7 showed that J. sasakii sp. nov. are highly differentiated from J. heterolepis (16S: 10.4%, S7: 5.8%), J. carouna (16S:19.3%, S7:8.4%); and J. macrorhynus (16S: 16.7%, S7: 8.1%) respectively. The study highlights that the genetic approach from mtDNA and nDNA can contribute to the confirmation of taxonomic status of sympatric species in genus Johnius.

Redescription of Stolephorus ronquilloi Wongratana, 1983 and Description of Stolephorus hindustanensis, a New Anchovy from the Western Coast of India (Teleostei: Clupeiformes: Engraulidae)

The new anchovy Stolephorus hindustanensis n. sp., described on the basis of 11 specimens collected from Mumbai, western coast of India, closely resembles Stolephorus ronquilloi Wongratana, 1983 in sharing an indented preopercle posterior margin, long maxilla extending beyond the preopercle posterior margin, double pigmented lines on the dorsum behind the dorsal fin, and lacking a predorsal scute. However, the new species differs from S. ronquilloi in having lower counts of gill rakers on the first and second gill arches, higher counts of total vertebrae, a deeper body, greater distances between the snout tip and anal-fin origin, origins of the dorsal and anal fins, and pelvic-fin insertion and anal-fin origin, and longer pelvic fin, third dorsal-fin ray, third anal-fin ray, and postorbital length.