Freshwater Shark Research Articles

Diversity and genetic structure of freshwater shark Wallago attu: an emerging species of commercial interest.

Pakistan has natural freshwater resources acting as a hotspot for diverse fish fauna. However, this aquatic fauna is declining at an alarming rate due to over-exploitation, habitat degradation, water pollution, climate change, and certain anthropogenic activities. The freshwater shark, Wallago attu, is a popular edible catfish inhabiting these freshwater ecosystems. Habitat degradation, overfishing, and human activities are heavily impacting the natural population of this species. So, sound knowledge about its population structure is necessary for its proper management in natural waters. The current study involves utilizing two mtDNA markers (COI, Cytb) to assess the genetic structure and differentiation among W. attu populations of Pakistani Rivers. Genetic variability analysis indicated a high haplotype (0.343 ± 0.046-0.870 ± 0.023) and low nucleotide diversity (0.0024 ± 0.012-0.0038 ± 0.018) among single and combined gene sequences, respectively. Overall, River Indus was populated with more diverse fauna of Wallago attu as compared to River Chenab and River Ravi. Population pairwise, Fst values (0.40-0.61) were found to be significantly different (p < 0.01) among three Riverine populations based upon combined gene sequences. The gene flow for the combined gene (COI + Cytb) dataset among three populations was less than 1.0. The transition/transversion bias value R (0.58) was calculated for testing of neutral evolution, and it declared low genetic polymorphism among natural riverine populations of Wallago attu. The current study's findings would be meaningful in planning the management and conservation of this economically important catfish in future.

Fish Sanctuaries as an Ecological Approach to Management for Restoring Fish Biodiversity: A Study on Chikadubi Beel Fish Sanctuary, Bangladesh

The fish biodiversity of open water is reducing as rice culture has been intensified due to other environmental threats. The establishment of a fish sanctuary is a way to conserve fish for future generation. A study was conducted to know the impact of the sanctuary on fish biodiversity for six months from August to December 2020. Various Participatory rural appraisal (PRA) tools were used such as Questionnaire interviews, focus group discussion (FGD), Catch monitoring and cross-check interviews were carried out. Data were collected from 50 fishermen using a semi-structured questionnaire interview, Group discussion, and gathering secondary information from different sources. According to the findings, 78 fish species were recorded in the study area where 60 fish species were recorded to be found before establishment of the sanctuary. Baseline production of the sanctuary was 0.58 MT/ha in 2015 which increased to 1.12 MT/ha in 2020 after establishment of the sanctuary. The highest total number of fish species were caught in August (68.45%) and lowest (41.55%) in December in the Chikadubi beel. The dominant fish species in Chikadubi beel was Freshwater shark (Wallago attu) followed by Spotted snakehead (Channa punctatus), Indian river shad (Gadusia chapra) and Jatiputi (Puntius sophore) whereas the least available fish species was Koitor poa (Johnius coitor). Among the total catch comprises different family such Cyprinidae 58.33%, Channidae 16.60%, Bagridae 14.58%, Siluridae 6.25% &amp; Schilbeidae 8.33 % respectively. The outcomes suggest that careful planning, management and regular practices, along with active community participation, can have positive impact on fish sanctuary.

Dinosaur fauna from the Lower Cretaceous of Phu Kao-Phu Phan Kham, northeastern Thailand: a review and update

Phu Kao-Phu Phan Kham Mountain ranges, situated on the border of Nong Bua Lamphu, Udon Thani, and Khon Kaen provinces, northeastern Thailand, bear several localities that yield dinosaurs and other vertebrate faunas in the Lower Cretaceous. However, this area has received relatively little attention from the scientific community and the public. Here we review and report new dinosaur materials recovered from this region, some found decades ago, others discovered recently. We identify and discuss their taxonomy and paleobiodiversity. In the Barremian Sao Khua Formation, theropod dinosaurs were represented by spinosaurids, an early branching megaraptoran, a large indeterminate theropod, and small indeterminate theropods. Sauropods were represented by an indeterminate sauropod, a neosauropod, and titanosauriforms, including probable brachiosaurid and non-titanosaur somphospondylans. Other vertebrate groups, including crocodilians, turtles, fishes, and sharks, indicate a similar composition to other Sao Khua Formation communities in northeastern Thailand. The Sao Khua vertebrate assemblage exhibits the taxonomic diversity of dinosaur fauna and is currently the best-documented assemblage in the Early Cretaceous of Southeast Asia. The Aptian–Albian Khok Kruat Formation, however, yields less diverse vertebrates. They are represented by freshwater sharks, crocodilians, and spinosaurid theropods. This may be due to sampling bias, environmental, or taphonomic conditions. This study provides the basis for future paleontological exploration and research of Mesozoic vertebrates in northeastern Thailand.

Effect of formalin preservation on studies on morphology and condition factor of the freshwater shark Wallago attu (Bloch and Schneider, 1801) using truss network system

The study was aimed to evaluate the effect of formalin preservatiion on the shape, size and condition factor of the freshwater silurid catfish Wallago attu (Bloch and Schneider, 1801) using length-weight relationship (LWR), condition factor and truss analysis. A total of 50 specimens of the fish were procured from the river Ganga at Kanpur region. The fresh and formalin preserved fish were measured for total length, standard length and body weight. Results of LWR revealed that the fresh and preserved fish followed different growth pattern and cube law. High values of r2 were obtained for the relationship between length and weight of the fish before and after preservation of the fish in formalin. Decrease in length and an increase in weight was observed in the preserved specimens of the fish due to the effect of formalin but were not statistically significant. The mean condition factor (K) showed significant (p<0.05) change in the fish after preservation. The univariate and multivariate analysis of truss measurements, two partially overlapping different convex hulls of the scatter plot of PC1 on PC2 and canonical discriminant functions showed highly significant morphometric heterogeneity between the specimens of fresh and preserved fish. The results of the present study suggest that fresh specimens of the fish should be used in research studies based on weight and linear body measurements of the fish. Keywords: Condition Factor, Formalin, Length-weight relationship, Truss network system

Late Carboniferous paleoelevation of the Variscan Belt of Western Europe

We present the first stable isotope paleoaltimetry estimates for the hinterland of the eroded Variscan Belt of Western Europe based on the hydrogen isotope ratios of muscovite from syntectonic leucogranites that have been emplaced at ∼315 Ma. We focus on the Limousin region (Western Massif Central, France) where peraluminous granites are spatially associated with strike-slip and detachment shear zones that developed as a consequence of Late Carboniferous syn- to post-orogenic extension. In this region, we show that the north-east corner of the Millevaches massif (located at the junction between brittle and ductile fault systems) represented a pathway for Earth surface-derived fluids that penetrated the crust and reached the ductile segment of the low-angle Felletin detachment zone. Using microstructural, thermometry, hydrogen isotope and 40Ar/39Ar geochronological data, we show that these Variscan meteoric fluids interacted with hydrous silicates during high temperature deformation between ∼318 and 310 Ma. For paleoaltimetry purposes, we reference our hydrogen isotope record (δD) of ancient meteoric fluids from mylonitic rocks to ∼295 Myr-old records retrieved from freshwater shark remains preserved in the Bourbon l'Archambault basin that developed in the external zones of the orogen. A ∼76‰ difference in δDmeteoric water values between the Millevaches massif (δDmeteoric water value = −96 ± 8‰) and the Bourbon l'Archambault foreland basin (δDwater value = −20 ± 6‰) is consistent with paleoaltimetry estimates of 3.4 ± 0.7 km based on a modern lapse rate of ∼-22‰/km for δDwater values. The rather large difference in δD values between the foreland basin and the continental interior suggests that the hinterland of the Variscan belt of western Europe was high enough to act as a barrier to moisture transport from the south-south-east and induce an orographic rain shadow to the north.

A Hooghly head‐scratcher

A Hooghly head‐scratcher

The Effects of Adding Lysin Essential Amino Acid to Commercial Feed on Fatty Acid Contents of Pangasius Fish

Pangasius is a medium to very large freshwater shark catfish primarily used for consumption with high economic value. The content of pangasius fatty acids is higher than in marine fish, since marine fish have a lower saturated fatty acid composition than freshwater fish. The present research aimed to determine the effects of adding lysine essential amino acid to commercial feeds on the saturated and unsaturated fatty acids contents of pangasius fish. In the present research, an experimental method with completely randomized design was used. The treatment was done by adding lysine with different doses including P0 (0%), P1 (1.2%), P2 (2.2%), and P3 (3.2%). Each treatment was repeated five times. The main parameters studied were the content of saturated and unsaturated fatty acids in pangasius fish meat. The observed parameter was water quality. The present results indicated the use of lysine in commercial feed caused significant differences in the content of saturated fatty acids, Monounsaturated Fatty Acids (MUFA) and Polyunsaturated Fatty Acids (PUFA) in pangasius meat; a decrease in the saturated fatty acids content was found in P3 with 3.2% (3.5882 mg/dl). In P2, an increase in the MUFA content of 2.2% (5.9630 mg/dl) was found. An increase in the PUFA content was found in P3 treatment with 3.2% Lysin (23.1082 mg/dl). P1, P2 and P3 indicated lower results than control treatments (P0). The use of lysine in commercial feed indicated significant differences in the content of saturated fatty acids, MUFA and PUFA in pangasius.

New Vertebrate Fossil Site from the Early Cretaceous Sao Khua Formation, Sakon Nakhon Province, Northeastern Thailand

A new vertebrate fossil site, “Phu Sung” in Sakon Nakhon Province was discovered. Various vertebrate fossils belonging to fresh water shark, bony fish, turtle, crocodile and dinosaur were found in reddish silty mudstone of the Early Cretaceous Sao Khua Formation of the Khorat Group. Crocodilian remains including a complete skull and partial articulated skeleton are very well preserved associated with turtle remains. Moreover, well preserved 19 turtle shells were found accumulated together. These discoveries will certainly fulfill our knowledge about these aquatic taxa from the Early Cretaceous Sao Khua Formation. The exceptional preservation of Phu Sung fossils could probably relate to the paleoenvironment in the Early Cretaceous of Thailand.

A record of new lungfishes (Osteichthyes: Dipnoi) from the Carnian (Upper Triassic) of India

ABSTRACTNumerous tooth plates of different types were recovered from the Upper Triassic Tiki Formation of India. Sharp crested tooth plates with five acute ridges, tubercles on the crests, robust and deep furrows, wide spaces between successive ridges and reticulate ornamentation on the occlusal surfaces are assigned to a new species of the dipnoan genus Ptychoceratodus. Another tooth plate, characterized by four ridges with conical and cusplet-like denticles is identified as a Gnathorhiza. This is the first record of gnathorhizid fishes from the Upper Triassic sediments around the world. The Tiki aquatic realm was inhabited by different types of fishes including freshwater sharks, omnivorous/carnivorous dipnoans and other bony fishes. Palaeobiogeographic distribution of the dipnoans suggests that these were restricted to a high palaeolatitude in the southern hemisphere, where co-occurrences of several genera are seen in India.

First molecular evidence of Thelohanellus wallagoi Sarkar, 1985 (Myxozoa) from economically important food fish, freshwater shark Wallago attu (Siluridae) in India

The freshwater shark Wallago attu (Bl. and Schn.) is a frequent silurid in the River Ganga and one of the most commercially exploit fish in India. In a survey on its infection with myxosporeans, spore type belongs to Thelohanellus species was found in the gills, kidney and intestine respectively. Through morphological and molecular investigations, we identified the spore as Thelohanellus wallagoi Sarkar, 1985. They were pyriform in valvular view and slim in sutural view, and had one pyriform polar capsule with four to five turns. The spores measured 8.0 × 4.0 × 2.3 μm. T. wallagoi developed in small cysts in the gill lamellae, whereas cyst and scattered spores of T. wallagoi were also found in the kidney and intestine respectively. The 18S rDNA sequence of T. wallagoi isolates recovered from gills, kidney and intestine were found similar to each other and differed from any other Thelohanellus species available in GenBank and validated its status after 32 years of original description. Phylogenetic analysis signified that T. wallagoi was placed sister to Myxobolus species in the clade that indicated the polyphyletic nature of the genus Thelohanellus.

A new assemblage of freshwater sharks (Chondrichthyes: Elasmobranchii) from the Upper Triassic of India

This study reports the first occurrence of a varied xenacanth assemblage from the Upper Triassic Tiki Formation of India, based on multiple well-preserved isolated teeth. Based on distinct tooth morphology, two species of the genus Mooreodontus are described: M. indicus and a new species, M. jaini. The new species is diagnosed based on a tricuspid crown containing two stout, slightly diverging lateral cusps pointing in the same direction, a high median cusp, crown-base angle almost at 90°, large, rounded, apical button with several foramina and multiple, 8–9 coarse vertical cristae on all the cusps. Dental anomaly in the form of a partial quadri-cuspidate xenacanthid tooth is present in the collection. Another group of xenacanthid teeth have bicuspid crowns with two upright, asymmetric cusps, where the mesial cusp is thicker than the distal one, and consistently lack a median cusp. Such distinct bicuspid tooth morphology is usually present in Palaeozoic forms and is reported for the first time from the Late Triassic. It is considered to belong to a new taxon, Tikiodontus asymmetricus nov. gen., nov. sp., of indeterminate family. Distinctive tooth histology also differentiates the two Indian genera Mooreodontus and Tikiodontus nov. gen. from other xenacanthid taxa. In addition, the Tiki assemblage has yielded multiple chondrichthyan dermal denticles, which may be subdivided into two morphotypes based on their robustness and presence/absence of linear ridges on the fused cusps. India holds a unique position in terms of its Late Triassic freshwater shark fauna, as it exhibits distinct Laurasian affinities. These freshwater sharks had restricted occurrences in other parts of the Gondwanan landmass.

First report on a diverse Neogene cartilaginous fish fauna from Borneo (Ambug Hill, Brunei Darussalam)

The highest biodiversity of marine fishes occurs in South-east Asia in the Indo-Australian Archipelago (IAA). However, the fossil record of fishes is very sparse and extremely incomplete in the IAA. Here we present a diverse fossil cartilaginous fish fauna from Borneo, found in late Miocene sediments in Brunei Darussalam. This fauna provides the first insight into the types of fishes that existed in the IAA region about 6.5–8 million years ago. The chondrichthyan remains belong to 24 selachian and batoid taxa. The shark fauna is dominated by Carcharhiniformes, comprising three families with at least 12 taxa, most related to modern species: Hemigaleidae (one species), Carcharhinidae (nine) and Sphyrnidae (two). In addition, the teeth of one Lamniformes shark, the extinct giant macro-predator Otodus (Megaselachus) megalodon, are present in the fauna. The batoids are dominated by Myliobatiformes from the following families: Dasyatidae (three species), Aetobatidae (one), Myliobatidae (three), Rhinopteridae (one), while three taxa of the order Rhinopristiformes were also recovered: Pristidae (one species), and Rhinidae (two). Such diversity of fossil cartilaginous fish has never before been reported from the tropical region of South-east Asia. The dominance of the carcharhinid sharks and small rays suggests a shallow marine, coastal palaeoenvironment. The presence of the freshwater shark genus Glyphis indicates a nearby fluvial influence. Some species of the ray genera, such as Himantura or Pastinachus, have also been reported from estuaries and fresh water. The lack of some generally common Neogene taxa, such as Odontaspididae, Lamnidae and Alopidae, may be linked to such local factors and the coastal shallow-water environment.

A new hybodont shark (Chondrichthyes, Elasmobranchii) from the Upper Triassic Tiki Formation of India with remarks on its dental histology and biostratigraphy

AbstractA new lonchidiid genus,Pristrisodus, from the Upper Triassic Tiki Formation of India is described based on multiple, well-preserved, isolated teeth. Comparative analysis resulted in synonymizingParvodus tikiensisandLissodus duffini,which are known from the same horizon and resulted in a new taxon,Pristrisodus tikiensisn. comb. These teeth are elongated with mesiodistal length greater than or equal to twice the labiolingual width and have a high principal cusp, lateral cusplets, a distinct ridge near the crown-root junction labially and higher up on the crown lingually, weak ornamentation, and linear depression along the crown-root junction. Five morphotypes based on overall shape, robustness and crown height are determined. The teeth show a gradual monognathic heterodonty. The anterolateral teeth (morphotypes I−II) have high, pyramidal principal cusp with two or three small but pointed cusplets, and triangular labial and lingual protuberance. The posterolateral teeth (morphotypes III−IV) have four incipient cusplets, relatively low principal cusp, bilobed/rounded, hanging labial and incipient lingual protuberances. Morphotype V comprises anterior teeth that are broad, triangular and robust, and have rounded/blunt principal cusp, one cusplet, and low, hanging labial peg. Multivariate analyses corroborate the qualitative assessment of the Indian hybodonts. Dental histology ofPristrisodusn. gen., shows that it is distinctly different from other lonchidiid genera. The assemblage of freshwater sharks, along with other vertebrate microfossils of the Tiki Formation, shows similarity with that of the lower Tecovas Formation of the Chinle Group, USA. The euryhaline nature resulted in the adaptation of the hybodonts to freshwater systems in India during the Carnian.

The Middle Triassic (Anisian) Otter Sandstone biota (Devon, UK): review, recent discoveries and ways ahead

The Middle Triassic (Anisian) Otter Sandstone was laid down mostly by braided rivers in a desert environment and is now well exposed along the south-east Devon coast in south-west England, part of the ‘Jurassic Coast’ World Heritage Site. It yields uncommon and generally fragmentary fossils, principally of vertebrates, including fish, temnospondyl amphibians and reptiles such as rhynchosaurs, predatory archosaurs, and small superficially lizard-like forms. These provide important information about a freshwater and terrestrial ecosystem that marks recovery from the end-Permian mass extinction, but pre-dated the appearance of dinosaurs and mammals. The constantly eroding Otter Sandstone exposures continue to reveal new taxa (for example, freshwater sharks). Furthermore, microvertebrate material obtained by sieving bone-bearing levels has the potential to further expand the faunal list. Newly discovered associated and articulated vertebrate remains, including small tetrapods, improve knowledge of whole-body anatomy and facilitate systematic work. Invertebrate burrows and reptile footprints provide information on ecological interactions and detailed bed-by-bed collecting casts light on taphonomic processes and faunal changes over time.

Vertebrate fauna from the Late Triassic Tiki Formation of India: new finds and their biostratigraphic implications

Recent work on the Tiki Formation has resulted in the collection of new and varied vertebrate micro–and megafossils, including a new bonebed containing low diversity, mono–dominant, multitaxic vertebrate accumulation where the rhynchosaur, Hyperodapedon tikiensis constitute the dominant component. This bonebed has also yielded a large traversodontid cynodont Ruberodon roychowdhurii. In addition, there are several diagnostic postcrania such as vertebrae and incomplete limb bones belonging to a basal saurischian dinosaur. Systematic exploration and collection has yielded numerous isolated teeth and postcrania of small vertebrates such as different types of freshwater sharks, bony fishes, archosauriforms, lepidosauromorphs, cynodonts and other reptiles. Based on its fossil flora and fauna, the Tiki Formation is globally correlated with other coeval horizons such as the lower member of the Maleri Formation of the Pranhita–Godavari basin, the upper part of the Santa Maria Formation of Brazil, the Camp Springs and lower Tecovas formations of the Chinle Group, USA. A Carnian (Otischalkian to early Adamanian) age is proposed for the Tiki Formation.

Thaparocleidus gangus sp. nov. (Monogenea: Dactylogyridae) fromgill filaments of Wallago attu Bloch and Schn., 1801, India

The examination of gill parasites from the freshwater shark Wallago attu Bloch and Schn., 1801 (Siluriformes: Siluridae) in India revealed the presence of a new species of the genus Thaparocleidus Jain, 1952 from the Ganga River, Uttar Pradesh, India. The new species can be discriminated from its congeners by the combination of the following characteristics: accessory piece much smaller than cirrus tube, dorsal anchor with well-developed inner root and small outer root, shaft smoothly bent to form recurved point, inner and outer roots of ventral anchors developed equally so that attain almost equal length, dorsal bar curved in the medial part with expanded lateral ends slightly curved in posterior direction, ventral bar narrowly V-shaped. Thaparocleidus gangus sp. nov. was found to be closely related to T. indicus and T. sudhakari as indicated by their similar morphological appearance. It is a larger worm than T. indicus and T. sudhakari species and can further be separated from them by means of the comparative morphology of the anchors, bars, and cirrus.

Revision of Isanodus paladeji (Elasmobranchii, Hybodontiformes) from the Lower Cretaceous of Thailand

Microremains from the Lower Cretaceous Phu Phan Thong locality, Nong Bua Lam Phu Province, northeastern Thailand, yielded ten tooth morphotypes of the freshwater shark genus Isanodus, which allow the revision of this genus. Two new morphotypes assigned to anterolateral and posterolateral teeth possess shared characters with anterior and posterior teeth of Isanodus paladeji whereas its former anterolateral and posterolateral teeth appear to belong to a new species, Isanodusnongbualamphuensis sp. nov. The pattern of ornamentation in some teeth of I. paladeji and I. nongbualamphuensis is quite similar to that observed in the genus Heteroptychodus, suggesting these two genera are closely related.

Freshwater sharks and rays

Fil: Lucifora, Luis Omar. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Nordeste. Instituto de Biologia Subtropical. Instituto de Biologia Subtropical - Nodo Puerto Iguazu | Universidad Nacional de Misiones. Instituto de Biologia Subtropical. Instituto de Biologia Subtropical - Nodo Puerto Iguazu; Argentina

Review of the Freshwater Sharks of Iran (Family Carcharhinidae)

The systematics, morphology, distribution, biology, economic importance and conservation of the bull shark ( Carcharhinus leucas ) in Iran are described, the species is illustrated, and a bibliography on this fish in Iran is provided.

Identification of Thaparocleidus caecus (Mizelle & Kritsky, 1969) (Monogenea: Dactylogyridae) using morphological and molecular tools: a parasite invasion in Indian freshwater

The freshwater iridescent shark, Pangasianodon hypophthalmus (previously Pangasius sutchi) (Pangasiidae), was found in fish markets in Meerut, Uttar Pradesh, India. Parasitological examination of P. hypophthalmus revealed the presence of a non-native monogenean parasite (genus Thaparocleidus) found on gill filaments. Initial morphology and morphometrics of the parasite showed characteristics of Thaparocleidus caecus, known from Southeast Asia. Genetic analyses of the partial 28S rDNA confirmed the parasite as the first record of T. caecus in India provided.