Caudal Peduncle Research Articles

Oxynoemacheilus fatsaensis, a new nemacheilid loach from the Elekçi Stream in Northern Anatolia (Teleostei: Nemacheilidae)

We report a new species, Oxynoemacheilus fatsaensis, from the Elekçi Stream, a small stream that flows to the Black Sea in Northern Turkey. It is distinguished from other Oxynoemacheilus species in the Black Sea, Upper Euphrates, and Kura-Aras River basins by having a suborbital groove in males, an axillary lobe at the pelvic-fin base, no dorsal adipose crest on the caudal peduncle, a deeply emarginate caudal fin, small inner and outer rostral barbels, and mottled flank pattern. Molecular data suggest that the new species is separated by a minimum p-distance of 3.3% from O. banarescui in the mitochondrial DNA COI barcode region.

Stolephorus grandis, a new anchovy (Teleostei: Clupeiformes: Engraulidae) from New Guinea and Australia.

The new anchovy Stolephorus grandis n. sp., described on the basis of 10 specimens collected from Papua, Indonesia, and Australia, closely resembles Stolephorus mercurius Hata, Lavou Motomura, 2021, Stolephorus multibranchus Wongratana, 1987, and Stolephorus rex Jordan Seale, 1926, all having double pigmented lines on the dorsum from the occiput to the dorsal-fin origin, a long maxilla (posterior tip just reaching or slightly beyond the posterior margin of preopercle), and lacking a predorsal scute. However, the new species clearly differs from the others in having fewer gill rakers (3539 total gill rakers on the first gill arch in S. grandis vs. > 38 in the other species), a greater number of vertebrae (total vertebrae 4243 vs. fewer than 41), longer caudal peduncle (21.923.7% SL vs. 20.8%), and the depressed pelvic fin not reaching posteriorly to vertical through the dorsal fin-origin (vs. reaching beyond level of dorsal-fin origin).

Nanoemulsion boosts anesthetic activity and reduces the side effects of Nectandra grandiflora Nees essential oil in fish

Nectandra grandiflora essential oil has become an alternative to synthetic anesthetics and sedation in fish. However, essential oil volatility, light sensitivity, and low water-solubility may limit its use in the fish farm. To overcome these drawbacks, we developed a new nanoemulsion product that may be applied as an anesthetic. We evaluated the anesthetic property and safety of free essential oil (FEO) and its nanoemulsion (NEN) for Nile tilapia (Oreochromis niloticus). Formulations were made using the spontaneous emulsification process, and stability was tested for NEN and FEO at 4, 25, and 40 °C for 90 days. The NEN contained 95% of FEO, the major compounds remained stable up to 60 days, and the NEN protected the active substances at all temperatures. Fish behavior was observed during a bath with FEO and NEN 3–300 mg/L concentrations for 30 min. The difference between sedated and anesthetized fish was detected by their swimming behavior and response to stimuli on the caudal peduncle. Behavior score, survival, or adverse effects were accessed with 10 and 30 mg/L concentrations of FEO and NEN during 24 h exposure and 72 h recovery. Only 100 mg/L of NEN induced anesthesia without side effects. Long-term exposure tests confirmed the 30 mg/L NEN safety, with a 100% survival rate for fish exposed to NEN and a 25.5% survival rate for fish exposed to surfactants. Therefore, this poorly water-soluble essential oil was converted into a novel sedative and anesthetic for fish through nanoemulsion. Thus, nanoemulsion protects the essential oil and improves the pharmacological activity, with the suggested use of 30 mg/L during 24 h, for sedation, and 100 mg/L, for anesthesia.

Isolation and characterisation of a novel rhabdovirus from snakehead fish showing surface ulcerations and mortality from India: First report

A novel viral agent was isolated from striped snakehead (Channa striata Bloch, 1793) suffering from mortality with dermal ulcerations and haemorrhagic areas in South India. The virus growth was well supported in striped snakehead (SSN-1) and sea bass caudal peduncle (SBCP2a) cell lines at 27 °C while EPC cells were refractory to the virus. Transmission electron microscopy of the infected cells revealed bullet shaped virions with the size ranging from 150 to190 nm length and 46 to 60 nm width. RT-PCR targeting block III fragment of the rhabdovirus L polymerase gene amplified an expected genomic portion of 483 bp. Phylogenetic analysis indicated 91% homology to the equivalent region of the reported snakehead rhabdovirus L polymerase. Experimental infection studies using cell culture grown virus induced 100% morality in juvenile snakehead in five days. Fish showed listlessness, neural pathology and lethargy before dying. Clinical signs included haemorrhages at the fin bases, exophthalmia, darkening of the skin, vascular congestion around the eyes and reddish iris and surface ulcers. The virus caused extensive necrosis of kidney, spleen and liver. The clinical pathology along with the morphology and phylogenetic homogeneity indicates that the virus belongs to the genus Novirhabdovirus under the family Rhabdoviridae. The present study forms the first report of isolation of a fish rhabdovirus in India.

New record of the Red Shoulder Wrasse, Stethojulis bandanensis (Bleeker, 1851) (Perciformes, Labridae), from Korea

A single female juvenile specimen of Stethojulis bandanensis (Bleeker, 1851) was collected from Korea. The specimen is characterized by the 14 pectoral fin rays, the orange-red spot on upper pectoral fin base, and two small light-blue-edged black dots on the caudal peduncle. This species is the third species of the genus Stethojulis Günther, 1861 in Korea, and the newly proposed Korean name for the species is “Ju-hwang-jeom-mu-ji-gae-nol-lae-gi”.

Homatula guanheensis sp. nov. (Teleostei: Nemacheilidae), a new species of loach from Henan Province, China.

BackgroundThe genus Homatula belongs to the order Cypriniformes and family Nemacheilidae. Nichols (1925) set up the genus as a subgenus of Barbatula by the type species of Nemacheilus potanini. Currently, it is recognised as a valid genus. Nineteen valid species have been already reported in the drainage of the Yellow, Yangtze, Pearl, Lancang, Red and Nujiang Rivers. H. variegata, H. longidorsalis, H. berezowskii and H. potanini are distributed in the Yangtze River drainage in China. H. laxiclathra is mainly distributed in the Weihe River, a tributary of the Yellow River. The remaining species are mainly distributed in the rivers of Yunnan Province.New informationHomatula guanheensis sp. nov., a new species, is described from the Guanhe River of the HanJiang River drainage (a tributary of the Yangtze River), Xixia County, Henan Province, China. It can be distinguished from its congeners by a combination of the following characters: the vertical brown bars on the body are wider than their interspaces, numbering 19–22; predorsal body partially scaled; the lateral line complete; adipose crest on caudal peduncle not reaching forward; the position of the anal-fin origin and the intestinal form. The new species displays distinct molecular divergence in the Cytochrome oxidase I (COI) and Cytochrome b (Cyt b) genes.

Patterns of morphological traits shaping the feeding guilds in the intertidal mudflat fishes of the Indian Sundarbans

Broad-scale patterns of resource utilization and the corresponding morphological evolution is a result of an integral relationship among form and function. In addition, there is also an inherent role of the latter in determining species co-interaction and assemblage pattern that forms an integral aspect of ecological research. The present study aimed to evaluate the ecomorphological relationship among 37 fish species inhabiting the intertidal mudflats of the Indian Sundarbans by outlining the following objectives: (i) identifying and characterizing feeding guilds/groups and (ii) understanding the inter-relationship between morphometry with (a) the established feeding guild classifications and (b) observed prey taxa (that characterizes these feeding groups) for determining the role of morphometry in prey acquisition followed by (iii) the evaluation of their potential phylogenetic convergence among the species. For the first objective, two approaches for feeding guild classification were made (3-Guild and 8-Guild) for assessing the prediction accuracy of morphological characters in identifying the different guilds. While the former was based on troph values, the latter classification mode relied on the similarities in diet composition among the different fish species. For addressing the second objective, we employed two different models namely, linear discriminant (LDA) and redundancy analysis (RDA). While the LDA model tested the prediction accuracy of morphological traits in classifying the different feeding guilds, RDA was applied to model the correlation between the morphological traits and the prey categories. In the LDA model, morphological characters showed higher accuracy (78.4%) in classifying three feeding groups rather than eight feeding groups (73%). Following this, the RDA model (explaining 79.78% of constrained variance) showed gill raker intensity, protrusion length, head depth, caudal peduncle, eye diameter and inter-orbital distance to be highly associated with selection of specific prey types by species, thereby characterizing a particular feeding guild. However, generalized linear models testing for correlation between troph value and feeding groups showed substantial variation (90.35%) in the dietary index being explained by the 8-Guild classification. Hence, our study maintains the assumption that broad morphological differentiation acts as one of the underlying processes resulting in dietary variations that results in the varying modes of resource utilization by the coexisting species, thereby determining the structure of a trophic guild. Furthermore, it also suggests that in terms of prey abundance or selectivity, the 8-Guild model is much more conducive in representing the feeding habits of the species while the morphological traits reflected a relatively broader scheme of classification, (i.e., 3-Guild model) with certain traits being phylogenetically conserved within these groups.

Oxynoemacheilus isauricus, a new nemacheilid loach from Central Anatolia (Teleostei: Nemacheilidae).

Oxynoemacheilus isauricus, new species, from the Lakes Beyşehir and Suğla basins in Central Anatolia is distinguished from all other species of the O. angorae group by having a very slender caudal peduncle (its depth 2.22.6 times in its length). The new species is further distinguished by having a short head (head length 2124% SL), and a midlateral series of irregularly shaped blotches on the flank. Oxynoemacheilus isauricus is also distinguished by a minimum K2P sequence divergence of 7.5% and 8.0% in the mtDNA-COI barcode region from O. eregliensis and O. atili, its closest relatives.

Two new species of Hypostomus suckermouth-armoured catfishes (Teleostei: Loricariidae) from central Brazil.

This study describes two new endemic Hypostomus species from central Brazil, which were previously identified as genetically distinct lineages in a recent genomic study that recommended their testing and potential description based on morphological data. A machine learning classification procedure (random forest) was used to investigate morphological variation and identify putatively diagnostic characters for these candidate species and revealed that each is morphologically distinct. The new species Hypostomus cafuringa is characterized by small size, dark spots under a light background, deeper caudal peduncle and shorter first ray of the pectoral fin and base of the dorsal fin when compared to congeneric species from the region. H. cafuringa is known from the headwaters of the Maranhão River, upper Tocantins River basin, Distrito Federal, Brazil. The second new species, Hypostomus crulsi, is characterized by dark spots under a light background, absence of plates along the abdomen region, shorter first ray of the pelvic fin, shorter first ray of the pectoral fin and smaller body size. H. crulsi is known from the headwaters of the São Bartolomeu River, upper Paraná River basin, Distrito Federal, Brazil. The rapid conversion of natural habitats for agricultural development and the isolation of protected areas represent a serious threat to the continued existence of these two newly described endemic species, which warrant conservation assessment.

Optimum Curvature Characteristics of Body/Caudal Fin Locomotion

Fish propelled by body and/or caudal fin (BCF) locomotion can achieve high-efficiency and high-speed swimming performance, by changing their body motion to interact with external fluids. This flexural body motion can be prescribed through its curvature profile. This work indicates that when the fish swims with high efficiency, the curvature amplitude reaches a maximum at the caudal peduncle. In the case of high-speed swimming, the curvature amplitude shows three maxima on the entire body length. It is also demonstrated that, when the Reynolds number is in the range of 104–106, the swimming speed, stride length, and Cost of Transport (COT) are all positively correlated with the tail-beat frequency. A sensitivity analysis of curvature amplitude explains which locations change the most when the fish switches from the high-efficiency swimming mode to the high-speed swimming mode. The comparison among three kinds of BCF fish shows that the optimal swimming performance of thunniform fish is almost the same as that of carangiform fish, while it is better not to neglect the reaction force acting on an anguilliform fish. This study provides a reference for curvature control of bionic fish in a future time.

Genetic Differentiation of Clariid Populations using Microsatellite Markers in Kano State Rivers

This study aimed to investigate the genetic characterization of strains of Clariid fish species in some river bodies in Kano State using microsatellite markers.One hundred and seventy seven Clariid fish samples (Clariasgariepinus and Heterobranchuslongifilis) were collected from six rivers (Thomas, Ghari, Tiga dam, Duddurun Gaya, Karaye and Bagwai) in Kano state. Blood sample was taken from each fish sample by severing the caudal peduncle and drained into FTA cards for DNA extraction, Polymerase Chain Reaction and electrophoresis to determine genetic variation between the Clariid fish populations.Genealex 6.4 software package was used to analyse the resolve bands from DNA extraction to determine their base pair and genetic variation. Results showed that the Fst values ranged from 0.00 to 0.66, Fit ranged from -0.04 to 0.12, Fis ranged from -0.35 to -0.26. It indicated a large number of gene flow (exchange) among the populations with a range of 0.46 to 0.87. There was an established magnitude of genetic divergence (91.86%) among the populations as shown by the result of the percentage polymorphism which depends on the number of alleles detected per locus and their frequencies. It can be concluded that since there was no inbreeding as shown in the study, none of the population exhibited genetic uniqueness. The populations had a high genetic differentiation between populations but moderate differentiation within populations. The populations were outbred populations; an indication that relatives avoided mating in the population.

Hydrodynamical effect of parallelly swimming fish using computational fluid dynamics method.

Fish form schools because of many possible reasons. However, the hydrodynamic mechanism whereby the energy efficiency of fish schools is improved still remains unclear. There are limited examples of fish models based on actual swimming movements using simulation, and the movements in existing models are simple. Therefore, in this study, we analyzed the swimming behavior of Biwa salmon (Oncorhynchus sp., a salmonid fish) using image analyses and formulated its swimming motion. Moreover, computational fluid dynamics analysis was carried out using the formulated swimming motion to determine the fluid force acting on the fish body model with real fish swimming motion. The swimming efficiency of the fish model under parallel swimming was obtained from the calculated surrounding fluid force and compared for different neighboring distances. The flow field around the fish model was also examined. The swimming efficiency of two fish models swimming parallelly was improved by approximately 10% when they were separated by a distance of 0.4L, where L is the total length of the model. In addition, the flow field behind the fish body was examined under both inphase and antiphase conditions and at inter-individual distances of 0.8L and 1.2L. The apparent flow speed in the distance range of 0.5-2.0L from the midpoint of the snouts of the two individuals was lower than the swimming speed. The pressure distribution on the fish model showed an elevated pressure at the caudal fin. Interestingly, we obtained an isopleth map similar to that of a caudal peduncle. To avoid a negative thrust, the aft part of the body must be thin, as shown in the isopleth map obtained in this study.

Long lasting effects of early temperature exposure on the swimming performance and skeleton development of metamorphosing Gilthead seabream (Sparus aurata L.) larvae

Temperatures experienced during early ontogeny significantly influence fish phenotypes, with clear consequences for the wild and reared stocks. We examined the effect of temperature (17, 20, or 23 °C) during the short embryonic and yolk-sac larval period, on the swimming performance and skeleton of metamorphosing Gilthead seabream larvae. In the following ontogenetic period, all fish were subjected to common temperature (20 °C). The critical swimming speed of metamorphosing larvae was significantly decreased from 9.7 ± 0.6 TL/s (total length per second) at 17 °C developmental temperature (DT) to 8.7 ± 0.6 and 8.8 ± 0.7 TL/s at 20 and 23 °C DT respectively (p < 0.05). Swimming performance was significantly correlated with fish body shape (p < 0.05). Compared with the rest groups, fish of 17 °C DT presented a slender body shape, longer caudal peduncle, terminal mouth and ventrally transposed pectoral fins. Moreover, DT significantly affected the relative depth of heart ventricle (VD/TL,p < 0.05), which was comparatively increased at 17 °C DT. Finally, the incidence of caudal-fin abnormalities significantly decreased (p < 0.05) with the increase of DT. To our knowledge, this is the first evidence for the significant effect of DT during the short embryonic and yolk-sac larval period on the swimming performance of the later stages.

Two new catfish species of typically Amazonian lineages in the Upper Rio Paraguay (Aspredinidae: Hoplomyzontinae and Trichomycteridae: Vandelliinae), with a biogeographic discussion

Two new species of particular biogeographic significance are described from the upper rio Paraguay basin, one of the genus Paracanthopoma (Trichomycteridae, Vandelliinae) and the other of the genus Ernstichthys (Aspredinidae, Hoplomyzontinae). The two species occur sympatrically in the Rio Taquarizinho, tributary of the Rio Taquari, in the upper Paraguay system. Paracanthopoma saci is distinguished from its only congener, P. parva, by a spatulate caudal peduncle; a minuscule premaxillary dentition (reduced to three delicate teeth); the supraorbital latero-sensory canals opening as two separate s6 pores; the caudal fin slightly convex or truncate with round edges; the skull roof entirely open, unossified; the origins of dorsal and anal fins approximately at same vertical; and the pelvic fin with three rays. Ernstichthys taquari is diagnosed among congeners by the narrow bony shields on dorsal and ventral series, not overlapping or contacting each other; by the presence of seven or eight serrations on the posterior margin of the pectoral spine; and by the pectoral-fin spine only slightly larger than subsequent soft rays. Both Paracanthopoma and Ernstichthys were previously unknown outside of the Greater Amazonian river systems (Amazon, Orinoco, Essequibo and smaller surrounding drainages). Their presence restricted to the Rio Taquari is unexpected and suggests a peculiar biogeographical history. Ancestral geographic distributions were reconstructed using S-DIVA and BBM methods in RASP. A majority of resulting hypotheses support that the two species reached the Paraguay from the Amazon. The alternative explanation accounts for their presence in the Paraguay by vicariant events. In no case, their presence in the Paraguay is an ancestral distribution with subsequent Amazonian dispersal. Though unusual, this pattern is also seen in a few other fish taxa, showing that the Rio Taquari is biogeographically hybrid, combining elements from both the Paraguay and Amazon drainages.

Cast netting new species: Integrative taxonomy of emDistichodus/em emnotospilus/em (Characiformes: Distichodontidae) discovers new species and overlooked areas of endemism in Central Africa.

Distichodus notospilus was described from the Ogooué River and is considered to occur throughout the Lower Guinea ichthyofaunal province and the western tributaries of the middle and lower Congo River. Recent expeditions in Equatorial Guinea collected D. notospilus specimens in the Mbini River drainage and the Mbia River; a small coastal river that is located between the Ntem and Mbini river drainages. Detailed morphological analyses and multilocus molecular analyses confirm that these two populations are distinct from one another. Topotypic populations of D. notospilus were included in the analyses and demonstrated that populations in the Mbini and Mbia rivers are distinct and these two new species are described herein. Distichodus microps sp. nov. is endemic to the Mbia River drainage and is distinguished from D. notospilus in having more scales along the lateral line (41, rarely 40 versus 37-39, rarely 40), a nearly inferior mouth versus subterminal in D. notospilus, a curved posterolateral margin of the opercle versus straight in D. notospilus, a smaller eye (56.7-80.4 versus 70.1-104.3 % of snout length), and a less prominent elongated spot at the base of the caudal fin. Distichodus mbiniensis sp. nov. is endemic to the upper Mbini River drainage and distinguished from D. notospilus in having more scales along the lateral line (41-42, rarely 40 versus 37-39, rarely 40), a much less prominent elongated dark spot at the base of the caudal fin, and a shorter dorsal fin (21.4-27.2 versus 22.7-34.2% standard length). Distichodus microps is distinguished from D. mbiniensis in having a shallower body (usually six scales from lateral line to the pelvic fin versus seven), fewer anal-fin rays (usually 12 total rays versus 13 or 14), a more inferior mouth, a deeper and longer caudal peduncle, a smaller eye, and differences in several features associated with the head. In addition to the two new species described this study also revealed potential undescribed diversity in the D. notospilus species complex in the Ntem River and Dja River (Congo R. basin) in Cameroon. The biogeography of these fishes in the rivers of Lower Guinea suggests that the Mbini River and smaller coastal rivers are overlooked areas of endemism. Studies of other reported widespread species will likely reveal additional diversity and further elucidate the processes promoting and maintaining freshwater diversity in Central Africa.

EmOxynoemacheilus/em emphasicus/em, a new nemacheilid loach from the eastern Black Sea basin with some remarks on other Caucasian emOxynoemacheilus/em (Teleostei: Nemacheilidae).

Oxynoemacheilus phasicus, new species, is described from the Rioni and Enguri River drainages in Georgia. It is distinguished from other Oxynoemacheilus species in the O. brandtii group by a mottled or marbled flank pattern in adults, a slightly emarginate caudal fin, and a deep caudal peduncle. Molecular data suggest that the new species is characterized by a minimum K2P distance of 7.5% from O. brandtii from the Kura drainage in the mtDNA COI barcode region. Oxynoemacheilus brandtii and O. elsae are re-diagnosed. A very slender Oxynoemacheilus from the Aras drainage clusters as sister to O. elsae in our molecular analysis and not with O. brandtii from the Kura River. However, it is identified as O. brandtii as it is indistinguishable from this species in morphological characters.

Confirmation on the occurrence of Cymothoa indica, and first record of Norileca indica, with a note on new host records of Nerocila arres, and Nerocila depressa (Isopoda: Cymothoidae) from Odisha coast, India.

The parasitic isopod Cymothoa indica Schiöedte and Meinert, 1884 was recorded from the buccal cavity of the host Glossogobius giuris (Hamilton, 1822) collected from Chilka Lake, Odisha in 1924, but its identification was doubtful as mentioned by the author in his book on "Fauna of Chilika Lake: Tanaidacea and Isopoda". The present report of parasitic isopodC. indicafrom the buccal cavity of the host Sphyraena obtusata Cuvier, 1833 collected from the water of Bay of Bengal, Gopalpur-on-Sea confirms its occurrence along the Odisha coast. The record of the isopod parasite Norileca indica (H. MilneEdwards, 1840) from the branchial cavity of the host Atule mate (Cuvier, 1833) collected from the water of Bay of Bengal, Gopalpur-on-Sea is the first record of this parasite from the coastal water of Odisha, India. The record of Nerocila arres Bowman and Tareen, 1983 from the caudal peduncle of the host fish species Terapon puta Cuvier, 1829, and the isopod N. depressa Milne Edwards, 1840 from the host fish species Megalaspis cordyla (Linnaeus, 1758) are the new host records for these respective parasites.

A New Species of Bridled Darter Endemic to the Etowah River System in Georgia (Percidae: Etheostomatinae: Percina)

Percina freemanorum, the Etowah Bridled Darter, is described as a new species endemic to the Etowah River system in Georgia, specifically in Long Swamp Creek, Amicalola Creek, and the upper portion of the Etowah River. The earliest collection records for Percina freemanorum date to 1948 and in 2007 the species was delimited as populations of Percina kusha. Our investigation into the systematics of Percina kusha is motivated by the uncertain status of populations in the Coosawattee River system and observed morphological disparity in several meristic traits between populations in the Conasauga and Etowah River systems. Our analyses of morphological divergence, nuclear genotypes, and mitochondrial DNA (mtDNA) haplotype networks confirm the distinctiveness of Percina freemanorum. Morphologically, Percina freemanorum is distinguished from Percina kusha through lower average numbers of lateral line scales (65.4 vs. 72.3); rows of transverse scales (18.0 vs. 21.4); scales around the caudal peduncle (22.1 vs. 24.9); and modally more pectoral fin rays (14 vs. 13). The two species are not reciprocally monophyletic in phylogenetic analysis of mtDNA sequences, but the two species do not share mtDNA haplotypes. Analysis of up to 158,000 double digest restriction-site associated DNA (ddRAD) sequencing loci resolve each of the two species as reciprocally monophyletic and genomic clustering analysis of single nucleotide polymorphisms identifies two genetic clusters that correspond to the morphologically delimited Percina freemanorum and Percina kusha.

The fast and the tendinous? Locomotor modifications of the caudal peduncle in Gila spp. from the American Southwest

In the American Southwest, the fishes within the genus Gila evolved in an environment with seasonal rainstorms that caused stochastic flooding. Some species within this genus, such as bonytail (Gila elegans), possess locomotor morphologies that are similar to those seen in high-performance swimmers such as tuna and lamnid sharks. These shared features include a shallow caudal peduncle, lunate tail, and mechanisms to transmit force from the anterior musculature to the tail fin. We compared the skeletal anatomy of the caudal region of bonytail to roundtail chub (Gila robusta) and humpback chub (Gila cypha) to determine which vertebral elements have been modified to create a shallow peduncle. We also tested the tensile strength of the red (slow oxidative) axial muscle by performing a standard stress test. If the muscle can withstand a large load, this suggests it may play a tendon-like role in transmitting force from the anterior muscle to the hypural plate of the tail. Lastly, we measured the collagen content of the red axial muscle (visualized using serial sections and Masson’s trichrome stain) to determine if increased tensile strength is associated with increased collagen content. We found bonytail caudal peduncles are characterized by acute vertebral spines and have red axial muscle that can resist tearing under tension. Roundtail chub peduncles are characterized by relatively more obtuse angles and the red muscle tears easily under tension. Humpback chub possess an intermediate morphology, with relatively obtuse vertebral spine angles and the red muscle can resist tearing under tension. Bonytail have increased collagen content in posterior red axial muscle compared to the anterior musculature also suggesting a tendon-like role of the posterior red muscle. In combination with previous studies of swimming performance, our findings suggest that the axial musculature of bonytail may play a role in transmitting force directly to the shallow peduncle in a manner similar to that of the great lateral tendon of scombrids.

Developmental morphology and growth in early stages of laboratory-reared Cirrhinus molitorella and C. microlepis (Cypriniformes: Cyprinidae)

The morphological developments in laboratory-reared larval and juvenile Cirrhinus molitorella and larval C. microlepis were described, and ontogenies (including yolk sizes and absorptions, fin-ray and myomere numbers, allometric changes in the snout, upper jaw, head and pre-anal lengths, maximum body depth, eye diameter and melanophore distributions) were compared. Body lengths (BL) just after hatching were smaller in C. molitorella [3.3 ± 0.1 (mean ± SD) mm] than in C. microlepis (4.4 ± 0.1 mm), and subsequent increase in body lengths were slower in C. molitorella than in C. microlepis. Yolk sizes just after hatching were correspondingly smaller in C. molitorella than in C. microlepis and the yolks were completely absorbed by ca. 95 hours after hatching in the former and ca. 118 hours in the latter. In C. molitorella, fin-rays started appearing at a smaller size than in C. microlepis, with full complements attained by 14.4 mm BL (day 35) in the former, while they did not attain by 16.4 mm BL (day 20) in the latter. Allometric changes started in smaller sizes in C. molitorella than in C. microlepis. Total myomeres were 38–41 in C. molitorella and 39–43 in C. microlepis. Melanophore distributions progressed similarly in both species, except for a darker deposition on the caudal peduncle of C. molitorella of ca. 7–10 mm BL. Larvae of these species were identifiable mainly by differences in fin-ray numbers and allometries by size.