Caudal Peduncle Research Articles

Discovery of two new species of cobia (Pisces; Rachycentridae) inhabiting the makran coast of the northern Arabian Sea with notes on their biology and ecology

Cobia, Rachycentron canadum has long been regarded as the sole species in the family Rachycentridae, and has a wide distribution in tropical and sub-tropical regions of the Atlantic, Indian Ocean and western Pacific. This study describes two newly identified species, Rachycentron blochii sp. nov. and Rachycentron makranesis sp. nov. from Gwadar in the northern Arabian Sea. The newly discovered species differ significantly from their relatives in multiple morphological traits, such as head profile, mouth, pectoral fin, caudal fin, caudal peduncle, dorsal and anal fin bases, gill rakers, and body coloration. Additionally, species delimitation was further supported by examining body scales and otoliths (sagitta, lapillus, and asteriscus), with shapes also delimiting species. The recent finding increases the number of cobia species in the northern Arabian Sea, Pakistan. Moreover, details on the biological and ecological aspects such as feeding habits, age assessment, habitat preferences and fishery-related details are presented.

Effect of climatic factors on sexual maturity Labeo rohita fish

<p>This study examined the varying levels of thyroxine hormone impact (at doses of 2, 10, and 50 µg g-1 BW) as an environmentally responsive hormone on the fatty acid and sexual steroid profiles in male Labeo rohita fish. Each treatment group comprised six male fish with an average weight of 5.4 ± 0.58 kg. Blood samples were collected from male rohu fish pre-and post-injection, as well as following sperm retrieval from the caudal peduncle. Biotechnical parameters were evaluated post-fertilization. Among male breeders, the pituitary treatment and the 50 µg g-1 BW thyroxine treatment exhibited the highest levels of estradiol, testosterone, 17-alpha hydroxyprogesterone, cortisol, LH, as well as testicular protein and fat content. Whereas the lowest levels were observed in the LHRH recipient and control groups (p < 0.05). Moreover, the saturated fatty acids C16:0 and C18:0, monounsaturated fatty acids C18:1n9c and C24:1n9, along with polyunsaturated fatty acids C20:3n6 and C22:6n3 in male breeders, were found to be the predominant fatty acids in the testes under hormonal treatment. The pituitary treatment and the 50 µg g-1 BW thyroxine treatment demonstrated a greater total percentage of testicular fatty acids compared to other interventions (p < 0.05). These findings emphasize the heightened efficacy of pituitary hormone and subsequent thyroxine hormone administration at a dose of 50 µg g-1 BW, relative to lower thyroxine doses and LHRH. The aforementioned treatment can increase the levels of sex hormones that are important for sexual responsiveness, emphasizing their pivotal role in facilitating successful artificial reproduction in male Rohu breeders.</p>

Caudal peduncle-inspired two-degree-of-freedom elastic coupling fin propulsion method

Marine animals orchestrate the swimming process through the coordinated interplay of body musculature, the caudal peduncle, and the caudal fin. However, understanding the coordinated action of these components to achieve high propulsive performance remains a significant challenge. The study proposes a self-propulsive physical model with two-degree-of-freedom (DoF) elastic coupling inspired by the caudal peduncle, where the caudal peduncle exhibits spring-like behaviors influencing the tail's motion along heave/pitch directions. The complex nonlinear fluid–structure interaction issues are addressed via the nonlinear vortex sheet method. The study primarily compares the propulsive performance of the two-DoF elastic coupling caudal fin model with the pitch caudal fin model. Numerical results show that the peak efficiency of the proposed model is nearly eight times that of the pitch caudal fin model. Additionally, the study reveals that the high-propulsive mechanism lies in generating the figure of a butterfly phase diagram for the hydrodynamic forces and exploiting vortices to decrease energy consumption. These findings offer novel perspectives for the future design of high-efficiency underwater robots.

A new species of Opsariichthys (Teleostei, Cypriniformes, Xenocyprididae) from Southeast China.

Opsariichthysiridescens sp. nov. is described from the Qiantang and Oujiang rivers in Zhejiang Province and a tributary of the Yangtze River adjacent to the Qiantang River. It is distinguished from congeners by the following combination of morphological features: no obvious anterior notch on the tip of the upper lip; 45-52 lateral-line scales; 18-21 pre-dorsal scales; two rows of pharyngeal teeth; a maxillary extending to or slightly beyond the vertical anterior margin of the orbit in adult males; a pectoral fin extending to the pelvic fin in adult males; nuptial tubercles on the cheeks and lower jaw of males, which are usually united basally to form a plate; uniform narrow pale pink cross-bars on trunk and two widening significantly on caudal peduncle. Its validity was also supported by its distinct Cyt b gene sequence divergence from all congeners and its monophyly recovered in a Cyt b gene-based phylogenetic analysis.

Psilorhynchus kosygini, a new species of torrent minnow (Teleostei: Psilorhynchidae) from Nagaland, north-east India

ABSTRACT Psilorhynchus kosygini, a new species, is described from the Tepuiki River, a tributary of the Barak drainage in Nagaland, north-east India. The new species, belonging to the P. homaloptera species group, is characterised by possessing a unique pattern of 3–4 scales positioned along the mid-ventral region between the posterior base of the pelvic fin and the anal opening, body elongate with 41–42 scales along the lateral line, 14 scales in the pre-dorsal region, 8 scales around the caudal peduncle and 9–10 branched pectoral-fin rays. http://www.zoobank.org/urn:lsid:zoobank.org:pub:00002407-A5D2-40F5-BB6B-624F00676BA8

Pseudomystus tuberosus, a new species of catfish from central Borneo (Actinopterygii: Bagridae)

Pseudomystus tuberosus, a new species of bagrid catfish from the Kahayan River drainage in south central Borneo, is described in this study. It can be distinguished from all congeners in having a strongly humped dorsal profile (vs. dorsal profile weakly humped or without hump), as well as its head and flanks covered with rounded tubercles (vs. smooth or with capillaceous epithelial projections). Pseudomystus tuberosus most closely resembles P. vaillantii, but can be further distinguished from it in having a smaller eye (8% HL vs. 9–12) and a slenderer caudal peduncle (5.5–6.0% SL vs. 6.8–8.1). The identity of P. carnosus, described from southern Sumatra, is also discussed, and the species treated as a junior synonym of P. moeschii.

Bisecting the type series of Leporinus paranensis Garavello and Britski, 1987 (Characiformes, Anostomidae)

The type series of Leporinus paranensis includes two distinct species, one of which is herein described as new. Leporinus paranensis is redescribed based on its holotype, two paratypes, and additional specimens recently sampled in tributaries of the Grande river, in the north portion of the upper Paraná basin in Brazil. A new species of Leporinus is described based on specimens collected in all major tributaries of the upper Paraná basin in Brazil, and tributaries of the Paraná river in Paraguay. Both species share the presence of three unicuspid teeth on the premaxillary and four on dentary, terminal mouth and three dark midlateral blotches on the body. The new species is distinguished from L. paranensis based on the number of scale series around the caudal peduncle (12 vs. 16). The variation in the body shape of both species were compared through a Principal Component Analysis and showed that they share a similar body shape. Species delimitation analyses using DNA Barcode were applied to compare samples of the new species to congeners and corroborated the uniqueness of the new species. In addition, molecular data revealed that L. bahiensis, L. octofasciatus, and L. taeniatus are possibly closely related to the new species. The conservation status of L. paranensis and the new species are discussed using the IUCN criteria.

New species of Batrochoglanis Gill (Siluriformes: Pseudopimelodidae) from the Capim River basin, State of Pará, Brazil

Batrochoglanis labrosus new species, is described from the Capim River Basin, State of Pará, Brazil. The new species differs from congeners by the stout, inferior mandible, hypertrophied lips on the lateral of the mouth, a broad dark brown band extending dorsoventrally from the beginning of the trunk to the posterior third of the adipose fin followed by a second dark brown band on the caudal peduncle, dark brown pelvic fin, and caudal fin hyaline with a concentration of dark brown spots on the posterior margin, sometimes forming an irregular band. The morphometric variables of B. labrosus are similar in B. villosus and B. castaneus, forming a B. villosus species group. The B. villosus group is distinct from other group formed by B. acanthochiroides and B. transmontanus in the third axis of the Principal Components Analysis. The variables with higher positive loadings in the B. villosus group, representing larger measurements, were adipose-fin base length, eye diameter, maxillary barbel length, head depth, and mouth width; the higher negative loadings representing shorter measurements were pelvic fin to anal fin distance and pectoral-fin spine length. The species is known only from the Capim River basin, where it is possibly endemic.

FOUR CASES OF SEVERED PEDUNCLES IN BOTTLENOSE DOLPHINS (TURSIOPS TRUNCATUS) ALONG THE ALABAMA COAST.

Alabama (AL) is a hotspot in the Gulf of Mexico (GoM) for human interaction-related cetacean strandings, including harassment, vessel strikes, and fisheries interactions. We examined four bottlenose dolphins (Tursiops truncatus) stranded dead along the AL coast during 2012-2017 with severed peduncles suspected to be related to human interaction (HI). Evidence from each case, including photographs, gross necropsy results, and histopathologic findings when available, was reviewed to determine the mode of severance and whether it contributed to death. In each case, the severance site had smooth, clean edges on at least one side, indicating the use of a sharp instrument to remove the caudal peduncle and flukes. Three cases also had evidence of fisheries interactions, including linear impressions around the rostrum, fins and/or flukes, indicating that these animals may have been entangled in fisheries gear prior to death. Histopathology in one of these cases revealed that the severance occurred perimortem; speculatively, the caudal peduncle and flukes may have been cut off to facilitate removing the dolphin from its entanglement. Although cases of amputation and mutilation are not uncommon globally among stranding reports, few cases have been described and analyzed in the literature. This paper is the first to document and compare multiple cases of severed peduncles with evidence of HI, including fisheries, in the GoM. This case series enhances our understanding of the types of HI occurring in bottlenose dolphins and highlights the need for continued public education, policy, and management to address cases like these.

Terrestrial locomotion characteristics of climbing perch (Anabas testudineus).

The evolution and utilization of limbs facilitated terrestrial vertebrate movement on land, but little is known about how other lateral structures enhance terrestrial locomotion in amphibian fishes without terrestrialized limb structures. Climbing perch (Anabas testudineus) exhibit sustained terrestrial locomotion using uniaxial rotating gill covers instead of appendages. To investigate the role of such simple lateral structures in terrestrial locomotion and the motion-generating mechanism of the corresponding locomotor structure configuration (gill covers and body undulation), we measured the terrestrial kinematics of climbing perch and quantitatively analysed its motion characteristics. The digitized locomotor kinematics showed a unique body postural adjustment ability that enables the regulation of the posture of the caudal peduncle for converting lateral bending force into propulsion. An analysis of the coordination characteristics demonstrated that the motion of the gill cover is kinematically independent of axial undulation, suggesting that the gill cover functions as an anchored simple support pole while axial undulation actively mediates body posture and produces propulsive force. The two identified feature shapes explained more than 87% of the complex lateral undulation in multistage locomotion. The kinematic characteristics enhance our understanding of the underlying coordinating mechanism corresponding to locomotor configurations. Our work provides quantitative insight into the terrestrial locomotor adaptation of climbing perch and sheds light on terrestrial motion potential of locomotor configurations containing a typical aquatic body and restricted lateral structure.

Cobitis feroniae, a new spined loach from southern Latium, Italy (Teleostei: Cobitidae)

Cobitis feroniae, new species, is described from central Italy. It is distinguished from C. zanandreai, its putatively closest relative, by having several, small, black dots below Z4; minute, black spot at the upper caudal peduncle, and the pigmentation in Z2 separated from pigmentation in Z1 anterior to the dorsal-fin origin. It is further distinguished from C. zanandreai by having 13 diagnostic nucleotide substitutions in the mtDNA COI barcode region, and a K2P nearest–neighbour distance of 2.9%.

Oxynoemacheilus fatmae, a new species from the Güzelhisar Stream in the Aegean Sea basin, Türkiye (Teleostei: Nemacheilidae).

Oxynoemacheilus fatmae, a new species, is found in the Güzelhisar Stream in the northern Aegean Sea basin. It is differentiated from all other species of Oxynoemacheilus in the northern Aegean Sea and adjacent basins by having four to eight irregularly shaped narrow black bars on the posterior part of flank, and anterior parts of the flank with a marbled pattern. O. fatmae is differentiated from the closest species Oxynoemacheilus theophilii by having 14 fixed diagnostic nucleotide substitution sites, and the pair-wise genetic distance is 2.22%. It further differs from O. theophilii by having a slenderer body (body at dorsal-fin origin: 15%-17% standard length [SL] vs. 17%-18%), a slenderer caudal peduncle (10%-12% SL vs. 12%-13%), a more forked caudal fin (length of middle caudal-fin lope: 16%-19% SL vs. 19%-23%), and the absence the dorsal and ventral adipose crests on the caudal peduncle behind the vertical of the posterior anal-fin base (vs. present). Three species delimitation tests (assemble species by automatic partitioning (ASAP), automatic barcode gap discovery (ABGD) and generalized mixed yule-coalescent (GMYC)) and phylogenetic analyses reinforce the validity of O. fatmae as a distinct species.

Ecomorphology of yellowtail lambari (Characiformes: Characidae) in the neotropical semi-arid region, Brazil

The ecomorphological patterns of the Astyanax lacustris in different environments (lotic and lentic) of the semiarid region of Pernambuco were analyzed using 25 linear morphometric measurements on 240 specimens (120 males and 120 females), with standard lengths ranging from 24.25 to 91.50 mm. These data were converted into 16 ecomorphological attributes and correlated with environmental characteristics. The principal component analysis (PCA) explained 81.64% (first and second components) of the data variation, highlighting sexual dimorphism in specimen size and noticeable variation among individuals of the same sex in different environments. Specimens from lotic environments showed higher caudal peduncle compression index (CPCI) values, while the pectoral fin aspect ration (PFAR) was more pronounced in lentic environments. Overall, females exhibited a wide morphometric variation. Analysis of linear morphometry in different water bodies indicated an intrinsic variation related to hydrodynamics linked to sexual dimorphism and water flow speed. Further studies are suggested to investigate whether factors such as macrophytes and different levels of water depth and flow contribute to this morphometric variation of species in the semi-arid region.

Oxynoemacheilus kottelati, a new species from the Havran and Karınca streams in Northern Aegean Basin, Türkiye (Teleostei, Nemacheilidae)

The taxonomic status of the Oxynoemacheilus from the Karınca and Havran streams in the north Aegean Basin was evaluated, and it was concluded that these populations contain a new species. The new species, Oxynoemacheilus kottelatisp. nov., is distinguished by a body with a marbled pattern, a deeper caudal peduncle, a shorter caudal peduncle, a wider interorbital distance, and a shorter middle caudal-fin lope. Oxynoemacheilus kottelatisp. nov. is differentiated from the closest species, O. marmaraensis, in possessing 51 nucleotide substitution sites, a genetic distance of 8.40%, the presence of an axillary lobe at the base of the pelvic fin (vs. absent), and a narrower median incision in the upper lip (vs. absent). Three species delimitation tests (ASAP, ABGD, and PTP) and phylogenetic analyses reinforce the validity of O. kottelatisp. nov. as a distinct species.

Oxynoemacheilus chaboras, a new loach species from the Euphrates drainage in Türkiye (Teleostei, Nemacheilidae)

Oxynoemacheilus chaboras, new species, from the stream Beyazsu in the Euphrates drainage, belongs to the O. persa species group, being closely related to O. shehabi from the Orontes, O. sarus from the Seyhan and Ceyhan, O. euphraticus from the Euphrates and Tigris, O. karunensis from the Karkheh, and O. persa from Central Iran. The new species is distinguished from others in the O. persa group by having 8–9 pores in the supraorbital canal, two distinct black blotches at the caudal-fin base, a rudimentary and shallow pelvic axillary lobe, 6–10 irregularly shaped bars on the flank, and a deep head, body, and caudal peduncle. Oxynoemacheilus chaborassp. nov. is most closely related to O. euphraticus, from which it is differentiated by a mean uncorrected p-distance of 3.24% (min. 3.09%) in its COI barcode gene.

The complete genome sequence of the protogynous hermaphrodite North American annual killifish Millerichthys robustus (Rivulidae, Cyprinodontiformes).

The Mexican Rivulus, Millerichthys robustus, is an enigmatic species of seasonal killifish endemic of the Southeast Mexico that has changed paradigms on the evolution of annualism in killifishes. This species survives in ephemeral environments that experience a period of seasonal drought that causes the death of all adult fish. However, populations persist due to their drought-resistant embryos capable of arresting their development in diapause until the next the rainy season. Millerichthys evolved unique characteristics within annual killifishes as a functional sequential hermaphroditism, in which females change to males (protogynous) under perceived conditions of mate competition. Also, M. robustus express different color phenotypes in both sexes: five-color phenotypes continuously distributed in various perceptual units between yellow and red in males, and different number of ocelli disposed in caudal peduncle in females. The phylogenetic relationships of M. robustus revealed that it is a sister clade to two non-annual species found exclusively in Cuba (Rivulus cylindraceus and Rivulus berovidesi), indicating that the annual life cycle, through the acquisition of embryonic diapause, has evolved independently in this species. Here, we present the complete genome sequences for the North American annual killifish Millerichthys robustus. The raw data and assembled genome are available in GeneBank.

A new species of trout from the Köprüçay River, a drainage of Mediterranean Sea, Türkiye (Salmoniformes, Salmonidae)

Salmo ekmekciae, new species, is described from the Köprüçay River, a drainage of Mediterranean Sea. It is distinguished from Salmo species in adjacent water by having 9–10 parr marks on flank; 11–13 scale rows between end of base of adipose-fin and lateral line; 22–24 gill rakers on first gill arch; a shorter distance between adipose-fin and caudal-fin base; a slenderer caudal peduncle; and a slenderer body at adipose-fin origin. According to the Bayesian, and maximum likelihood analyses, Salmo ekmekciae cyt b gene resulted in coherent trees supported by high bootstrap values.

Analysis of morphology, histology characteristics, and circadian clock gene expression of Onychostoma macrolepis at the overwintering period and the breeding period.

Fish typically adapt to their environment through evolutionary traits, and this adaptive strategy plays a critical role in promoting species diversity. Onychostoma macrolepis is a rare and endangered wild species that exhibits a life history of overwintering in caves and breeding in mountain streams. We analyzed the morphological characteristics, histological structure, and expression of circadian clock genes in O. macrolepis to elucidate its adaptive strategies to environmental changes in this study. The results showed that the relative values of O. macrolepis eye diameter, body height, and caudal peduncle height enlarged significantly during the breeding period. The outer layer of the heart was dense; the ventricular myocardial wall was thickened; the fat was accumulated in the liver cells; the red and white pulp structures of the spleen, renal tubules, and glomeruli were increased; and the goblet cells of the intestine were decreased in the breeding period. In addition, the spermatogenic cyst contained mature sperm, and the ovaries were filled with eggs at various stages of development. Throughout the overwintering period, the melano-macrophage center is located between the spleen and kidney, and the melano-macrophage center in the cytoplasm has the ability to synthesize melanin, and is arranged in clusters to form cell clusters or white pulp scattered in it. Circadian clock genes were identified in all organs, exhibiting significant differences between the before/after overwintering period and the breeding period. These findings indicate that the environment plays an important role in shaping the behavior of O. macrolepis, helping the animals to build self-defense mechanisms during cyclical habitat changes. Studying the morphological, histological structure and circadian clock gene expression of O. macrolepis during the overwintering and breeding periods is beneficial for understanding its unique hibernation behavior in caves. Additionally, it provides an excellent biological sample for investigating the environmental adaptability of atypical cavefish species.

Halichoeres sanchezi n. sp., a new wrasse from the Revillagigedo Archipelago of Mexico, tropical eastern Pacific Ocean (Teleostei: Labridae).

A new labrid fish species, Halichoeres sanchezi n. sp., is described from eight specimens collected in the Revillagigedo Archipelago in the tropical eastern Pacific Ocean, off the coast of Mexico. The new species belongs to the Halichoeres melanotis species complex that is found throughout the region, differing by 2.4% in the mtDNA cytochrome c oxidase I sequence from its nearest relative, H. melanotis from Panama, and 2.9% from Halichoeres salmofasciatus from Cocos Island, off Costa Rica. The complex is distinguished from others in the region by having a black spot on the opercular flap and a prominent black area on the caudal fin of males. The juveniles and initial phase of the new species closely resemble those of H. salmofasciatus and Halichoeres malpelo from Malpelo Island of Colombia, differing in having an oblong black spot with a yellow dorsal margin on the mid-dorsal fin of initial-phase adults as well as on juveniles. In contrast, the terminal-phase male color pattern is distinct from other relatives, being vermilion to orangish brown with dark scale outlines, a white patch on the upper abdomen, and a prominent black band covering the posterior caudal peduncle and base of the caudal fin. The new species adds to the list of endemic fish species for the isolated archipelago and is an interesting case of island endemism in the region. The discovery was made during the joint 2022 collecting expedition to the archipelago, which featured a pioneering collaborative approach to an inventory of an island ichthyofauna, specifically including expert underwater photographers systematically documenting specimens in situ, before hand-collection, and then photographed fresh, tissue-sampled, and subsequently vouchered in museum collections.

Stock identification of the Mediterranean horse mackerel (Carangidae: Trachurus mediterraneus) in the Marmara and Black Seas using body and otolith shape analyses

The Mediterranean horse mackerel (Trachurus mediterraneus) has been managed as a single stock in the Black Sea and adjacent regions, and its genetic structure has been under debate for decades, emphasising the necessity for additional research to validate the stock structure. This study used geometric morphometrics for body shape, shape indices, and elliptical Fourier analysis for otolith shape to explore their morphological differences in the Eastern Black Sea, Middle Black Sea, and Sea of Marmara. The findings revealed considerable differences in body and otolith shapes across the examined regions, suggesting the existence of three separate stocks. The geometric morphometrics revealed evident differences in the snout, followed by the caudal peduncle and body depths. Both otolith shape indices and elliptic Fourier analysis revealed significant directional bilateral asymmetry between the left- and right-sided otoliths. The elliptic Fourier analysis revealed a non-overlapping surface difference of 2.12% between the reconstructed left and right otolith outline shapes. However, no significant differences in otolith shape were observed between males and females using either otolith side. In addition, otolith shape analysis using shape indices and elliptic Fourier analysis reliably supported the presence of three distinct stocks of T. mediterraneus. This study provides evidence supporting the recognition of multiple phenotypic stocks of T. mediterraneus.