Number Of Lamellae Research Articles

Small angle X-ray scattering from finite sequence of lamellar stacks of crystalline polymers

An analysis method using small-angle X-ray scattering (SAXS) of the lamellar stacks of crystalline polymers was examined. The scattering profile was expressed by a fitting function on the basis of a paracrystalline stacking model of finite sequence of parallel lamellae in a stack with border zones continuously connecting to the mean density in spherulites. The SAXS pattern of poly(butylene terephthalate) was able to be fitted to both the conventional model with infinite number of parallel lamellae in a stack and the present model with finite number. The SAXS pattern of polyethylene could not be fitted by the conventional model supposing an infinite sequence, and it was necessary to suppose a lower finite number; the best fit result was obtained with two crystalline layers. A lower number of parallel lamellae in a stack is consistent with the fact that polyethylene lamellar crystals are twisted in three-dimensional space, and cannot form an infinite sequence of simple stacked structure of lamellae oriented parallel to each other. For the finite sequence with lower number, the determination of crystalline lamellar thickness requires the consideration of border zones. It was also confirmed that an alternative method using triangular shape of a one-dimensional auto-correlation function could be acceptable with better level of agreement for narrower distributions of thickness.

A new species of Odontostilbe cope (Characiformes: Cheirodontinae) from rio Madeira basin diagnosed based on morphological and molecular data.

A new species of Odontostilbe is described from the rio Jaciparaná, rio Madeira basin, Rondônia, Brazil. Odontostilbe pacaasnovos differs from all its congeners, except O. pequira, by the colour pattern. Additionally, it differs from its congeners by the terminal mouth, number of cusps in the teeth of the premaxilla (5-7), number of branched rays in the anal fin (19-22), by the shape of dentary teeth (5-7 cusps with central cusp larger and longer than laterals cusps) and by the number of lamellae of the olfactory rosette (17-18 in male and 14 in female). Morphological and molecular comparisons corroborate the distinctiveness between O. pacaasnovos and its congeners, justifying its recognition as a new species.

A brain and a head for a different habitat: Size variation in four morphs of Arctic charr (Salvelinus alpinus (L.)) in a deep oligotrophic lake.

Adaptive radiation is the diversification of species to different ecological niches and has repeatedly occurred in different salmonid fish of postglacial lakes. In Lake Tinnsjøen, one of the largest and deepest lakes in Norway, the salmonid fish, Arctic charr (Salvelinus alpinus (L.)), has likely radiated within 9,700 years after deglaciation into ecologically and genetically segregated Piscivore, Planktivore, Dwarf, and Abyssal morphs in the pelagial, littoral, shallow‐moderate profundal, and deep‐profundal habitats. We compared trait variation in the size of the head, the eye and olfactory organs, as well as the volumes of five brain regions of these four Arctic charr morphs. We hypothesised that specific habitat characteristics have promoted divergent body, head, and brain sizes related to utilized depth differing in environmental constraints (e.g., light, oxygen, pressure, temperature, and food quality). The most important ecomorphological variables differentiating morphs were eye area, habitat, and number of lamellae. The Abyssal morph living in the deepest areas of the lake had the smallest brain region volumes, head, and eye size. Comparing the olfactory bulb with the optic tectum in size, it was larger in the Abyssal morph than in the Piscivore morph. The Piscivore and Planktivore morphs that use more illuminated habitats have the largest optic tectum volume, followed by the Dwarf. The observed differences in body size and sensory capacities in terms of vision and olfaction in shallow and deepwater morphs likely relates to foraging and mating habitats in Lake Tinnsjøen. Further seasonal and experimental studies of brain volume in polymorphic species are needed to test the role of plasticity and adaptive evolution behind the observed differences.

Towards understanding plastic deformation in hardmetal turning inserts with different binders

This works investigates the deformation of coated hardmetal turning inserts used until the end of life. Three hardmetals with different binder phases, pure cobalt, 15 wt% iron 85 wt% nickel and 85 wt% iron 15 wt% nickel are tested. It is shown that grain boundary sliding accommodated by formation of binder phase lamellae is present in all tested inserts, given by a clear increase in number of lamellae in the microstructure of a tested cutting edge compared to a pristine cutting edge of the same material. The lamellae formation is discussed and can be explained by the stresses experienced by the cutting edge during turning. In addition the importance of good coating adhesion was shown by formation of cavities in inserts that experienced flaking of the coating.

Effect of the transgenerational exposure to elevated CO2 on low temperature tolerance of winter wheat: Chloroplast ultrastructure and carbohydrate metabolism

AbstractThe transgenerational effect of elevated atmospheric CO2 concentration (e[CO2]) on low temperature response in wheat is still little investigated, through the interaction of e[CO2], and low‐temperature stress has been reported in a single generation. Here, the low temperature‐induced modifications of chloroplast ultrastructure and carbohydrate metabolism in wheat after four generations continuously grown under ambient CO2 concentration (a[CO2]) and e[CO2] (2014–2018) were investigated. The results indicated that the transgenerational exposure to e[CO2] increased the number of grana lamellae and the amounts of osmiophilic lipid droplets, attenuating the negative effect of low temperature on chloroplast ultrastructure. The transgenerational e[CO2] enhanced the activities of antioxidant enzymes (i.e. SOD, POD and CAT) and concentrations of osmotic substances (i.e. proline and soluble sugar), which alleviated the low temperature‐induced oxidative damage to the chloroplast ultrastructure. In addition, transgenerational exposure of wheat to e[CO2] increased activities of vacInv and cwInv, while decreased fructokinase activity, which affected the sucrose metabolism in wheat leaf. These findings elucidated that transgenerational exposure to e[CO2] could improve low temperature tolerance of winter wheat, which provide novel insights to the response of wheat to future climate change.

Cyclic Hypoxia Exposure Accelerates the Progression of Amoebic Gill Disease

Amoebic gill disease (AGD), caused by the amoeba Neoparamoeba perurans, has led to considerable economic losses in every major Atlantic salmon producing country, and is increasing in frequency. The most serious infections occur during summer and autumn, when temperatures are high and poor dissolved oxygen (DO) conditions are most common. Here, we tested if exposure to cyclic hypoxia at DO saturations of 40–60% altered the course of infection with N. perurans compared to normoxic controls maintained at ≥90% DO saturation. Although hypoxia exposure did not increase initial susceptibility to N. perurans, it accelerated progression of the disease. By 7 days post-inoculation, amoeba counts estimated from qPCR analysis were 1.7 times higher in the hypoxic treatment than in normoxic controls, and cumulative mortalities were twice as high (16 ± 4% and 8 ± 2%), respectively. At 10 days post-inoculation, however, there were no differences between amoeba counts in the hypoxic and normoxic treatments, nor in the percentage of filaments with AGD lesions (control = 74 ± 2.8%, hypoxic = 69 ± 3.3%), or number of lamellae per lesion (control = 30 ± 0.9%, hypoxic = 27.9 ± 0.9%) as determined by histological examination. Cumulative mortalities at the termination of the experiment were similarly high in both treatments (hypoxic = 60 ± 2%, normoxic = 53 ± 11%). These results reveal that exposure to cyclic hypoxia in a diel pattern, equivalent to what salmon are exposed to in marine aquaculture cages, accelerated the progression of AGD in post-smolts.

Pore Network Investigation of Gas Trapping and Mobility During Foam Propagation Using Invasion Percolation with Memory

Foam reduces the gas mobility in porous media both by increasing the effective viscosity of the gas phase and by trapping a large portion of the gas in place. This reduction is directly related to the number density of lamellae in the gas phase. Therefore, understanding the pore-level events associated with lamella generation and destruction processes and investigating the trapped foam behavior are of great importance in modeling foam mobility. In this paper, a pore network model based on the statistical physics method of invasion percolation with memory (IPM) is developed to simulate foam propagation as a drainage process of gas invasion into a porous media initially saturated with a surfactant solution. During this process, lamella generation, destruction, and mobilization are involved. This study sets out to explore the roles of pore level events that lead to foam destruction. To do so, static lamella destruction by capillary suction at the plateau borders is modeled using the Reynolds equation for film thinning and lamella rupture is assumed to occur when the film thickness falls below a certain critical thickness (hfc) at which the maximum disjoining pressure (Πmax) is attained. This mechanism is incorporated in the pore network model to which we add a notional time dependency of the invasion percolation with memory mechanism. Flowing lamellae are assumed to rupture at a fixed limiting capillary pressure (Pcap ) lower than Πmax. Results show that a critical regeneration probability (freg ) is required for the generation of strong foam in the network. The mobilization pressure gradient depends on both the number of lamellae in the flow path and the sizes of the throats that make up of this path. At the same freg, the mobilization pressure gradient markedly decreases after incorporating lamella destruction mechanism. The structure of the displacement pattern of the invading phase at breakthrough changes under the competition between capillary and yield stress-like forces. During transient foam displacement, gas saturation increases, and foam texture becomes finer with increasing freg. The flowing foam fraction increases much more slowly with pressure gradient after accounting for the viscous friction associated with the flow in the already open paths. Comparison with experiments shows that current pore network model can capture the main features of the transient foam flow in porous media.

A new large-bodied, rupicolous Cnemaspis Strauch, 1887 (Squamata: Gekkonidae) allied to Cnemaspis heteropholis Bauer, 2002 from the Central Western Ghats of Karnataka, India.

We describe a new large-bodied, rupicolous Cnemaspis from near Sakleshpur in the Central Western Ghats of Karnataka, India. Cnemaspis magnifica sp. nov. is allied to C. heteropholis and can be diagnosed from all other Indian Cnemaspis by the absence of spine-like scales on flank; heterogeneous dorsal pholidosis, presence of only femoral pores in males, homogenous dorsal pholidosis of tail with small, smooth, regularly arranged, flattened, subimbricate scales, without whorls of enlarged tubercles, median row of sub-caudals enlarged and smooth. The new species differs from its closest congener C. heteropholis in body size, the number of longitudinal ventral scales, number of lamellae under digit I and IV of manus and pes, and subtle colour pattern differences; besides 9.1 % uncorrected ND2 sequence divergence. We provide the first description of topotypic male of C. heteropholis along with data on its distribution and natural history. The discovery of Cnemaspis magnifica sp. nov. with minimal field survey effort indicates the need for further herpetological exploration in the region.

Structure-rheological properties relationships in model drilling fluids formulated in aqueous solutions of carrageenan with varying chemical structures

Water-based drilling fluids (WDF) formulated with hybrid carrageenans (HY) recently showed attractive rheological and filtration properties, but the role of HY chemical structure on such WDF characteristics could not be established. Here, model drilling fluids were prepared by suspending sodium activated bentonite in two HY aqueous solutions, in order to assess relationships between the polysaccharide chemistry and the rheological-structural properties of the fluids. The rheological analysis of HY solutions indicates that the more sulfated HY is in coil conformation, whereas the other forms helices. The less sulfated HY promotes the slow build-up of a more elastic bentonite gel showing a larger yield stress, due to a less flocculated structure. A similar microscopic structure is achieved with the more sulfated HY, but a weaker gel is formed. In this suspension, the strain hardening behavior indicates that elasticity is ruled by flocs internal structure. Wide angle X-ray diffraction suggests that the weaker bentonite floc elasticity is related with a smaller number of bentonite lamellae in the aggregating stacks within the flocs. Overall, the set of results suggests that the carrageenan chemistry modulates the gel viscoelasticity by tuning the bentonite suspension structure at different length scales, from inter bentonite stacks to inter flocs distances.

A new species of Lobulia (Squamata: Scincidae) from Papua New Guinea.

I describe a new skink of the genus Lobulia from Mt. Simpson in southeasternmost New Guinea. This species differs from all other members of the genus in having only three pairs of enlarged chin shields and only the first pair in medial contact. It is most similar in scalation to L. elegans but is readily distinguished from that species by its color pattern, body size and shape, and numbers of lamellae. Morphological data on L. elegans have not been reported since the description of the holotype in 1897, so I provide a redescription of that species based on six specimens-including the holotype-of certain conspecificity and from within approximately 100 km of the type locality at Mt. Victoria. I also elevate Lygosoma elegantoides lobulus from synonymy with Lobulia elegans, from which it is readily distinguished on the basis of scalational and color-pattern features. The resurrected L. lobulus and the new species from Mt. Simpson represent the seventh and eighth recognized species of Lobulia, and the Mt. Simpson species is the fifth member of the Papuan herpetofauna that is apparently endemic to Mt. Simpson. Mt. Simpson appears to be a moderate center of local endemism within southeastern New Guinea.

Acanthosaura aurantiacrista (Squamata: Agamidae), a new long horn lizard from northern Thailand.

BackgroundIn Thailand, five species of Acanthosaura have been recorded so far, including Acanthosaura armata from the southern region, A. cardamomensis from the eastern region, A. crucigera from the western region, A. lepidogaster from the northern region and A. phuketensis from the Phuket Island and south-western region. However, comprehensive studies of diversity patterns and distribution of Acanthosaura are still lacking in some areas and need further information for designating areas of special conservation importance and nature protection planning in Thailand.New informationAcanthosaura aurantiacrista is a new species of long-horned lizard of the genus Acanthosaura from northern Thailand. It is distinguished from all other species of Acanthosaura by a dagger-like nuchal spine with yellowish-orange colouration in females, bright yellow colouration in males and a combination of other morphological characters: a greater tail length to snout-vent length ratio; a larger postorbital spine, nuchal spine, dorsal spine and occipital spine compared to its head length; a smaller diastema to snout-vent length ratio; a greater number of subdigital lamellae on the fourth finger and fourth toe; and a larger gular pouch than other Acanthosaura species. Analysis of mitochondrial ND2 gene sequences revealed a sister clade between the A. aurantiacrista lineage and the A. crucigera lineage with a 100% probability of divergence, according to Bayesian analysis and strong support value for Maximum Likelihood analysis. The pairwise distance ranged from 13.8-15.0% between A. aurantiacrista and A. cardamomensis, 10.9-14.5% between A. aurantiacrista and A. crucigera and 0-1.2% amongst A. aurantiacrista populations. The discovery of this lizard increases the known endemic herpetological diversity and underscores the importance of conservation in the mountain rainforest region of northern Thailand.

Aging-related histomorphometric changes in cortical bone tissue of bottlenose dolphins (Tursiops truncatus)

Morphological characteristics of bones have shaped as a result of adaptation to life in the aquatic environment and whale diving habits. This study deals with the postnatal bone development and microscopic characteristics of bones of bottlenose dolphins (Tursiops truncatus). Bone sections of the right humerus and the fifth right rib of 106 dolphins aged less than 1–21 years were used to determine the density of the primary, secondary and remodelling osteons, the magnitude of the area occupied by the osteons, and the number of osteon lamellae. Bone sections were analysed using a compound microscope with standard and polarized light. Our study showed the primary osteons of bones to occupy a smaller area than the secondary ones. The secondary osteon area in the humerus is significantly larger than that in the rib. All rib osteons are significantly denser than those of the humerus. In both bones, the number of osteon lamellae is higher in secondary than in primary osteons. The number of secondary and remodelling osteons and the areas occupied by them increase with age, as opposed to primary osteons in which a decrease was noted. The number of lamellae in primary osteons decreases with age, while in secondary osteons their number increases. Within the study frame, morphometric osteon values of the bottlenose dolphin were determined, to the best of our knowledge, for the first time ever as concerns the aquatic mammals.

Combined Morpho-Chemical Profiling of Individual Extracellular Vesicles and Functional Nanoparticles without Labels.

Biological nanoparticles are important targets of study, yet their small size and tendency to aggregate makes their heterogeneity difficult to profile on a truly single-particle basis. Here we present a label-free system called 'Raman-enabled nanoparticle trapping analysis' (R-NTA) that optically traps individual nanoparticles, records Raman spectra and tracks particle motion to identify chemical composition, size, and refractive index. R-NTA has the unique capacity to characterize aggregation status and absolute chemical concentration at the single-particle level. We validate the method on NIST standards and liposomes, demonstrating that R-NTA can accurately characterize size and chemical heterogeneity, including determining combined morpho-chemical properties such as the number of lamellae in individual liposomes. Applied to extracellular vesicles (EVs), we find distinct differences between EVs from cancerous and noncancerous cells, and that knockdown of the TRPP2 ion channel, which is pathologically highly expressed in laryngeal cancer cells, leads the EVs to more closely resemble EVs from normal epithelial cells. Intriguingly, the differences in EV content are found in small subpopulations of EVs, highlighting the importance of single-particle measurements. These experiments demonstrate the power of the R-NTA system to measure and characterize the morpho-chemical heterogeneity of bionanoparticles.

Effects of temperature on the growth and microstructure formation of cuttlebone from cuttlefish Sepia pharaonis

ABSTRACTThis study investigated the effects of three temperatures (20°C, 27°C, and 31°C) on the physiological performance (survival and growth) and cuttlebone micromorphological features (chamber number, chamber height and lamellae number) of cuttlefish Sepia pharaonis. We examined gross morphological characteristics of the internal calcareous cuttlebone to determine whether lamellar matrix was impacted by temperature. Juvenile survival was significantly affected by temperature (χ2 = 54.580, df = 2, P < 0.001). Cuttlebone weight, length and width were also positively correlated with temperature. Scanning electron microscopy revealed that a single chamber structure consists of septa, lamellae and pillars. At 20°C the chamber number of 89.0 ± 10.8 was significantly higher than at 27°C with 44.8 ± 3.6 or 31°C with 47.5 ± 4.3 (Kruskal–Wallis [KW], χ2 = 26.391, df = 2, P = 0.0001), whilst chamber height was lower at 20°C (KW χ2 = 27.842, df = 2, P = 0.0001). Moreover, lamellae number varied among the treatments (KW χ2 = 22.411, df = 2, P = 0.0002). Lamellae numbers at 20°C, 27°C and 31°C were 3–6, 6–9 and 5–8, respectively. The results indicated that the intrinsic lamellar matrix structure was significantly affected by temperature and that this effect may be used in cuttlebone growth studies.

Morphogenesis of Olfactory Organ of Bushymouth Catfish Ancistrus dolichopterus (Teleostei: Loricariidae) before Switching to Exogenous Feeding.

Olfaction plays an important role in a fish's life. Its value may differ at different developmental stages, depending on the feeding style of the species. The goal of the present study was to investigate the olfactory organ of a species that feeds mainly on algae- the bushymouth catfish, Ancistrus dolichopterus-at developmental stages from olfactory placode to the definitive olfactory chamber. For this study, we used light and electron (scanning) microscopy. The topography of the olfactory placode of A. dolichopterus is typical for teleostei. Formation of olfactory pit takes place at the same time as rostral elevation formation. Rostral elevation participates in the formation of the nasal bridge and anterior tubular nostril. It was found out that the anlage of olfactory rosette in A. dolichopterus arises earlier than in most teleostei. However, the number of lamellae does not increase until switching to exogenous feeding. We suppose that the early development of olfactory organ is necessary for intraspecific communication, not just for finding food.

Synthesis of polyacrylonitrile nanoflowers and their controlled pH-sensitive drug release behavior.

A novel controlled drug release system based on pH sensitive polyacrylonitrile (PAN) nanoflowers in different kinds of solvents was successfully prepared with azobisisobutyronitrile (AIBN) as the initiator and without any emulsifier or stabilizer by a one step static polymerization method. The composition and structure of the PAN nanoflowers were analyzed by FTIR, XRD, SEM, TEM, and laser particle size analysis. The polymer particles consisted of a number of lamellae, with a sheet thickness of about 10 nm, and were similar to the shape of flowers with a particle diameter of about 350 nm. The mechanism of the polymerization reaction and the formation were studied. Moreover, the effects of monomer ratio, initiator concentration, reaction time, dispersion medium and co-monomer on the morphology and particle size of the nanoflowers were also discussed. A relatively large specific surface area was formed during the formation of the nanoflowers, which favored drug adsorption. The results of the in vitro experiments revealed that PAN(TBP) nanoflowers, containing BSA in buffer solution of pH 7.4, demonstrated good sustained-release and the cumulative release rate was about 83% after 260 h. The results also showed that the sustained-release from the PAN(TBP) nanoflowers best fitted the Riger-Peppas model. This study indicated that PAN(TBP) nanoflowers provided a theoretical base for the development of carriers for sustainable drug-release.

Mechanisms of formation of the structure of welded joints, performed by friction stir welding

The analysis of welded joints of structural materials is carried out. As a result of this, in addition to the traditionally formed zone of thermal influence (HAZ), a zone of thermal deformation influence is formed in the near-seam zone, located between the welded nugget and the HAZ. The welded nugget joints in FSW is formed in the regime of structural superplasticity (SP). The structure of the welded nugget has a sheared band structure in the form of an "onion pattern" consisting of a large number of lamellas forming shear bands under the influence of a movable welding tool. The attainment of the superplastic state (SPS) during the formation of the welded nugget is ensured by the stepwise flow of various mechanisms of plastic deformation in the regime of simple, collective, anomalous dynamic recrystallization, prepared by dynamic return processes, polygonization with transition to postdynamic recrystallization by the mechanisms of Bailey- Hirsch, Kahn-Burgers-Taylor. For the group of metals and alloys with polyformism (high-alloy steels of different structural classes, Ti- alloys), SPS is supported additionally by recrystallization by twinning (copper, austenitic steel and other structural classes, Ti and its alloys) and as a result of phase transformations of alpha-gamma or alpha-beta phases).

Mechanical and structural changes in human thoracic aortas with age

Aortic mechanical and structural characteristics have profound effects on pathophysiology, but many aspects of physiologic stress-stretch state and intramural changes due to aging remain poorly understood in human tissues. While difficult to assess in vivo due to residual stresses and pre-stretch, physiologic stress-stretch characteristics can be calculated using experimentally-measured mechanical properties and constitutive modeling. Mechanical properties of 76 human descending thoracic aortas (TA) from 13 to 78-year-old donors (mean age 51±18 years) were measured using multi-ratio planar biaxial extension. Constitutive parameters were derived for aortas in 7 age groups, and the physiologic stress-stretch state was calculated. Intramural characteristics were quantified from histological images and related to aortic morphometry and mechanics. TA stiffness increased with age, and aortas became more nonlinear and anisotropic. Systolic and diastolic elastic energy available for pulsation decreased with age from 30 to 8 kPa and from 18 to 5 kPa, respectively. Cardiac cycle circumferential stretch dropped from 1.14 to 1.04, and circumferential and longitudinal physiologic stresses decreased with age from 90 to 72 kPa and from 90 to 17 kPa, respectively. Aortic wall thickness and radii increased with age, while the density of elastin in the tunica media decreased. The number of elastic lamellae and circumferential physiologic stress per lamellae unit remained constant with age at 102±10 and 0.85±0.04 kPa, respectively. Characterization of mechanical, physiological, and structural features in human aortas of different ages can help understand aortic pathology, inform the development of animal models that simulate human aging, and assist with designing devices for open and endovascular aortic repairs. Statement of significanceThis manuscript describes mechanical and structural changes occurring in human thoracic aortas with age, and presents material parameters for 4 commonly used constitutive models. Presented data can help better understand aortic pathology, inform the development of animal models that simulate human aging, and assist with designing devices for open and endovascular aortic repairs.

A REVIEW ON PHYSICO-CHEMICAL PARAMETERS OF LIPOSOMAL DOXORUBICIN

The development of a generic liposomal doxorubicin product requires the study of critical physicochemical properties of the formulation. Food and Drug Administration (FDA) draft guideline has suggested few parameters to be tested for in vitro bioequivalence study which include liposomal composition, state of encapsulated drug, internal environment, liposomal morphology and number of lamellae, lipid bilayer phase transition, liposomal size distribution, grafted Polyethylene Glycol (PEG) at liposomal surface, electric surface potential or charge and in vitro leakage under multiple conditions. Characteristic features of components of liposomal doxorubicin formulation and detail of parameters to be studied have been discussed. This review compile specific, current and historical research outcomes on in vitro analysis of liposomal doxorubicin and highlights the important features that have a critical impact on properties of liposomal doxorubicin formulation. It will provide a better insight to the generic manufacturers and will help them to identify the critical quality attributes during the formulation development phase.

On a remarkable sexual dimorphic trait in the Characiformes related to the olfactory organ and description of a new miniature species of Tyttobrycon Géry (Characiformes: Characidae).

Among the order Characiformes, secondary sexual dimorphism is commonly associated to the occurrence of bony hooks on fins, shape and length of the dorsal and anal fins, and sexual dichromatism. The analysis of a new miniature Characidae species of the genus Tyttobrycon, described herein, yielded to the discovery of a sexually dimorphic trait related to nostril aperture and number of olfactory lamellae. In this type of dimorphism, mature males present larger nostril aperture and higher number of olfactory lamella than females. A dimorphic olfactory organ is for the first time recorded and described for a member of the Characiformes. Gross morphology and development of brain and peripheral olfactory organ of Tyttobrycon sp. n. are described and compared to other species of Characidae. It is hypothesized that such dimorphic trait is related to male-male detection during cohort competition in small characids. The new species of Tyttobrycon is diagnosed from its congeners by the number of branched anal-fin rays (19–21) and the absence of a caudal-peduncle blotch. It occurs in a small tributary of Rio Madeira basin, near to the limit between Brazil and Bolivia, Acre State, Brazil.