Dark Stripes Research Articles

Characterizing approach behavior of Drosophila melanogaster in Buridan's paradigm.

The Buridan’s paradigm is a behavioral task designed for testing visuomotor responses or phototaxis in fruit fly Drosophila melanogaster. In the task, a wing-shortened fruit fly freely moves on a round platform surrounded by a 360° white screen with two vertical black stripes placed at 0° and 180°. A normal fly will tend to approach the stripes one at a time and move back and forth between them. A variety of tasks developed based on the Buridan’s paradigm were designed to test other cognitive functions such as visual spatial memory. Although the movement patterns and the behavioral preferences of the flies in the Buridan’s or similar tasks have been extensively studies a few decades ago, the protocol and experimental settings are markedly different from what are used today. We revisited the Buridan’s paradigm and systematically investigated the approach behavior of fruit flies under different stimulus settings. While early studies revealed an edge-fixation behavior for a wide stripe in the initial visuomotor responses, we did not discover such tendency in the Buridan’s paradigm when observing a longer-term behavior up to minutes, a memory-task relevant time scale. Instead, we observed robust negative photoaxis in which the flies approached the central part of the dark stripes of all sizes. In addition, we found that stripes of 20°-30° width yielded the best performance of approach. We further varied the luminance of the stripes and the background screen, and discovered that the performance depended on the luminance ratio between the stripes and the screen. Our study provided useful information for designing and optimizing the Buridan’s paradigm and other behavioral tasks that utilize the approach behavior.

A new species of Microcharacidium (Characiformes: Crenuchidae) from the Central Amazon, Brazil

A new species (Microcharacidium bombioides sp. nov.) of the genus Microcharacidium Buckup, 1993 is described from the Rio Negro, Rio Trombetas, Rio Tapajós, tributaries of the Rio Madeira, and the middle Rio Amazonas. The new species is promptly distinguished from all congeners (Microcharacidium eleotrioides (Géry, 1960), Microcharacidium gnomus Buckup, 1993, and Microcharacidium weitzmani Buckup, 1993) by the presence of 12 circumpeduncular scales, 19 precaudal vertebrae, and 7 dark bars on the flanks connected to their contralateral parts both dorsally and ventrally; 2 short, dark suborbital stripes; all teeth on both jaws conical; 10–11 total dorsal-fin rays; and 3–4 perforated lateral line scales. An updated identification key for the genus is provided and the affinities of the new species with other Microcharacidium are discussed.

Problems of phytoimmunity of grain crops in the Euro-Northeast of the Russian Federation and ways their solution

Breeding of grain crops for phytoimmunity in the FSBSU FASC of the Northeast is carried out in the conditions of natural and artificial epiphytotics. Every year, more than 1000 samples of winter rye, spring soft wheat, barley and oats of their own breeding and from the VIR collection are studied. In winter rye, studies are conducted on snow mold, root rot, powdery mildew, brown and stem rust, septoria blight, fusarium head blight, and ergot; in spring wheat – on root rot, septoria blight, fusarium head blight, powdery mildew, brown rust, loose smut; in barley – on root rot, net, dark brown blotch and stripe disease, loose smut; in oats - on red-brown blotch, root rot, crown rust, panicle fusarium and loose smut. Resistant samples detected on infectious backgrounds will be included in the breeding process as sources of the trait. With the participation of source genes, new varieties of winter rye were created, Snezhana, Grefinya, and others, which are being studied at different breeding stages. Long-term studies (2014-2020) on infectious and provocative backgrounds among the breeding material of the FASC of the Northeast and collection samples of spring soft wheat, oats, barley revealed sources of nonspecific resistance (6-9 points). They are used in crossbreeding programs with the best varieties to obtain high-yielding and resistant to biotic stressors hybrids that are being studied at different breeding stages.

A new Hyphessobrycon (Characiformes: Characidae) of the Hyphessobrycon heterorhabdus species-group from the lower Amazon basin, Brazil

ABSTRACT A new species of Hyphessobrycon belonging to the Hyphessobrycon heterorhabdus species-group from the lower rio Tapajós, state of Pará, Brazil, is described. The new species is allocated into the Hyphessobrycon heterorhabdus species-group due to its color pattern, composed by an anteriorly well-defined, horizontally elongated humeral blotch that becomes diffuse and blurred posteriorly, where it overlaps with a conspicuous midlateral dark stripe that becomes blurred towards the caudal peduncle and the presence, in living specimens, of a tricolored longitudinal pattern composed by a dorsal red or reddish longitudinal stripe, a middle iridescent, golden or silvery longitudinal stripe, and a more ventrally-lying longitudinal dark pattern composed by the humeral blotch and dark midlateral stripe. It can be distinguished from all other species of the group by possessing humeral blotch with a straight or slightly rounded ventral profile, lacking a ventral expansion present in all other species of the group. The new species is also distinguished from Hyphessobrycon heterorhabdus by a 9.6% genetic distance in the cytochrome c oxidase I gene. The little morphological distinction of the new species when compared with its most similar congener, H. heterorhabdus, indicates that the new species is one of the first truly cryptic fish species described from the Amazon basin.

Surface and electronic structure of antiferromagnetic axion insulator candidate EuIn<sub>2</sub>As<sub>2</sub>

The interplay between non-trivial band topology and magnetic order can induce exotic quantum phenomena, such as the quantum anomalous Hall effect and axion insulator state. A prevalent approach to realizing such topological states is either by magnetic doping or through heterostructure engineering, while the former will bring in inhomogeneity and the latter requires complex procedures. Intrinsic magnetic topological insulators are expected to avoid the aforementioned disadvantages, which is of great significance in both studying and practically using these exotic quantum phenomena. Recently, a Zintl compound EuIn<sub>2</sub>As<sub>2</sub> is predicted to be an intrinsic antiferromagnetic axion insulator. The bulk magnetic order of EuIn<sub>2</sub>As<sub>2</sub> has been reported in a lot of experiments, while the topological nature has not yet been confirmed. The surface properties of intrinsic magnetic topological insulators play an important role in the interplay between magnetic order and non-trivial surface state. Here in this work, we study the surface structure and electronic property of EuIn<sub>2</sub>As<sub>2</sub> single crystal by using scanning tunneling microscopy/spectroscopy (STM/S) and non-contact atomic force microscopy (NC-AFM). Considering the strength of bonds, the easy cleavage plane of the crystals possibly lies between In-In layers or between Eu-As layers. The STM topographies show that the cleaved surface is dominated by a striped pattern. And the dominated step height is an integer multiple of <i>c</i>/2, which implies that only one kind of cleavage plane is preferred. Atomic-resolved surface topographies show that the striped pattern is the <inline-formula><tex-math id="M2">\begin{document}$ 1\times 2 $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="18-20210783_M2.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="18-20210783_M2.png"/></alternatives></inline-formula> surface reconstruction with 50% coverage. Hence an In-terminated surface which will be 100% coverage is ruled out. The spatial evolution of STS near vacancies on the striped pattern shows a hole-doping feature. All of these results reveal that the striped pattern is the <inline-formula><tex-math id="M3">\begin{document}$ 1\times 2 $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="18-20210783_M3.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="18-20210783_M3.png"/></alternatives></inline-formula> surface reconstruction of the Eu terminated surface with 50% coverage. Using the STS, we measure the local densities of states on the striped surface at various temperatures. We find that there is an asymmetric valley-peak feature in the density of states near the Fermi energy at 4 K, which is gradually weakened with increasing temperature, and disappears above the antiferromagnetic Néel temperature, indicating that the asymmetric valley-peak feature is closely related to the antiferromagnetic order. Besides, a maze-like pattern is observed occasionally near some step edges. The STM topographies show atoms both on bright and dark stripes of the maze-like pattern, which form a whole hexagonal lattice. And the NC-AFM images show that the maze-like pattern is about 1 Å higher than the Eu terminated striped pattern. Based on these results, the maze-like pattern can be explained as the buckled Eu surface with 100% coverage. These results provide important information for understanding the surface electronic band structure and topological nature of EuIn<sub>2</sub>As<sub>2</sub>.

LED-ID detection and recognition method based on optical camera communication using discrete Fourier transform

Optical camera communication (OCC) traditionally uses the bright and dark stripes of a rolling shutter pattern captured by the complementary metal–oxide–semiconductor image sensor to realize communication. We assign a unique identification [LED’s unique identification (LED-ID)] to each LED and introduce an LED-ID detection and recognition method of OCC using discrete Fourier transform (DFT). It is different from the traditional LED modulation and demodulation method. In this approach, LED-IDs are modulated to possess different frequency characteristics instead of transmitting data. Taking the DFT of the rolling shutter pattern to obtain a spectrum image, we can recognize the LED-ID according to the characteristics of the spectrum image. The experiment results show that the proposed method has good performance, with at least 426 recognizable LED-IDs and a recognition distance reaching 3 m. Therefore, the proposed method can be considered as one of the effective methods for OCC.

A new species of Leucostethus (Anura: Dendrobatidae) from the Cordillera Mache-Chindul in northwestern Ecuador, with comments on similar Colostethus and Hyloxalus.

We describe a new species of dendrobatid frog, Leucostethus bilsa sp. nov., using molecular, morphological, and acoustic evidence. We also comment on the taxonomic status of four similar Hyloxalus and Colostethus. We provide an updated phylogeny of Leucostethus that corroborates previous hypotheses of relationships of nine species. Phylogenetic analysis using mitochondrial (i.e., 7095 bp of combined data from NADH1, NAHD2, cytochrome c oxidase I, cytochrome b and 12S-16S rRNA) and seven nuclear genes (i.e., 4739 bp) indicate a close relationship of L. bilsa to an undescribed species from Gorgona Island, Colombia, both of which apparently diverged in the Pliocene about 3 million years ago with about 6.25% (i.e., 146/2335 bp) differences for the section of 12S-16S mitochondrial fragment. Leucostethus bilsa is diurnal and riparian, characterized by distinctive bright mustard-yellow flash marks in the axillar and groin regions, posterior belly, and in the hindlimbs, the presence of dark gray lower labial stripe or marks, sexual dimorphism in ventral pattern, and by having male uniparental care. We describe its osteology and the male advertisement call, which is a series of peep notes. Osteological microCT images of representatives of each of the Colostethinae genera reveal a number of intriguing characters that may prove to be useful in phylogenetic studies. In terms of its distribution, Leucostethus bilsa is currently known only from a very small area within the Reserva Biológica Bilsa, located within the Cordillera Mache-Chindul in the Chocoan region of northwestern Ecuador, which was a Pliocene-Pleistocene refugium. This region is highly threatened with habitat degradation and remains as the last surviving refuge for a forest community known for a high proportion of endemic species of both flora and fauna.

A NEW CRYPTIC SPECIES OF THE GENUS Microhyla (AMPHIBIA: MICROHYLIDAE) FROM LANGBIAN PLATEAU, VIETNAM

An integrative taxonomic analysis combining molecular and morphological lines of evidence revealed a new cryptic species of the Microhyla achatina species group from the Langbian Plateau of southern Vietnam. The new species was previously confused with its recently described morphologically similar and sympatric sister species, M. pineticola. The new species can be distinguished from M. pineticola by the presence of a continuous dark stripe running from the posterior edge of its eye towards the groin (vs dark markings interrupted above the axilla), snout acuminate in lateral profile (vs rounded), belly colour pattern, and foot webbing. The new species is currently known only from Bidoup–Nui Ba National Park in Lam Dong Province, Langbian Plateau in southern Vietnam (at elevations of 1300–1600 m a.s.l). We suggest the new species to be considered as Near Threatened (NT) in the IUCN Red List. Our results emphasize that our understanding of the diversity of genus Microhyla is still far from complete, and provide further evidence for montane areas of southern Vietnam to be a centre of Microhyla species richness. Our study further underscores the urgent need for intensified integrative taxonomic research on Microhyla spp. in order to clarify the taxonomy of wide-ranging species complexes and to elaborate effective conservation measures.

Three new species of frogs of the genus Pristimantis (Anura, Strabomantidae) with a redefinition of the P. lacrimosus species group.

A new phylogeny for the Pristimantis lacrimosus species group is presented, its species content reviewed, and three new species described from the eastern slopes of the Ecuadorian Andes. Our phylogeny includes, for the first time, samples of P. aureolineatus, P. bromeliaceus, and P. lacrimosus. The morphology of hyperdistal subarticular tubercles is also assessed among 21 species of Pristimantis. The P. lacrimosus species group is composed of 36 species distributed in the Chocó, Guiana, and Amazon regions of tropical South America with a single species reaching Central America. Ancestral area reconstruction indicates that, despite its high diversity in the Amazon region, the P. lacrimosus group originated in the Pacific basin, Chocó region of Ecuador and Colombia. Pristimantis amaguanaesp. nov. is most closely related to P. bromeliaceus. It differs from P. bromeliaceus by being smaller, having transversal dark bands in the hindlimbs (absent or faint in P. bromeliaceus) and the absence of discoidal fold (present in P. bromeliaceus). Pristimantis nankintssp. nov. and P. romeroaesp. nov. are part of a clade of predominantly light-green frogs that includes P. acuminatus, P. enigmaticus, P. limoncochensis, and P. omeviridis. Pristimantis nankintssp. nov. and P. romeroaesp. nov. can be distinguished from all of them by the presence of a dark dorsolateral stripe that borders a light green band on a green background. Hyperdistal tubercles are present in all examined species of the P. lacrimosus species group and its sister clade. Species with hyperdistal tubercles are characterized by having relatively long terminal phalanges and narrow T-shaped expansion at the end of the terminal phalange. We discuss the phylogenetic distribution of these characters and their potential diagnostic significance.

Systematics of Calliophis intestinalis with the Resurrection of Calliophis nigrotaeniatus (Elapidae, Serpentes)

The red-bellied form of Calliophis intestinalis (Laurenti, 1768) sensu lato was originally reported from Pahang, west Malaysia. To determine the taxonomic status of this form, we examined the type specimens of Elaps sumatranus Lidth De Jeude, 1890, Calliophis intestinalis everetti (Boulenger, 1896), and Callophis furcatus var. nigrotaeniatus Peters, 1863. The results indicated that the red-bellied form of C. intestinalis should be named as Calliophis nigrotaeniatus comb. nov., whose valid species status was based on morphological and molecular analyses. We designate a lectotype and redescribe the species, which is genetically close to Calliophis bilineatus (Peters, 1881) from the Philippines, and is clearly distinguishable from other congeners by possessing a pair of gray or dark blue lateral stripes and by being bright red on the ventrum. Elaps sumatranus and C. i. everetti are relegated to subjective junior synonyms of C. nigrotaeniatus.

A new species of the Pareas monticola complex (Squamata: Serpentes: Pareidae) from Chin Mountains with additions to the Pareas fauna of Myanmar

ABSTRACT A review of the taxonomic status of Pareas monticola (Himalaya slug snake) based on morphological and molecular data revealed a new species from Myanmar. Pareas victorianus sp. nov. Vogel, Nguyen and Poyarkov from the Nat Ma Taung National Park in western Chin State is suggested to be a sister species to P. monticola sensu stricto, and can be separated from the latter by the absence of preoculars, by the subocular separating the eye from the labials, by seven keeled dorsal scale rows at midbody, by a lower number of ventrals (164) and by a lower number of subcaudals (58). Another new population from the Hkakabo Razi National Park in the northernmost part of Kachin State was previously confused with P. monticola, but can be differentiated from the latter and from Pareas victorianus sp. nov. by the presence of preoculars, by the number of ventrals (182) and subcaudals (71), by the absence of dark postorbital stripes, and by the lateral and ventral surfaces of the head with dense brown dusting; we herein refer to this population as Pareas sp. pending further molecular data confirming its taxonomic status. We also confirm the occurrence of P. monticola sensu stricto in Myanmar based on specimens from Kachin State and Sagaing Division. Furthermore, we discuss the actual distribution, genetic differentiation and taxonomic problems of P. monticola species complex. Our work brings the total number of species recognised within the genus Pareas to 20, of which nine species occur in Myanmar. An updated key for the Pareas species of Myanmar is provided. http://www.zoobank.org/urn:lsid:zoobank.org:pub:7591231C-475C-4F86-9376-BB48DA937D1A

A new species of Characidium (Characiformes: Crenuchidae) from the rio Madeira basin, Brazil.

This study describes Characidium nambiquara, a new species from the upper rio Guaporé, rio Madeira basin, Brazil. The new species differs from most congeners by the presence of isthmus and area between the contralateral pectoral-fin bases completely naked. From congeners with some degree of scaleless ventral surface of the body C. nambiquara differs by having 10 circumpeduncular scales. The new species is also distinguished from congeners by the spotted colour pattern on body of the large-sized specimens and by having black dashes on all fins and conspicuous midlateral longitudinal dark stripe or conspicuous vertical bars absent. Characidium nambiquara further differs from most congeners by the presence of 34-36 pored scales on the lateral line, 3 horizontal scale rows above the lateral line and 3 horizontal scale rows from the lateral line to the midventral scale series. Remarks on intraspecific colour variation within the genus, not related to sexual dimorphism, are also provided.

A new Hyphessobrycon (Characiformes: Characidae) of the Hyphessobrycon heterorhabdus species-group from the Central Amazon basin, Brazil.

A new species of Hyphessobrycon Durbin from the Paraná do Urariá system in Central Amazon region, Amazonas state, Brazil, is described. The new species is allocated into the Hyphessobrycon heterorhabdus species-group due to its color pattern, composed by a well-defined, horizontally elongated humeral blotch continuous with a conspicuous midlateral dark stripe that becomes blurred towards the caudal peduncle, and can be distinguished from all other species of the group by possessing humeral blotch and continuous midlateral stripe broad, occupying vertical height equivalent of two scale rows. A tricolored pattern composed dorsally by a red or reddish longitudinal stripe, a middle iridescent, golden or silvery longitudinal stripe, and ventrally by a variably-developed longitudinal dark stripe is identified as a putative additional character shared by the species of the Hyphessobrycon heterorhabdus species-group. The presence of bony hooks in all fins in mature males of some species of the Hyphessobrycon heterorhabdus species-group is also discussed.

Taxonomic study of Moenkhausia cotinho Eigenmann, 1908 and Hemigrammus newboldi (Fernández-Yépez, 1949) with the description of two new speciesof Moenkhausia (Teleostei: Characiformes: Characidae).

Moenkhausia cotinho is redescribed based on the examination of meristic and morphometric data and external morphological characters of specimens from the Amazon and Orinoco basins and from rivers in the Guyana. The species is distinguished from congeners based on the combination of a reticulate color pattern, the presence of dark spots on the posterior edge of scales of the longitudinal rows dorsal to the lateral line, the presence of a dark blotch on the caudal-fin base failing to reach the posterior tip of the middle caudal-fin rays; the dorsal region of the eyes red to orange in life; 5/3 longitudinal series of scales, above and below the lateral line, respectively; and the tips of the pectoral-fin rays not extending beyond the base of the pelvic fin. All specimens of M. cotinho have a completely pored literal line except for a few specimens from drainages in the Guyana. The redefinition of the taxonomic limits and geographic distribution of M. cotinho allowed us to reevaluate the taxonomic limits and geographic distribution of Hemigrammus newboldi, the identity of which has been previously questioned, but which is clearly diagnosed from M. cotinho based on the relatively longer pectoral fin, the presence of conical teeth in the posterior portion of the dentary, the absence of a reticulate color pattern of body and in the shorter longitudinal dark stripe on body. In addition, two new species of Moenkhausia are described: Moenkhausia rondoni sp n. from the rio Madeira basin, Brazil and Moenkhausia pirahan sp n. from the lower rio Madeira and rio Trombetas and rio Tapajós basins, Brazil.

Decoding scheme based on CNN for mobile optical camera communication

A decoding scheme based on a convolution neural network (CNN) is proposed and experimentally demonstrated in mobile optical camera communication (OCC). The CNN can be used to extract features between bright and dark stripes in images effectively. Thus, it can alleviate the stripe distortion in the mobile environment and reduce bit error rates (BERs) by using the proposed decoding scheme based on CNN. A controllable lateral and vertical mobile platform is built to simulate the mobile scenarios with different moving speeds (40-80 cm/s). The experimental results show that, at the moving speed of 80 cm/s, the proposed scheme based on CNN can achieve the BERs of 3.8×10-5 at the lateral case and 1×10-5 at the vertical case in a mobile OCC system.

A new species of Hemiphyllodactylus (Squamata: Gekkonidae) from Tuyen Quang Province, Vietnam.

A new species of the gekkonid genus Hemiphyllodactylus is described from limestone karst forest of Tuyen Quang Province, northern Vietnam based on morphological differences and molecular divergence. Hemiphyllodactylus nahangensis sp. nov. is distinguished from the remaining congeners by having the unique combination of the following characters: a bisexual taxon; SVL of adults 41.4-43.6 mm; dorsal scale rows 18-23; ventral scale rows 9-13; chin scales bordering mental and first infralabial distinctly enlarged; 22-24 pore-bearing femoral and precloacal scales, in a continuous row, absent in females; digital lamella formula 3-4-5-4 (forefoot) and 4-5-5-5 (hindfoot); cloacal spur single, present in both sexes; dark lateral head stripe indistinct; postsacral mark cream and bearing anteriorly projecting arms. In phylogenetic analyses, the new species is placed in a clade that includes H. dushanensis, H. hongkongensis, H. huishuiensis, H. ngocsonensis and H. zugi. In terms of pairwise genetic distance, the new species is at least 5.9%-6.6% divergent from other congeners based on a fragment of the mitochondrial gene ND2.

Transverse dynamics of vector solitons in defocusing nonlocal media

The transverse instability of line solitons of a multicomponent nonlocal defocusing nonlinear Schrodinger (NLS) system is utilized to construct lump and vortex-like structures in 2D nonlocal media, such as nematic liquid crystals. These line solitons are found by means of a perturbation expansion technique, which reduces the nonintegrable vector NLS model to a completely integrable scalar one, namely to a Kadomtsev–Petviashvili equation. It is shown that dark or antidark soliton stripes, as well as dark lumps, are possible depending on the strength of nonlocality: dark (antidark) solitons are formed for weaker (stronger) nonlocality, relatively to a threshold that is analytically determined in terms of the parameters of the system and the continuous-wave amplitude. Direct numerical simulations are used to show that dark lump-like- and vortex-like-structures can spontaneously be formed as a result of the transverse instability of the dark soliton stripes.

Hexagonal iron nitride monolayer on Cu(001): Zigzag-line-in-trough alignment

Strong interaction between metal atoms and adsorbates sometimes leads to the formation of surface compounds. In such cases, the registry with a metal substrate plays a key role in determining the overlayer stability. In this paper, we present a structural model for a hexagonal Fe-N monolayer grown on a square Cu(001) substrate. The system exhibits a stripe pattern composed of dark (1 × 1) stripes (A-stripes) and bright (3×3) stripes (B-stripes). We suppose the FeN stoichiometry and the structure similar to a single (111) layer of zincblende type γ″-FeN. Based on protrusion alignment observed by scanning tunneling microscopy (STM), we propose that the A-stripe has a relaxed hexagonal lattice composed of equilateral Fe triangles with N atoms at the center whereas the B-stripe has a uniaxially-compressed lattice composed of isosceles Fe triangles. Connection of these two lattice with small inclination produces zigzag Fe-atom rows embedded in [110] troughs on the Cu(001) substrate. Thus, the FeN overlayer is commensurate with Cu(001) along the [1¯10] direction. The (3×3) reconstruction in B-stripes effectively relieves the compressive stress. Our model shows the way in which a stable overlayer exists on the substrate of different symmetry and lattice constants by forming a stripe pattern.

Systematic reappraisal of the anti-equatorial fish genus Microcanthus Swainson (Teleostei: Microcanthidae), with redescription and resurrection of Microcanthus joyceae Whitley.

The taxonomy and classification of the microcanthid fish genus Microcanthus Swainson has been a subject of contention dating back to the 19th century. Its allopatric, disjunct anti-equatorial distribution across the Indo-West Pacific has resulted in the recognition of several nominal taxa, though these have been widely regarded as synonyms of Microcanthus strigatus (Cuvier). Following the results published in a companion study elsewhere by the authors, the taxonomy of Microcanthus and the validity of these nominal synonyms are herewith revised. Microcanthus strigatus is redescribed on the basis of 66 specimens from East Asia, Hawaii and Western Australia, and M. joyceae is resurrected and redescribed on the basis of 25 specimens from eastern Australia and the southwest Pacific. Microcanthus differs from other microcanthid genera in having the following combination of characters: dorsal-fin rays XI,15-17 (usually XI,16); anal-fin rays III,13-15 (usually III,14); pectoral-fin rays 15-17 (usually 16); scales ctenoid with ctenial bases present; lateral-line scales partially or heavily obscured by adjacent scales; and body pale in preservation with five horizontal dark stripes reaching the posterior edges of dorsal and anal fins, and base of caudal fin. The review is accompanied by a key to the genera of Microcanthidae.

Measuring the Topological Charge of Optical Vortices Using Elliptical Airy Phase Mask

Measuring the topological charge(TC) of optical vortices is of great importance in applications of vortex beams. A flexible and convenient method to determine the TC of an optical vortex is proposed by using an elliptical airy phase mask (EAPM). The mask can be embedded into a typical vortex generation setup, in which no additional optical elements are required. The number and the sign of TC are respectively obtained by analyzing the number and the direction of dark stripes in the far-field diffraction patterns of the vortex beam companied with EAPM. It is experimentally demonstrated that this method is able to measure TCs of both conventional and perfect vortex up to ±120.