In the present study two new species of Tetragonocephalum Shipley et Hornell, 1905, T. mackenziei sp. n. and T. kazemii sp. n., are described from the spiral intestine of the cowtail stingray, Pastinachus sephen (Forsskål), from the northern coast of the Gulf of Oman. Tetragonocephalum mackenziei is distinguished from the 16 other valid species of Tetragonocephalum by a unique combination of characteristics, i.e. sperm-filled seminal receptacle in immature proglottids, body length (7.7-17.5 mm), body width (213-288 µm), number of proglottids (34-49), number of testes (10-14), size of scolex (228-315 µm × 213-288 µm) and size of acetabula (56-73 µm × 61-75 µm). Tetragonocephalum kazemii is morphologically distinguishable from its valid congeners and T. mackenziei based on a combination of characteristics, including body length (28.8-36.6 mm), number of proglottids (50-65), number of testes (30-42), size of scolex (388-564 µm × 326-448 µm), size of acetabula (62-86 µm × 57-90 µm) and testes (25-39 × 21-32). This brings the total number of validly described species of Tetragonocephalum to 18 and expands our knowledge of this diverse genus to now include the Gulf of Oman, as well as Arafura Sea, northern Indian Ocean and western Pacific Ocean., Atabak Roohi Aminjan, Masoumeh Malek., and Obsahuje bibliografii
Two new species of the syringophilid mites (Acari: Syringophilidae) are described from quills of passeriform birds. Syringophilopsis faini sp. n. is described from Sylvia curruca (L.) (Sylviidae) and Syringophiloidus carpodaci sp. n. is described from Carpodacus erythrinus (Pall.) (Fringillidae). Characters are detailed that differentiate Syringophilopsis faini from three species of a new "turdus" group, and Syringophiloidus carpodaci from S. minor.
Examination of freshwater fishes from the Parana River in southern Brazil during March 1992, revealed the presence of two new, previously undescribed species of the genus Goezia: G. brasiliensis sp. n. is described from the stomach of Brycon hilarii (family Characidae) (type host) and the intestine of Pseudoplatystoma coruscans (Pimelodidae) and it is characterized mainly by the length (0.802 mm) of spicules, number and arrangement of male caudal papillae (10 pairs of preanals and 4 pairs of postanals) and body measurements (male 11 mm, female 10-16 mm); the main characteristics of G. brevicaeca sp. n„ described from the stomach of Brycon hilarii, are a short anterior intestinal caecum reaching anteriorly only to the posterior end of oesophagus, comparatively short spicules (0.367 mm), number of male caudal papillae (20 pairs of preanals and 4 pairs of postanals) and an elongate, rather long body (male 17 mm, female 23 mm).
During investigations of gill ectoparasites (Platyhelminthes) parasitising freshwater fish from Central America (Guatemala, Honduras, El Salvador and Panama) and southeastern Mexico (Guerrero, Oaxaca and Chiapas), the following dactylogyrid monogenoidean were found: Urocleidoides simonae sp. n. from Profundulus punctatus (Günther) (type host), Profundulus balsanus Ahl, Profundulus guatemalensis (Günther), Profundulus kreiseri Matamoros, Shaefer, Hernández et Chakrabarty, Profundulus labialis (Günther), Profundulus oaxacae (Meek), Profundulus sp. 1 and Profundulus sp. 2 (all Profundulidae); Urocleidoides vaginoclaustroides sp. n. from Pseudoxiphophorus bimaculata (Heckel) (type host) and Poeciliopsis retropinna (Regan) (both Poeciliidae); and Urocleidoides vaginoclaustrum Jogunoori, Kritsky et Venkatanarasaiah, 2004 from P. labialis, Profundulus portillorum Matamoros et Shaefer and Xiphophorus hellerii Heckel (Poeciliidae). Urocleidoides simonae sp. n. differs from all other congeneric species in having anchors with well-differentiated roots, curved elongate shaft and short point. Urocleidoides vaginoclaustroides sp. n. most closely resembles U. vaginoclaustrum, but differs from this species mainly in the shape of its anchors (i.e. evenly curved shaft and short point vs curved shaft and elongate point extending just past the tip of the superficial anchor root). The complexity of potential hosts for species of Urocleidoides and their effect on its distribution on profundulid and poeciliid fishes are briefly discussed., Edgar F. Mendoza-Franco, Juan Manuel Caspeta-Mandujano, Guillermo Salgado-Maldonado, Wilfredo Antonio Matamoros., and Obsahuje bibliografii
Paleoripiphorus deploegi gen. n., sp. n. and Macrosiagon ebboi sp. n., described from two French Albo-Cenomanian ambers (mid Cretaceous), are the oldest definitely identified representatives of the Ripiphoridae: Ripiphorinae. They belong to or are closely related to extant genera of this coleopteran subfamily. Together with Myodites burmiticus Cockerell, 1917 from the Albian Burmese amber, they demonstrate that the group is distinctly older than suggested by the hitherto available fossil record. By inference after the biology of the extant Ripiphorinae, Macrosiagon ebboi may have been parasitic on wasps and Paleoripiphorus deploegi on bees, suggesting that Apoidea may have been present in the Lower Cretaceous.
General mathematical theories usually originate from the investigation of particular problems and notions which could not be handled by available tools and methods. The Fučík spectrum and the p-Laplacian are typical examples in the field of nonlinear analysis. The systematic study of these notions during the last four decades led to several interesting and surprising results and revealed deep relationship between the linear and the nonlinear structures. This paper does not provide a complete survey. We focus on some pioneering works and present some contributions of the author. From this point of view the list of references is by no means exhaustive.
In this paper we study two operations of merging components in a chain graph, which appear to be elementary operations yielding an equivalent graph in the respective sense. At first, we recall basic results on the operation of {\em feasible merging} components, which is related to classic LWF (Lauritzen, Wermuth and Frydenberg) Markov equivalence of chain graphs. These results are used to get a graphical characterisation of {\em factorisation equivalence} of classic chain graphs. As another example of the use of this operation, we derive some important invariants of LWF Markov equivalence of chain graphs. Last, we recall analogous basic results on the operation of {\em legal merging} components. This operation is related to the so-called {\em strong equivalence} of chain graphs, which includes both classic LWF equivalence and alternative AMP (Andersson, Madigan and Perlman) Markov equivalence.
Let $G=(V(G),E(G))$ be a graph. Gould and Hynds (1999) showed a well-known characterization of $G$ by its line graph $L(G)$ that has a 2-factor. In this paper, by defining two operations, we present a characterization for a graph $G$ to have a 2-factor in its line graph $L(G).$ A graph $G$ is called $N^{2}$-locally connected if for every vertex $x\in V(G),$ $G[\{y\in V(G)\; 1\leq {\rm dist}_{G}(x,y)\leq 2\}]$ is connected. By applying the new characterization, we prove that every claw-free graph in which every edge lies on a cycle of length at most five and in which every vertex of degree two that lies on a triangle has two $N^{2}$-locally connected adjacent neighbors, has a $2$-factor. This result generalizes the previous results in papers: Li, Liu (1995) and Tian, Xiong, Niu (2012), and is the best possible.
A subset of the plane is called a two point set if it intersects any line in exactly two points. We give constructions of two point sets possessing some additional properties. Among these properties we consider: being a Hamel base, belonging to some $\sigma $-ideal, being (completely) nonmeasurable with respect to different $\sigma $-ideals, being a $\kappa $-covering. We also give examples of properties that are not satisfied by any two point set: being Luzin, Sierpiński and Bernstein set. We also consider natural generalizations of two point sets, namely: partial two point sets and $n$ point sets for $n=3,4,\ldots , \aleph _0,$ $\aleph _1.$ We obtain consistent results connecting partial two point sets and some combinatorial properties (e.g. being an m.a.d. family).