Reidi Research Articles

The Species versus Subspecies Conundrum: Quantitative Delimitation from Integrating Multiple Data Types within a Single Bayesian Approach in Hercules Beetles.

With the recent attention and focus on quantitative methods for species delimitation, an overlooked but equally important issue regards what has actually been delimited. This study investigates the apparent arbitrariness of some taxonomic distinctions, and in particular how species and subspecies are assigned. Specifically, we use a recently developed Bayesian model-based approach to show that in the Hercules beetles (genus Dynastes) there is no statistical difference in the probability that putative taxa represent different species, irrespective of whether they were given species or subspecies designations. By considering multiple data types, as opposed to relying exclusively on genetic data alone, we also show that both previously recognized species and subspecies represent a variety of points along the speciation spectrum (i.e., previously recognized species are not systematically further along the continuum than subspecies). For example, based on evolutionary models of divergence, some taxa are statistically distinguishable on more than one axis of differentiation (e.g., along both phenotypic and genetic dimensions), whereas other taxa can only be delimited statistically from a single data type. Because both phenotypic and genetic data are analyzed in a common Bayesian framework, our study provides a framework for investigating whether disagreements in species boundaries among data types reflect (i) actual discordance with the actual history of lineage splitting, or instead (ii) differences among data types in the amount of time required for differentiation to become apparent among the delimited taxa. We discuss what the answers to these questions imply about what characters are used to delimit species, as well as the diverse processes involved in the origin and maintenance of species boundaries. With this in mind, we then reflect more generally on how quantitative methods for species delimitation are used to assign taxonomic status.

A simple molecular protocol for the identification of hybrid Western Atlantic seahorses, Hippocampus erectus × H. reidi, and potential consequences of hybrids for conservation

Seahorses hold an iconic status and are popular exhibits in zoos and public aquaria, where they are often on display in multi-species systems. Two of the more popularly kept species are the lined seahorse, Hippocampus erectus , and the longsnout seahorse, H. reidi . These two species are from different evolutionary subclades, but can produce viable hybrid F 1 offspring, therefore species segregation should be maintained for seahorse conservation breeding programmes. Hybrid H . erectus ♂ × H . reidi ♀ F 1 offspring exhibit higher median meristic counts for various traits, although large ranges in counts make it difficult to identify hybrids by meristics alone. A molecular protocol was developed to identify both the parent species and the reciprocal hybrids using polymerase chain reaction restriction-fragment length polymorphism (PCR-RFLP). The PCR-RFLP protocol employed the use of the BsrBI and Ms1I restriction enzymes at the Tmo-4c4 and S7 loci, respectively. The developed protocol was effective at discerning hybrids (F 1 ) from the parent species and identifying some post-F 1 H . erectus × H . reidi hybrids, but not the direction of the cross. Although captive-bred hybrids may be considered to pose a threat to wild populations if released, there are many benefits to producing captive hybrid seahorses, including improved aquaculture techniques that can curb the wild collection of seahorses.

Case 3590ScarabaeusLinnaeus, 1758,DynastesMacLeay, 1819, scarabaeinae Latreille, 1802, and dynastinae MacLeay, 1819 (Insecta, Coleoptera, scarabaeoidea): proposed conservation of usage

The purpose of this application, under Articles 65.2.2 and 70.2 of the Code, is to conserve the usage of the widely used names Scarabaeus Linnaeus, 1758 for a dung roller beetle, scarabaeinae Latreille, 1802 for the dung beetles subfamily, Dynastes MacLeay, 1819 for the hercules beetles genus, and dynastinae MacLeay, 1819, for the rhinoceros beetles subfamily. The current usage of these names is threatened by the overlooked type species designation of Scarabaeus hercules Linnaeus, 1758 (currently Dynastes hercules) for Scarabaeus by Lamarck in Jolyclerc, 1807b. Lamarck's designation would transfer the name Scarabaeus from the widely known dung roller beetles to hercules beetles (currently Dynastes) and the family-group name scarabaeinae from the dung beetles to the rhinoceros beetles (currently dynastinae). lt is proposed to set aside all type species fixations for Scarabaeus before Hope's designation (1837) of Scarabaeus sacer Linnaeus, 1758, which would maintain the current usage of all names involved.

Récords olímpicos: humanos vs insectos

Basado en observaciones, en mediciones y en literatura acerca de las habilidades deportivas de los insectos, en los tres deportes reconocidos de los Juegos Olímpicos de Verano, el atletismo, la gimnasia y la natación, se comparan algunas marcas deportivas, recientemente establecidas por hombres y por mujeres con aquellos que, determinados insectos, sostienen desde hace millones de años. Estos artrópodos, si compitiesen con los humanos, ganarían en la mayoría de las justas, en las que, por sus características, podrían participar, ya sea a nivel mundial o en juegos olímpicos. En el levantamiento de pesas, en cualquiera de las modalidades, compiten los escarabajos peloteros y las hormigas con los insectos; ganarían los cucarrones, reconocidos también como los insectos sagrados de los antiguos egipcios. Disputa con ellos la medalla, el escarabajo hércules o rinoceronte, Dynastes hercules, cucarrón emblemático de las selvas tropicales de Suramérica, incluyendo a Colombia. Las chinches acuáticas de las familias Notonectidae y Corixidae son nadadores por excelencia de dos estilos, espalda y pecho y no es la pulga, que se pensaba sostenía el récord mundial de salto alto y largo, sino un insecto salivazo o mión (Cercopidae), plaga de alfalfa. Igualmente, y como ocurre casi siempre en los juegos olímpicos, donde alguien le quita el récord a un atleta, hace poco, otro insecto le quitó la marca de corredor más rápido a la cucaracha americana. Afortunadamente, los humanos no compiten en deportes con los insectos, pero sí luchan con algunos de ellos, con éxito limitado, principalmente, por alimentos.

Biologically inspired humidity sensor based on three-dimensional photonic crystals

This letter presents a biomimetic humidity sensor inspired by the humidity-dependent color change observed in the cuticle of the Hercules beetle. A thin-film-type humidity sensor with nanoporous structures (three-dimensional photonic crystals) mimicking the spongy multilayer in the beetles was designed and fabricated using the colloidal templating method and a hydrophilic surface treatment. The visible color of the fabricated humidity sensor changes from blue-green to red as the environmental humidity increases. The wavelength of reflected light that is predicted by Bragg’s equation considering the effect of water absorption shows a good agreement with experimental results.

Diffractive hygrochromic effect in the cuticle of the hercules beetle Dynastes hercules

The elytra from dry specimens of the hercules beetle, Dynastes hercules appear khaki-green in a dry atmosphere and turn black passively under high humidity levels. New scanning electron images, spectrophotometric measurements and physical modelling are used to unveil the mechanism of this colouration switch. The visible dry-state greenish colouration originates from a widely open porous layer located 3 μm below the cuticle surface. The structure of this layer is three-dimensional, with a network of filamentary strings, arranged in layers parallel to the cuticle surface and stiffening an array of strong cylindrical pillars oriented normal to the surface. Unexpectedly, diffraction plays a significant role in the broadband colouration of the cuticle in the dry state. The backscattering caused by this layer disappears when water infiltrates the structure and weakens the refractive index differences.

X-Y-autosome translocation, chromosome compaction, NOR expression and heterochromatin insulation in the Scarabaeid beetle Dynastes hercules hercules

The karyotype of the giant beetle Dynastes hercules hercules is composed of only 16 autosomes and large sex chromosomes. Meiotic studies in the males showed that a large part of the sex chromosomes undergo synapsis at pachynema similarly to autosomes, demonstrating that both derived from an autosome-gonosome translocation. Therefore, karyotype formula is 18,neoXY. The heterochromatisation of the neoX short arm at pachynema indicates that it corresponds to the ancestral X. It carries the nucleolar organizer region (NOR) in its proximal part, which is undercondensed, especially in male mitotic and meiotic cells. In female mitotic cells, both NOR staining and undercondensation were more difficult to observe in the neoX short arms. In somatic interphase nuclei, NOR expression strongly varies with the sex. Two separated compact groups of silver dots were observed in female nuclei, while a single dispersed and large group of silver deposit exists in the males. Both the lower condensation and the higher NOR expression of the single neoX of the males, compared to each of the two neoXs of the females, is interpreted to be a consequence of dosage compensation, a mechanism not yet described in Coleoptera. In mammals as well as in Coleoptera, the carriers of gonosome-autosome translocations not exhibiting deleterious phenotypes show constitutive heterochromatin at the autosome-gonosome junction. Thus, heterochromatin may play an important universal role by clearly separating chromosome segments with different regulations of gene expression, such as inactivation or dosage compensation of the X chromosome on the one side and a conventional autosomal structure on the other side.

Some defence mechanisms of the Hercules beetle, Dynastes hercules

SYNOPSISMeasurements are given of the forces that can be applied to an object held between the prothoracic and cephalic horns of a large male Hercules beetle. The ways in which the horns are adapted for gripping objects are discussed. The intensity and form of the sound produced by the stridulatory organs of the male are described.

Physiological colour change in the elytra of the hercules beetle, Dynastes hercules

The male of the hercules beetle, Dynastes hercules, is able to change the colour of its elytra from yellowish to black and back again to yellowish within a few minutes. The epicuticle of the elytra is transparent and about 3 μm thick. Below it is a yellow spongy layer that is usually about 5 μm thick. The cuticle below the yellow sponge is black. When the layer of yellow sponge is air filled it becomes optically heterogeneous, and the light reflected from the elytra is yellow. When the yellow sponge is liquid filled it becomes optically homogeneous, and the black cuticle below is seen. If a beetle that has yellowish elytra is placed in a saturated atmosphere, the elytra become black. When the relative humidity is appreciably reduced, yellow patches begin to appear on the elytra, usually within 30 sec to 2 min. However, if the beetle is kept at a constant relative humidity that previously caused yellowing, it will become black given enough time. Most colour changes observed were clearly in response to changes in the ambient humidity and were not affected when the beetles were kept in the light or in total darkness nor by blackening their eyes or prodding them or exposing them to sounds of different intensities or frequencies. If an elytron is removed from a live beetle, it changes colour in response to changes in relative humidity exactly like the elytron left attached. When a restricted area of the elytra is subjected to a humidity that normally causes blackening and an adjacent area to a humidity that normally causes yellowing, both change colour in the expected way. This local control of colour change seems to preclude hormonal control. It is suggested that the epidermal cells or both the epidermal and blood cells in the elytra are responsible for the hydration and dehydration of the layer of yellow sponge.

Physiological Colour Change in the Hercules Beetle

THE Hercules beetle, Dynastes Hercules L., can change the colour of its elytra—horny fore-wings—from black to greenish yellow and back again to black all within a few minutes. It does this in a way previously unknown among insects. Apart from the reversible migrations of pigment granules in the iris cells, physiological or rapidly reversible colour changes are very rare in insects1–4. Among beetles, Coptocyclia5, Aspidomorpha, and many other Cassidinae can change the colour of their elytra by varying the amount of water in the cuticle and thereby the thickness of the thin films responsible for the interference colours.

Notes on the hercules beetle, Dynastes hercules (Linn.), at Rancho Grande, Venezuela, with special reference to combat behavior

Notes on the hercules beetle, Dynastes hercules (Linn.), at Rancho Grande, Venezuela, with special reference to combat behavior

New species or sub-species of Hercules beetles from Dominica Island, B. W. I., with notes on the habits and larvae of the common species and other beetles

New species or sub-species of Hercules beetles from Dominica Island, B. W. I., with notes on the habits and larvae of the common species and other beetles

Branch-Cutting Beetles

IT is rather curious that the story which Mr. Ober was told in the Carribbees (NATURE, vol. xxii. p. 216) should be generally believed in Southern Brazil also, viz., that a large beetle “seizes a small branch of a tree between its enormously long nippers, and buzzes round and round the branch till this is cut off.” Only in the Antilles this cutting of branches is attributed to a huge Lamellicorn, the Dynastes hercules, and in Santa Catharina to a large Longicorn, the Macrodontia cervicornis.

Dynastes Hercules

THE reviewer of Ober's “Camps in the Caribbees” (NATURE, vol. xxii. p. 216) appears to doubt the story of the habits of the large Hercules beetle, Dynastes hercules, given by Ober on the authority of his guide. It is nevertheless perfectly true, and I have myself witnessed the occurrence twice in this neighbourhood, where the beetle is not uncommon. In the first instance I noticed it on a branch of Ochroma lagopus, and the second time on a species of Bombax, both very soft-wooded trees. The branches in each case were about three-quarters of an inch in diameter, half an inch being formed by the wood. In both cases I saw the performance of the animal most distinctly, just as described by Ober's guide, and I took not only a piece of the severed branch with me, but secured also the second animal. The noise is not so much produced by the cutting of the branch as by the open wings passing rapidly through the air during the rotation of the beetle. I do not believe there is anything or a sexual call in the manoeuvre. The beetle wants to get at the abundant juice of the young branches. It is called in this country aserrador, i.e. sawyer. Golofa porteri, an allied insect of the same family as Lamellicornes, behaves in a similar way, but chooses of course thinner branches.