Dark Form Research Articles

Rhizosphere and root surface fungi of some heath plants and the role of Dark Sterile forms

Many different species of fungi have been isolated from the root region of heath plants. In the absence of rapidly growing species,Dark Sterile forms predominated in culture plates. It is suggested that these have an important ecological role in the soil-root interface. AsDS forms do not appear in culture plates easily any floristic list of fungi from the root surface not mentioningDS forms must be accepted with caution. Attention is drawn to the fact that these are truly root-inhabiting fungi possessing some parasitic or mycorrhizal propensities.

Genetic structure of the East African domestic populations of Aedes aegypti.

THE yellow fever mosquito, Aedes aegypti, is a complex species. Morphological, physiological, and behavioural variation is extensive and complex1–4. In the Rabai area near Mombasa, Kenya, three forms of A. aegypti can be distinguished5. A light coloured population breeds exclusively in water jars stored inside houses; this is referred to as the domestic form. In disturbed areas adjacent to villages (such as farmland), a form of varying darkness is found breeding in discarded containers or footholds cut in coconut palms; this is the peridomestic form. In tropical forests, an exclusively dark form is found breeding in tree-holes or occasionally rock-holes; this is the feral form. These forms are behaviourally distinct from one another5; and, even though they can be found in close proximity to each other, they are often also genetically distinct6 (W.J.T., L. E. Munstermann and J.R.P. in preparation). We present here a population genetic analysis of the domestic populations of A. aegypti in villages in the Rabai area. We conclude that the mosquito population in each village is a panmictic unit with no significant genetic substructuring ; that significant genetic differences exist between villages less than 2 km apart ; and that gene frequencies are temporally stable.

The growth and maturation of the “tarantula”, Avicularia avicularia L.

The growth of the theraphosid spider, Avicularia avicularia L. was studied principally by taking measurements of the fang length of exuviae and dead specimens. The relatic ships between fang length and increment at ecdysis and fang length and instar duration were investigated and used to construct a projected growth curve for the species. This suggests that males reach sexual maturity in approximately 13 instars and at a minimum age of about two and a half years. In males the adult instar is terminal and rarely lasts more than three months. Reproductive maturity in females is probably not reached earlier than the XIVth instar or three years from birth. The females continue to moult annually after maturity and have a longevity in excess of seven years. The pattern of colouration shows characteristic changes in early immature life and develops a slight sexual dimorphism in adults. Type II urticating hairs are present throughout life and occur in light and dark forms in the IInd instar. The mean length of the urticating hairs increases during the life cycle and a sexual dimorphism develops in the XIIth or XIIth instar. In adult males the urticating hairs are uniformly barbed whereas in the adult females the barbs are restricted to the proximal end.

A Re-Evaluation of Introgression Between Dacus Tryoni and Dacus Neohumeralis (Diptera: Tephritidae).

The humeral calli in D. tryoni range from completely yellow to almost entirely brown. This variation is largely genetic and the character responds readily to selection in the laboratory. In field populations, selection favours flies with little or no brown pigment on the calli (around 3% brown) and there is a strong natural selection against the darker forms. However, field populations of D. tryoni show only a limited response to this selection, since flies with dark calli are regularly present in field samples. One possible explanation is that the loss of genes through selection is balanced by recurrent gene exchange with D. neohumeralis, a species in which selection favours flies with dark calli. Gene exchange between the two species is restricted, because their periods of sexual activity do not coincide. This mating barrier is incomplete however, since limited gene exchange can be induced in the laboratory. D. tryoni is sympatric with D. neohumevalis for only part of its range in eastern Australia. It is shown that callus variability in D. tryoni is uniform over its entire range and is therefore independent of possible gene exchange with D. neohumeralis. An alternative mechanism is proposed to explain the maintenance of callus variability in D. tryoni, namely, a stabilizing selection that operates against flies at both extremes of its callus range.

The isomeric configuration of the bacteriorhodopsin chromophore

Oesterhelt and Stoeckenius in 1971 found a pigment in Halobacterium halobium which they called bacteriorhodopsin because it resembles rhodopsin in many aspects. The isomeric configurations of its chromophore were studied by thin layer chromatography of the retinal and of the retinal oxime derivatives. The dark form of bacteriorhodopsin (R 560) contains 13- cis retinal, in contrast to the 11- cis retinal of rhodopsin. Both the R 570 and the M 412 forms of bacteriorhodopsin were found to contain all- trans retinal. Implications of the different isomeric forms found in bacteriorhodopsin are discussed.

Electrophoretic differences between sympatric ecotypes.

ELECTROPHORESIS has been used extensively for characterising genetic variability within and between natural populations1,2 but has not been applied to sympatric ecotypes. In the mosquito Aedes aegypti a dark feral form predominates throughout sub-Saharan Africa, but elsewhere in the tropics and moist subtropics a paler domestic form is found. The two ecotypes occur together in Africa in areas with a dry season during which natives store water in pots inside huts3,4. The indoor ecotype breeds continually in water stored in human dwellings, and the outdoor ecotype lives in treeholes and other sites around the dwellings and breeds seasonally. Our data provide the first demonstration of electrophoretic differences between sympatric ecotypes.

Multiple-Discriminant Analysis of Geographical Variation in the Aquatic Beetle, Rhantus Gutticollis (Say) (Dytiscidae)

Zimmerman, James R., and John A. Ludwig (Department of Biology, New Mexico State University, Las Cruces, New Mexico 88003) 1974. Multiple discriminant analysis of geographical variation in the aquatic beetle Rhantus gutticollis (Say) (Dytiscidae). Syst. Zool. 24:63-71.-Multiple-discriminant analysis with aid of the Mahalanobis D2 statistic is a useful way of.-analyzing geographical variation in Rhantus gutticollis (Say). A moderate number of mensural characters (14) and rather small sample sizes (N 25 or 30) give results which permit discrimination to a fine degree among apparently very similar populations. The approach reveals more features of geographical variation than would probably be seen in the usual one-character comparisons. It is a widespread species with considerable regional differentiation and with well-marked boundaries between different population groups. In spite of those differences, the situation does not readily lend itself to conventional subspecific fractionation. The results from MDA are interpreted as reflections of gene flow rather than differentiation of local populations. [multiple-discriminant analysis, geographic variation, Dytiscidae, gene flow.] The problem of analyzing geographical variation within species continues to receive attention by taxonomists. For the traditional taxonomist, recognition of geographical and ecological races, clines, chromosomal differences, and polymorphs has probably been the principal means of illustrating regional variations in species. Some character differences between populations have traditionally been compared using univariate statistical procedures. Increasingly more multivariate statistical studies have been used to examine geographical variation (see the review of Gould & Johnston 1972, and Genoways & Choate 1972, Rohwer 1972, Jackson 1973, Johnston 1973, Niles 1973). Among the techniques is multiple-discriminant analysis (MDA) which includes both discriminant functions and generalized distance, or the D2 statistic. Discriminant function is a linear function that will best discriminate between two sample populations based on multiple characteristics. Generalized distance is a measure of a statistical distance between two sample populations. D2 is easily calculated using a discriminant function (Rao 1952). We wish to examine geographic variation in the aquatic beetle Rhantus gutticollis (Say) using the D2 statistic. R. gutticollis is a medium-sized species of predacious diving beetle ranging from British Columbia to Costa Rica, and from the Pacific Coast to the western edge of the Great Plains (Fig. 1). Zimmerman and Smith (In press) document the species limits and synonymy used for this paper. R. gutticollis, described by Say in 1834 from Mexico, was long unknown and usually confused with R. binotatus (Harris). Wallis (1933) recognized gutticollis and considered it as distinct from a Pacific Northwest population which he described as hoppingi. Leech and Chandler (1956) confirmed that the two forms were separable and noted the occurrence of gutticollis and hoppingi in California. Another nominal species, R. mexicanus (Aube'), has proven to be a dark polymorphic form of gutticollis which occurs throughout the southern part of the range. It differs only in its mostly black rather than the irrorated (color applied as grains of sand) elytral pattern which is found in the more common morph. The mexicanus morph is indistinguishable from the common form in the 14 characters used in this study. Intergrades (with the penis and male protarsal claws as diagnostic characters) be-

Role of form vision in habitat selection of the grass shrimp Hippolyte californiensis

The caridean shrimp Hippolyte californiensis Holmes locates its host plant, the eel grass Zostera marina, visually, discriminating it on the basis of its form. Using models of the plant, the form-specific sign stimuli optimally releasing the host-selection response were investigated. Shrimps preferentially approached dark forms presented against a lighter background. The more a form contrasted with the background, the higher was its stimulatory value. Shrimps showed differential responses to solid forms of varying shape, preferring a stripe-like rectangle in a vertical orientation. Rectangular forms 50° (visual angle) or more in height and between 12° and 20° in width were maximally stimulating. Patterns of several vertical stripes had a greater releasing value for the approach response than a solid rectangle form of optimal dimensions. The greater the spatial frequency of a striped pattern, the reater was its attractiveness. Shrimps discriminated patterns of stripes whose elements were as small as 2° wide, giving an estimate of their visual acuity. Along with the relative contrast, the most important stimulus parameters of striped patterns are the continuous, straight form of the edges and their vertical orientation. It is postulated that the scototactic response of H. californiensis to relatively large, dark, solid forms is involved in the distant detection of clumps of eel grass. At closer range, the eel grass plants are then discriminated on the basis of the stripelike pattern of the leaves.

ON THE ETHOLOGICAL DIFFERENTIATION OF DROSOPHILA ANANASSAE AND DROSOPHILA PALLIDOSA IN SAMOA.

A number of significant studies of genetic divergence and speciation in island populations of Drosophila have been undertaken in recent years. Certainly the grandest example of this has been the detailed study of the spectacular array of Drosophila species native to the Hawaiian Islands begun under the leadership of the late Professor Wilson S. Stone of the University of Texas and Professor D. Elmo Hardy of the University of Hawaii, and still being carried on by Hardy and a number of their colleagues; e.g., see Carson et al. (1970). Other island groups and Drosophila species have also been investigated by Stone and others at the University of Texas. Among these studies are those on Drosophila ananassae populations from island groups in the central and western Pacific Ocean, including light (brownish-yellow) and dark (blackish-brown) D. ananassae-like populations found on the American Samoan island of Tutuila. These populations are especially interesting in that, aside from the pigmentation difference, they are morphologically nearly indistinguishable and, in spite of exhibiting no apparent postmating reproductive barriers (Stone et al., 1966), they coexist together on this island as separate, reproductively isolated units. That they are sexually isolated has been shown cytologically (Futch, 1966) and ethologically (Futch, 1966; Spieth, 1966) with strains from Pago Pago, Tutuila. In recent years other collections of similar light and dark D. ananassae-like flies have been obtained from other islands in the Samoan archipelago as well as from islands in the Fijian group. Based mainly on the cytological and ethological evidence cited above concerning the genetic isolation of these light and dark forms, Bock and Wheeler (1972) recognize the two as distinct species belonging to the D. ananassae subgroup of the D. melanogaster species group of Drosophila. The dark flies have been identified as Drosophila ananassae Doleschall, a polytypic, widespread (circumtropical) domestic species of the tropical and sub-tropical world, whereas they describe the light flies as Drosophila pallidosa. This recently described species has a relatively localized distribution presently known only to include the southcentral Pacific islands of Samoa and Fiji where it exists side-by-side with its widely distributed sibling, D. ananassae. That two such very closely related, potentially interfertile sympatric species have been found living together successfully and separately in the island groups of Samoa and Fiji seems to warrant further investigation. As a part of this continuing investigation, populations from other islands of the Samoan group have been analyzed cytologically and for crossing fertility as stocks have become available to me.

THE SENSORY BASIS OF HOST RECOGNITION BY SYMBIOTIC SHRIMPS, GENUSBETAEUS

1. The sensory basis of host-oriented locomotion in the caridean Betaeus macginitieae contrasts with that of the congeneric B. harfordi. Both of these shrimps can locate their respective host organisms utilizing chemical stimuli of host origin. Only B. macginitieae demonstrates the ability to utilize visual stimuli for this same purpose.2. By using information contained in multiple stimulus modalities, B. macginitieae is able to maintain a more restricted host association than its congener.3. Visual recognition of its urchin host by B. macginitieae does not involve any parameter of the total visual pattern of the urchin that uniquely characterizes the urchin species, but appears to be a generalized response to larger, dark forms of undefined peripheral outline.4. Positive rheotaxis in the presence of appropriate non-directional chemical stimuli is suggested as the mechanism by which B. harfordi effects chemically-mediated host location.

Ultraviolet irradiation of tobacco leaves: inhibition of tobacco mosaic virus-ribonucleic acid photoreactivation.

Abstract— Short‐wave (254‐nm) ultraviolet irradiation of the leaves of Nicotiana tabacum var. Xanthi, n.c. inhibits their ability to photoreactivate ultraviolet‐inactivated tobacco mosaic virus ribonucleic acid (TMV‐RNA). The inhibition is stable in the dark; however, subsequent illumination of the leaves relaxes the inhibition. The spectral region most effective in relaxing the inhibition is the same one effective in photoreactivation. These results are consistent with the hypothesis that ultraviolet‐induced lesions in cellular nucleic acids in the dark form stable complexes with agents responsible for the photoreactivation of TMV‐RNA (effectively isolating the agents from the TMV‐RNA) and that upon illumination these complexes dissociate (presumably with repair of the lesions). We therefore suggest that the system which photoreactivates ultraviolet‐damaged TMV‐RNA also photorepairs ultraviolet damage in cellular nucleic acids.

Polymorphism and behaviour in the Arctic Skua (Stercorarius Parasiticus (L.))

Arctic Skuas are birds of the Arctic and sub-Arctic. The majority of them are light-coloured, but there is a Dark form which constitutes 70 to 80% of the population at the southern­ most limit of the breeding range of the species in northern Britain, decreasing further in frequency towards the north. Birds intermediate in colour phase can be recognized. The colour variation is largely due to two allelomorphs at a single locus. The heterozygotes are variable in expression and the Intermediate class contains representatives of both homozygotes. The Skua colony on Fair Isle, Shetland, was intensively studied from 1949 to 1963. During this time most birds (both chick and adult) were individually marked and the phases of nesting birds and their young noted. There were no differences between mating types in either breeding success or fecundity. In matings between phases, 60% involved pairs where the male was darker than the female. This arises because Dark males pair earlier than Pale ones. Since Arctic Skuas pair for life (although ‘divorce’ and ‘remarriage’ are not uncommon), this behaviour gives an advantage to males carrying the allelomorph for dark colour unless early hatching clutches are at some disadvantage. It is suggested that later hatching may be favoured in inland and northern parts of the species range, where the main food is small mammals (which usually become plentiful only later in the summer). The frequency of Pale birds is much higher in such areas. 'There is a fowl called the Scutiallan, of a black colour and as big as a Wild Duck, which doth live upon the vomit and Excrements of other Fowls whom they pursue and having apprehended them, they cause them to Vomit up what meat they have lately taken, not yet digested: The Lord’s Works both of Nature and Grace are wonderful, all speaking forth His Glorious Goodness, Wisdom and Power ' (Brand 1701).

The Relationship of the Brown and Black-Backed Treecreepers

The typical form of the Brown Treecreeper Climacteris p. picumnus occurs in south-eastern Australia, a darker form with paler head markings C. p. melanota occupying the peninsula east of the Gulf of Carpentaria. Specimens from near Cardwell are intermediate, not faded, examples of melanora. Variation' occurs in C. p. picumllus, specimens from the north-east being slightly darker with slightly paler head markings. These four groups might form an interrupted cline. Alternatively, the north·eastern forms of picumnus might be regarded as intermediate. In either case it seems preferable to regard picumnus and melanota as forms of a single species.

GLOGER'S RULE AND PIGMENTATION OF COLLEMBOLA.

Pigmentation in warm-blooded animals has been related to latitude, temperature, humidity, rainfall, and solar radiation. The original observations by Gloger (1833) on the coloration of birds in relation to their geographical position have been confirmed for different species belonging to several taxa, though some important exceptions were pointed out by Burt (1954) and Croizat (1964). The decrease of pigmentation at higher latitudes, however, does not seem to be valid for invertebrates. Moreover, in many instances a negative or inverse Gloger's rule has been reported. Dobzhansky (1933) speaks of centers of light and dark forms in coccinellid Coleoptera; the former lie in Iran, southern Turkestan, southern United States and Mexico, and the latter lie in Siberia and Kamchatka. Low temperatures (and higher latitudes) favor melanin formation in insects (Vernberg, 1962) resulting in more obscure populations (Ehrlich and Holm, 1963; Gillham, 1956; Hovanitz, 1941; Kalmus, 1941; Timofeeff-Ressovsky, 1940). The same phenomenon has been also reported for the marine snail Thais lapillus (Clench, 1954), and for land snails. The latter show darker brown coloration at higher latitudes. An analysis is made here of the amount of pigmentation observed in entire associations of different species, taking the collembolan insects as the main example, and trying to quantify in some way the phenomenon as Amtmann (1965) did with the mammal Protoxerus stangeri. Yosii (1938) provided some early observations on this group of apterygotan insects: referring to Agrenia bidenticulata he mentions their ability to show color variations according to the habitat. Specimens collected from riversides and other hygropetric habitats show dull yellowish coloration, while those collected on snow in spring are always pigmented deep purple.

The influence of soil colour on subspeciation of mammals in eastern Arabia

Some subspecies of mammals described from the Batinah Coast of Oman are discussed. The coloration of certain terrestrial forms is considered to be correlated with predominant soil coloration in their habitats. The Baluchistan gerbil, Gerbillus nanus, exists in two quite distinct colour forms on each side of the Oman range, which we have shown to correspond closely with the coloration of soil samples obtained from the areas in which they were collected. A pale sandy form near to G.n. arabium lives on the pale sands fringing Rub al Khali, while a much darker form G.n. setonbrownei lives on the darker soil of the Batinah Coast.

Coproporphyrinogenase activity in extracts from rhodopseudomonas spheroides

An extract from Rhodopseudomonas spheroides , grown semi-anaerobically in the light, converts coproporph rinogen to protoporphyrin when incubated anaerobically in the dark with Mg 2+, ATP and L-methionine. Extracts from R. spheroides grown under air or oxygen in the dark are inactive when assayed under these conditions. Extracts from organisms grown in the light or in the dark form protoporphyrin in the absence of ATP and methionine when incubated with coproporphyrinoren in the presence of oxygen. The anaerobic reaction is inhibited by 1,10-phenanthroline, whilst the aerobic reaction is not.

In Vitro Phytochrome Dark Reversion Process

Thermal reversion of the far-red absorbing form of phytochrome to the red absorbing form in darkness has been investigated in crude and partially purified isolates from a number of etiolated and light grown higher plants. The influence of temperature, aging and urea on the rate of reversion was also determined.Phytochrome isolated from all higher plants underwent reversion. The reversion proceeded in at least 2 distinct stages; a short rapid initial phase being followed a slow phase which continued for many hours. Reversion rate was highest in phytochrome isolated from green leaves of parsnip (Pastinacea sativa) and lowest in that isolated from etiolated oats (Avena sativa). Although the rate of reversion could be changed by modifying the tertiary structure of the protein component, the large differences in rate appeared to be characteristic of the plant source. Observed in vitro rates of reversion are slower than those occurring in vivo. Removal of other buffer solubilized material during purification had little effect on the rate of reversion of phytochrome isolated from etiolated material.

Fully saturated brines

This type of subsurface water contains more solutes than solvent and is found only at depths exceeding 1000–3000 m, where it exists at high pressures and temperatures, in the form of a dark heavy liquor in rocks ranging in age from Lower Cambrian to Upper Jurassic. The eight specimens of such brines here reported are characteristically devoid of SO4 and HCO3, with K > Na and even K > Mg, at pH 2.8 to 4.6, containing up to 9 g of Br and up to 4 g Sr/lit; the Br:1 ratio is extraordinarily high and the brines are supercharged with H2S. They may be interpreted as end-products of concentration and metamorphism. Such brines, when tapped, e.g. by drilling for hydrocarbons, produde powerful salt plugs in drillholes, capable even of stopping an oil gusher, as their solutes (up to 650 g/lit) are precipitated rapidly at reduced pressures. – IGR Staff.

Polymorphism of Philaenus spumarius (L.) (Homoptera, Cercopidae) in England

The recent writings ofHalkka(1962,1964), Halkka et al. (1966,1967 a, b), Owen W Weaver & King 1954; Halkka 1962, 1964). This type of colour polymorphism is not unique in the family Cercopidae. The African Ptyelus grossus F., for example, has many colour forms. Amongst the ten British species in this family,, there is evidence of colour polymorphism in one species other than Philaenius spumarius. Le Quesne (1965) describes a dark form of Neophilaenus lineatus L. which appears to be associated with one of its many host plants, Molinia caerulea (L.) Moench. Wagner in 1955 attempted to provide a genetic basis for the colour variation of Philaenus spumarius and this approach has been developed mainly by Halkka (1962, 1964). The latter author has recently shown that six major genes are each responsible for a distinct colour pattern and that some of these show their effect only in the females (Halkka et al. 1966). He further concludes (Halkka et al. 1967a) that 'within the limits of our material [food plant preferences] were found to bear no relation to colour forms. However, the age of a ley seems to be significant both for the density of the population and for the distribution of the colour form frequencies. This change may be in some way causally connected with a change in the composition of the vegetation of the ley'. Weaver & King (1954), however, could find no biological significance in the colour forms beyond the absence of some of them in the male sex, and Regnier (1936) concluded that host plants had little or no significance. The present study adds to Hutchinson's findings on variation in Britain, and includes some ecological observations and rearing experiments. As a result of these the questions of the demarcation of colour forms and the relations of different colour forms with different host plants are reconsidered.

Eggs of Moths among the Ethmiidae, Acrolophidae and Hepialidae: Microlepidoptera

This publication describes, discusses, and illustrates eggs of moths that belong to the Ethmiidae, Acrolophidae, and Hepialidae. It is a continuation of studies made on eggs from 15 families of the microlepidoptera published in The Florida Entomologist during 1963(B), 1965, and 1967. The techniques employed to locate, collect or produce eggs, to record all pertinent factors, and prepare photographs are similar to those used and discussed in the numerous papers the author has published on eggs of insects, especially eggs of moths, which have appeared in The Florida Entomologist from 1960 to 1967. The 30 or more species of moths that belong to the Ethmiidae in the United States and Canada are represented here by two species of Ethmia captured at black light lures located near Portal, Arizona. The females deposited their eggs on the interior of polyethylene bags. The eggs of the two species seen, except for a small difference in size and color, resemble each other closely especially in their manner of deposition and structural details. The family Acrolophidae in Canada and the United States according to McDunnough possesses 45 species and all belong to one genus, Acrolophus. Eggs of eight or more species have been seen and all resemble each other closely. All are under 0.5 mm in length, nearly spherical, non adhesive, and roll about freely, when deposited in a vial or polyethylene bag. All are near white when deposited. Most species within 6 to 48 hours after deposition change to a dark color which may be dark grey, brown, or near black. The light colored phase in each species may be a trifle larger (0.05-0.1 mm) than the dark form. The chorion of all species seen possesses 20 to 24 narrow elevated lines which extend lengthwise between the two somewhat smooth ends of the egg. The females seen to date, that produced eggs, were collected in numbers in Arizona, Florida, North Carolina, Ohio, and Michigan at black-light lures or traps. For Hepialidae see Fig. 8.