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71.
72.
Jakob Vinther Derek E. G. Briggs Julia Clarke Gerald Mayr Richard O. Prum 《Biology letters》2010,6(1):128-131
Investigation of feathers from the famous Middle Eocene Messel Oil Shale near Darmstadt, Germany shows that they are preserved as arrays of fossilized melanosomes, the surrounding beta-keratin having degraded. The majority of feathers are preserved as aligned rod-shaped eumelanosomes. In some, however, the barbules of the open pennaceous, distal portion of the feather vane are preserved as a continuous external layer of closely packed melanosomes enclosing loosely aligned melanosomes. This arrangement is similar to the single thin-film nanostructure that generates an iridescent, structurally coloured sheen on the surface of black feathers in many lineages of living birds. This is, to our knowledge, the first evidence of preservation of a colour-producing nanostructure in a fossil feather and confirms the potential for determining colour differences in ancient birds and other dinosaurs. 相似文献
73.
The Australian wolf spider genus Hoggicosa Roewer, 1960 with the type species Hoggicosa errans (Hogg, 1905) is revised to include ten species: Hoggicosa alfi sp. nov. ; Hoggicosa castanea (Hogg, 1905) comb. nov. (= Lycosa errans Hogg, 1905 syn. nov. ; = Lycosa perinflata Pulleine, 1922 syn. nov. ; = Lycosa skeeti Pulleine, 1922 syn. nov. ); Hoggicosa bicolor (McKay, 1973) comb. nov. ; Hoggicosa brennani sp. nov. ; Hoggicosa duracki (McKay, 1975) comb. nov. ; Hoggicosa forresti (McKay, 1973) comb. nov. ; Hoggicosa natashae sp. nov. ; Hoggicosa snelli (McKay, 1975) comb. nov. ; Hoggicosa storri (McKay, 1973) comb. nov. ; and Hoggicosa wolodymyri sp. nov. The Namibian Hoggicosa exigua Roewer, 1960 is transferred to Hogna, Hogna exigua (Roewer, 1960) comb. nov. A phylogenetic analysis including nine Hoggicosa species, 11 lycosine species from Australia and four from overseas, with Arctosa cinerea Fabricius, 1777 as outgroup, supported the monophyly of Hoggicosa, with a larger distance between the epigynum anterior pockets compared to the width of the posterior transverse part. The analysis found that an unusual sexual dimorphism for wolf spiders (females more colourful than males), evident in four species of Hoggicosa, has evolved multiple times. Hoggicosa are burrowing lycosids, several constructing doors from sand or debris, and are predominantly found in semi‐arid to arid regions of Australia. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 158 , 83–123. 相似文献
74.
D. L. RAYMOND 《Biological journal of the Linnean Society. Linnean Society of London》1984,23(2-3):229-235
Previous work has shown that wild birds can become trained to search for a prey type on the basis of its colour. The experiments presented in this paper extended this work to two types of green artificial prey that were identical except for the presence or absence of a red stripe. Wild birds at six widely separated sites were trained on populations of one type and then were offered a choice between equal numbers of the familiar type and a second type. All the populations were presented on lawn backgrounds. The experiments were then repeated at each site with the birds being trained on the second prey type. The results showed that there was a consistent tendency for the familiar prey type to be overpredated and this was statistically significant. The behaviour described in this paper, if it occurs in nature, could lead to frequency-dependent (apostatic) selection and the maintenance of polymorphism in prey species in which the morphs are distinguished by colour patterns. 相似文献
75.
The growth of pikeperch Sander lucioperca was studied in 41 lakes in central Finland. The backcalculated average total length of 3 year‐old pikeperch was used as an indicator of growth. The growth correlated positively with total phosphorus and water colour and negatively with lake area and depth. The reason for differences in growth may be differences in the amount of suitable food, foraging success or temperature dynamics in different lakes. 相似文献
76.
S. Siligato 《Journal of fish biology》1999,55(2):376-381
The migrations of Gymnocephalus baloni Balon's ruffe into the side branch of the Danube at Schönbühel were restricted to the spawning season between the end of April and mid-June. The main environmental factor correlating with the immigration is assumed to be water temperature. Water level changes influence emigration. 相似文献
77.
Predator–prey encounter rates in freshwater piscivores: effects of prey density and water transparency 总被引:1,自引:0,他引:1
One of the most fundamental components of predator–prey models is encounter rate, modelled as the product of prey density
and search efficiency. Encounter rates have, however, rarely been measured in empirical studies. In this study, we used a
video system approach to estimate how encounter rates between piscivorous fish that use a sit-and-wait foraging strategy and
their prey depend on prey density and environmental factors such as turbidity. We first manipulated prey density in a controlled
pool and field enclosure experiments where environmental factors were held constant. In a correlative study of 15 freshwater
lakes we then estimated encounter rates in natural habitats and related the results to both prey fish density and environmental
factors. We found the expected positive dependence of individual encounter rates on prey density in our pool and enclosure
experiments, whereas the relation between school encounter rate and prey density was less clear. In the field survey, encounter
rates did not correlate with prey density but instead correlated positively with water transparency. Water transparency decreases
with increasing prey density along the productivity gradient and will reduce prey detection distance and thus predator search
efficiency. Therefore, visual predator–prey encounter rates do not increase, and may even decrease, with increasing productivity
despite increasing prey densities. 相似文献
78.
79.
Ana Carolina Luchiari Cristiane Regina do Amaral Duarte Fúlvio Aurélio de Morais Freire Kari Nissinen 《Journal of Ethology》2007,25(2):169-175
We studied the colour preference of isolated Nile tilapia (Oreochromis niloticus) and whether previous residence or body size can affect environmental colour choice. In the first phase, a cylindrical tank
was divided into five differently coloured compartments (yellow, blue, green, white and red), a single fish was introduced
into the tank and the frequency at which this fish visited each compartment was recorded over a 2-day study period. An increasingly
larger fish (approx +2 cm in length each time) was then added into the tank on each of days 3, 5 and 7 (=four fish in the
tank by day 7), and the frequency at which each fish visited the different compartments of the tank was observed twice a day
to obtain visit frequency data on the differently sized fishes. This experiment was replicated six times. In the first phase,
the solitary fish established residence inside the yellow compartment on the first and second days. Following the
introduction of a larger fish, the smaller fish was displaced from the occupied compartment. Nile tilapia possibly shows this
preference for yellow as a function of its visual spectral sensitivity and/or the spectral characteristics of its natural
environment. Moreover, body size is an important factor in determining hierarchical dominance and territorial defence, and
dominant fish chose the preferred environmental colour compartment as their territory. 相似文献
80.
Sexual selection theory has primarily focussed on the role of mating preferences for the best individuals in the evolution
of condition-dependent ornaments, traits that signal absolute quality. Because the most suitable mate for one individual is
not always the best for others, however, we argue that non-directional mate choice can promote the evolution of alternative
morphs that are not condition-dependent in their expression (i.e. genetic polymorphism). We list the different mate-choice
rules (i.e. all individuals have the same preference; preference depends on the chooser’s morph; individuals mate preferentially
with conspecifics displaying an uncommon or the most frequent morph) and review experimental studies that investigated mate
choice in natural populations of colour-polymorphic animals. Our review emphasises that although the experimental data support
the idea that sexual selection plays an important role in the evolution of genetic colour polymorphism in many different ways,
little is known about the adaptive value of each mate-choice strategy and about their implication in the evolutionary stability
of colour polymorphism. One way of solving this problem is to determine the adaptive function of colour morphs, a worthwhile
objective, because better understanding of mate-choice rules in polymorphic species should provide important insights into
sexual-selection processes and, in turn, into the maintenance of genetic variation. 相似文献