Ladybird defence alkaloids: Structural,chemotaxonomic and biosynthetic aspects (Col.: Coccinellidae)

Summary The defensive mechanisms which protect ladybird beetles (Coccinellidae) against predators are reviewed. Besides behavioural mechanisms, such as thanatosis and reflex bleeding, chemical defence mechanisms are playing a prevalent role. Indeed, ladybirds are protected not only by their smell, but also by repulsive alkaloids, most of which are considered to be of autogenous origin. In a few cases, dietarily-acquired substances are also involved. Particular emphasis is laid on the repellent alkaloids which are contained in the haemolymph of many species. The structures of 34 nitrogen-containing compounds isolated so far are presented, and their distribution within the family is discussed in the light of the most widely accepted classification of these beetles. To conclude, the mode of release of the alkaloids, their variation through the life cycle and their repellent and toxic properties are discussed, as well as the few biosynthetic data yet available.     

Causative species of diarrhetic shellfish poisoning (DSP) in Norway

This study was performed at Vikane in the Sognefjord, Norway, from September 1987 to October 1988 on the blue musselMytilus edulis collected monthly at three different depths (3 to 6, 6 to 8 and 8 to 12 m). Cell numbers of three species ofDinophysis from mussel digestive glands and in seawater were counted for each specimen. Multivariable statistical methods were used to detect annual cycles of phytoplankton abundance in the fjord and to examine the contribution of each species to toxification of mussels. Cluster analysis and principal component analysis indicated the following results: (1) an annual cycle and an inter-specific association of threeDinophysis species populations were pointed out.D. acuta andD. norvegica were well associated over the entire period of this study, and exhibited an autumnal peak.D. acuminata was dissociated from these species and reached its maximum abundance between spring and early summer. (2) The threeDinophysis species induced toxicity in the blue mussels in different manners.D. acuta andD. norvegica were responsible for high autumnal toxicity, andD. acuminata for the spring peak. (3) A long persistence of diarrhetic shellfish poisoning (DSP) in blue mussels (from April to February), and a depth gradient of toxicity were observed — the toxicity value in the upper layer being double those of other depths.     

Self-monitoring of reproductive success: nest switching in the redlip blenny (Pisces: Blenniidae)

Summary In the redlip blenny Ophioblennius atlanticus, commonly found on Caribbean reefs, eggs are laid in a male's nest and are guarded by the male until they hatch as planktonic larvae. Male reproductive success, defined as the number of egg batches hatched per reproductive period, was positively correlated with male size and with the inner surface area of the male's nest. Male blennies often switch nests between reproductive periods. Most nest switching (83%) occurred following periods of low reproductive success. Moreover, a male having low reproductive success was more likely to switch if the inner surface area of his nest was small. Most nest switching (72–80%) was to a nest of larger surface area than the previous nest. In 72% of all switches, males had higher reproductive success in the period following the switch than in the one preceding it. The results suggest that male redlip blennies monitor their current reproductive success and the characteristics of their current nests, switch to better nests if their reproductive success is low, and typically benefit from the decision to do so. These capabilities have seldom been demonstrated in any phylum.     

The contribution of L. C. Gray to the economic theory of exhaustible natural resources and its roots in the history of economic thought

The paper opens with an assessment of natural resources economics up to 1913–14 when Gray published his two pioneering articles in natural resources economics (Part I). An in-depth study of Gray, weighing his contribution to the microeconomic theory of the mine and the macroeconomic theory of conservation against current literature, constitutes the main body of the paper (Part II). Gray and Hotelling's contributions to the theory of the mine are compared (Part III). The paper concludes with a comparison drawn between the author's findings and the scant attention previously paid to Gray's contributions to natural resources economics.“So far as I know, this is the first attempt to apply economic theory to this particular problem of conservation.” (H. C. Taylor, unpublished letter to C. R. Van Hise, May 23, 1913, a reference to Gray's “Economic Possibilities of Conservation”).     

Mating system and individual reproductive success of sympatric anadromous and resident brook charr, <Emphasis Type="Italic">Salvelinus fontinalis</Emphasis>, under natural conditions

Salmonids are known for the occurrence in sympatry of two life-history forms, one that undergoes migration to sea before returning to freshwater to reproduce (anadromous) and one that inhabits freshwater without a migration phase (resident). Whereas one breeding population is often suggested by population genetic studies, mating patterns have rarely been directly assessed, especially when both sexes are found within each life-history form. By using highly polymorphic microsatellite loci and parentage analysis in a natural population of sympatric anadromous and resident brook charr (Salvelinus fontinalis), we found that gene flow occurred between the two forms and was mediated by resident males mating with both resident and anadromous females. Determinants of reproductive success, estimated by the number of surviving juveniles (ages 1 and 2 years), differed between the sexes. No strong evidence of the influence of size on individual reproductive success was found for males, whereas larger females (and hence most likely to be anadromous) were more successful. The higher individual reproductive success of anadromous fish compared to residents was mainly explained by this higher reproductive success of anadromous females. We suggest that resident males adopt a “sneaking” reproductive tactic as a way of increasing their reproductive success by mating with females of all sizes in all habitats. The persistence of the resident tactic among females may be linked to their advantage in accessing spatially constrained spawning areas in small tributary streams unavailable to larger females.     

Carotenoid-based colouration and ultraviolet reflectance of the sexual ornaments of grouse

Among the most familiar sexual signals are red, yellow, and orange sexual traits pigmented by carotenoids. Many birds can detect near-ultraviolet (UV) light, and UV signals can play key roles in mate choice. Grouse (Tetraonidae) exhibit bright carotenoid-dependent sexual ornaments, their supra-orbital combs, which to humans appear orange-red. Combs also reflect in the UV, which is not visible to humans but is likely to be visible to grouse. In male red grouse Lagopus lagopus scoticus, we show that comb UV reflectance decreases with increasing comb size and redness. By removing the epidermis of combs, where carotenoid pigments are, we show that the UV reflectance is a property of the dermis, underneath the red pigmented epidermis. Carotenoid pigmentation of combs acted as a mask to reduce reflectance by the dermis in the range 400–550 nm and in the UV, 300–400 nm. Patagium skin (non-ornamental skin under the wing) also reflects in the UV, but epidermis removal on this bare part tended to reduce UV reflectance, whereas removal of the red epidermis of combs increased UV reflectance. Males in better condition (greater body mass relative to size) had bigger and redder combs, but with less UV. Thus, carotenoid pigments of grouse combs are deposited on a white background with significant UV reflectance, which can influence how the signal is perceived by conspecifics. Carotenoid-based traits exhibit UV reflectance in a number of species, but how UV reflectance and carotenoid pigmentation influence colour remains little known for integumentary ornaments compared to plumage traits. UV vision is not uncommon in birds and other animals, so future studies should investigate how UV reflectance influences the perception of carotenoid-based signals of quality.     

Environmental conditions influence egg color of reed warblers <Emphasis Type="Italic">Acrocephalus scirpaceus</Emphasis> and their parasite,the common cuckoo <Emphasis Type="Italic">Cuculus canorus</Emphasis>

The outer layer of the eggshell in birds is in many cases covered by pigments that are assumed to be genetically determined traits with a negligible environmental component. To test the hypothesis that spring environmental conditions (i.e., temperature and rainfall) may affect bird egg pigmentation, we measured by spectrophotometry and photography egg coloration and spottiness on reed warbler (Acrocephalus scirpaceus L.) clutches parasitized by the common cuckoo (Cuculus canorus L.) collected over a period of 24 years and preserved in the Zoological Museum, Copenhagen, Denmark. In addition, we investigated whether spring environmental conditions may influence the coevolutionary relationship between the cuckoo and its host via changes in cuckoo–host egg matching. Generalized mixed models revealed that reed warbler eggs were more brilliant in those springs with a higher rainfall and tended to be bluer and greener in springs with a lower relative temperature. On the other hand, cuckoo eggs were bluer and greener in springs with a higher rainfall. Cuckoo–host egg matching in blue-greenness and spottiness was better in springs with a higher rainfall. These results provide support for the existence of an environmental component on bird egg coloration and suggest that environmental factors may potentially affect the outcome of important features of the arms race between cuckoos and reed warblers.     

Unusual echolocation behavior in a small molossid bat, <Emphasis Type="Italic">Molossops temminckii,</Emphasis> that forages near background clutter

When searching for flying insects, Molossops temminckii uses unusual echolocation calls characterized by upward modulation of frequency vs time (UFM). Call frequency increases asymptotically in the relatively long (∼8 ms) pulses from a starting frequency of ∼40 kHz to a long narrowband tail at ∼50 kHz. When approaching a prey, the bat progressively increases the duration of calls and intersperses in the sequence broadband downwardly frequency-modulated signals with a terminal frequency of about 53 kHz, which totally replaces the UFM signals at the end of the approach phase. The sequence progresses to a capture buzz resembling those from other molossid and vespertilionid bats. The M. temminckii wing morphology is characterized by an average aspect ratio and a high wing loading, suggesting that it is more maneuverable than the typical Molossidae but less than typical Vespertilionidae. M. temminckii regularly forages near clutter, where it needs to pay attention to the background and might face forward and backward masking of signals. We hypothesize that the UFM echolocation signals of M. temminckii represent an adaptation to foraging near background clutter in a not very maneuverable bat needing a broad attention window. The broadband component of the signal might serve for the perception of the background and the narrowband tail for detection and perhaps classification of prey. Bats may solve the signal masking problems by separating emission and echoes in the frequency domain. The echolocation behavior of M. temminckii may shed light on the evolution of the narrowband frequency analysis echolocation systems adopted by some bats foraging within clutter.     

Chemical defense: incorporation of diet-derived pyrrolizidine alkaloid into the integumental scales of a moth (<Emphasis Type="Italic">Utetheisa ornatrix</Emphasis>)

Summary. Evidence is presented that pyrrolizidine alkaloid acquired by Utetheisa ornatrix (Lepidoptera, Arctiidae) as a larva from Crotalaria foodplants is incorporated in part into the scales of the adult. A single forewing of a male or female moth may contain in the order of 6 to 13 g monocrotaline in its scale cover or about 1 to 2% of the moths systemic monocrotaline content. Based on estimates of the number of scales per forewing, the monocrotaline content of individual scales is calculated to be in the order of 0.1 and 0.2 ng monocrotaline per male and female scale, respectively. This amounts to concentrations of about 1 and 3%, values roughly at a par with the average systemic concentration (0.5-0.6%) previously determined for monocrotaline in Utetheisa. It is argued that the presence of pyrrolizidine alkaloid in the moths scale coating could account for the promptness with which adult Utetheisa are rejected by spiders. It is suggested further that chemical impregnation of scales with substances deterrent to predators may be more widespread among insects than generally assumed.     

Application of adaptive cluster sampling to low-density populations of freshwater mussels

Freshwater mussels appear to be promising candidates for adaptive cluster sampling because they are benthic macroinvertebrates that cluster spatially and are frequently found at low densities. We applied adaptive cluster sampling to estimate density of freshwater mussels at 24 sites along the Cacapon River, WV, where a preliminary timed search indicated that mussels were present at low density. Adaptive cluster sampling increased yield of individual mussels and detection of uncommon species; however, it did not improve precision of density estimates. Because finding uncommon species, collecting individuals of those species, and estimating their densities are important conservation activities, additional research is warranted on application of adaptive cluster sampling to freshwater mussels. However, at this time we do not recommend routine application of adaptive cluster sampling to freshwater mussel populations. The ultimate, and currently unanswered, question is how to tell when adaptive cluster sampling should be used, i.e., when is a population sufficiently rare and clustered for adaptive cluster sampling to be efficient and practical? A cost-effective procedure needs to be developed to identify biological populations for which adaptive cluster sampling is appropriate.