Physiology of diapause in the adult bark beetle, Ips acuminatus Gyll., studied in relation to cold hardiness

The ovarioles of the bark beetle, Ips acuminatus are telotrophic. Ovarian development is suppressed at an immature stage with primary germ cells present in the germaria. Lower oxygen consumption is found in beetles during autumn and early winter, and a substantial rise in mean respiration rates occurs in the beginning of January paralleled by a resumption of pre-vitellogenesis in all females maintained either at 3°C or out of doors after return to 21°C for 2 weeks. It is concluded that I. acuminatus enters faculative diapause soon after enclosure to the adult, and that diapause is terminated by mid-winter in beetles kept for 18 weeks at either 3°C or out of doors. The specimens remain thereafter in reproductive quiescence until ovarian development can proceed.Photic cues are neither involved in the elevation of mean respiration rates, nor needed to abolish the inhibition of ovarian maturation in beetles kept at 3°C or in those returned to 21°C. However, follicle formation in ovarioles is only seen in positive phototactic females reared during “long-day” conditions, suggesting a photoperiodic regulation of the later stages of vitellogenesis.Detectable amounts of ethylene glycol are found at the beginning of November in freezing-susceptible I. acuminatus hibernating in its galleries underneath bark of Scots pine (Pinus silvestris) at 3°C. The gradual catabolism of the cryoprotective solute at 3°C through December occurred at a time when individuals achieved the competence to resume ovarian maturation during 2 weeks at 21°C, but prior to the substantial rise in their mean respiration rates. However, resumption of ovarian development in spring had no effect on the capability of outdoor beetles to enhance their supercooling capacity when subjected to sub-zero temperatures. Since the ability to respond to temperature changes occurred in post-diapause I. acuminatus as well, the maintenance of prolonged cold hardiness in specimens could not be related to diapause itself. Apparently, the ability of beetles to resynthesize ethylene glycol when a detectable level is present in the organism remains unaltered during overwintering.     

Spider mite (Acari: Tetranychidae) mitochondrial COI phylogeny reviewed: host plant relationships,phylogeography, reproductive parasites and barcoding

The past 15 years have witnessed a number of molecular studies that aimed to resolve issues of species delineation and phylogeny of mites in the family Tetranychidae. The central part of the mitochondrial COI region has frequently been used for investigating intra- and interspecific variation. All these studies combined yield an extensive database of sequence information of the family Tetranychidae. We assembled this information in a single alignment and performed an overall phylogenetic analysis. The resulting phylogeny shows that important patterns have been overlooked in previous studies, whereas others disappear. It also reveals that mistakes were made in submitting the data to GenBank, which further disturbed interpretation of the data. Our total analysis clearly shows three clades that most likely correspond to the species T. urticae, T. kanzawai and T. truncatus. Intraspecific variation is very high, possibly due to selective sweeps caused by reproductive parasites. We found no evidence for host plant associations and phylogeographic patterns in T. urticae are absent. Finally we evaluate the application of DNA barcoding.     

Maternal investment in reproduction and its consequences in leatherback turtles

Maternal investment in reproduction by oviparous non-avian reptiles is usually limited to pre-ovipositional allocations to the number and size of eggs and clutches, thus making these species good subjects for testing hypotheses of reproductive optimality models. Because leatherback turtles (Dermochelys coriacea) stand out among oviparous amniotes by having the highest clutch frequency and producing the largest mass of eggs per reproductive season, we quantified maternal investment of 146 female leatherbacks over four nesting seasons (2001–2004) and found high inter- and intra-female variation in several reproductive characteristics. Estimated clutch frequency [coefficient of variation (CV) = 31%] and clutch size (CV = 26%) varied more among females than did egg mass (CV = 9%) and hatchling mass (CV = 7%). Moreover, clutch size had an approximately threefold higher effect on clutch mass than did egg mass. These results generally support predictions of reproductive optimality models in which species that lay several, large clutches per reproductive season should exhibit low variation in egg size and instead maximize egg number (clutch frequency and/or size). The number of hatchlings emerging per nest was positively correlated with clutch size, but fraction of eggs in a clutch yielding hatchlings (emergence success) was not correlated with clutch size and varied highly among females. In addition, seasonal fecundity and seasonal hatchling production increased with the frequency and the size of clutches (in order of effect size). Our results demonstrate that female leatherbacks exhibit high phenotypic variation in reproductive traits, possibly in response to environmental variability and/or resulting from genotypic variability within the population. Furthermore, high seasonal and lifetime fecundity of leatherbacks probably reflect compensation for high and unpredictable mortality during early life history stages in this species.     

Reproductive and Mating Success in the Small-Mouthed Salamander (Ambystoma texanum) Estimated via Microsatellite Parentage Analysis

Bateman’s principles of sexual selection predict that the sex with “cheaper” gametes may maximize reproductive efforts by mating multiply and so display greater positive covariance between reproductive and mating success. We conducted a semi-controlled breeding experiment to genetically quantify sexual selection in adult Ambystoma texanum, a sexually monomorphic salamander with simple courtship behaviors. We used four polymorphic microsatellite loci to genotype 57 adults enclosed in a breeding wetland and compared their multilocus profiles to that of 862 embryos collected from the enclosure. The molecular data were used to assign parentage, investigate the mating system, and measure sexual selection intensity. Parentage analyses indicated 36% of dams and 93% of sires were genetically sampled via their gametes but physically unsampled, suggesting that a large number of breeders over-wintered within the enclosure and/or some females released into the enclosure were already inseminated. We used the genetic data to generate estimates of individual reproductive and mating success and we interpret these in light of salamander behavior and sexual selection theory. The incidence of multiple mating in females (86%) was considerably higher than in males (32%) and the standardized variance in mating success was significantly greater in females. The correlations between reproductive and mating success were significant and of similar magnitude between the sexes, indicating that both sexes increased reproductive success through increased mating success. This pattern may be a function of differential opportunities for mating success between the sexes. Electronic Supplementary Material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Ecological character displacement caused by reproductive interference

We carried out a theoretical investigation of whether ecological character displacement can be caused by reproductive interference. Our model assumes that a quantitative character is associated with both resource use and species recognition, and that heterospecific mating incurs costs. The model shows that ecological character displacement can occur as a consequence of evolution of premating isolation; this conclusion is based on the premise that resource competition is less intense between species than within species and that the ecological character also contributes to premating isolation. When resource competition between species is intense, extinction of either species may occur by competitive exclusion before ecological character divergence. Some observational studies have shown that character displacement in body size is associated with not only resources use but also species recognition. We propose that body size displacement can occur as a consequence of evolution of premating isolation. Our results suggest that ecological character displacement results from reproductive character displacement.     

Swimming performance of silver eels is severely impaired by the swim-bladder parasite Anguillicola crassus

Infection with the swim-bladder parasite Anguillicola crassus is suggested as one of the principal causes of the collapse of the European eel population. This nematode has been introduced in Europe from Asia in the 80s and parasitized in a short time Anguilla eel species in different geographical regions across the globe. The parasites drain energy due to their sanguivorous feeding and they cause mechanical damage on the swim-bladder wall. These two effects are hypothesized to impair the spawning migration of the European eel. In this study, we have investigated both effects on swimming performance. We hypothesized that parasitic sanguivorous activities - related to parasite weight - reduce swimming endurance, while mechanical damage of the swim-bladder impairs buoyancy control. Eighty eels suffering various degrees of infection were introduced in swim-tunnels and subjected to a swimming fitness test. The relation between A. crassus infection and swimming efficiency was measured for large female silver eels swimming at various speeds. Infected eels had lower cruising speeds and a higher cost of transport. Eels without parasites, but with a damaged swim-bladder showed similar effects. Almost half of the eels that contained damaged swim-bladders (43%) stopped swimming at low aerobic swimming speeds (< 0.7 m/s). Simulated migration trials in a recent related study have confirmed that eels with a high parasite level or with damaged swim-bladder show early migration failure (< 1000-km). Reduced swimming performance appears to be associated with swim-bladder dysfunction. As we found that especially silver eels have much higher infection levels than yellow eels, it is concluded that migrating silver eels with severely infected or damaged swim-bladders are unable to reach the spawning grounds.     

Sexual selection effects on the evolution of senescence

Although the basic theories concerning evolution of senescence have been generally accepted for a half-century, interpretation of this paradigm has been constrained by an over-reliance on mortality as both the cause and the measure of senescence. Consideration of both survival and fecundity as components of reproductive value, and integration of sexual selection theory with senescence theory allows reconciliation of long-standing, as well as recent, discrepancies between data and theory. This approach demonstrates that sexual selection on males in polygynous mating systems can have significant effects on the evolution of senescence that could overshadow the selection effects of mortality rates among such animals.     

Male foraging avoidance in female feeding territories in a harem polygynous cichlid in Lake Tanganyika

We studied foraging site partitioning between the sexes in Neolamprologus tetracanthus, a shrimp-eating Tanganyikan cichlid with harem-polygyny. Females maintained small territories against heterospecific food competitors within large territories of males, foraging exclusively at the inner side of their own territories (foraging areas). Males fed as frequently as females in their own territories, but mostly outside female foraging areas, although they frequently entered female territories and repelled food competitors from the territories. Soon after removal of the resident females, however, harem males, as well as many food competitors, invaded the vacant territories and intensively devoured prey of female foraging areas. This indicates that although female foraging areas appear to contain more food than outside the areas, harem males refrained from foraging there when the resident females were present. We suggest that harem males will attempt to keep female foraging areas in good condition, whereby they may get females to reside in male territories and/or promote female gonadal maturation.     

The lower salivary testosterone levels among unmarried and married sexually active men

We examined the influences of regular sexual activity and marital status on salivary testosterone levels in healthy adult Japanese men. Forty-four men (20–66 years) collected their saliva thrice a day (0900–1000, 1300–1400, and 1700–1800). The testosterone levels at each collection time negatively correlated with the ages of the participants; therefore, residual testosterone levels were used for analyses after correcting for age by linear regression. The testosterone-lowering effect of marriage was marginal and the regular sexual activity more strongly associated with lower testosterone levels in morning saliva. The possible neurofeedback systems underlying the phenomenon are discussed.     

Reduced reproductive function in wild baboons (Papio hamadryas anubis) related to natural consumption of the African black plum (Vitex doniana)

Several authors have suggested that the consumption of plant compounds may have direct effects on wild primate reproductive biology, but no studies have presented physiological evidence of such effects. Here, for two troops of olive baboons (Papio hamadryas anubis) at Gashaka-Gumti National Park, Nigeria, we show major seasonal increases in levels of fecal progesterone metabolites in females, and provide evidence that this is linked to the consumption of natural plant compounds. Increases in fecal progestogen excretion occurred seasonally in all females, in all reproductive states, including lactation. Detailed feeding data on the study animals showed that only one food species is consumed by both troops at the time of observed progestogen peaks, and at no other times of the year: the African black plum, Vitex doniana. Laboratory tests demonstrated the presence of high concentrations of progestogen-like compounds in V. doniana. Together with published findings linking the consumption of a related Vitex species (Vitex agnus castus) to increased progestogen levels in humans, our data suggest that natural consumption of V. doniana was a likely cause of the observed increases in progestogens. Levels of progestogen excretion in the study baboons during periods of V. doniana consumption are higher than those found during pregnancy, and prevent the expression of the sexual swelling, which is associated with ovulatory activity. As consortship and copulatory activity in baboons occur almost exclusively in the presence of a sexual swelling, V. doniana appears to act on cycling females as both a physiological contraceptive (simulating pregnancy in a similar way to some forms of the human contraceptive pill) and a social contraceptive (preventing sexual swelling, thus reducing association and copulation with males). The negative effects of V. doniana on reproduction may be counter-balanced by the wide-range of medicinal properties attributed to plants in this genus. This is the first time that physiological evidence has been presented of direct effects of plant consumption on the reproductive biology of wild primates.