A reliable indicator of female fecundity: the case of the yellow belly in<Emphasis Type="Italic"> Knipowitschia panizzae</Emphasis> (Teleostei: Gobiidae)

A large body of research has developed on male ornaments and their role in sexual selection while female ornaments have been less investigated. This study focused on the presence, function, and possible role of a sexually dimorphic nuptial trait as an indicator of female quality in a fish species presenting conventional sex roles: the yellow patch on the belly of Knipowitschia panizzae females. Aquarium spawning experiments demonstrated that this ornament is due to dermal pigments, is displayed only when the female is ready to spawn, and is switched off within minutes from the end of egg deposition. This sexual trait is variable in size among females and indicates female fecundity relative to her own body size. As a consequence, female yellow belly appears to be a reliable indicator of female quality as measured by current fecundity. Field data on natural nests highlights that males usually perform parental care on only one egg batch at a time. The modality of egg deposition suggests that males may be limited in their potential reproductive rates by environmental factors. Male limitations in egg care could favour male choosiness and the evolution of female nuptial displays.Communicated by R. Cattaneo-Vietti, Genova     

Reproduction and colony integration of the sea pen<Emphasis Type="Italic"> Virgularia juncea</Emphasis>

The distribution of fertile polyps, and the functional variations of polyps within sea-pen colonies, were investigated in Virgularia juncea, a species inhabiting shallow waters in the Penghu Islands, west of Taiwan. This gonochoristic species started gametogenesis between July and September, and mature gametes were broadcast in late summer the following year. Fertile pinnae and their constituent polyps were located in the middle region of the rachis; the upper and lower regions were infertile. Within the fertile regions, fecundity per centimeter decreased linearly toward the tips of the colonies. Abundant zooxanthellae were found in the upper part of the rachis; algal densities decreased down the axis of the colonies, and no algae were present in the lower part. New pinnae were generated only at the basal part of the rachis, They moved upward in relative position with growth of the colonies. These young pinnae near the peduncle were small and infertile. With time, they became fertile and started to harbor a few zooxanthellae. The old pinnae at the upper part of the rachis were large and infertile and contained numerous zooxanthellae. The tips of the colonies were often damaged, and the bare axial rods there were often fragile and could be easily broken off. The developmental gradient of pinnae (and their constituent polyps) along the axes of the colonies, coupled with the environmental gradient within a sea-pen colony, facilitates the functional differentiation within the rachis that may be an adaptation for inhabiting the interface between the water column and the sediment.Communicated by P.W. Sammarco, Chauvin     

Effects of dietary fatty acids on the reproductive success of the calanoid copepod<Emphasis Type="Italic"> Temora longicornis</Emphasis>

Egg production and hatching success of the copepod Temora longicornis were measured in laboratory experiments and in the field (North Sea). In the laboratory, ingestion of four algal species (Thalassiosira weissflogii, Phaeocystis globosa, Isochrysis sp. and Dunaliella tertiolecta) was followed and the content of fatty acids in the algae was determined. The two food types (T. weissflogii and Isochrysis sp.) that provided the highest ingestion of carbon and long chain fatty acids also resulted in the highest egg production rate (E_r) and hatching success (H%). In contrast, D. tertiolecta led to both low ingestion of carbon and long chain fatty acids, resulting in low reproductive success. There was a positive relationship between the amount of eicosapentaenoic fatty acid [20:5(n-3), EPA] ingested and E_r and H%, and of the ratio between docosahexaenoic and eicosapentaenoic fatty acid [22:6(n-3)/20:5(n-3), DHA/EPA] in the ingested food and H%. In the field, chlorophyll a and specific fatty acids were measured and protists were enumerated, in order to investigate the link between these factors and the reproductive success of T. longicornis. Hatching time was found to be related to temperature and exceeded 120 h at 6°C. No relationship was found between chlorophyll a and reproductive success (E_r or H%). E_r correlated with the concentration of diatoms and ciliates, which were the dominating protists in early spring, indicating that food quantity was the limiting factor for E_r. As in the laboratory experiments, H% was dependent on the fatty acid DHA and the ratio of DHA/EPA, which indicates that the quality of eggs (H%) is linked to the quality of food.Communicated by M. Kühl, Helsingør     

Variation at local scales need not impede tests for broader scale patterns

Ecologists are not always mindful of the constraints imposed by their scale of observation and sometimes prematurely attempt broad generalisations or become mesmerised by local details depending on their predilections. We specifically chose a character that is known for its local and unpredictable variation (morphology of kelp) to test the effect of scale on our ability to determine spatial patterns. We compared the morphology of Ecklonia radiata between monospecific and mixed stands of canopy-forming algae across temperate Australia (>5,100 km coastal distance) within a hierarchy of several spatial scales. While E. radiata specimens were generally larger in monospecific than in mixed stands, we failed to observe differences in morphology between stands at many sites and locations. Despite substantial local variation, differences between stands became increasingly clear at broader scales. The frequency of inconsistent differences between stands was greatest at local scales (sites separated by kms), intermediate at intermediate scales (locations separated by 100s of kms) and least at regional scales (regions separated by 1,000s of kms). These observations support the idea that large scale patterns can emerge from apparent stochasticity at small scales, and that unaccountable variation at local scales need not impede tests for similar patterns at broader scales. Most ecologists work at scales where complexity tends to be greatest (i.e. local) and is likely to be explained by special and unique events. It is encouraging, therefore, to observe that patterns can emerge from complexity at local scales to provide new opportunities to answer some of the more interesting questions about the relative importance of processes across the vast parts of the worlds coast.Communicated by M.S. Johnson, Crawley     

Pacific harbor seals (<Emphasis Type="Italic">Phoca vitulina</Emphasis>) and salmon: genetics presents hard numbers for elucidating predator-prey dynamics

We used a PCR-based species test and microsatellite genotyping to determine salmonid species composition and quantity of Chinook among Pacific harbor seal (Phoca vitulina) prey. Tests were applied to DNA extracted from all salmonid bones recovered from scat (fecal) samples. Condition of bone samples and quantity of DNA varied substantially. Although DNA extraction and species identification was only successful for just over half of the bone samples, 93% of all scat samples had bones that were identified to species. Most often only a single salmonid prey species was evident within a scat sample (39% exclusively coho and 46% exclusively Chinook) but 13% contained bones from more than one species of salmonid. For scat samples that contained Chinook bones, 68% had skeletal remains from the same fish and 32% had bones from more than one individual Chinook, varying in number from two to four individuals per scat. In one case, bones from one individual Chinook were recovered in three different scat samples.     

Monitoring of waste deposit derived groundwater contamination with organic tracers

Specific anthropogenic substances derived from seepage and leakage water from a waste deposit landfill were analysed in groundwater and drainage effluents using gas chromatography-mass spectrometry (GC/MS). Here, we demonstrate the application of an organic marker approach to study lateral and vertical distribution of contamination as well as the long-term emission behaviour. Source-specific and environmentally-stable pesticides, plasticisers and pharmaceuticals, such as N,N-diethyl toluamide, N-butyl benzene sulfonamide, clofibric acid, mecoprop and bisphenol A, were quantitatively analysed. A distinct lateral expansion was detected. Although temporal variations were high, no significant trend was observed.     

Neighborhood Level Spatial Analysis of the Relationship Between Alcohol Outlet Density and Criminal Violence

Misuse of alcohol is a significant public health problem, potentially resulting in unintentional injuries, motor vehicle crashes, drownings, and, perhaps of greatest concern, serious acts of violence, including assaults, rapes, suicides, and homicides. Although previous research establishes a link between alcohol consumption increased levels of violence, studies relating the density of alcohol outlets (e.g., restaurants, bars, liquor stores) and the likelihood of violent crime have been less common. In this paper we test for such a relationship at the small area level, using data from 79 neighborhoods in the city of Minneapolis, Minnesota. We adopt a fully Bayesian point of view using Markov chain Monte Carlo (MCMC) computational methods as available in the popular and freely available WinBUGS language. Our models control for important covariates (e.g., neighborhood racial heterogeneity, age heterogeneity) and also account for spatial association in unexplained variability using conditionally autoregressive (CAR) random effects. Our results indicate a significant positive relationship between alcohol outlet density and violent crime, while also permitting easy mapping of neighborhood-level predicted and residual values, the former useful for intervention in the most at-risk neighborhoods and the latter potentially useful in identifying covariates still missing from the fixed effects portion of the model.     

How do slugs cope with toxic alkaloids?

Summary. Arion lusitanicus and other slugs are able to feed on a variety of plants, even those containing toxic secondary metabolites, such as alkaloids. Alkaloids, like sparteine, lupanine, quinidine and atropine are avoided in no-choice feeding experiments only when they are present in concentrations above 1 mg/g food pellet. Alkaloids (sparteine, lupanine, cytisine, quinidine, atropine, senecionine, eserine, and harmaline) are toxic to Arion lusitanicus when injected. LD₅₀ values are 10 to 20 fold higher than in vertebrates indicating that slugs have a high tolerance towards food toxins. The tolerance is higher in young animals than in adult slugs. Injected alkaloids are rapidly detoxified within 72 h. Tolerance and detoxification can be induced by feeding slugs on non-lethal doses of lupin alkaloids. Using isolated microsomal preparations from the digestive gland, active detoxification was observed in vitro. Evidence is presented that cytochrome p450 plays an important role in detoxification of the applied alkaloids. A powerful and inducible detoxification systems appears to be the main mechanism that allows slugs to feed on plants rich in secondary metabolites (when no other food is available), that are usually avoided by other herbivores.     

Allopatric differentiation in the acoustic communication of a weakly electric fish from southern Africa, <Emphasis Type="Italic">Marcusenius macrolepidotus</Emphasis> (Mormyridae,Teleostei)

A few species of the weakly electric snoutfish, the African freshwater family Mormyridae, have been reported to vocalise. However, allopatric populations of a single species were never compared. Members of three allopatric Marcusenius macrolepidotus populations, originating from the Upper Zambezi River in Namibia, the Buzi River (Mozambique), and the Incomati River system in South Africa, vocalised with pulsatile growl- and tonal hoot sounds in dyadic confrontation experiments. A high rate of growling accompanied territorial and agonistic interactions and also non-threatening interactions between males and females, which in one pair appeared to be courtship. Growl sound characteristics of M. macrolepidotus from the Incomati system differed from those of the Upper Zambezi in a significantly higher frequency of the first harmonic (mean, 355 Hz vs 266 Hz). The two vocalising males from the Buzi River generated growls about twice as long as the other fish. Furthermore, the growl pulse period was about 4 ms in M. macrolepidotus from the Upper Zambezi River and from the Incomati system, but 6 ms in M. macrolepidotus from the Buzi River. Hoots were only observed in agonistic encounters. Hoot oscillograms showed a sinusoidal waveform, and the mean duration of this sound was similar in Incomati system fish (mean, 161 ms), Upper Zambezi fish (172 ms) and Buzi fish (103 and 145 ms for the two vocalising individuals). The mean frequency of the first hoot harmonic was higher in Incomati system fish (326 Hz) than in Upper Zambezi fish (245 Hz). Both growl and hoot occurred only in the presence of conspecifics, probably signalling the presence and condition of an opponent, territory owner or potential mate. This is the first evidence for (1) sound production and acoustical communication in another species and genus, M. macrolepidotus, from southern Africa to be (2) geographically differentiated.