A comparison of the efficiency of the bottom samplers used in benthic studies off Cochin

The efficiency of the van Veen and Foerst Petersen grabs used in sampling the bottom fauna near the Cochin Harbour area has been compared in two selected stations having different hydrographic and substratic conditions. The results indicate that the heavier grab is generally more efficient than a lighter one, especially when the substratum is sandy. An examination of the quantity of the sediment and the total number of species brought by the two grabs showed that the design of the van Veen is superior to the Petersen type grab used in the present study. However, due to the highly patchy distribution of the organisms the superiority of the van Veen was less evident when a comparison was made of the total number of animals sampled by the two grabs. When the distribution is bunched it is suggested that samples are drawn, as far as possible, from the same sampling position. The grabs should also be of the same weight and biting area.     

Diversity of ground arthropod community at organic and chemically intensive tea plantation of Darjeeling terai

Tea in Darjeeling foothills and terai are grown conventionally, with application of chemical fertilizers and pesticides, as well as organically without these inputs. Ground level arthropod community was collected from the above two types of tea plots using pitfall traps. Catches from these environments showed variation in the arthropod faunal structure with numerically and taxonomically greater abundance in the organic than that of the conventional plot. Coleopterans were more diverse with largest number of families and Recognizable Taxonomic Units (or morphospecies) in the organic tea plot. The diversity and similarity indices for coleopterans were comparable, in organic and conventional tea plots at species and family levels. The close relationship of the indices suggested that diversity study at family level could be used as surrogate for species level diversity; thus alleviating the laborious and expertise job of taxonomic identification of arthropod species. Faunal diversity study at ground level gave the clue that soil of the organic plantation was healthier than that of the conventional tea plot.     

Digestive mechanics and gluttonous feeding in the feather starOligometra serripinna (Echinodermata: Crinoidea)

The movement and digestion of food in the gut ofOligometra serripinna (Carpenter) were studied at Lizard Island (14°3842S; 145°2710E) in the austral winter of 1986. Feather stars in the laboratory were fed a brief, small meal of brine shrimp nauplii and killed at increasing time intervals thereafter. Histological reconstructions showed that the ingested nauplii progressed along the digestive tract surprisingly quickly. Some nauplii were found in the mid and hind intestine in only 30 min, and all of the nauplii had reached the hind intestine and rectum in 1 h. Digestion of the nauplii had started at 1 h, and only a few fragments of naupliar exoskeleton remained in the hind intestine and rectum 5 h after the start of feeding. Videotape analysis showed that no fecal pellets were released during this experiment. In the natural environment ofO. serripinna, ingested particles may similarly be transported quickly to the hind part of the gut and digested there — when feather stars were fixed in the field, most of the gut contents were found in the hind intestine and rectum.O. serripinna, which efficiently rejects inert particles before they are ingested, usually defecates infrequently (probably not more than once over a span of many hours) and differs from some other feather stars that ingest numerous inert particles and defecate much more frequently. When specimens ofO. serripinna were fed continuously on brine shrimp nauplii,Artemia sp. (San Francisco strain), in the laboratory, the feather stars fed gluttonously, packing their guts with several hundred nauplii in 1 to 2 h. Thereafter, superfluous feeding began (i.e., further ingestions appeared to force undigested nauplii, some of them still living, out of the anus). These observations suggest thatO. serripinna usually feeds at relatively modest rates in its natural habitat, but can feed gluttonously to take advantage of infrequent patches of highly concentrated, nutritious particles (e.g. copepod swarms, migrating demersal zooplankton, and invertebrate gametes from mass spawnings). It is likely that such patches of nutritious particles are usually small enough to drift out of reach of the feather stars before gluttonous feeding proceeds to superfluous feeding. Opportunities for superfluous feeding in nature are probably very infrequent (e.g. ingestion of coral gametes and embryos after a mass spawning), and the feather stars evidently have no behavior that stops further ingestions after the gut becomes filled to capacity.     

Human teeth as historical biomonitors of environmental and dietary lead: some lessons from isotopic studies of 19th and 20th century archival material

The lead isotopic composition of various sections (crown, crown base, root) of teeth was determined in specimens collected from 19th century skulls preserved in museum collections and, upon extraction or exfoliation, from humans of known ages residing in Scotland in the 1990s. For most 20th century samples, calculation of accurate crown-complete or root-complete dates of tooth formation ranging from the 1920s to the 1990s enabled comparison of ²⁰⁶Pb/²⁰⁷Pb ratios for teeth sections (crown base root) with corresponding decadally averaged data for archival herbarium Sphagnum moss samples. This showed that the teeth sections had been significantly influenced by incorporation of non-contemporaneous (more recent) lead subsequent to the time of tooth formation, most probably via continuous uptake by dentine. This finding confirmed that separation of enamel from dentine is necessary for the potential of teeth sections as historical biomonitors of environmental (and dietary) lead exposure at the time of tooth formation to be realised. Nevertheless, the mean 19th century value of 1.172±0.007 for the ²⁰⁶Pb/²⁰⁷Pb ratio in teeth was very similar to the corresponding mean value of 1.173±0.004 for 19th century archival moss, although relative contributions from environmental sources – whether direct, by inhalation/ingestion of dust contaminated by local lead smelting (²⁰⁶Pb/²⁰⁷Pb~1.17) and coal combustion (²⁰⁶Pb/²⁰⁷Pb~1.18) emissions, or indirect, through ingestion of similarly contaminated food – and drinking/cooking water contaminated by lead pipes of local origin, cannot readily be determined. In the 20th century, however, the much lower values of the ²⁰⁶Pb/²⁰⁷Pb ratio (range 1.100–1.166, mean 1.126±0.013, median 1.124) for the teeth collected from various age groups in the 1990s reflect the significant influence of imported Australian lead of lower ²⁰⁶Pb/²⁰⁷Pb ratio (~1.04) and released to the environment most notably through car-exhaust emissions arising from the use of alkyl lead additives (²⁰⁶Pb/²⁰⁷Pb~1.06–1.09) in petrol in the U.K. from ca. 1930 until the end of the 20th century.     

Frailty in state-space models: application to actuarial senescence in the Dipper

Senescence, a decrease in life history traits with age, is a within-individual process. The lack of suitable methods to deal with individual heterogeneity has long impeded progress in exploring senescence in wild populations. Analyses of survival senescence are additionally complicated by the often neglected issue of imperfect detectability. To deal with both these issues, we developed state-space models to analyze capture-mark-recapture data while accounting for individual heterogeneity by incorporating random effects. We illustrated our approach by applying it to 29 years of data on breeding females in a Dipper (Cinclus cinclus) population. We highlighted patterns of age-related variation in annual survival by statistical comparisons of piecewise linear, quadratic, Gompertz, and Weibull survival models. The Gompertz model was ranked first in our set. It provided strong evidence for actuarial senescence with an onset of senescence estimated at about 2.3 years. The probability for this model to involve a frailty was 0.15, and the probability to involve an individual latent effect in detection was about 0.4. The estimated mean age at first reproduction was 1.2 years. The general case model described here in detail should encourage the reanalysis of actuarial senescence in cases where imperfect detection or individual heterogeneity is suspected.     

Sexual selection and the function of a melanin-based plumage ornament in polygamous penduline tits <Emphasis Type="Italic">Remiz pendulinus</Emphasis>

Melanin-based ornaments are often involved in signaling aggression and dominance, and their role in sexual selection is increasingly recognized. We investigated the functions of a melanin-based plumage ornament (facial ‘mask’) in male Eurasian penduline tits Remiz pendulinus in the contexts of male–male aggression, mating success, and parental care. The penduline tit is a passerine bird with a unique mating system in which both sexes may mate with several mates in a breeding season, and one (or both) parent deserts the clutch. Our study revealed that mask size of males is more likely an honest signal used by females in their mate choice decisions than a trait involved in male–male competition. First, mask size increased with both age and body condition, indicating that the mask may signal male quality. Second, males with larger masks paired more quickly and had more mates over the breeding season than males with smaller masks. Third, we found no evidence that male mask size signals male–male aggression or dominance during competitive encounters. The increased mating success of large-masked males, however, did not translate into higher reproductive success, as nestling survival decreased with mask size. Therefore, we conclude that there is either no directional selection on male mask size or males with larger masks receive indirect, long-term benefits.     

Effect of ambient air sulphur dioxide on sulphate accumulation in plants

Present study deals with the relationship between ambient air sulphurdioxide and sulphate content in leaf of selected tropical plant species, Ficus religiosa. The study reveals a positive correlation between ambient air sulphur dioxide and sulphate in the leaves. Two way ANOVA finds the obtained values to be highly significant (p < 0.001). Amount of sulphate in leaves shows positive correlation with sulphur dioxide in air (p < 0.001) during most part of the study A marked reduction of sulphate content in leaf was found during October when reduction in ambient air sulphur dioxide was recorded.     

Effects of high temperature on larval development and metamorphosis of Arachnoides placenta (Echinodermata: Echinoidea)

Adults of the sea urchin Arachnoides placenta (L.) were induced to spawn, and eggs were fertilized at 28°C in September 1989. After 5 min, eggs were transferred to 28, 31, 34, or 37°C and reared to metamorphosis. Embryos were observed at 20-min intervals during the first 2 h; larvae were observed daily. The cleavage was higher at higher temperatures. Embryos reared at 28°C were still at the 4th cleavage (16-cell stage) after 100 min, while those at 34°C had reached the 5th cleavage (32-cell stage). All embryos reared at 37°C died on the second day. Incidence of abnormality was 20 to 30% at 28 and 31°C, 48% at 34°C, and 77% at 37°C. The 8-arm stage was reached after 4 d at 28°C, 3 d at 31°C and 2 d at 34°C. Larvae displayed decreasing body length and arm length with increasing temperature. Larvae at 31°C have relatively long arms, as a result of a decrease in body length, not because of increased arm length. Incidence of metamorphosis was 43.9±1.7% (mean/plusmn;SD) at 28°C, 24.5±1.9% at 31°C, and 5.3% at 34°C. The size of metamorphosed juveniles was significantly larger at 28°C than at 31 and 34°C. Temperatures of 31°C negatively affect larvae and juveniles of the sand dollar.     

Gene flow among vestimentiferan tube worm (Riftia pachyptila) populations from hydrothermal vents of the eastern Pacific

Allozyme data are presented for six discrete populations of the giant hydrothermal vent tube worm Riftia pachyptila Jones, 1981 collected throughout the species' known range along mid-ocean spreading ridges of the eastern Pacific Ocean. Contrary to an earlier report, levels of genetic variation are relatively high in this species. Estimates of gene flow based on F-statistics revealed that dispersal throughout the surveyed region is sufficiently high to counter random processes that would lead to losses of genetic diversity and significant population differentiation. R. pachyptila, like other species of tube worms, displays considerable morphologic variation among populations, but this diversity is not reflected in allozyme variation. Vestimentifera, in general, appear to show extensive phenotypic plasticity. In the light of the available genetic data, caution is warranted when making inferences about the taxonomic status of collections based on morphological variation alone. A general decrease in estimated rates of gene flow between geographically more distant populations supports the hypothesis that dispersal in this species follows a stepping-stone model, with exchange between neighboring populations in great excess of long-distance dispersal. High levels of gene flow have been recorded in a variety of vent fauna and may be a prerequisite for success of species found in the ephemeral habitats associated with regions of sea-floor hydrothermal activity.