Mitochondrial gene variation in Mercenaria clam sibling species reveals a relict secondary contact zone in the western Gulf of Mexico

We investigated phylogeographic relationships among American Mercenaria taxa by assessing variation in a 444 nucleotide fragment of the mitochondrial 16S ribosomal gene in clams sampled from four representative sites in January to November 1994. Three of these sites were in the Gulf of Mexico, one was on the Atlantic coast in South Carolina. Direct sequencing of this amplified gene fragment in 85 individuals revealed 21 haplotypes. Phylogenetic analyses consistently resolved this variation into three well supported clades, and within-clade genetic divergence levels were markedly lower than among-clade values. One of the clades, A, was taxon-specific, in that it solely and exclusively contained specimens of M. mercenaria (Linnaeus, 1758) sampled in South Carolina. The other two clades, B and C, were the most divergent and both encompassed specimens of M. campechiensis (Gmelin, 1791) and of M. campechiensis texana (Dall, 1902), sampled from the three Gulf of Mexico sites. Clade B was found at high frequencies at all three Gulf sites, whereas Clade C occurred at low frequencies at two western Gulf sites. We interpret this pattern as resulting from the secondary contact and introgression of two allopatrically differentiated Mercenaria taxa in the western Gulf of Mexico. Clade C haplotypes may represent relict mitochondrial lineages from original Gulf Mercenaria spp. populations that predate massive mitochondrial introgression by M. campechiensis. We further propose that the M. campechiensis texana nuclear genome is a mosaic, heavily weighted toward M. campechiensis, but containing some relict alleles inherited from the precontact population, especially those governing shell characteristics, which may be adaptive in cohesive sediments of bays and estuaries in the northwestern Gulf of Mexico.     

Rotational application of bioinsecticide with deltamethrin-An antilarval measure for the control of filarial vector, Culex quinquefasciatus (Culicidae: Diptera)

A laboratory investigation was undertaken to study the cyclic usage of field recommended doses of Bacillus thuringiensis israelensis (Bti), Bacillus sphaericus (Bsp) and combination of Bti and Bsp (half the recommended dose of each) with deltamethrin 2.8 EC to attain better control of mosquito larvae. To understand the susceptibility status of the Culex quinquefasciatus larvae in the field, early fourth instar field collected larvae were exposed to the above treatments of biopesticides and were monitored for their persistency till 50% mortality was obtained. The larvae those survived in each treatment were transferred to the concentration of deltamethrin that gave 50% mortality. Observations on larval mortality after the treatment with deltamethrin were recorded after 24 h. The results revealed that Bti excels Bsp, as it recorded 54% mortality only on 17th day after application. The other salient finding of this study is LC50 of deltamethrin is sufficient to follow the biopesticides application for an effective control of Culex larvae.     

Reproductive status of Octopus pallidus, and its relationship to age and size

Age-specific information on individual octopus reproductive development and investment from wild populations has until recently been unobtainable. Using daily-formed increments within stylets (internal shells) the individual ages of 503 wild Octopus pallidus were determined. In addition, detailed reproductive information was collected for each of the aged octopus, along with reproductive data for an additional 925 octopus. All of the octopus were collected from Bass Strait waters in south-eastern Australia from November 2004 to November 2006. This information was used to investigate seasonal trends in reproductive scheduling and investment, fecundity and egg size. Maturation in O. pallidus primarily depends on size with little relationship to age and is highly variable between genders, with females >350 days still maturing in comparison to all males >142 days being mature. Size at 50% maturity for females was approximately 473 g, which is considerably larger than male 100% maturity at <250 g. This indicates that for females at least, maturity does not necessarily come with age. Seasonal scheduling in reproductive investment between genders revealed an optimal spawning period between late summer and early autumn. These results reinforce the view that individual growth and maturity is highly variable in cephalopods.     

The biological degradation of arginine and glutamic acid in seawater in relation to the growth of phytoplankton

The responses of natural summer coastal plankton communities to low-level additions (10^-5 to 10^-7 M) of arginine and glutamic acid has been followed by in vivo measurement of chlorophyll fluorescence. This technique is capable of detecting a response to a 10^-6 M enrichment under most conditions. The time sequence of the response varied with the amino acid used and with the enantiomeric form of the amino acid. Ammonia and carbon dioxide were liberated before the increase in chlorophyll fluorescence occurred. Liberation of ammonia in a dark bottle from L-arginine was from 75 to 85% of the theoretical yield. Microautoradiography using ¹⁴C L-arginine or L-glutamic acid at 10^-7 M showed heavy labeling associated with fecal pellets and detrital aggregates. Phytoplankton cells were not appreciably labeled. The evidence suggests that bacteria are important in the cycling of these compunds.     

Influence of diatoms on copepod reproduction. III. Consequences of abnormal oocyte maturation on reproductive factors in <Emphasis Type="Italic">Calanus helgolandicus</Emphasis>

Observations of gonads and oocyte development stages (OS) have been achieved in Calanus helgolandicus females fed different algal diets and starved in filtered sea water under laboratory conditions during 8 days. The effects of 20 diets on egg production rates (EPR), hatching success (HS) and proportion of abnormal larvae (AL, development stages N1-2) were examined. With the control diet Prorocentrum minimum EPR and HS values were high, while AL was very low, coinciding with intact cell structures in oogonia (OO) and normal OS (OS1-OS4). With the other diets, oocyte maturation, EPR, HS and AL patterns were partially or totally impaired. Decrease of EPR coincided with the arrest of OS3 maturation and oocyte degradations, characterised by cell fragmentation, presence of apoptotic bodies in the OS3, degradation of cytoplasm in OS3 and OS4 and consequently the arrest of OS4 formation. These degradations were reversible when females were fed a favourable diet. Results reflect the presence of two distinct inhibitory mechanisms. Inhibition mechanism (1) impairs egg production. It was induced by starvation or by several species belonging to Bacillariophyceae (Chaetoceros calcitrans, Guinardia delicatula, Guinardia striata, Odontella regia, Rhizosolenia setigera, Stephanopyxis turris, Thalassiosira pseudonana) and mixed-diatom assemblages (collected in the field) and to the prymnesiophyte Pavlova lutherii. Remarkably other diatoms like Navicula sp., Nitzschia sp., Skeletonema costatum and Thalassiosira rotula did not induce mechanism (1) Inhibitory mechanism (2) affected exclusively HS and AL and was triggered by species independent of the production of polyunsaturated aldehydes (PUA), which are supposed to have adverse impacts on HS and larval development.     

A test of alternate hypotheses for helping behavior in white-fronted bee-eaters of Kenya

Summary Considerable controversy exists over the question of the importance of kin selection in the maintenance of helping behaviors among birds. We examined nine different hypotheses of how helpers might benefit from engaging in alloparental care activities. We break these into four categories: Through its activities the helper may A) improve its probability of surviving to the following breeding season, B) enhance its probability of becoming a breeder in the future, C) increase its reproductive success when it does become a breeder, and D) increase the production of non-descendent kin. The first three categories provide direct fitness gains to the helper; in the fourth, the benefit is indirect. The hypotheses are not mutually exclusive; rather their fitness effects are additive. Each hypothesis, however, makes specific and often separable predictions about both 1) the type of fitness benefits expected, and 2) the characteristics of the birds that serve as helpers. We tested these predictions using five year's data from a color marked and geneologically known population of white-fronted bee-eaters (Merops bullockoides) in Kenya. A) Survival was not related to status (breeder, helper, non-participant); nor did individuals living in large clans have better survival than those living in small ones. B) Newly formed pairs were equally likely to become future breeders irrespective of whether or not one or both individuals had helped previously. C) The mean number of young fledged by a first time breeder was unaffected by its prior helping experience. Neither were first time breeding pairs more likely to gain the services of others as their helpers than were pairs without prior helping experience. Taken together these results demonstrate that beeeaters gain very little direct benefit from alloparenting. D) Helpers did not enhance the survival of the breeders that they helped. But they did have a major effect in increasing nestling survival. Because bee-eater helpers are closely related to the nestlings they help to rear (average r=0.33), they obtain a large indirect benefit by increasing the production of non-descendent kin. We quantified the relative importance of indirect and direct benefits of helping (to the helper) using Vehrencamp's kin index, I _k (1979). I _k compares the fitness consequences of helping against an alternative strategy and calculates the proportion of the inclusive fitness gain or loss that is due to kin (indirect) benefits. Comparing the strategy sets of helping versus not helping for bee-eaters, I _k=0.89 (indicating that 89% of the benefit derived from helping is indirect). When helping was compared against the alternative of breeding, I _k=2.17. Values of I _k greater than 1.0 indicate that direct fitness gains from the alternate strategy (breeding) are greater than those from helping. The value of 2.17 indicates that the helping strategy would not be maintained except for the indirect fitness gained through the increased production of close kin. Alloparenting in white-fronted bee-eaters can thus be considered as altruistic.     

Hepatopancreatic endosymbionts in coastal isopods (Crustacea: Isopoda), and their contribution to digestion

Three isopod species (Crustacea: Isopoda), commonly found in the intertidal and supratidal zones of the North American Pacific coast, were studied with respect to symbiotic microbiota in their midgut glands (hepatopancreas). Ligia pallasii (Oniscidea: Ligiidae) contained high numbers of microbial symbionts in its hepatopancreatic caeca. Numbers of endosymbionts were strongly reduced by ingestion of antibiotics. By contrast, the hepatopancreas of Idotea wosnesenskii (Valvifera: Idoteidae) and Gnorimosphaeroma oregonense (Sphaeromatidea: Sphaeromatidae) did not contain any microbiota. Results of feeding experiments suggest that microbial endosymbionts contribute to digestive processes in L. pallasii, the most terrestrial of the three isopods that we studied. The acquisition of digestion-enhancing endosymbionts may have been an important evolutionary step allowing isopods to colonize terrestrial habitats where relatively indigestible leaf litter is the primary food source. By contrast, the ability to digest phenolic compounds was most developed in one of the more marine species, suggesting that this trait may have evolved independently in isopod species that consume a phenolic-rich diet, whether in marine habitats or on land. Received: 28 August 2000 / Accepted: 8 December 2000     

Concentrations of inorganic elements in bottled waters on the Swedish market

This study presents the concentrations of about 50 metals and ions in 33 different brands of bottled waters on the Swedish market. Ten of the brands showed calcium (Ca) concentrations ≤10 mg L⁻¹ and magnesium (Mg) levels <3 mg L⁻¹, implying very soft waters. Three of these waters had in addition low concentrations of sodium (Na; <7 mg L⁻¹), potassium (K; <3 mg L⁻¹) and bicarbonate (HCO₃ ≤31 mg L⁻¹). These brands were collected from barren districts. Nine of the brands were collected from limestone regions. They showed increased Ca-levels exceeding 50 mg L⁻¹ with a maximum of 289 mg L⁻¹. Corresponding Mg-levels were also raised in two brands exceeding 90 mg L⁻¹. Two soft and carbonated waters were supplemented with Na₂CO₃ and NaCl, resulting in high concentrations of Na (644 and 648 mg L⁻¹) and chloride (Cl; 204 and 219 mg L⁻¹). Such waters may make a substantial contribution to the daily intake of NaCl in high water consumers. The storage of carbonated drinking water in aluminum (Al) cans increased the Al-concentration to about 70 μg L⁻¹. Conclusion As there was a large variation in the material as regards concentrations of macro-elements such as Ca, Mg, Na, K and Cl. Supplementation with salts, e.g., Na₂CO₃, K₂ CO₃ and NaCl, can lead to increased concentrations of Na, K and Cl, as well as decreased ratios of Ca/Na and larger ratios of Na/K. Water with high concentrations of e.g., Ca and Mg, may make a substantial contribution to the daily intake of these elements in high water consumers. Al cans are less suited for storage of carbonated waters, as the lowered pH-values may dissolve Al. The levels of potentially toxic metals in the studied brands were generally low.