Excitation evoked by FMRFamide and FLRFamide in the heart of Buccinum undatum and evidence for inositol 1,4,5-trisphosphate as an RF-tetrapeptide second messenger

In this study the relative potencies of four established molluscan cardioexcitatory agents were examined on Buccinum heart. The potencies were, in decending order: phenylalanine-leucine-arginine-phenylalanine-NH₂ (FLRFamide) > phenylalanine-methionine-arginine-phenylalanine-NH₂ (FMRFamide; 80% of maximum) > 5-hydroxytryptamine (5HT; 60% of maximum) > guanosine triphosphate (GTP; 15% of maximum). FMRFamide and FLRFamide had similar dose-response curve patterns with thresholds at 10⁻⁹ mol l⁻¹ but FLRFamide was more potent than FMRFamide. The superfused atrium was much less sensitive to all agonists than the internally perfused ventricle. FLRFamide and FMRFamide induced small depolarizations (1–2 mV) which triggered a burst of action potentials of about 5 mV which on reaching 4 mV triggered a burst of fast twitch contractions. Lithium, at high concentrations inhibited FMRFamide and 5-HT responses of internally perfused ventricles. Neomycin also inhibited peptide responses, but was without effect on 5-HT responses. Heparin, however, for technical reasons was without effect on ventricular responses to all three agonists. FMRFamide and FLRFamide appear to share a common receptor, the potency difference being due to the substitution of leucine for methionine in FLRFamide. The RF N-terminal sequence appears crucial for receptor activation. The Phospholipase C inhibitor neomycin equally inhibits responses to the two peptides while 5-HT responses are unaffected. This implicates a peptide/receptor interaction which activated inositol 1,4,5-trisphosphate (IP₃) as a second messenger. Accepted: 22 March 2000     

Shell morphology and color of the subtidal whelk Buccinum undatum exhibit fine‐scaled spatial patterns

Geographical patterns in morphology can be the result of divergence among populations due to neutral or selective changes and/or phenotypic plasticity in response to different environments. Marine gastropods are ideal subjects on which to explore these patterns, by virtue of the remarkable intraspecific variation in life‐history traits and morphology often observed across relatively small spatial scales. The ubiquitous N‐Atlantic common whelk (Buccinum undatum) is well known for spatial variation in life‐history traits and morphology. Previous studies on genetic population structure have revealed that it exhibits significant differentiation across geographic distances. Within Breiðafjörður Bay, a large and shallow bay in W‐Iceland, genetic differentiation was demonstrated between whelks from sites separated by just 20 km. Here, we extended our previous studies on the common whelk in Breiðafjörður Bay by quantifying phenotypic variation in shell morphology and color throughout the Bay. We sought to test whether trait differentiation is dependent on geographic distance and/or environmental variability. Whelk in Breiðafjörður Bay displayed fine‐scale patterns of spatial variation in shape, thickness, and color diversity. Differentiation increased with increasing distance between populations, indicating that population connectivity is limited. Both shape and color varied along a gradient from the inner part of the bay in the east to the outer part in the west. Whelk shells in the innermost part of Breiðafjörður Bay were thick with an elongate shell, round aperture, and low color diversity, whereas in the outer part of the bay the shells were thinner, rounder, with a more elongate aperture and richer color diversity. Significant site‐specific difference in shell traits of the common whelk in correlation with environmental variables indicates the presence of local ecotypes and limited demographic connectivity.     

Calcium dependency and the effect of calcium antagonists on molluscan proboscis smooth muscles from the whelk,Buccinum undatum

In all four proboscis muscles of the whelk Buccinum undatum, the potassium-induced depolarization response was acutely dependent upon extracellular calcium, being eliminated in calcium-free conditions. The responses to acetylcholine were found to be partly dependent upon intracellular calcium. Responses to the peptides phenylalanine-methionine-arginine-phenylalanine-NH₂ and phenylalanine-leucine-arginine-phenylalanine-NH₂ were much more resistant to calcium-free conditions and appeared to engage the excitation-contraction coupling mechanism by mobilizing stored intracellular calcium. Sucrose-gap studies of radular retractor muscles showed that the organic calcium “antagonist” nifedipine enhanced potassium-induced depolarization responses, initiating spike-like action potentials and associated fast twitch activity. The inorganic calcium antagonist gadolinium exerted concentration-dependent inhibitory actions on these muscles. Basal tonus and fast twitch activity in response to potassium-induced depolarization were eliminated as were the spike-like action potentials of the membrane electrical response. The inorganic calcium “antagonist” cadmium greatly enhanced potassium-induced contractures in all four muscles, and on its own it induced tonic force and fast twitches in all the muscles. It seems likely that cadmium may have displaced stored intracellular calcium to induce myofilament activation. While these molluscan smooth muscles appear to possess calcium channels with fast and slow characteristics, their behaviour and pharmacological manipulation is very different from their more well known mammalian transient and long-lasting channel counterparts.     

Microsatellite markers for the earthworm Lumbricus rubellus

We describe eight microsatellite markers for the earthworm Lumbricus rubellus, a commonly used ‘biological sentinel’ species in ecotoxicology studies. Thirty‐four individuals from a single population were tested for polymorphism. Markers possessed between two and 15 alleles per locus, and expected heterozygosity ranged between 0.06 and 0.92 (observed heterozygosity 0.03–0.92). Unfortunately, no consistent cross‐species amplification was observed in the related congeners Lumbricus castaneus and Lumbricus terrestris.     

The relation between excitation-contraction coupling and fine structure of a molluscan muscle,the radular retractor of the whelk,Buccinum undatum

The Buccinum radula is of the rachiglossate type with two outer rows of fierce hook-like attack teeth and a medial row of straight sharp-pointed shredding teeth. Individual cells of the radular retractor muscle are 10–12 m in diameter and separated at the closest by gaps of only 40 nm, providing areas of potential electrical contact. The cell membranes are heavily invested with long finger-like invaginations, associated with sarcoplasmic reticular cisternae, and surface caveolae; the latter are associated with the numerous dense body membrane attachment plaques found in this muscle. The radular retractor muscle possesses a significant sarcoplasmic reticulum of peripheral cisternae and deeper vesicles associated with mitochondria. The surface caveolae may result from myofilament force exerted via attachment plaques at the cell membrane, while deeper invaginations may constitute a rudimentary transverse tubular system to relay surface depolarization to associated sarcoplasmic reticular cisternae inducing calcium release to effect excitation-contraction coupling. The radular retractor muscle possesses the usual thick paramyosin and thin actin myofilaments, the latter associated with dense bodies and attachment plaques presumably to transduce force to the cell membrane. The mitochondria are unusually large and packed into dense central clusters surrounded by large deposits of glycogen granules. The nerve endings on the radular retractor muscle fibres show four different types of transmitter vesicle, presumably related to the four kinds of agonist action in this muscle, cholinergic, serotonergic, peptidergic and purinergic. All nerve endings have mixed vesicle populations, clear evidence of co-transmission. In this muscle we see a modification of usual smooth muscle structure to effect fast sustained contractions, an ultrastructural configuration functionally designed for the muscle's central role in the feeding cycle.Abbreviations ABRM anterior byssus retractor muscle - EC coupling excitation-contraction coupling - RP radular protractor muscle - RR radular retractor muscle - SR sarcoplasmic reticulum - T-system transverse tubular system     

Microsatellite markers for mungbean developed from sequence database

A novel set of microsatellite markers for mungbean [Vigna radiata (L.) Wilczek] was developed from the public sequence database. Seventy-eight primers were designed and evaluated for polymorphism among 22 cultivated accessions. Eight polymorphic loci detected two to three alleles per locus with an average of 2.25. The observed heterozygosity varied from 0.00 to 0.18, while the expected heterozygosity ranged from 0.09 to 0.46. Among them, all eight loci showed significant departuring from Hardy-Weinberg equilibrium, while four pairs of loci displayed significant pairwise linkage disequilibrium values. All eight loci except DMB-SSR1 showed heterozygote deficiency.     

The hypobranchial mucin of the whelk Buccinum undatum L. The polysaccharide sulphate component

1. A polysaccharide sulphate has been isolated from the hypobranchial mucin of the whelk Buccinum undatum. 2. The molecular weight of this polysaccharide, which is a glucan carrying one ester sulphate group per monosaccharide residue, is 1.7x10(5). 3. Some investigations bearing on the location of the ester sulphate groups are reported. 4. The viscosity of the whole mucin has been shown to depend mainly on the glucan sulphate.     

Conflict between two inshore fisheries: for whelk (Buccinum undatum) and brown crab (Cancer pagurus), in the southwest Irish Sea

Landings from the whelk fishery in the southwest Irish Sea rose from 63 t in 1990 to 6587 t in 1996 although landings declined to 2919 tonnes in 1998. Whelk are caught in pots baited with a combination of dogfish Scyliorhinus spp and brown crab Cancer pagurus. The input of bait crab is estimated at 7.2% of whelk landed. Most of the crab comes from southeast Ireland where some of it is a by-product of the claw fishery; some is targeted as bait crab, and this includes sub-size or recently moulted individuals. Fishing effort has been increasing on brown crab for human consumption also and there is concern about the sustainability of the crab fishery. Alternative bait trials examined a number of readily available fish species, some of them offals, whose attractiveness was evaluated by reference to crab and dogfish: whitefish (whiting and cod), pelagic species (mackerel and scad) and blue mussel. An artificial bait ration which included some crab meat, but 60% less than its natural equivalent, proved as effective as natural bait crab. A bait which consisted of a single species was less successful than two species fished together and some of the combinations (notably of whitefish) performed very effectively. Pelagic species performed poorly. The trade in brown crab for human consumption will always produce some form of discards which should be used; extending its use in an artificial bait is desirable.     

Predation of cockles (Cerastoderma edule) by the whelk (Buccinum undatum) under laboratory conditions

The feeding rate and behaviour of whelks (Buccinum undatum)offered cockles (Cerastoderma edule) in laboratory experimentswere examined. When presented with cockles in a range of sizes(10–40 mm), 14 B. undatum (34.6–88.3 mm),held individually in aquaria, consumed a wide size range ofcockles. Small whelks (<40 mm) consumed cockles (<23 mm),whereas large whelks, (>60 mm) ate a greater numberof larger cockles (>30 mm) and a wider size range ofcockles (12–40 mm) than smaller whelks. The majority(90%) of the shells of the predated cockles were undamaged andthe few (<10%) that were damaged showed only slight abrasionsto the anterior and posterior shell margin. Filmed observationsof B. undatum feeding on C. edule showed a method of attackthat has not previously been reported and involved the use ofthe whelk's foot to asphyxiate the cockle or to pull the shellvalves apart. No filmed evidence was found for the previouslyreported shell ‘wedging’ technique for prising openthe closed shell valves of C. edule, although 10% of the shellsof consumed cockles in feeding experiments had damaged shellmargins. (Received 4 April 2007; accepted 30 June 2007)     

The hypobranchial mucin of the whelk Buccinum undatum L. Properties of the mucin and of the glycoprotein component

1. The composition of the hypobranchial mucin from Buccinum undatum is reported. 2. The amino acid composition was determined; aspartic acid and glutamic acid contribute almost 24% of the total amino acids in the mucin. 3. Serine, threonine and alanine, in the proportions 2:1:1 respectively, were detected as N-terminal residues, implying the presence of at least four protein chains. 4. A glycoprotein component was isolated by phenol precipitation. 5. The glycoprotein contained 8% of neutral sugars comprising glucose, galactose, mannose and fucose, and 4.5% of hexosamine, comprising glucosamine and galactosamine in equal proportions. 6. A method is described for the preparation of glycopeptides from the glycoprotein. 7. The comparative biochemistry of the mucin is discussed.     

Microsatellite DNA markers in the giant freshwater prawn, Macrobrachium rosenbergii: a tool for genetic analysis

Eight microsatellite loci were identified and characterized in the commercially important giant freshwater prawn, Macrobrachium rosenbergii. The microsatellite loci were detected by the random screening for dinucleotide repeat units within a partial genomic library developed for the species with biotinylated probes (CA)(15) , (AT)(15) and (GA)(15) . All the eight loci were found to be polymorphic. The number of alleles and observed heterozygosities per locus ranged between three to 16 and 0.22 to 0.71, respectively. These microsatellite markers will be useful for the conservation and management of wild and cultured stocks and population genetic studies of freshwater prawn.     

Microsatellite markers for the ectomycorrhizal basidiomycete Lactarius mammosus

We report the characterization of polymorphic microsatellite markers in the ectomycorrhizal fungus Lactarius mammosus Fr. Two enrichment protocols were used to isolate microsatellite loci and polymorphism was explored within 31 sporocarps originating from a forest site in northern Sweden. We found nine variable microsatellite loci with the number of alleles per locus varying between 2 and 5, and expected heterozygosities ranging from 0 to 0.84. These loci are available for the analysis of genetic structure and gene flow in L. mammosus populations.     

The dependence of oxygen consumption of the common whelk (Buccinum undatum) on hypoxia,salinity and air exposure

• 1.1. Oxygen consumption of low salinity (20‰) acclimated whelks decreases markedly upon acute exposure to hypoxia (P_WO₂ = 35 Torr), but almost regenerates its original level within 48 hr exposure to the hypoxic condition.
• 2.2. This ability to regain the original level of oxygen consumption is not seen in high salinity (35‰) acclimated whelks.
• 3.3. Oxygen consumption in air at 10°C is more than twice the rate shown by low salinity acclimated whelks in normoxic water (P_WO₂ = 150 Torr).
• 4.4. Q₁₀ for oxygen consumption in air is about 1.0 in the temperature range 10–20°C.

     

Microsatellite markers for the drought-resistant earthworm Hormogaster elisae

We developed and characterized 10 highly polymorphic microsatellite loci from a simple sequence repeat-enriched genomic DNA library of the earthworm Hormogaster elisae. Characterization of these loci using 26 individuals revealed eight to 25 alleles per locus and high levels of heterozygosity. These loci will be used for paternity analysis and population genetic studies.     

Polymorphic microsatellite markers isolated from the neptune whelk Neptunea arthritica

Eight polymorphic microsatellite DNA loci were isolated from the neptune whelk Neptunea arthritica, which is an important fishery resource in northern Japan. The number of alleles at the loci ranged from two to six, with observed and expected heterozygosities of 0.192-0.807 and 0.233-0.738, respectively. The observed variations suggest that these loci can be used as markers for population and kinship analyses in this species.     

Microsatellite DNA markers for Lysiphlebus testaceipes

Microsatellite loci were isolated from the aphid parasitoid Lysiphlebus testaceipes (Hymenoptera: Braconidae). Ten loci were obtained from an enriched partial genomic library. Genetic diversity was analysed at seven of these loci and two natural populations, one on oleander and one on citrus. The observed number of alleles ranged from one to 17, and the observed heterozygosity ranged from 0.37 to 0.82. In both populations, no departure from Hardy–Weinberg equilibrium was detected except for one locus. The differentiation between the two populations was characterized by an F_ST of 0.09.