Allozyme and colour differences between two sibling species of the heteronemertean Lineus torquatus from the Sea of Japan

Brown and cherry colour morphs of the heteronemertean Lineus torquatus Coe, 1901 from the Vostok Bay of the Sea of Japan were compared using allele frequencies at 18 isozyme loci. These morphs shared no common alleles at 9 of the 18 loci. The observed genetic differences are strong evidence that the brown and cherry colour morphs, which occur sympatrically, are different species. Nei's genetic distance between these species (D=1.135) is considerably higher than typical D values for congeneric animal species. As with much previous work on nemerteans, intraspecific allozymic variability in both species was high, with mean expected heterozygosity values 0.286±0.049 and 0.159±0.051 for L. torquatus (brown) and L. torquatus (cherry) species, respectively.     

Potential effects of a resuspension event on the vertical distribution of copepod eggs in the sea bed: a laboratory simulation

Adult female Acartia tonsa and Labidocera aestiva were obtained from inshore marine waters near Turkey Point, Florida (29°54.5N;84°31W) during April and May 1991. For each species, eggs spawned overnight in the laboratory were collected, mixed with sediment, and added to a plastic tube (26 to 29 cm longx5 cm diam) to yield a 2 cm-thick layer. This tube was connected to a 245 cm-long tube, seawater was added and the contents were thoroughly mixed by turning the assembly end-over-end several times. The vertical distribution of eggs in the sediments following resuspension varied according to the grain size of the sediments. For sediments of 125 m particle-diameter, 68 to 72%, and 70 to 73% of the eggs of A. tonsa and L. aestiva, respectively, occurred in the upper 4 mm.For sediments 63 to <125 m particle-diameter, 34 to 36% of the eggs of A. tonsa and L. aestiva, respectively, occurred in the upper 4 mm. For sediments of <63 m particle-diameter, egg distribution was uniform for both species throughout the 2 cm layer. The results indicate that the vertical distribution of eggs in the sea bed following a resuspension event should be highly dependent upon the grain-size composition of the sediments.     

Temporal variation and distribution of trace metals in freshwater and fish from Calabar River, S.E. Nigeria

An investigation on the abundance and distribution of trace metals (Fe, Cu, Zn, Mn, Cr, Cd and Pb) in water, and nine species of fish samples from Calabar river was carried out in 1992. The concentrations of iron (6000–7240gl^–1), zinc (4910–7230gl^–1), and cadmium (3–7gl^–1) showed moderate pollution while those of copper (420–630gl^–1), manganese (23–48gl^–1), chromium (<10–20gl^–1) and lead (<1–10gl^–1) in water were well below WHO permissible levels. Significant seasonal changes (0.001p0.25) were obtained for iron, copper, zinc, manganese and cadmium in water. Furthermore, iron, zinc and cadmium showed statistically significant spatial changes (0.005p0.10). Of the nine fish species studied, no statistically significant relationship between body weight and the concentrations of the metals was observed. The concentrations of the metals per mean total body weight apparently decreases in the order Fe>Zn>Cu>Mn>Pb>Cd=Cr and were within the limits that were safe for consumption.     

Growth and survival of Mytilus edulis larvae exposed to low levels of dibutyltin and tributyltin

Two studies were conducted to observe effects of dibutyltin (DBT) and tributyltin (TBT) on larvae of Mytilus edulis for an exposure period of 25 d. Endpoints for evaluation were shell growth and mortality measured at 33 d. Larvae were cultured in a new laboratory assay chamber in a recirculating static test. The control, 2, 20, and 200 g/l DBT-treated populations had mean shell lengths of 527, 523, 417, and 180 m, respectively. Survival was 1% for the 200 g/l DBT-treated population, but ranged from 73 to 83% for controls, 2, and 20 g/l treatments. The no-observed-effect concentration (NOEC) was 2 g/l for DBT, while the lowest-observed-effect concentration (LOEC) was 20 g/l. The chronic toxicity value was 6.3 g/l. In the TBT bioassay, mean shell lengths for the control, 0.006, 0.050, and 0.130 g/l-treated populations were 565, 437, 385, and 292 m, respectively. Control survival was 74%, whereas TBT-treated populations survival ranged from 52 to 58%. The NOEC for TBT was 0.006 g/l TBT and the LOEC was 0.050. A chronic toxicity value of 0.017 g/l was calculated. The results of this study indicated that the toxicity of DBT was less than that of TBT. It was concluded that shell length was inversely related to exposure level in both DBT and TBT bioassays. In this study, we have observed TBT effects at lower exposure levels in the laboratory than previously reported, and also report the first data for DBT effects on mussel larvae.     

Lead-based paint in dwellings: The potential for contamination of the home environment during renovation

The quantity and particle size characteristics of lead in dust released during three different paint removal techniques was determined under controlled conditions and in situ in a dwelling. Air-lead and deposited dust-lead levels were highest after sanding but burning-off and hot-air removal methods also produced significant contamination. The importance of dust particle-size and lead is discussed in relation to the potential hazard to home renovators via inhalation and to children via the hand-to-mouth route.This paper is also being published in Proceedings of the Conference on Lead in the Home Environment and is one of several selected from SEGH sponsored conferences for simultaneous publication in this journal.     

Arsenic tissue concentration of immature mice one hour after oral exposure to gold mine tailings

A potentially high bioavailability of arsenic in gold mine tailings from a site in northern California has been suggested by solubility studies. To help address this issue, an in vivo dosing study was conducted using 12dayold Swiss Webster mouse pups (n=8/group). A sample of sizefractionated mine tailings from the site (<20m particle size, 691g g^–1 arsenic) was prepared as an aqueous suspension and administered by gavage in a volume that provided 4mg As/kg body weight. The control group received the same volume of a commercial soil (1g g^–1 As) of similar particle size (<60m). No mortality or toxic signs were noted in either group. Tissue samples were collected 1h after gavage, freezedried, microwavedigested and analysed for arsenic by ICP/MS (detection limit 2ng As g^–1 dry weight). Arsenic concentrations (ng As g^–1 dry weight) in tissues from the pups who received mine tailings were significantly higher than in control tissues. The mean elevation in arsenic concentration was highest in the liver (3364% of control, p<0.0001), followed by blood (818 of control, p<0.0001), skin (207% of control, p=0.07), and brain (143% of control, p<0.0001). The carcass arsenic concentration (excluding the GI tract, liver, brain and skin) was 138 of control (p=0.02). The data indicate uptake of arsenic from weathered mine tailings by the immature mouse pups after oral exposure.     

Population dynamics of Amphiura chiajei (Echinodermata: Ophiuroidea) in Killary Harbour,on the west coast of Ireland

The infaunal ophiuroid Amphiura chiajei Forbes is a dominant member of the A. chiajei community in Killary Harbour, a fjord-like inlet on the west coast of Ireland. High density populations (700 individuals/ m²) occur in sediments with a silt/clay content of 80 to 90% and organic carbon levels of 5 to 7%. A study of the population dynamics of this species was carried out from November 1985 to October 1988. At the outset, the population consisted of approximately equal numbers of adults and juveniles. By October 1988, the percentage of adults had increased to 95%, with little or no change in the mean annual dersities. However, there was some degree of variability between the mean monthly densities. Such variability may have been due to very low bottom temperatures, resulting in mortality among the older members of the population. Observations suggest that in Killary Harbour the species may attain an age of 10 yr, with an early annual growth rate of 0.5 mm (oral width). Annual recruitment was variable and low, due presumably to intraspecific competition with the adults; recruitment success may be very closely linked to adult mortality. The Killary Harbour findings are considered in the light of what is currently known of similar amphiurid populations in different geographical locations.     

Population characteristics of the deep-sea lobsters Polycheles typhlops and Stereomastis sculpta (Decapoda: Polychelidae) in a bathyal mud community of the Mediterranean Sea

Distribution and abundance as a function of depth, and population parameters such as sex and size structure of the population and aspects of reproductive biology have been studied in the deep-sea polychelid lobsters Polycheles typhlops and Stereomastis sculpta. Samples were taken by otter trawl in the Balearic Sea, a deepsea basin in the northwestern Mediterranean Sea from 1985 to 1989. In both species the largest size classes were dominated by females. In S. sculpta, male and female sizes were very similar. In P. typhlops, ovigerous females and those with external spermatophores were 23 and 25 mm in carapace length (CL), respectively; males with external spermatophores were 17 mm in CL. In S. sculpta, ovigerous females and those with external spermatophores were 24 and 19 mm CL, respectively, and males with external spermatophores 19 mm CL. Highest densities of P. typhlops occurred along the middle slope at depths between 500 and 1000 m. Only small-sized individuals were found at the deepest depths sampled; some recruitment must therefore occur in waters much deeper than those usually inhabited by the adult population. The sex-ratio was 1:1 in most samples, but in some of the shallowest samples females predominated. The depth distribution range of S. sculpta was 981 to 2253 m: densities clearly increased with increasing depth. There were no apparent variations in size distribution as a function of depth. Since very few adult males and females were captured, the population in the survey area would seem to be comprised mainly of juveniles. As a function of depth, females were numerically dominant only in some of the shallowest samples taken in the distribution range of this species. There is strict habitat partitioning between the two species. In both species, the variation in the sex-ratio as a function of depth suggests differential migration between the sexes, probably related to egg incubation and hatching.     

13C/12C ratios and the trophic importance of algae in Florida Syringodium filiforme seagrass meadows

Over 380 stable carbon isotope (¹³C) analyses made during 1981–82 showed that Syringodium filiforme Kutz seagrass meadows in the Indian River lagoon of eastern Florida have food webs based on algal rather than seagrass carbon. Seagrasses averaging approximately-8 were isotopically distinct from algae epiphytic on seagrass blades (X=-19.3) and particulate organic matter in the water column X=-21.6. ¹³C values of most fauna ranged between-16 and-22, as would be expected if food web carbon were derived solely from algal sources. These results counter the idea that seagrass detritus is the dominant carbon source in seagrass ecosystems. Two factors that may contribute to the low apparent importance of seagrass in the study area are high algal productivities that equal or exceed S. filiforme productivity and the high rates of seagrass leaf export from meadows.     

Comparative feeding ecology of two sympatric rockfish congeners,Sebastes caurinus (copper rockfish) and S. maliger (quillback rockfish)

Possible differences in the diet or metabolism of sympatric finback and humpback whales in the Gulf of St. Lawrence were investigated through analysis of their blubber fatty acids. Free-ranging finback (Balaenoptera physalus, n=19) and humpback (Megaptera novaeangliae, n=10) whales were sampled through biopsy during summer 1991. The two species differed in the chemical composition and stable carbon isotope distribution of fatty acids extracted from their outermost blubber layer. Finback blubber was slightly but significantly richer in its relative proportions of 12:0, 13:0, i14:0, 17:0, 18:1 n9, 18:1 n7, and 20:0 (probability of difference 99%), 18:2 n6, 18:0, and 19:0 (probability 95%), and 16:1 n5 and 16:0 (90%). The stable isotope ratio of finback total fatty acids averaged-25.5±0.4%. Humpbacks contained relatively more i16:0, 18:1 n5, 20:5 n3, and 22:6 n3 (probability 99%), 16:1 n7, i18:0, 20:4 n6, and 22:5 n3 (95%), and 20:4 n3 (>90%). Their fatty acid ¹³ averaged -25.8±0.5% (different from finbacks with a probability of 95%). There was no significant difference between the two species in the relative proportions of 14:1, 14:0, i15:0, a15:0, 15:0, i17:0, a17:0, 17:1, 20:1 n9, 20:1 n7, 22:1 n11, or 22:1 n9, which together made up one-third of total fatty acids. We used principal component and cluster analyses to integrate and visualize the differences in the chemometric data sets. The chemical and isotopic differences found in the present study are consistent with a slightly lower trophic position for humpbacks compared to finbacks in the Gulf of St. Lawrence, reflecting a difference in long-term, average diet.     

Exosmosis and “free space” in marine benthic algae

In distilled water, marine benthic algae immediately lose ions. This can be demonstrated by means of chloride titration or conductivity measurements. The rapidity and the complete reversibility of this process show that ion movements out of and into the free space are involved. When Laminaria saccharina thalli, exposed to a series of increasing NaCl-concentrations, are subsequently transferred into distilled water, the external concentration increases proportionally to rate of ion loss. Through its free space, the alga establishes an ionic equilibrium with its external medium. If the alga thallus is killed (20 sec boiling in isosmotic sea water), the extent of chloride loss is much higher. Because of thermal destruction of the osmotic space, the chloride can then escape from the entirc thallus. Since sublittoral algae die upon drying, chloride loss from dry thalli is much higher than that from wet thalli: this difference is small in littoral algae, which tolerate short periods of dryness. A close relationship exists between extent of chloride loss and degree of resistance to drying.     

Acute and chronic toxicity of tributyltin (TBT) to pediveliger larvae of the bivalve Scrobicularia plana

A static renewal test was run for 30 d to assess the effects of the antifoulant tributyltin (TBT, nominal concentrations of 50, 125, 250 and 500 ng Sn l^-1) on the survival and growth of 240 m-long pediveliger larvae of the bivalve Scrobicularia plana (da Costa) settling in fine sand. Exposure to nominal TBT levels of 125 ng Sn l^-1 (actual range of 37 to 102 ng Sn l^-1, as analysed) resulted in substantial mortalities and negligible shell growth of individuals. More importantly, larval shell growth at the lowest concentration tested (i.e. nominal 50 ng Sn l^-1 or 14 to 32 ng Sn l^-1, as analysed) was significantly reduced (by a factor of 4) and grossly abnormal. In contrast, some control postlarvae had begun developing siphons as they attained a length of 600 to 700 m by the end of this test, thereby completing metamorphosis and becoming juveniles. The results are discussed in relation to the widespread disappearance of S. plana in North Atlantic European estuaries during the 1980s and the concurrent TBT pollution in their waters. It is inferred that TBT is likely to have contributed to the reported demise of clam populations by preventing the successful and timely progress of their pediveliger larvae.     

Male capacity as related to sperm production,pregnancy initiation,and sperm competition in deer mice (Peromyscus maniculatus)

Summary Limitations on male capacity may be important to the evolution of mating strategies and behavior. Sperm counts in successive ejaculates of deer mice (Peromyscus maniculatus) decreased progressively through six ejaculations and remained depressed the following day. Males were as effective in inseminating females in cycling estrus with their second two ejaculates as with their first two and as effective in inseminating postpartum females with their fifth as with their first. In sperm competition situations males competed with rested males as effectively with their fourth, fifth, and sixth ejaculates as with their first. Thus, although sperm counts decrease in successive ejaculates, males suffer no apparent functional deficiency as long as they continue ejaculating. It is not clear whether or not deer mice are honest salesmen but they appear to be honest ejaculators and usually are honest intromitters.     

Photoacclimation of Ulva rotundata (Chlorophyta) under natural irradiance

Two vegetative clones (designated 11/85 and 7/86 in accordance with month/year of collection) of the green macroalga Ulva rotundata were collected in the vicinity of Beaufort, North Carolina, USA. Each was grown in an outdoor continuous-flow system in summer (20°C) of 1986 and late winter (10° to 17°C) of 1987, in irradiances ranging from 9 to 100% of full sunlight, with and without NH ₄ ⁺ enrichment. Continuous enrichment of influent estuarine water (dissolved inorganic nitrogen 2 M, N:P5) to 8–12 M NH ₄ ⁺ had only a slight effect on growth rate. Temperature changes of 2 to 3°C had a much greater effect. Prolonged exposure to a given daily irradiance resulted in acclimation, exposure to a given daily irradiance resulted in acclimation, indicated by faster growth of conditioned plants relative to those transferred from a different irradiance. Most of the difference in growth rates between transferred and control plants was attributed to differences in thallus absorptance. Growth was photoinhibited above 40% sunlight at temperatures below 15°C, but not above 20°C. Following interday irradiance transfers, thallus percent dry weight changed in a manner that suggests different response times for photosynthesis and cell division.     

The effect of a “permanent” clock-shift on the orientation of experienced homing pigeons

Summary A group of experienced homing pigeons vas subjected to a 6 h slow shift of their internal clock and kept under these conditions for more than 2 months. During the overlap time between the natural and artificial photoperiods they were released for training flights to familiarize them with an area while living in a permanent shift.Tested outside the permanent shift training range, the experimentals always deviated about 30° clockwise from the mean of their controls, markedly less than in a regular 6 h slow shift. Inside the permanent shift training range, however, they oriented like the controls (Fig. 2). When their internal clock was returned to normal, the birds showed a larger counterclockwise deflection on their first flight, which was roughly comparable to the effect of a regular 6 h fast shift (Fig. 3). On later flights after normalization, this large shift was no longer found; instead we observed a roughly 30° counterclockwise deflection when they were released inside the permanent shift training range in the morning. This deflection did not seem to occur in the afternoon or outside the permanent shift training range (Figs. 4, 5), and it disappeared when the birds were repeatedly released from the same site (Fig. 6).The occurrence or non-occurrence of the deflection was independent of the duration of the shift or the time passed after normalization; it seemed to depend solely on whether the birds had become familiar with a given site in the situation of the permanent shift. This argues against an effect based on the sun compass. We tend to assume that the still unknown navigational map is involved. In this case, however, as the deflection is independent of the home direction and the type of release site bias, the factors in question would act very differently from the gradients on which the traditional concepts of the navigational map are based. The processes establishing and updating the map and their possible differences are discussed.Died on August 17, 1980     

Grazing and ingestion rates of nauplii,copepodids and adults of the marine planktonic copepod Calanus helgolandicus

The average grazing and ingestion rates of all stages of the marine planktonic copepod Calanus helgolandicus (Calanoida) from nauplius stage IV to adults were measured experimentally at 15°C in agitated cultures. The chain-forming diatom Lauderia borealis and the unarmoured dinoflagellate Gymnodinium splendens were offered as food. The food concentrations were close to natural conditions and ranged from 36 to 101 g of organic carbon per liter. The medium body weights expressed in g of organic carbon of almost all larval stages raised at 49 g C/1 were identical with the weight of the same stages caught in the Pacific Ocean off La Jolla, California, USA. In a log-log system, grazing and ingestion rates increased almost linearly with increasing body weight. Grazing rates ranged from 4 to 21 ml/day/nauplius stage IV to 286 ml to 773 ml/day/female. Ingestion rates increased from 0.2 g to 0.8 g C/day/nauplius stage IV to 18 g to 69 g C/day/female. Grazing and ingestion rates per unit body weight decreased gradually with increasing body weight. The daily ingested amount of food decreased from 292 to 481% of the body weight (g C) of nauplius stage V to 28–85% of the body weight of adult females. Grazing and ingestion performances of all stages increased with increasing particle size. Grazing rates decreased and ingestion rates increased with increasing food concentrations. The published data on food intake of the different age groups of C. helgolandicus show that the young stages of herbivorous planktonic copepods can play a major part in the consumption of phytoplankton in the sea due to their high grazing and ingestion rates.     

Distribution of algae on tropical rocky shores: spatial and temporal patterns of non-coralline encrusting algae in Hong Kong

Encrusting algae have been described as dominant space occupying species on rocky shores around the world. Despite their abundance, however, most studies classify species under generic names (e.g. Ralfsia sp.) or as a functional group (e.g. encrusting algae), thereby underestimating the number of species present and their ecological importance. Studies on six rocky shores of varying exposure, in Hong Kong, recorded eight common species of encrusting algae. The greatest abundance of encrusting algae was recorded on shores of intermediate exposure, where four distinct zonation bands could be identified; a cyanobacterial Kyrtuthrix-Zone in the upper midlittoral, a Bare-Zone below this, a Mixed-Zone in the lower midlittoral and a Coralline-Zone in the infralittoral fringe. Abundance declined on shores of greater and lower exposure to wave action, where bivalves and barnacles were competitively dominant. Certain species were found in greater abundance on exposed shores (e.g. Dermocarpa sp. and Hildenbrandia occidentalis), while others preferred more sheltered shores (e.g. Hildenbrandia prototypus and Kyrtuthrix maculans). With the exception of some cyanobacterial crusts, the abundance of encrusting algae was always greatest towards the low shore, an area of decreased physical stress and increased herbivore density. Zonation patterns showed seasonal variation associated with the monsoonal climate of Hong Kong. Most species increased in abundance during the cool season, while during the summer months the cover and vertical extent of encrusting algae decreased in relation to summer temperatures, although K. maculans increased in abundance during the summer. On Hong Kong shores, encrusting algae have a high species richness and exhibit within-functional group spatial and temporal variation which is mediated by herbivory and seasonal, physical stresses.     

Investigation of potential gene flow limitation of behavioral adaptation in an aridlands spider

Summary This study investigates the possibility that gene flow underlies the apparently maladaptive behavior of a riparian woodland population of the desert spider Agelenopsis aperta with respect to territorial, foraging, and antipredatory behaviors. I found that other local populations of A. aperta in the vicinity of the riparian woodland habitat are prey-limited and exhibit an aridlands phenotype (high aggressiveness in competitive interactions over energy-based territories and a lack of discrimination among potential prey types). The riparian woodland population deviates from surrounding populations in the area in that prey are abundant and this population shows a mixture of aridlands and riparian (low aggressiveness towards conspecifics and discrimination of prey profitability) phenotypes. Electrophoretic analyses of population subdivision in the area indicate that significant levels of gene flow have occurred, at least, sometime in the past. Drift fence analyses of spider movement futher indicate that there is marked unidirectional movement of spiders each year from the more arid habitats into the riparian woodland. Experimental manipulation of gene flow and predation pressure demonstrates that gene flow restricts adaptation in this habitat: one generation of predation pressure in the absence of gene flow is sufficient to cause a marked shift in spider behavior towards the expected riparian phenotype.     

Differential parental care behaviors of arboreal and terrestrial microhylid frogs from Papua New Guinea

I studied the ecology of parental care behaviors displayed by two closely related sympatric species of microhylid frogs in Papua New Guinea that occupy different microhabitats. Adult removal experiments on the terrestrial frog Hylophorbus rufescens and the undescribed arboreal frog Oreophryne sp. A demonstrate a significant positive effect of parental attendance on offspring survivorship and differential causes of egg mortality between microhabitats. Desiccation was the primary cause of egg mortality for the arboreal frog, whereas predation was the main source of mortality for the terrestrial frog. These selection pressures (desiccation and predation) are comparable to two of Wilsons prime movers of the evolution of parental care (harsh environment and predation) and may have driven and/or are maintaining the evolution of parental care behaviors in these Papuan microhylid frogs. These results highlight microhabitat-specific selection pressures in the evolution and maintenance of parental care behaviors.Communicated by A. Mathis     

Grazing of the mixotrophic dinoflagellate Gymnodinium sanguineum on ciliate populations of Chesapeake Bay

In situ grazing rates for the mixotrophic dinoflagellate Gymnodinium sanguineum Hirasaka feeding on nanociliate populations of Chesapeake Bay were determined in June and October of 1990 using a gut clearance/gut fullness approach. Recently ingested prey were digested beyond the point of recognition at a rate of 23% h^-1. Estimates of in situ ingestion and clearance ranged from 0 to 0.06 prey dinoflagellate^-1 h^-1 and 0 to 5.8 l dinoflagellate^-1 h^-1, respectively, with daily removal of ciliate biomass representing 6 to 67% of the 20-m oligotrich standing stock. Daily consumption of ciliate biomass by G. sanguineum averaged 2.5% of body carbon and 4.0% of body nitrogen with maximal values of 11.6 and 18.5%, respectively. Ingestion of ciliates may help balance nitrogen requirements for G. sanguineum and give this species an advantage over purely photosynthetic dinoflagellates in nitrogen limited environments. By preying on ciliates, these dinoflagellates reverse the normal flow of material from primary producer to consumer and thereby influence trophodynamics of the microbial food web in Chesapeake Bay.