Effects of a haplosporidian parasite,Haplosporidium sp., on species of the molluscan woodborer Teredo in Barnegat Bay,New Jersey

Abundance of the molluscan woodborer, Teredo navalis, in Barnegat Bay, New Jersey, was reduced in breeding seasons following levels of infection of 40% or more by a haplosporidian parasite of the genus Haplosporidium. Infections also occurred in T. bartschi and T. furcifera, subtropical species which have been introduced into Barnegat Bay, and which may have originally introduced the parasite. Infections were not observed in Bankia gouldi, the most common molluscan woodborer in the bay.     

Encystment of the ciliate Boveria teredinidi in the tissues of the molluscan woodborer Bankia gouldi in Barnegat Bay,New Jersey

Histological sections of Bankia gouldi from several stations in Barnegat Bay, New Jersey, were found to contain encysted Boveria teredinidi. The process of encapsulation appeared to be of the leukocytic type, and there was usually considerable leukocytic infiltration into the tissues in the areas of the cysts. No cysts were observed in tissues of Teredo navalis, T. furcifera, or T. bartschi, although ciliates were observed on the gill surfaces of these species. This report is believed to be the first of encystment in B. gouldi.     

Climate Envelope Modeling and Dispersal Simulations Show Little Risk of Range Extension of the Shipworm,Teredo navalis (L.), in the Baltic Sea

The shipworm, Teredo navalis, is absent from most of the Baltic Sea. In the last 20 years, increased frequency of T. navalis has been reported along the southern Baltic Sea coasts of Denmark, Germany, and Sweden, indicating possible range-extensions into previously unoccupied areas. We evaluated the effects of historical and projected near-future changes in salinity, temperature, and oxygen on the risk of spread of T. navalis in the Baltic. Specifically, we developed a simple, GIS-based, mechanistic climate envelope model to predict the spatial distribution of favourable conditions for adult reproduction and larval metamorphosis of T. navalis, based on published environmental tolerances to these factors. In addition, we used a high-resolution three-dimensional hydrographic model to simulate the probability of spread of T. navalis larvae within the study area. Climate envelope modeling showed that projected near-future climate change is not likely to change the overall distribution of T. navalis in the region, but will prolong the breeding season and increase the risk of shipworm establishment at the margins of the current range. Dispersal simulations indicated that the majority of larvae were philopatric, but those that spread over a wider area typically spread to areas unfavourable for their survival. Overall, therefore, we found no substantive evidence for climate-change related shifts in the distribution of T. navalis in the Baltic Sea, and no evidence for increased risk of spread in the near-future.     

Effect of light intensity and eye development on prey capture by larval striped bass Morone saxatilis

The efficacy of visual and non-visual feeding among pelagic striped bass Morone saxatilis larvae adapted to a turbid estuary was determined in the laboratory in clear water. Capture of Artemia salina (density 100 l⁻¹) was significantly affected by the interaction between age of larvae (range: 8–25 days post-hatch, dph) and light intensity (range: 0–10·6 μmol s⁻¹ m⁻² at the water surface). Visual feeding by larvae aged 9–11 dph was highest in dim light (0·086–0·79 μmol s⁻¹ m⁻²), with fish capturing up to 5 prey larva⁻¹ h⁻¹. As the larvae grew, prey capture in brighter light improved, associated with an increasing proportion of twin cone photoreceptors and improving ability of the retina to light- and dark-adapt. By age >22 dph, mean prey capture was greatest at highest light intensities (0·79 and 10·6 μmol s⁻¹ m⁻²) exceeding 100 prey larva⁻¹ h⁻¹. Incidence of feeding larvae generally improved as the larvae grew, reaching >80% in all light intensities from 16 dph onwards. The lower threshold for visual feeding, between 0·0084 and 0·03 μmol s⁻¹ m⁻², remained constant as the larvae grew, despite an increasing density of rod photoreceptors. Below this threshold, non-visual feeding was evident at a low rate (<6 prey larva⁻¹ h⁻¹) that was independent of larval age.     

The effects of light intensity and algae-induced turbidity on feeding behaviour of larval striped trumpeter

Striped trumpeter larvae reared in algal cell‐induced turbid water (greenwater) fed equally well in clearwater in a light intensity range of 1–10 μmol s^‐1 m^‐2, when evaluated in terms of both the proportion of larvae feeding and larval feeding intensity. An ontogenetic improvement in photopic visual sensitivity of larvae was indicated by improved feeding at 0·1 μmol s^‐1 m^‐2, from 26±5% of larvae feeding and 0·027±0·005 rotifers consumed per feeding larva min^‐1 on day 8, to 96±2% and 0·221±0·007 rotifers consumed larva^‐1 min^‐1 on day 23 post‐hatching. Algal cell‐induced turbidity was shown to reduce incident irradiance with depth, indicated by increasing coefficients of attenuation (1·4–33·1) with increasing cell densities (0–2×10⁶ cells ml^‐1), though light intensities in the feeding experiment test chambers, at the algal cell densities tested, were within the optimal range for feeding (1–10 μmol s^‐1 m^‐2). Algae‐induced turbidity had different effects on larval feeding response dependent upon the previous visual environment of the larvae. Young larvae (day 9 post‐hatching) reared in clearwater showed decreased feeding capabilities with increasing turbidity, from 98±1% feeding and 0·153±0·022 rotifers consumed larva^‐1 min^‐1 in clearwater to 61±10% feeding and 0·042±0·004 rotifers consumed larva^‐1 min^‐1 at 56 NTU, while older clearwater reared larvae fed well at all turbidities tested. Likewise, greenwater reared larvae had increased feeding capabilities in the highest algal cell densities tested (32 and 66 NTU) compared with those in low algal cell density (6 NTU), and clearwater (0·7 NTU) to which they were naïve.     

Occurrence and settlement of the common shipworm Teredo navalis (Bivalvia: Teredinidae) in Bremerhaven harbours, northern Germany

The shipworm Teredo navalis L. is a xylophagous bivalve mollusc (Bivalvia: Teredinidae) with a long record of being very destructive to wooden ships and harbour buildings. It has been reported from numerous sites at the coasts of both the North and Baltic Seas since the eighteenth century. Here, we document for the first time the occurrence of live adult T. navalis in the harbours of Bremerhaven (Weser estuary, northern Germany). From August to December 1998, various wooden structures (fir floating fenders and pier posts, oak piles) from seven stations in different docks of two harbours (überseehafen, Fischereihafen) were investigated for the presence and density of live specimens and burrows of T. navalis. The settlement of larval shipworms was studied by exposing experimental fir panels 0.06 m² in size at 20 stations at water depths between 1 and 2 m for periods of 4 months between July and November. In addition, hydrographic profiles (0–8 m water depth) were obtained at 17 stations in five docks once every month from August to December. Live adult shipworms were found in both fir floating fenders and oak piles at four stations. The largest specimen found was 250 mm long. Shipworm burrows were detected at five stations in almost every wooden structure investigated but their abundances differed significantly: Maximum values were >10,000 m^–2 in fir floating fenders, 4,600 m^–2 in oak piles and 200 m^–2 in fir pier posts. Actual shipworm infestation was detected at three of 16 stations in the exposed fir panels (1–3 burrow holes per panel). Water temperatures and salinities varied considerably during the 4-month investigation period. Temperatures decreased from 19.9°C in August to 0.7°C in December. Salinities ranged from 17.6 in August to 1.1 in November, but only at two lock stations during November and December did value drop below 5, which is regarded as the lethal limit for the larvae of this euryhaline teredinid species. We conclude that T. navalis encounters favourable conditions for growth and reproduction in the harbours of Bremerhaven, at least during summer and autumn, and is a common element of the harbour ecosystem. Therefore, a persistent infestation of all wooden structures after a relatively short period of time seems to be highly probable. Electronic Publication     

Pelagic larvae of bivalve mollusks of Amursky Bay,Sea of Japan

Larvae of 63 Bivalvia taxa were found in Amursky Bay. Of these, 47 were identified to the species level. Larvae of 55 taxa were found throughout the bay. The highest species diversity was recorded in the northeastern part and in the center of the southern part of the bay, as well as at the exit from it. Larvae of Mactra chinensis, Mytilus coruscus, Crassostrea gigas, Teredo navalis, Mya japonica, and Mysella ventricosa were widely distributed in the bay. The maximum numbers of species were observed in July and September. A comparison of species lists using the set-theory method showed that the species complexes typical of different parts of Amursky Bay are formed under the influence of the Razdolnaya River runoff flow from the north and marine waters coming from the south. The mean density of larvae during the observation period was 1100 specimens/m³ in the northern and 735 specimens/m³ in the southern part of the bay. The highest density of larvae in Amursky Bay was observed at the end of June, the beginning of July, and in September; the minimal larval density occurred in April, May, and August. While the species diversity was similarly high, the density of larvae was significantly higher in Amursky Bay than in the nearby Ussuriisky Bay.     

Pelagic larvae of the bivalves of Ussuriysky Bay, Sea of Japan

Based on materials of plankton surveying carried out in May–October 2008, the species composition, distribution, and density of pelagic larvae of bivalves of the Ussuriysky Bay (Peter the Great Bay, Sea of Japan) were studied. Larvae of 66 taxa were revealed and identified. The Bivalvia larvae occurred in the plankton during the entire period of study. Two areas, the inner and open part of the bay, which vary in the composition, concentration, and terms of larva occurrence in the plankton were distinguished. The larvae of Mytilus coruscus, Mactra chinensis, Modiolus kurilensis, Ruditapes philippinarum, Mya uzenensis and Teredo navalis were the most numerous and widespread. It was shown that despite high taxonomic diversity, the density of Bivalvia larvae in the Ussuriysky Bay was an order of magnitude lower, even in terms of their maximum number, than in other studied areas of the Peter the Great Bay.     

Larvae of phoronids (Phoronida) from Terpeniya Bay (Southeastern Sakhalin)

Phoronid larvae were found in planktonic samples from the northern coast of Terpeniya Bay. In some samples, their density was up to 220 specimens/m³. Larval stages having 10, 12, 16, 20, and 22 tentacles are described. Larvae were identified as Actinotrocha branchiata and belong to the species Phoronis muelleri Selys-Longchamps, 1903. However, unlike the Ph. muelleri larvae described in the literature, the larvae we found are smaller (not more than 900 μm) before metamorphosis and have fewer tentacles (24). They lack paired vacuolated diverticula of the stomach, which are characteristic of Ph. muelleri larvae. However, judging by all other characters, namely transparency, the absence of coelomic cylinder in the preoral lobe, and the presence of adult tentacle primordia, one pair of blood cell aggregations, and a pyriform organ, these larvae are similar to the previously described larvae of Ph. muelleri. Adult forms of Ph. muelleri were previously found in Terpeniya Bay and described by Mamkaev (1962) and Emig (1984).     

Respiration,energy balance and development during growth and starvation of Carcinus maenas L. larvae (Decapoda:Portunidae)

In all larval stages of Carcinus maenas L. oxygen consumption was measured at three temperatures (12,18,25 °C). Values increased during development and were in the range of 0.037 ± 0.01 (zoea-1, 12°C, $\text{x}\text{?}\text{± 95\% CL}$) to 0.734 ± 0.047 μl O₂ · h^?1 · ind^?1 (megalopa, 25 °C). Growing larvae showed temperature dependent trends in weight specific respiration rates (referred to dry wt; DW), with values between ≈2.4 and 9.4 μl O₂· h^?1·mg DW^?1. Increase in oxygen consumption of megalops did not differ much at temperatures between 18 and 25 °C. This points to an exceptional physiological position of this stage. Fed zoea-1 of C. maenas (18 °C) revealed growth rates in terms of 40% DW, 20% carbon (C), 30% nitrogen (N) and 65% hydrogen (H). At the same time larvae gained individual energy by 13% (J · ind^?1), while weight specific energy dropped by ≈ 19% (J · mg DW^?1) during the first day and remained constant until the moult. Starved zoea-1 of C. maenas (18 ° C) gained ≈ 20 % in DW through the first day, probably caused by inorganic salts which enter the organism after the moult of the prezoea. DW dropped to ≈ 25 % of initial value, when starvation continued. Single components decreased by ≈50% (C), 54% (N), 57% (J · ind^?1). Weight specific energy (J · mg DW^?1) decreased by 40% during the first 4 days of starvation, remaining constant thereafter. Individual respiration rate (R) dropped by 61 %, weight specific respiration rate (QO₂) by 55 %. Individual energy loss in starved zoea-1 was 0.077 J over a period of 11 days. In this period ≈ 9.3 μl O₂·ind^?1 were consumed. Thus effective oxygen capacity was lower than in growing larvae. It dropped to 5.3 J·mlO₂^?1 after 4 days and remained constant if starvation continued, i.e. 65 % of possible energy loss occurred during the first 4 days. Decrease in requirement for oxygen and its effective capacity were both recognized as independent components of survival during starvation. Partitioning of energy through individual larval development of C. maenas was investigated for all five larval stages. The cumulative budget could be calculated: consumption (C) = 28.23 J, growth (G) = 0.92 J, exoskeleton (Ex) = 0.20 J, metabolism (M) = 5.30 J, egestion and excretion (E) = 21.82 J. Mean gross and net growth efficiency were, K₁ = 3.3% and K₂ = 14.8%, respectively.     

Lipid class dynamics during larval ontogeny of sea scallops, Placopecten magellanicus, in relation to metamorphic success and response to antibiotics

This study examines ontogenetic changes in lipid class composition in relation to survival and growth of five batches of sea scallops, Placopecten magellanicus, from egg to dissoconch stages. It also investigates the effects of antibiotic addition during metamorphosis to determine whether transient treatment during this critical period is effective in increasing metamorphic success. The top-performing larvae (growth rate: 4.7-5.0 μm day^− 1, dissoconch survival: 32-57%) were characterized by a pronounced increase in absolute (ng larva^− 1) and relative concentrations (wt.% of total lipid) of triacylglycerol (TAG) during the pre-metamorphic period, followed by utilization during metamorphosis (0.5-1.4 μg day^− 1 larva^− 1). In contrast, the low-performing scallops (growth rate: 3.6-4.5 μm day^− 1, dissoconch survival < 1%) exhibited a constant, low level of TAG. These results strongly suggest that the accumulation of TAG during the pre-metamorphic period is a good predictor of scallop performance as measured by survival to dissoconch stage. Antibiotic treatment enhanced absolute and relative TAG concentrations in pre-metamorphic scallops and resulted in higher post-metamorphic survival and TAG concentration than in non-treated controls. However, the proportion of dissoconch to live larvae at the end of the experiment was significantly lower with antibiotic treatment (8% vs. 20% in controls), thus resulting in comparable yields of dissoconch larvae ∼ 8% irrespective of treatment. A possible negative effect of antibiotic treatment on bacterial induction of settlement and metamorphosis of sea scallop larvae is suggested.     

Relationships between irradiance and photosynthesis for marine benthic green algae (Chlorophyta) of differing morphologies

Photosynthesis-irradiance relationships were determined in the field for five species of littoral and shallow sublittoral marine benthic green algae (Chlorophyta) of differing morphologies. Each species exhibited a linear increase in photosynthetic rate with increasing irradiance up to a maximum light-saturated value. Full sunlight (1405 to 1956 μE·m^?2·s^?1) inhibited photosynthesis of all species except the thick, optically dense, Codium fragile (Sur.) Har. Compensation irradiances ranged from 6.1 μE·m^?2·s^?1 for Enteromorpha intestinalis (L.) Link to 11.4 μE·m^?2·s^?1 for Ulva lobata (Kütz) S. & G. and did not reveal a consistent relationship to seaweed morphology. Saturation irradiances were determined statistically (I_k) and visually from graphical plots. with the latter technique resulting in values three to eight times higher and different comparative rankings of species than the former. I_k saturation irradiances were highest for Chaetomorpha linum (Müll.) Kütz. (81.9 μE·m^?2·s^?1) and lowest for Codium fragile (49.6 μE·m^?2·s^?1) and did not reveal a relationship with seaweed morphology. Regression equations describing light-limited photosynthetic rates and the relative magnitudes of the maximal net photosynthetic responses both strongly suggested a relationship with seaweed morphology. Highest net photosynthetic rates were obtained for the thin, sheet-like algae Ulva lobata (9.2 mg C·g dry wt^?1·h^?1), U. rigida C. Ag. (6.5 mg C·g dry wt^?1·h^?1) and the tubular form, Enteromorpha intestinalis (7.3 mg C·g dry wt^?1·h^?1), while lowest rates occurred for Codium fragile (0.9 mg C·g dry wt^?1·h^?1). Similarly, steepest light-limited slopes were found for the algae of simpler morphology, while the most gradual slope was determined for Codium fragile, the alga with greatest thallus complexity.     

PHYSIOLOGICAL INDICATORS OF NUTRIENT DEFICIENCY IN CLADOPHORA (CHLOROPHYTA) IN THE CLARK FORK OF THE COLUMBIA RIVER,MONTANA1

Cellular nutrient concentrations and nutrient uptake rates of Cladophora glomerata (L.) Kuetzing were determined during summer and fall in 1989–1990 at a site on the upper Clark Fork of the Columbia River, Montana. Both physiological tests indicated that Cladophora growth is likely to be limited by nitrogen during late summer-early fall. Maximum uptake rates of ammonia-N and nitrate-N were 5935–6991 and 507–984 μg · g DW^?1· h^?1, respectively, during July–October when dissolved inorganic nitrogen (DIN) concentrations in the river were less than 10 μg · L^?1. During November-December, when DIN was 72–376 μg · L^?1, maximum ammonia-N uptake was 1137–1633 μg · g DW^?1· h^?1 and maximum nitrate-N uptake was 0–196 μg · g DW^?1· h^?1. Cellular nitrogen during summer–early fall was 0.78–1.80% of Cladophora dry weight, frequently at or below 1.1%, a level suggested as a critical minimum N concentration for maximum growth. In contrast, cellular P was 0.18–0.36% of dry weight, 3–6 times the suggested critical P concentration of 0.06%. Molar ratios of cellular N:P (< 16:1) and DIN: SRP (< 4:1) during late summer-early fall also indicated potential N limitation. Cellular N and P from Cladophora collected from a second site influenced by a municipal wastewater discharge in 1990 displayed similar seasonal trends. At both sites, seasonal fluctuations in DIN were closely tracked by changes in cellular N, Cellular P, however, increased through the growing season despite declining levels of SRP in the river.     

Life Cycle,Production and Survival Rates of Ptychoptera paludosa(Diptera: Ptychopteridae)

Life cycle, survival and production of the univoltine midge Ptychoptera paludosa whose larvae live in fine sandy sediments were studied in a German stream (1989–1990). Growth of the 4th larval instar was linear. Adults emerge from May, for ca 8 weeks (1985–1990); emergence was 0.56 g dry weight m^–2 lentic area (1990). Density decreased strongly only when larvae were young; except after an exceptional spate, numbers emerging were independent of discharge. Larval survival was ca 9%; only 10% of the potential offspring of the survivors actually appeared in the next generation. Secondary production (P) was 2.3 g ash free dry weight (AFDW) m^–2y^–1, mean biomass (B) was 0.6 g AFDW m^–2, i.e., the P/B ratio was 3.8.     

Wing and leg amputation induced oviposition pattern of tropical tasar silk moth,Antheraea mylitta Drury (Lepidoptera: Saturniidae) in oviposition devices – Earthen cups and paper sheets

Antheraea mylitta Drury (Lepidoptera: Saturniidae) is a tropical semi-domesticated wild tasar silkworm reared by marginal tribal farmers of India. Due to improper egg laying frequency, oviposition is generally kept for three continuous days after amputating the gravid moth wings (W^–) in earthen cups (C). In order to systematize the oviposition frequency, wing cut with leg cut (W^–L^–) was performed in ecorace Daba trivoltine (DTV) completing three life-cycles in a year. Oviposition of (C)W^–L^– was observed in all three grainages during the year 2020 and compared with (C)W^– moths. Oviposition was also accomplished on plain paper sheets (S). It is observed that (C)W^– obtained 63–67% and (C)W^–L^– obtained 72–80% egg laying on first day. Similarly, (S)W^– and (S)W^–L^– obtained 68–71% and 74–83% on first day. Further, significant high oviposition was observed within first four hours in both earthen cups and on paper sheets by W^–L^– moths laying 49–69% and 55–65% eggs compared to W^– laying 25–45% and 39–44% eggs, respectively. A total of 44–51, 47–54, 44–48 and 46–52 eggs/g moth weight was obtained in (C)W^–, (C)W^–L^–, (S)W^– and (S)W^–L^–, respectively in three consecutive grainage. Oviposition of W^– moths in earthen cups and on paper sheets are not significantly different indicating earthen cups in contemporary tasar grainage could be replaced with paper sheets. Thus, the paper demonstrates for the first time a fast, efficient and scalable cellular oviposition of A. mylitta on paper sheets comparable to Bombyx mori.     

Single-trait and antagonistic index selection for litter size and body weight in mice

Individual selection based on female performance only was conducted in four lines of mice: L⁺ for increased litter size, W⁺ for increased 6-week body weight, L^-W⁺ for a selection index aimed at decreasing litter size and increasing 6-week body weight and L⁺W^- for a selection index aimed at increasing litter size and decreasing 6-week body weight. A fifth line (K) served as an unselected control. All litters were standardized to eight mice at one day of age. Expected heritability was based on twice the regression of offspring on dam (h²_d), which contains additive genetic variance due to direct (σ²_Ao) and maternal (σ²_Am) effects and their covariance (σ_AoAm). Responses and correlated responses were measured either deviated (method 1) or not deviated (method 2) from the control line. Realized heritabilities (h²_R) for litter size were 0.19 ± 0.04 (1) and 0.16 ± 0.03 (2), which were similar to h ²_d of 0.17 ± 0.04. The h² _R for 6-week body weight of 0.55 ± 0.07 (1) and 0.44 ± 0.07 (2) agreed with h²_d of 0.42 ± 0.02. Realized genetic correlations (r*_GR) between litter size and 6-week body weight calculated from the double-selection experiment were 0.52 ± 0.10 (1) and 0.52 ± 0.13 (2), which were not significantly different from the base population estimate of r* _Gd = 0.63 ± 0.14. Divergence (L^-W ⁺ minus L⁺W^-) in the antagonistic index selection lines was 0.21 ± 0.01 index units (I = 0.305 P_W - 0.436 P_L, where P _W and P_L are the phenotypic values for 6-week body weight and litter size, respectively.). The h² _R of index units of 0.14 ± 0.02 calculated from divergence agreed with h²_d of 0.14 ± 0.04. Divergences in litter size (-0.19 ± 0.07) and 6-week body weight (0.46 ± 0.10) were in the expected direction. Antagonistic index selection yielded about one-half the expected divergence in litter size, while divergence in 6-week body weight was only slightly less than expected. Realized genetic correlations indicated that litter size, 6-week body weight and index units each showed positive pleiotropy with 3-week body weight, postweaning gain and weight at vaginal introitus and negative pleiotropy with age at vaginal introitus. Sex ratio and several components of fitness (days from joining to parturition, percent fertile matings and percent perinatal survival) did not change significantly in the selected lines.     

Laboratory and field experiments with methoxychlor as a larvicide for simuliidae (diptera)

The dispersion of methoxychlor and Rhodamine B dye in the Chalk River, Canada, was measured by chromatography and fluorometry. The accumulation of methoxychlor was studied in laboratory and field experiments.The river was treated for 15 min with an oil solution of methoxychlor (0·79 μg/litre). The numbers of drifting simuliid larvae reached maximum values 60 min after the start of treatment at stations 275 m and 550 m downstream from the point of application. The peak numbers decreased with distance downstream, and most of the larvae began to drift after the methoxychlor had passed by.No methoxychlor could be detected in water, larvae or moss collected from the Chalk River before the experiment, but drifting larvae caught after the treatment contained residues ranging from 0·24 to 2·57 mg/kg.The larvae which began drifting later generally contained more methoxychlor than those drifting soon after treatment. S. venustum began drifting sooner than S. vittatum, and the mean sizes of drifting larvae of both species tended to increase as time passed. Residues of methoxychlor ranging from 7·4 to 34·6 μg/kg were detected in moss and grasses in the river for up to 8 weeks after the treatment.Laboratory experiments indicated that simuliid larvae concentrate particulate formulations of methoxychlor more efficiently than ethanol ones. Residue values in the larvae reached 2310 μg/kg.Trichoptera larvae concentrated methoxychlor to levels up to 1563 μg/kg, and ethanol formulations to higher levels than particulate ones.     

Seasonal relationships between leaf nitrogen content (photosynthetic capacity) and leaf canopy light exposure in peach (Prunus persica)

Abstract Field gas exchange measurements on intact peach (Prunus persica (L.) Batsch) leaves indicate that leaf nitrogen content (N_L) and leaf weight per unit leaf area (W_a) are highly correlated with CO₂ assimilation rate (A) and mesophyll conductance (g_m). Therefore, N_L and W_a were used to study seasonal relationships between leaf carboxylation capacity and natural light exposure in tree canopies. From mid-season onwards, N_L and W_a were linearly correlated with light exposure expressed as the amount of time during a clear day that a leaf was exposed to a photosynthetic photon flux density (Q) of ≥ 100 μmol m^?2 s^?1. The data support the hypothesis that whole-tree photosynthesis is optimized by partitioning of photosynthetic capacity among leaves in deciduous tree canopies with respect to natural light exposure.     

Correlated Responses in Male Reproductive Traits in Mice Selected for Litter Size and Body Weight

Correlated responses in male reproductive traits were determined at 4, 6 and 8 weeks of age in lines of mice selected for large litter size (L⁺), large 6-week body weight (W⁺), large litter size and small body weight (L⁺W^-) and small litter size and large body weight (L^-W⁺), and in an unselected control (K). Concentration of serum testosterone and weights of testes, seminal vesicles, epididymides and adrenal glands increased with age. Line differences in testosterone concentration were not detected. L⁺ and W⁺ males exhibited positive correlated responses in testes, epididymides and seminal vescile weights. Testis weight adjusted for body weight was significantly larger for L⁺ than controls and approached significance for W⁺. Realized genetic correlation betestis weight and litter size was 0.60 ± 0.04, and the realized partial genetic correlation holding body weight constant was 0.42. Therefore, pleiotropic loci, acting via the hypothalamic-pituitary axis, affect testis weight and litter size independently of body weight. Additionally, genes influencing overall growth have a pleiotropic effect on testis weight and litter size in mice; the realized genetic correlations of body weight with testis weight and with litter size were 0.60 ± 0.03 and 0.52 ± 0.10. Testis weight increased in both L⁺W^- and L^-W⁺ males. The positive correlated response in L⁺W^- may have resulted from changes in frequency of genes controlling reproductive processes; whereas, in L^-W⁺ it could have been the result of changes in the frequency of genes associated with body weight.     

Estimation of larval dry weight of Chaoborus americanus

A method for estimating larval dry weight as a function of tracheal front air sac length and instar was developed for second, third, and fourth instar Chaoborus americanus using linear regression analysis. The following equation: where W = larval dry weight (μg), L = front air sac length (mm), a = the y-intercept, and b = the slope provided accurate estimates of larval dry weight for three C. americanus populations. No detectable change in size occurred in the air sacs of larvae preserved for one year in 5% formalin. This indicates that air sacs can be used to accurately estimate larval dry weight for preserved as well as living specimens.