Diel Movements of Bat Rays, Myliobatis californica, in Tomales Bay, California: Evidence for Behavioral Thermoregulation?

We used ultrasonic telemetry to examine movement patterns of 11 bat rays, Myliobatis californica, in Tomales Bay, California. Tomales Bay is long (20km) and narrow (1.4km), and is hydrographically separated into outer and inner bay regions. The outer bay (the outermost 8km) is characterized by oceanic conditions while the shallow inner bay (the innermost 12km) features wide seasonal temperature shifts. Five rays were tracked monthly from October 1990 to November 1991 and six rays (four of which carried temperature-sensing transmitters) were tracked daily from 30 June to 16 July 1992. Mean bat ray movement rate was 8.84mmin^–1 (range 4.49 to 13.40mmin^–1) and was not significantly affected by size (p=0.592), tidal stage (p=0.610), or time of day (p=0.327). Movement direction was unrelated to tidal stage (p=0.472) but showed a highly significant diel pattern (p<0.001). From 2:50–14:50h, rays moved toward the warmer and shallower inner bay, while from 14:50–2:50h they moved toward the cooler and deeper outer bay. These telemetry data, along with known bat ray foraging patterns and respiratory temperature-sensitivity, argue for behavioral thermoregulation as the primary influence on this movement pattern.     

Short-term Movements of Juvenile and Neonate Sandbar Sharks, Carcharhinus plumbeus, on their Nursery Grounds in Delaware Bay

We investigated short-term movements of neonate and juvenile sandbar sharks, Carcharhinus plumbeus, on their nursery grounds in Delaware Bay. The majority of sharks tracked limited their movements to water less than 5m deep, remained within 5km of the coastline, and occupied oblong activity spaces along the coast. In addition to site-attached coastal movements observed, several sharks moved entirely across Delaware Bay or spent considerable time in deeper portions of the central bay. Sharks tracked on the New Jersey side of the bay tended to spend more time in deeper water, farther from shore than sharks tracked on the Delaware side. Observation-area curves estimated that optimal tracking time for sandbar sharks in Delaware Bay was 41h. Indices of site attachment showed that movement patterns of tracked sandbar sharks varied from nomadic to home ranging. There was no significant difference in rate of movement for day/night, crepuscular periods, or between juveniles and neonates. In general, young sandbar sharks patrolled the coast and appeared to be site attached to some extent, but were capable of making longer excursions, including movement entirely across Delaware Bay.     

Distribution, Movements and Growth of Young Sandbar Sharks, Carcharhinus Plumbeus, in the Nursery Grounds of Delaware Bay

During the spring and summer months of 1995, 1996 and 1997, gillnet and longline surveys were conducted in conjunction with tag and recapture experiments to outline spatial and seasonal distribution of young sandbar sharks, Carcharhinus plumbeus, in Delaware Bay for essential fish habitat mapping, to assess abundance of young sandbar sharks, and to quantify growth during the summer nursery season. Sandbar sharks (n = 943) ranging from 40 to 120cm fork length (48 to 130cm total length) were captured; yearly totals were 199, 314 and 430 in 1995, 1996 and 1997, respectively. Individuals were captured between June and October in water temperatures ranging from 15.4° to 28.5°C and salinities ranging from 22.8 to 30.3 ppt. Presence of neonates and catch per unit effort data indicate that pupping begins in late June near the southwestern coast of the Bay. Juveniles were present from early June through September and their spatial distribution in the Bay appeared uniform. Of 782 sandbar sharks tagged and released during the three years, 50 were recaptured. Mean distance from tag to recapture location and mean days-at-liberty of sandbar sharks recaptured in Delaware Bay during the year of tagging were 10km and 18 days, respectively. Some sharks were recaptured as far as 957km from the release location. Length distributions show young-of-the-year sandbar sharks grow about 2–3cm in length during the nursery season.     

A Cytogenetic Study of the Leaf Beetle Genus Cyrtonus (Coleoptera, Chrysomelidae)

The chromosomes of ten species of Cyrtonus and the genome sizes of six are surveyed. Among the total of 15 chromosomally studied species, 11 have 2n=28 chromosomes and a 13+Xy_p male meioformula, three have 2n=40 and 19+Xy_p and one 2n=46 and 22+Xy_p. All but one species with 28 chromosomes show only metacentric or submetacentric chromosomes, whereas the species with 40 and 46 chromosomes display some telocentrics or subtelocentrics, that are probably derived from the former by centric fissions. However, since the number of major chromosome arms is strikingly higher in these latter species (NF=70 and 78) than in the 28-chromosome species (mostly NF=56), other chromosomal rearrangements such as pericentric inversions or heterochromatin accretions could also be involved. The genome sizes display a narrow range, from 1C=0.6–1.22pg, and they are not significantly correlated with the chromosome numbers. Some possible factors implied in the rough chromosomal evolution of Cyrtonus are discussed in relation to a few other genera of the subfamily Chrysomelinae.     

A comparison of Visual Prey Detection Among Species of Piscivorous Salmonids: Effects of Light and Low Turbidities

Differences in reaction distance to prey fish by piscivorous salmonids can alter predator–prey interactions under different visual conditions. We compared reaction distances of three piscivorous salmonids commonly found in western lakes: cutthroat trout, Oncorhynchus clarki utah, rainbow trout, O. mykiss, and the nonnative lake char, Salvelinus namaycush. Reaction distances to salmonid prey were measured as functions of light and turbidity in a controlled laboratory setting. In addition, predation rates and swimming speeds of lake char preying on juvenile cutthroat trout were measured experimentally under a range of light levels. Reaction distances for cutthroat trout and rainbow trout increased rapidly as light levels increased, reaching relatively constant reaction distances at higher light levels. Reaction distances for lake char were similar to cutthroat trout and rainbow trout at the lower light levels; however, lake char reaction distances continued to increase with increasing light intensity to asymptote at distances 65% higher than those for both cutthroat and rainbow trout. Predation rates by lake char were low for the darkest light levels, increased rapidly under low light levels (0.50–0.75lx), and then declined to an intermediate rate at all higher light levels. Swimming speeds by lake char also increased rapidly from extremely low light conditions to a peak and declined to an intermediate level at light levels above 1.00lx. These results suggest that, above the saturation intensity threshold, piscivorous lake char react to fish prey at greater distances than do cutthroat trout and rainbow trout. These differences may help explain the decline of native trout following the introductions of nonnative lake char in lakes and reservoirs of western North America.     

Microhabitat Preferences and Movements of the Weatherfish,Misgurnus fossilis,in a Drainage Channel

Habitat preferences and movements of the weatherfish, Misgurnus fossilis, were studied in a drainage channel of the lower River Havel region (Saxony-Anhalt) from July to November 1995. During summer, adult fish preferred dense vegetation patches (e.g. Elodea canadensis) whereas juveniles preferred the reed zones along the bank lines, characterized by coarse detritus and extremely shallow water depths (<0.1m). All size groups totally avoided open substratum without vegetation structures. In total, 166 weatherfish 14cm were marked individually by injected dyes and their movements were documented by recaptures (recapture rate 29%). Most of the weatherfish showed stationary behaviour or site constancy. The majority of fish (70.1%) were recaptured within ranges of 50m with reference to the first release point. The mean movement distances slightly increased during the search for overwintering habitats in the first weeks of October. Weatherfish stocks in drainage channels of the study area are strongly affected by annual machine weeding due to depletion of suitable microhabitats and direct removal of fish. Alternative maintenance protocols for drainage channels and ditches are proposed.     

Relations between hydrological variables and year-class strength of sportfish in eight Florida waterbodies

Hydrological variables have influenced fish recruitment in lakes, reservoirs and rivers. We evaluated how annual and seasonal hydrological variables were related to year-class strength (i.e., residuals from catch curves) of sportfish across eight Florida waterbodies (four rivers and four lakes). Multiple regression equations computed for black bass Micropterus spp. were combined across rivers and year-class strength was negatively related to spring median flow rates and in some cases positively related to winter median flow rates (all p0.10). Conversely, Lepomis spp. residuals combined from the rivers indicated that year-class strength was positively related to median flow rates in the fall prior to spawning and negatively related to post-spawn fall median flow rates (all p0.10). Fish recruitment combined across lakes were not related to water levels in this study, although within lake relationships did occur in some instances. Ecological implications of this work include regulations such as minimum flows and levels (MFLs) regarding sportfish species. Impacts of hydrology on year-class strength of sportfish were stronger in rivers than in lakes for these Florida systems. High flows at least once every 3years in the fall may allow inundation of floodplain habitat, providing favorable environmental conditions for Lepomis spp. reproduction. Setting MFLs during periods of drought (i.e., 3years or more) should consider impacts to short-lived species such as Lepomis spp.     

Spectral Sensitivity of the Hawaiian Saddle Wrasse, Thalassoma duperrey, and Implications for Visually Mediated Behaviour on Coral Reefs

Although tropical coral reefs are one of the most spectrally complex habitats, there is relatively little known about colour vision of reef fish. In this study, we measured the spectral sensitivity of an endemic Hawaiian coral reef fish, Thalassoma duperrey (family Labridae), and assessed the possible role of visual sensitivity in mediating intraspecific communication. Electrophysiological recordings of compound action potentials from retinal ganglion cells were used to generate spectral sensitivity curves for specific wavelengths (380–620nm). We found at least 2 sensitivity peaks for the on response (_max=460, 550nm). The off response lacked a short wavelength mechanism but a medium wavelength mechanism (_max=545nm) and a longwave mechanism (_max=570nm) were found. To quantify the visual stimulus provided by a conspecific individual, spectral reflectance from the colour pattern of T. duperrey was measured with a spectroradiometer. Luminance and spectral contrast were computed between colour patches of the pattern and between the patches and natural backgrounds (i.e., water and coral). Reflectance from the blue head and contrast from the blue, green and red patches matched the sensitivity maxima of T. duperrey, although this depended on the type of background. Our results indicate that T. duperrey should be able to visually detect the colour pattern of a conspecific fish and that T. duperrey's visual system is designed to enhance target detection in the coral reef habitat with matched and offset cone mechanisms.     

The stimulation of methylmercury production by decomposition of flooded birch leaves and jack pine needles

The link between methylmercury (MeHg) production and decomposition of flooded organic matter was examined using an enclosure experiment. Six plastic enclosures were filled with lake water containing low concentrations of dissolved organic carbon (146µmolL^–1) and MeHg (0.02ngL^–1) and anchored in a lake at the Experimental Lakes Area, northwestern Ontario. Either fresh birch leaves, fresh jack pine needles, or no plant tissues at all were added to enclosures. Birch leaves decomposed 2.4 times faster than jack pine needles as measured by the total carbon decomposition by-products produced in enclosures over time. However, measured net MeHg production in enclosures containing birch leaves (0.35±0.05ng per g carbon added) was five times lower than in the enclosures containing jack pine needles (1.94±0.28ng per g carbon added). These results showed that MeHg production is not solely related to rates of organic matter decomposition, and that increases in MeHg associated with flooded birch leaves and jack pine needles resulted from the production of new MeHg as opposed to leaching of MeHg already in the plant tissues during decomposition.     

Distribution and biology of Galaxias truttaceus (Galaxiidae) in south-western Australia, including first evidence of parasitism of fishes in Western Australia by Ligula intestinalis (Cestoda)

The freshwater trout minnow, Galaxias truttaceus, is restricted to the small catchments of the Goodga and Kalgan Rivers in Western Australia. Its large geographic separation from populations in south-eastern Australia, and subsequent reproductive isolation and variation in the prevailing environmental conditions, has created marked differences in biology (and morphology) between the eastern and western populations of G. truttaceus. The biology (spawning period, longevity, growth rates, diet and parasitism) of G. truttaceus in the Goodga River is described and then compared with information on the biology of diadromous and landlocked populations in south-eastern Australia (i.e. Tasmania) (see Humphries 1989). In the Goodga River, ca. 34 and 8% of males and females, respectively, attain maturity at the end of their first year, while only four mature males and one mature female 0+ fish were found in the Tasmanian populations. Adults migrate upstream prior to spawning which peaks during April and May. Larvae, which hatch at ca. 6.5mm (cf. 7.5–9.0mm in Tasmania), move downstream into Moates Lake for a few months before re-entering the river. Of the 810 G. truttaceus collected, ca. 53, 34, 10, 2, 1, 0.2 and 0.1% belonged to the 0+, 1+, 2+, 3+, 4+, 5+ and 7+ age classes, respectively. In contrast, the Tasmanian populations have a much higher proportion of older fish. At the end of their first, second and third years, the males on average attain 60, 84 and 95mm total length (TL), respectively, whereas females attain 63, 89 and 103mm TL, respectively at those ages. Only one fish > 140mm TL was captured, which contrasts with the Tasmanian fish, where a substantial proportion are > 140mm TL. The diet of fish > 40mm TL consisted of between 65 and 96% terrestrial fauna (mainly coleopterans and hymenopterans) in the different seasons. Larval fish diets were largely comprised of copepods.The occurrence of the introduced cestode Ligula intestinalis in ca. 7% of G. truttaceus represents the first record of this parasite in Western Australia. It was found to cause gonadal retardation and gross morphological deformities, the latter of which possibly increases the risk of avian predation.     

Movement of walleye in an impounded reach of the Au Sable River,Michigan, USA

Synopsis We estimated long-range spawning and foraging movements of walleye and observed their use of river and reservoir habitats between two large hydroelectric dams on the Au Sable River, Michigan. We used radiotelemetry to monitor seasonal and daily movements of 11 large walleye. Walleye ranged throughout the entire reach between the two dams. Eight of the 11 fish used both river and reservoir locations. Walleye migrated upriver in April or May and presumably spawned near the dam tailwaters. After spawning, walleye remained in the river for up to 6months, usually establishing local ranges. During this time, they occupied low-velocity refuges within the first 25 km of the upstream dam. They seldom occupied the downstream area, which has higher variation around the mean temperature. Food availability and water temperature may have affected the length of time that walleye remained in the river after spawning. All walleye overwintered in the reservoir. We designed this study to evaluate if walleye have a potential negative impact on brown trout, Salmo trutta. In summer, walleye were often present near sites where fingerling trout were stocked. We found the highest potential for interaction between the two species occurs within the first 25km of the upstream dam during summer. The movement patterns of and habitats used by large walleye validate concerns that walleye could compete with adult brown trout for food and resting sites and prey on juvenile brown trout.     

Movements and Habitat Use by the Endangered Australian Freshwater Mary River cod, Maccullochella peelii mariensis

The decline of the endangered Mary River cod, Maccullochella peelii mariensis, of Queensland, Australia, has been attributed to anthropomorphic habitat alterations, however, the relationships between this subspecies and its physical environment are poorly understood. We used radiotelemetry to investigate the movements and use of habitats by nine Mary River cod (total length 420–760mm; weight 1.3–5.5kg) in the Mary River system over a 20 month period. The mean distance moved each month was positively correlated with monthly stream discharge, but the direction of movements was unpredictable. Patterns of movement varied considerably among individuals and appeared to be unrelated to size. Cod established home ranges of between 70 and 820m in length. Five of the tagged cod returned to a previous home range after moving more than 10km, whereas three did not move more than 2km from their capture location for the duration of the study. Cod used large woody debris complexes more than any other type of habitat, and rarely used areas of open water. Managers should give high priority to maintenance of fish passage and protection/rehabilitation of large woody debris habitats if cod populations are to recover.     

Patterns of Fish Movement on Eastern Tasmanian Rocky Reefs

We assessed small-scale movement patterns of fishes on three eastern Tasmanian reefs by divers visually resighting 1040 individuals of 16 species marked with unique colour-coded tags. With the possible exception of the monacanthid Acanthaluteres vittiger, common species showed high fidelity to site, with individuals generally resighted <100m from the initial tagging site and remaining near the tagging site throughout the 1 year duration of study. The wrasses Pictilabrus laticlavius and Notolabrus tetricus were more sedentary than Notolabrus fucicola and the monacanthids Meuschenia australis and Meuschenia freycineti. Body length, sex, water temperature and time since tagging had little influence on distance moved compared to variation between individuals, other than movement distance increasing with body length for N. tetricus. Movement patterns were generally consistent at all three sites, although mean distance moved by N. fucicola was double at Swanport and Return Point compared to Lobster Point. N. tetricus but not P. laticlavius emigrated from areas artificially cleared of macroalgae. The sedentary nature of most small- to medium-sized reef fish species, particularly labrids, indicates that relatively small (1km diameter) marine protected areas should generally provide conservation benefits for these fishes but few `spillover' benefits in surrounding areas.     

Development and Aging of the Liver and Pancreas in the Domestic Carp, Cyprinus Carpio: From Embryogenesis to 15-year-old Fish

The cytology of development and aging of the liver and pancreas in domestic carp was studied in a large sample of EM and LM sections from larvae juveniles 1–10 year old adults and 15 year old experimentally stunted fish weighing 20g and of 110–120mm TL. The primordium of the two glands appears in embryos 3–4 days after fertilization as buds from the gut wall. Formation of the hepatic tubules is first seen in larvae 10 days after fertilization. Two types of hepatocytes are discernable: one with a pale cytoplasm and the other with a dense opaque cytoplasm; both extend microvilli into the sinusoidal space of Disse and bear intracellular bile canaliculi. With maturation and branching of the hepatic tubules a complicated hepatic muralium is formed. The pancreatic cells develop in 5–6mm TL embryos primarily along the blood capillaries and in 10–11 day old larvae exocrine A and B cells are seen prominent by their zymogen granules and spires and stacks of rough endoplasmic reticulum. Ripening of the Islets of Langerhans begin in larvae of 10mm TL. By 16mm TL two types of endocrine cells are visible. With aging three processes are recognizable in the liver: (1) increased branching of the blood net displaces the hepatic units and complicates the structure of the liver parenchyma; (2) a gradual increase in lipid vacuoles and debris deposition in secretory cells takes place; and (3) the number of melano-macrophage cells and melano-macrophage centers gradually increases. In 15-year-old experimentally stunted fish (110–120mm TL) the liver and pancreas resemble those of juvenile fish appearing much healthier than those of 8–10 year old large carp from commercial ponds. These findings provide evidence that aging is not a simple time-dependent mechanism but is also strongly modulated by environmental factors.     

The influence of temperature and habitat on the distribution of chiselmouth, Acrocheilus alutaceus, in British Columbia

We intensively sampled fish in rivers and streams within a single major drainage basin (the Blackwater River) and across major drainages in British Columbia to assess the factors influencing distribution of chiselmouth, Acrocheilus alutaceus, and to develop models for predicting chislemouth presence. Chiselmouth were typically absent from sites with maximum temperatures below 20°C or 2100 annual degree days, both within a single drainage and between larger drainages. Indices of stream size (bankfull channel width and basin area) were the most significant predictors of chiselmouth presence within the Blackwater drainage (p=0.016 and p=0.032, respectively), and inclusion of thermal variables only marginally increased classification success. In contrast, bankfull channel width and basin area were poor predictors of chiselmouth presence in mainstem habitat within larger drainage basins throughout British Columbia. Inclusion of thermal variables (particularly degree days > 12°C) doubled correct classification rates of chiselmouth presence across larger drainage basins. These habitat associations suggest that water temperature is the primary constraint on presence of chiselmouth populations in larger drainages across a landscape, while selection of different habitat types (mainstem habitat over smaller tributaries) determines distribution within any given basin.     

Mode of uptake of sterol by Arthrobacter simplex

The mechanism of uptake of water-insoluble -sitosterol by a newly isolated strain of Arthrobacter simplex SS-7 was studied. The production of an extracellular sterol-pseudosolubilizing protein during growth of A. simplex on -sitosterol was demonstrated by isolating the factor from the cell-free supernatant and its subsequent purification by Sephadex G-150 column chromatography. The M _r of the purified sterol-pseudosolubilizing protein determined by SDS–PAGE was 19kDa. The rate of sterol pseudosolubilization (5.2×10^–3g l^–1h^–1) could not adequately account for the rate of sterol uptake (72×10^–3g l^–1h^–1) and the specific growth rate (56×10^–3 h^–1). However in the unfavourable growth condition, when the cells were treated with sodium azide at the level of 30–60% of MIC, the sterol pseudosolubilization accounted for nearly 74% of the total growth containing 96% free cells. Cellular adherence to substrate particles was found to play an active role in the normal growth of the strain on -sitosterol. Unlike sodium acetate-grown cells, whose surface activity was negligible (60mNm^–1), the sterol-grown cells had strong surface activity (40mNm^–1). The high lipid content and long chain fatty acids in the cell-wall of -sitosterol-grown cells probably contribute to the high sterol adherence activity of the cells.     

On the Population Ecology of the Zebra Seabream Diplodus cervinus cervinus (Lowe 1838) from the Coasts of the Canarian archipelago, North West Africa

Zebra seabream, Diplodus cervinus cervinus, caught off the Canary Islands is characterized by protogynous hermaphroditism. The male:female ratio is in favour of females (1:2.16). The reproductive season extends from spring to summer, with a peak in spawning activity in May–June. Males reach maturity at a larger total length, 327mm (5 years old) than females 273mm (4 years old). Recruitment occurs from late October to January in shallow waters of 0.5–8m depth along the coastal line. The recruits are located over rocky substrates with an important algae vegetation forming schools lower than 2m². During the spawning season, schools of adults from 3 to 8 fish are observed. The schools are formed by one large individual and a few moderate size individuals. Mating takes place in small groups formed by one dominant male and a group of several females (polygamy). Moderate size individuals are often observed mixed in large schools (up to 30 individuals) of Diplodus sargus cadenati. Subadults form groups of a few fish (<5 individuals) or more commonly mixed groups (>15 individuals) with individuals of species of similar size. Otoliths age readings indicate that the population consists of 18 age groups, including a very high proportion of individuals between 2 and 4 years old. The von Bertalanffy growth parameters for the whole population are: L = 603mm, k = 0.149 year^–1, and t₀ = –0.22 year. The mean rates of total, natural and fishing mortality are 0.551, 0.215 and 0.336 year^–1, respectively. The length at first capture is 183mm. The exploitation rate indicates that the stock is overfished. The direct effects of fishing on the population result in changes in the abundance, with a reduction to 85% of the unexploited equilibrium level. The length at first capture by the commercial fishery is less than the length at maturity. With 58% of the total catch below this length there is a danger of recruitment overfishing.     

Coexistence of Anadromous and Resident Life History Styles of Pond Smelt, <Emphasis Type="Italic">Hypomesus nipponensis</Emphasis>, in Lake Ogawara,Japan, as determined by Analyses of Otolith Structure and Strontium:Calcium Ratios

Anadromous and resident forms of pond smelt, Hypomesus nipponensis, were found to occur in sympatry in Lake Ogawara, Japan. Profiles of Sr: Ca ratios from individuals could be grouped to two patterns (1) a resident pattern with low Sr: Ca ratios from core to edge and (2) an anadromous pattern with relatively low Sr: Ca ratios near the core with abrupt increases in ratios at a location approximately 0.3mm from the core. Spawners smaller than 60mm standard length (SL) were resident, between 60 to 80mm were mixed resident and anadromous, and larger than 80mm were anadromous. Anadromous individuals first migrated after 40 to 82 days from hatching (mean±sd, 59.1±13.5d) and 14.6 to 30.9mm SL (22.2±5.3mm). There was no difference in SL between resident and anadromous individuals during age at first migration, suggesting that size may not be the mechanism for divergence of alternative life history styles.     

Growth and Reproduction of Double-Ended Pipefish, Syngnathoides biaculeatus, in Moreton Bay, Queensland, Australia

Life-history characteristics of the double-ended pipefish, Syngnathoides biaculeatus (Bloch), were investigated to determine growth rate, degree of sexual dimorphism, size at maturity, and reproductive biology. Growth rates of wild juveniles and adults calculated from monthly progression of length-frequency modes ranged from 0.8mmd^–1 (fish lengths 120–145mm standard length (SL)) in summer to 0.2mmd^–1 in winter (185–200mm SL). Growth of laboratory-reared juveniles up to 63d old was greater, ranging from 0.8 to 2.3mmd^-1. The von Bertalanffy growth constant K was estimated at 0.0076d^{- 1}, or 2.8year^–1. Morphological differentiation between the sexes based upon abdominal pattern was possible for fish larger than 120mm SL, with females possessing a zigzag pattern on the abdomen. The association between this pattern and sex was confirmed by histological gonad analysis. Males were significantly longer than females during four of seven seasons examined, and a 1:1 sex ratio was determined for all seasons except autumn when the ratio was female biased. The breeding season was marked by the appearance of pregnant males between October and April, and during courtship both species exhibited increased pigmentation. The minimum paternal size at maturity was 185mm, the maximum length recorded 260mm. Clutch size ranged between 60 and 200 eggs, with a mean of 153. Ovaries had a sequential pattern of egg development, resulting in egg batches that approximated the number of eggs carried by brooding males. Additionally, all eggs in a brood were at the same developmental stage. This suggests that one female provides all of the eggs for one male per breeding event in a monogamous mating system.     

Flax anther culture: effect of genotype,cold treatment and media

We report on screening of wide range of flax cultivars for androgenic response and on testing of induction conditions for flax (Linum usitatissimum L.) anther culture and plant regeneration. Anthers were cultured on four different media: Mo, N6, MS and N&N supplemented with various combinations of growth regulators. The induction of callus formation from cultured anthers was the highest on N6 (with cultivar PR FGL 77 – 12 %) and N&N media (with cultivar Carolin – 2.8 %), preferentially after cold pretreatment (7days at 8 °C). Shoots were formed on calli derived from the microspores inside the cultured anthers on media N&N and N6 supplemented with 1mgl^–1 zeatin or 1mgl^–1BAP + 1mgl^–1NAA, respectively and elongated on MS medium supplemented with 2mgl^–1 zeatin. The highest number of shoots (120) was observed with cultivar Red Wing. Shoots were rooted on MS medium supplemented with 2mgl^–1IAA. Our experiments resulted in total in 62 % anther response and 155 plants regenerated and transferred into soil.