Effects of sex pheromone in electrostatic powder on mating behaviour by Lobesia botrana males

Abstract:  In laboratory trials, mating behaviour of males of Lobesia botrana Den. and Schiff. (Lep., Tortricidae) was investigated after treatment with an electrostatically chargeable powder, Entostat^TM. Male moths were powdered with either blank Entostat or Entostat containing sex pheromone. Significantly more Entostat adhered to L. botrana males when sex pheromone was added to the powder compared with blank Entostat. Powdering male moths with Entostat, with or without sex pheromone, caused a significant reduction in antennal response when antennae were placed 2 cm away in downwind direction, while there was little effect when antennae were placed 25–100 cm from the EAG in downwind direction. In a flight study, powdering males of L. botrana caused significant increase in time before flight initiation and reduction in proportion of males making contact with calling females compared with untreated males. In a mating experiment in Petri dishes (to minimize required search time to locate female), significantly fewer females mated successfully (based on dissection of bursa copulatrix) when males had been treated with pheromone-loaded powder. Overall, powdering males of L. botrana caused considerable suppression of mating behaviour on various levels, and these suppressing effects were increased after adding sex pheromone to Entostat.     

Uptake of adhesive powders from lure stations by Mediterranean fruit fly (Dipt., Tephritidae)

Powders that are capable of adhering to insect cuticles can act as carrier particles when combined with insecticides, entomopathogens, or pheromones, for targeted insect control. One potential method of delivering the powder to an insect is to lure the insects to stations containing powder using a species‐specific attractant. Here, we report on the uptake of two different powders from lure stations (henceforth called ‘dispensers’) by the Mediterranean fruit fly, Ceratitis capitata, and the transfer of the powders to conspecifics during field studies in Portugal, as part of a research programme to develop lure‐and‐kill technologies based on adhesive powder. Uptake of an electrostatic wax powder, Entostat?, from dispensers was greater than uptake of a proprietary metallic powder, Entomag?, for both wild male C. capitata visiting field‐placed dispensers and laboratory‐reared males confined with dispensers in field cages. In agreement with field data, C. capitata also took up more Entostat than Entomag when artificially dosed on dispenser trays containing powder in the laboratory, and the quantities taken up were shown to be greater than that calculated from field experiments. Increasing the amount of Entostat powder in field‐placed dispensers resulted in greater uptake of powder by visiting male C. capitata. Laboratory‐reared male and female C. capitata were released in field cages in which were hung dispensers containing adhesive powder that were baited with the male attractant trimedlure. After 24 h, the powder was successfully extracted from all males and nearly all females collected, indicating that males probably transferred powder to conspecific females after visiting dispensers. The results underscore that a lure‐and‐kill system based on adhesive powder might have potential for controlling Mediterranean fruit fly and other flying insects.     

Ultrastructural observations of euspermatozoa and paraspermatozoa in a copulatory cottoid fish Blepsias cirrhosus

Euspermatozoa and paraspermatozoa of a copulatory (internal insemination with external sperm transfer) cottoid fish Blepsias cirrhosus were observed ultrastructurally. Euspermatozoa of B. cirrhosus consisted of an acrosome‐less, thin, disk‐like sperm head (1·6-2·0 μm in length and 1·3-1·6 μm in width), a long middle piece, and a long flagellum ( c . 30 μm). Aberrant spermatids, which were rich in cytoplasm and possessed two nuclei, occurred in testicular lobules. They were also observed in semen and were round (5·0-5·3 μm in diameter) and biflagellate, suggesting that they are released along with euspermatozoa at ejaculation. The nuclei of aberrant spermatids developed into masses of highly electron‐dense globules. Judging from their form, nuclear condition, and connection with normal spermatids by intercellular bridges during spermiogenesis, aberrant spermatids of B. cirrhosus are considered hyperpyrenic paraspermatozoa formed by incomplete cytokinesis at the second meiotic division.     

Mating behaviors of Cydia pomonella (Lepidoptera: Tortricidae) as influenced by sex pheromone in electrostatic powder

Entostat is an electrostatically charged wax powder that can adhere strongly to insect cuticle, making it an ideal carrier to deliver pheromone for pheromone-based confusion techniques. We investigated the attractiveness of Cydia pomonella (L.) (Lepidoptera: Tortricidae) males treated with pheromone-laden Entostat powder to naive conspecifics as well as mating behaviors of males after such treatment in a laboratory flight tunnel. Male moths exposed to Entostat containing 1% E,E-8,10-dodecadien-1-ol (codlemone) acquired and retained the largest amount of the powder and became more attractive as point sources to naive moths compared with those treated with powder containing 5 or 10% codlemone. All Entostat-exposed males remained as attractive as a 0.1-mg codlemone lure for up to 24 h in flight tunnel investigations. Male moth orientation to normally attractive sources of codlemone was completely disrupted directly after treatment with Entostat powder. Males' ability to orient to 0.1-mg lures recovered progressively over a 6-d postexposure interval; however, their responses never reached the levels observed with untreated control moths. Entostat-exposed moths retained detectable amounts of codlemone up to 4 d. Our laboratory flight tunnel results suggest that the mode of action of Entostat powder as an autodissemination control tactic may be due to creating both attractive false point sources after exposure to the powder as well as directly inhibiting contaminated males' capability to orient to pheromone.     

Pinealectomy and ovarian development in the grey mullet, Liza ramada

Adult female specimens of Liza ramada were pinealectomized and sham-pinealectomized, and the development of their ovaries was followed over a period of 14 weeks and compared with those of untreated controls. Pinealectomized specimens exposed to long photoperiod (16L/8D) for 14 weeks, showed undeveloped ovaries, with a maximum oocyte diameter of less than 100 μm, and a gonadosomatic index of 0·6 similar to that of sham-pinealectomized and control specimens. In pinealectomized females exposed to short photoperiod (8L/16D) for 6 weeks, the mean diameter of oocytes was 270 μm v . 155 μm in control and sham-pinealectomized specimens. After 9 weeks, the oocytes in pinealectomized specimens reached 430 μm as against 265 μm in the controls. Within 14 weeks of pinealectomy, mean oocyte diameter was 480 um while it was 400 μm in controls and sham-pinealectomized specimens. It is tentatively concluded that the pineal complex has an inhibitory effect on ovarian function in Liza ramada exposed to short photoperiod.     

Fine root dynamics in a Norway spruce forest (Picea abies (L.) Karst) in eastern Sweden

The annual dynamics of live and dead fine roots for trees and the field layer species and live/dead ratios were investigated at a coniferous fern forest (Picea abies L. Karts) in Sweden. Our methods of estimating the average amount of fine roots involved the periodic sampling of fine roots in sequential cores on four sampling occasions. The highest live/dead ratio was found in the upper part of the humus layer for both tree and field-layer species and decreased with depth. Most tree fine roots on the four sampling occasions were found in the mineral soil horizon, where 86, 81, 85 and 89% of <1 mm and 89, 88, 89 and 92% of <2 mm diameter of the total amounts of live fine roots in the soil profile were found. The mean amounts of live fine roots of tree species for the total soil profile on the four sampling occasions was 317, 150, 139 and 248 g m^?2 for <1 mm and 410, 225, 224 and 351 g m^?2 for <2 mm diameter fine roots. The related amount of dead fine roots was 226, 321, 176 and 299 g m^?2 and 294, 424, 282 and 381 g m^?2, respectively. Average amounts of live and dead fine-roots and live/dead ratios from other Picea abies forest ecosystems were within the range of our estimates. The production of fine roots, <1 and <2 mm in diameter, estimated from the annual increments in live fine roots, was 207 and 303 g m^?2. The related accumulation of dead fine roots was 257 and 345 g m^?2, The turnover rate of tree fine roots <1 mm in diameter in the total soil profile amounted to 0.7 yr^?1 for live and 0.8 yr^?1 for dead fine roots. The related turnover rates for tree fine roots <2 mm were 0.4 yr^?1 and 0.7 yr^?1. Our data, although based on minimum estimates of the annual fluxes of live and dead fine roots, suggests a carbon flow to the forest soil from dead fine-roots even more substantial than from the needle litter fall. Fine-root data from several Picea abies forest ecosystems, suggest high turnover rates of both live and dead tree fine-roots.     

Reproduction and fecundity of tucunaré, Cichla kelberi (Perciformes: Cichlidae), an exotic species in Três Marias Reservoir, Southeastern Brazil

To evaluate the reproductive cycle and fecundity of tucunaré ( Cichla kelberi Kullander & Ferreira, 2006), 697 specimens were captured in Três Marias Reservoir, São Francisco River, Brazil during 1994–1995 and 2005–2006. Reproductive activity was recorded throughout the sampling periods, with females exhibiting asynchronous oocyte development and multiple spawnings with a peak in September–October. Vitellogenic oocytes of the tucunaré were elliptical in shape with the longest diameter approximately 1230 μm and the shortest 700 μm, yolk globules with ellipsoid inclusions, lipid vesicles, small cortical alveoli and thin zona radiata (9.3 ± 2.0 μm thickness). Follicular cells were prisma-shaped (49.0 ± 16.4 μm) in the vegetative pole, progressively becoming cubic cells in the animal pole toward the micropyle. Histochemical analyses indicated the presence of mucosubstances in the outer zona radiata and follicular cells that could be contributors to egg adhesiveness. Batch fecundity ranged from 4450 to 13 900 oocytes for females 31.5–43.5 cm total length, respectively, and correlated to gonadal weight ( r ² = 0.80) and body weight ( r ² = 0.70). Mean relative fecundity was 10.6 vitellogenic oocytes per gram body weight. As tucunaré is an exotic piscivorous species well-adapted to the Três Marias Reservoir, the present work may be considered a contribution toward future strategies for population control.     

Light and Electron Microscopy of the Spore of Myxobolus heckelii n. sp. (Myxozoa), Parasite from the Brazilian Fish Centromochlus heckelii (Teleostei, Auchenipteridae)

ABSTRACT. A myxosporean parasitizing the gill filaments of the freshwater teleost fish Centromochlus heckelii collected in the Tocantins River (Lower Amazonian Region, Brazil) is described using light and electron microscopy. This parasite produces spherical to ellipsoidal cyst-like plasmodia up to 250 μm in diameter, with a thick wall strengthened by several stratified juxtaposed crossed collagen layers, whose thickness varies according to the number of the layers. Several compressed fibroblasts are observed among the collagen fibrils. Deposits of spherical dense material are scattered at the internal periphery of the cysts. Plasmodia and different developmental stages, including immature and mature spores, filled the central region of the cysts. The spore body is ellipsoidal in valvar view and biconvex in sutural view. It is formed by two equal-sized and symmetric valves measuring 12.7 μm long (12.2–13.1) ( n =50), 6.6 μm wide (6.3–6.9) ( n =25), and 4.0 μm (3.7–4.4) ( n =20) thick. A thin layer formed by fine and anastomosed microfibrils is observed at the spore surface. Two equal, elongated pyriform polar capsules measure 2.9 μm (2.7–3.3) × 1.7 μm (1.4–2.0) ( n =25), each containing four or five oblique polar filament coils. The binucleated sporoplasm contains numerous spherical sporoplasmosomes, glycogen particles, and a large vacuole with fine granular matrix. Based on the morphological and ultrastructural differences and specificity of the host, we describe this isolate as a new myxosporidian, Myxobolus heckelii n. sp. (Myxozoa, Myxosporea).     

Metallothionein levels in sperm of various fish species

In the present paper we determined low molecular heavy metal binding protein called metallothionein (MT) in fish spermatozoa sampled from four fish species ( Acipenser baerii, Acipenser ruthenus, Perca fluviatilis and Sander lucioperca ). The spermatozoa samples were analyzed with differential pulse voltammetry DPV (Brdicka reaction). The average content of MT in the fish sperm was 0.64 ± 0.55 μ m . The highest content of MT was determined in spermatozoa of S. lucioperca (0.96 ± 0.86 μ m ), followed by P. fluviatilis (0.88 ± 0.11 μ m ), A. ruthenus (0.57 ± 0.60 μ m ) and A. baerii (0.43 ± 0.25 μ m ). The differences in the content of MT was probably related to the differences in age and perhaps to the health status based on the environmental conditions in which the tested specimens developed while also other still unknown factors may have been involved.     

Microbial distribution of Accumulibacter spp. and Competibacter spp. in aerobic granules from a lab-scale biological nutrient removal system

Granular sludge for simultaneous nitrification, denitrification and phosphorus removal (SNDPR) was generated and studied in a lab-scale sequencing batch reactor (SBR). The SBR was monitored for 450 days during which the biomass was transformed from flocs to granules, which persisted for the last 130 days of operation. Short sludge settling time was employed to successfully generate the granules, with the 10th and 90th percentiles of diameter being 0.7 and 1.6 mm respectively. Good phosphorus removal and nitrification occurred throughout the SBR operation but only when granules were generated were denitrification and full nutrient removal complete. Fluorescence in situ hybridization and oxygen microsensors were used to study the granules at a microscale. Accumulibacter spp. (a polyphosphate-accumulating organism, PAO) and Competibacter spp. (a glycogen non-polyphosphate-accumulating organism, GAO) were the most abundant microbial community members (together 74% of all Bacteria ) and both are capable of denitrification. In the aerobic period of the SBR operation, the oxygen penetrated 250 μm into the granules leaving large anoxic zones in the centre part where denitrification can occur. In granules > 500 μm in diameter, Accumulibacter spp. was dominant in the outermost 200 μm region of the granule while Competibacter spp. dominated in the granule central zone. The stratification of these two populations between the outer aerobic and inner anoxic part of the granule was highly significant ( P  < 0.003). We concluded that the GAO Competibacter spp., and not the PAO Accumulibacter spp., was responsible for denitrification in this SBR. This is undesirable for SNDPR as savings in carbon demand cannot be fulfilled with phosphorus removal and denitrification being achieved by different groups of bacteria.     

Electrokinetic movement of Escherichia coli in capillaries

The movement of Escherichia coli K-12 has been studied in capillaries with an 8 μm inside diameter under a DC electric field. At low applied voltages (< 0.2 V cm⁻¹), bacterial motility is the predominant mode of motion, with bacteria swimming, tumbling and moving unidirectionally towards the anode and the cathode, although a significant difference between the mean moving speeds towards the two electrodes was observed. When the electric field was removed, the mean swimming speeds were the same for both directions. At higher voltages, all the cells were swept by electro-osmotic flow exclusively towards the cathode.     

Reproduction of the lambari Astyanax scabripinnis (Jenyns, 1842) (Pisces: Characidae) in a small stream in Southeastern Brazil

The reproduction of Astyanax scabripinnis captured bimonthly in the Cristais small stream (20^o00'03'S and 43^o56'46'W), in the Das Velhas River basin, was studied using gross anatomical and histological techniques. Standard length of females (56 ± 8 mm) was longer than males (49 ± 6 mm). The diameter of the nucleus of the primary spermatogonia was 7.5 ± 0.9  μ m and of the spermatozoon head 1.8 ± 0.4  μ m. For the females, the oogonia nuclei measured 10.2 ± 2.2  μ m and the vitellogenic oocyte nuclei measured 675.0 ± 66.7  μ m. The following stages of the reproductive cycle were established: developing, mature, partially spent/spawned and completely spent/spawned. Maximum number of males (61.3%) and females (58.2%) at the mature stage was observed during November/December. The gonadosomatic index of males and females was highest during the mature stage (2.4 ± 0.6; 7.5 ± 1.3, respectively) and decreased in subsequent stages. In females, the hepatosomatic index was highest during the developing stage (2.8 ± 0.3), and slightly decreased in the following stages. The highest stomach repletion index found for males was observed during the partially spent stage (2.0 ± 1.2), while for the females, this index varied discretely between the reproductive stages. The highest values of Fulton's condition factor were registered during the mature stage in both sexes (2.9 ± 0.4 for males; 3.0 ± 0.3 for females). The continuous reproductive period and the presence of partially spawned females during the entire sampling period indicated that the species has fractional spawning.     

Growth characteristics of skeletal muscle tissue in Oreochromis niloticus larvae fed on a lysine supplemented diet

The effect of lysine amino acid supplementation on the growth characteristics and morphological pattern of skeletal muscle tissue in Nile tilapia Oreochromis niloticus larvae was evaluated. There were four treatments (T) with increasing levels of lysine supplement (T1 = 0·0%; T2 = 1·1%; T3 = 1·7%; T4 = 4·0%) and one treatment with a commercial diet (T5). In all treatments, morphological and histochemical muscle tissue analyses were similar. Two distinct layers were identified: a superficial red layer, more developed in the lateral line region, formed by fibres with intense to moderate NADH‐TR reaction and strong acid‐stable mATPase activity, and a deep white one, most of the muscle mass, formed by fibres with weak NADH‐TR reaction and strong alkali‐stable mATPase activity. There was an intermediate layer between these two layers with fibres exhibiting either weak acid‐stable or acid‐labile mATPase activity. Body mass increase was significantly higher in T5 than in the lysine treatments (T1–T4). There was no difference in number and diameters of muscle fibres between lysine treatments. In T5, muscle fibre diameter and number were higher. The frequency of red fibres with diameters ≤8 μm was higher in the lysine treatments, and with diameters between 16 and 24 μm, was higher in T5. Most white fibre diameters in T5 were significantly larger than 24 μm and in T1–T4 were between 8 and 16 μm. Cell proliferation was higher in the lysine treatments and muscle growth in T5 was mainly by fibre hypertrophy.     

What do dung beetles eat?

Abstract.  1. Most adult coprophagous beetles feed on fresh dung of mammalian herbivores, confining ingestion to small particles with measured maximum diameters from 2–5 to 130 μm, according to body size and kind of beetle. This study explores benefits and costs of selective feeding in a 'typical' dung beetle with a maximum diameter of ingested particles (MDIP) of 20 μm.
2. Examined dung types (from Danish domestic sheep, cattle and horse, and African wild buffalo, white rhino and elephant) contained 76–89% water. Costs of a 20 μm MDIP were often low, since 69–87% of the total nitrogen in bulk dung other than that of elephant and rhino (40–58%) was available to selective feeders.
3. Nitrogen concentrations were high – and C/N ratios low – in most types of bulk dung compared with the average food of terrestrial detritivores or herbivores. Exceptions were elephant and rhino dung with low nitrogen concentrations and high C/N ratios.
4. Estimated C/N ratios of 13–39 in bulk dung (sheep–elephant) were decreased by selective feeding to 7.3–12.6 in the ingested material. In assimilated food, ratios are probably only 5–7, as most assimilable nitrogen and carbon may be of microbial origin. If so, the assimilable food contains a surplus of nitrogen relative to carbon.
5. The primary advantage of selective feeding, particularly in dung with a high C/N ratio, may be to concentrate assimilable carbon in the ingested food. Effects of changing the MDIP within 20–106 μm are modest, especially in dung with a low C/N ratio.     

Cell surface appendages of lactobacilli

Abstract Seventeen vaginal isolates of lactobacillus were negatively stained using 1% phosphotungstic acid and examined by transmission electron microscopy. One or two flagella were observed in a polar or, less frequently, sub-polar position on 14 of the 17 isolates. The structures, measuring 12 nm in diameter and up to 12 μm long, were seen on cells cultured in both solid and liquid MRS medium. Fimbriae, measuring 3.5 nm in diameter and 0.1 μm to 1.0 μm in length, extended from the cell surface of 15 of the 17 lactobacillus isolates. Production of fimbriae was maximal when the lactobacilli were cultured on solid medium in an anaerobic atmosphere. Fimbriation significantly increased adhesion of lactobacilli to vaginal epithelial cells in vitro.     

Exoskeletal structure in the Ordovician trilobite Flexicalymene

Scanning Electron Microscope study of the exoskeletal ultrastructure of secondarily phosphatized material of Flexicalymene sp. from the Upper Ordovician Maquoketa Shale, Iowa, USA, shows that the exocuticle, comprising 20% of the total exoskeletal thickness, is composed of horizontal laminar units between 0.2 and 1 μm thick. These units consist of primarily mineralized organic fibres which form horizontal laminae interconnected by inter-laminae. The endocuticle is considerably more mineralized than the exocuticle, and its original organic structure cannot be observed in untreated preparations. Etching with chromium sulphate reveals: (1) horizontal organic laminar units, 0.2 to 2 μm thick, and (2) pore canals with non-twisted walls about 0.3 μm in diameter. Exuvia cannot be distinguished from the exoskeletons of dead animals. The exoskeletal ultrastructure in trilobites agrees essentially with that in crustaceans.     

The fecundity of the walleye pollock, Theragra chalcogramma (Pallas), spawning in Canadian waters

The ovaries of 113 walleye pollock from a resident stock in the Strait of Georgia, British Columbia were examined for determination of fecundity. Oocytes were sized and counted in 20 μm intervals of diameter. Without exception, ovaries contained a pronounced bimodal distribution of oocyte diameters with peaks at 100 and 400–600 μm. Oocytes ≥ 180 μm diameter were undergoing trophoplasmic growth leading to hydration. 'Apparent' fecundity is defined as the estimated number of yolked oocytes ≥ 180 μm diameter, regardless of potential resorbtion. Previous workers have not shown that significant resorbtion takes place in the post-spawned ovary. Total oocyte complement (≥40μm diameter) was best expressed by a linear model where F_t = 33004 f.l. – 869627, where f.l. = fork length in cm and r = 0.86. Estimates of F_t , ranged from 117700 to 1394 100 oocytes ≥40μm. Age was weakly related to fecundity, reflecting large individual differences in annual growth after age 4 years. Apparent fecundity best suited a linear model where F_a = 23522 f.l. – 599713 and r = 0.91. Estimates of F_a fell within the range 58 379–1 151 527. Relative fecundity (eggs g⁻¹) decreased over most of the length range encountered in the sample. The average-sized female in Georgia Strait is twice as fecund as her counterparts in the north-western Pacific Ocean, containing some 390 000 to 420 000 oocytes 7ge;180 μm diameter compared to about 200 000 oocytes in a north-western female of comparable length.     

The relationship between food particle size and larval size in Simulium noelleri Friederichs

SUMMARY. 1. In a laboratory experiment, larvae of Simulium noelleri were fed on polystyrene latex microspheres of a range of diameters from 5 to 100 μm.
2. Examination of the particle size distribution in the water used in the experiment showed those <13μm to be the most numerous (87% of all particles present). Particles of this size made up 57±2% (mean ±SE)of the total of those in the gut of larvae.
3. Comparison of particle composition in the gut contents and the water of the experiment, using Jacob's index of electivity, showed that larvae of all sizes filtered proportionally fewer of the particles <13 μm and more of those >13μm.
4. As larvae increased in size they became better able to filter the largest particles present (>52μm in diameter) and less well able to filter the smallest particles (<13μm in diameter).
5. Gut retention time was longer in larger larvae.
6. The biology of S. noelleri , which inhabits lake outlets in high population densities, is considered in the light of these findings.     

The nucleolus and its modifications during oogenesis of Torpedo marmorata

The structural organisation of the nucleolar apparatus during oogenesis of the spotted ray Torpedo marmorata was investigated. The observations showed that unlike other cartilaginous fishes, in T. marmorata the nucleolar apparatus was always represented by one or two conspicuous nucleoli, whose organization significantly changed during oocyte development. In the smallest follicles (follicles <300 μm in diameter) the nucleolus was made up of granular and fibrillar components, and actively incorporated ³H uridine; later it becomes more and more electron‐dense so in follicles of 400 μm in diameter its components and ³H uridine incorporation were no longer evident. These results indicate that in T. marmorata the nucleolar apparatus significantly changes and undergoes a possible impairment in rRNA synthesis. After nucleolus inactivation, the synthesis of rRNA may be substained by granulosa.     

Leaf vascular dimensions associated with freeze tolerance in bahiagrass (Paspalum notatum)

Foliage damage as a result of individual freeze events is a major limitation to the expansion of bahiagrass ( Paspalum notatum ) pastures and hay production in Southeastern USA. Greater tolerance to such freeze events would allow production deeper into the fall and winter and allow expansion of this species into colder regions. While it has been reported that small cells are more tolerant to freeze damage, this possibility has not been explored in bahiagrass. Specifically, the hypothesis was examined that xylem vessels with smaller diameter in the midrib of leaves are associated with freeze tolerance among bahiagrass genotypes. Vascular bundle diameter was also measured as a possible index of xylem cell size. A total of eight bahiagrass genotypes were eventually studied representing four freeze-sensitive and four freeze-tolerant lines. There was a clear distinction in xylem cell size between the freeze-sensitive and the freeze-tolerant lines. The freeze-tolerant genotypes had xylem element cells that were significantly smaller than the freeze-sensitive genotypes. Averaged across three leaf positions and all genotypes, the xylem element diameter for the freeze-sensitive lines was 222 μm and for the freeze-tolerant lines was only 164 μm. A similar difference was observed in overall vascular bundle diameter with freeze-sensitive lines having a mean of 1168 μm and the freeze-tolerant lines a mean of 917 μm. These results indicated that the diameter of the xylem cells in the vascular midrib of bahiagrass may be an important variable influencing the sensitivity among genotypes to freeze damage.