bluuebunny/crossref_metadata_2025 huggingface dataset:
Seasonal prevalence, intensity of infestation, and distribution of glochidia of Anodonta grandis simpsoniana Lea on yellow perch, Perca flavescens
Authors: Jansen Wolfgang A.
Published: August 2008

Five fish species were sampled at regular intervals in Narrow Lake, central Alberta, and examined for the prevalence and intensity of infestation by glochidia larvae of Anodonta grandis simpsoniana. Yellow perch (Perca flavescens) collected between January and May were infested with glochidia, whereas perch captured between June and October were free of larvae. The prevalence of infestation increased gradually from 86 to 95% between January and May, and the intensity of infestation increased from 5.7 to 49.4 glochidia per fish over the same period. Glochidia were found on most external body surfaces, including the gills. Glochidia attached preferentially to some anatomical areas, especially pectoral and pelvic fins. Furthermore, the relative importance of certain attachment sites differed significantly among sampling dates. Neither sex, size (length or weight), or age of perch significantly affected the intensity of infestation per fish. However, small (4.4–6.0 cm), 1- and 2-year-old fish carried more than 12 times the number of glochidia per gram of body weight than large (12.1–15.7 cm), 4- to 7-year-old fish. Both perch behavior and distribution and clam reproduction and distribution provide possible explanations for the observed patterns in the prevalence and intensity of infestation and in the distribution of the glochidia on the host.
Estimates of the number of glochidia produced by clams (Anodonta grandis simpsoniana Lea), attaching to yellow perch (Perca flavescens), and surviving to various ages in Narrow Lake, Alberta
Authors: Jansen Wolfgang A. , Hanson J. Mark
Published: August 2008

Between May 1986 and March 1989, the density, breeding cycle, and glochidia production of the unionid clam Anodonta grandis simpsoniana, and the population size and intensity of glochidia infestation of yellow perch, Perca flavescens, were evaluated in Narrow Lake, Alberta. The total number of glochidia produced was compared with the number of glochidia infesting yellow perch, and clam recruitment to age 2 and adulthood was estimated. Clams carried eggs and glochidia between July and, dependent on the prevailing water temperature, May or June of the following year. A total of 2.9 × 106 clams 2 years and older, of which approximately 50% were mature, produced 38.1 × 1012 glochidia in 1987. Of these, 2.6 × 106 (0.007%) glochidia attached to perch, predominantly (>92%) to 1- and 2-year-old fish. Once attached to perch, glochidia had a relatively high survival: 27% to 2 years of age and 9–18% to maturity. These results suggest that the parasitic phase in the life cycle of unionids is most critical.
Predation on fish and intersite variation in the diet of common garter snakes, Thamnophis sirtalis, on Vancouver Island
Authors: Gregory Patrick T. , Nelson Kari J.
Published: August 2008

Diets of garter snakes (Thamnophis) often vary in space or time in response to variations in prey abundance. We compared the diet of the common garter snake (T. sirtalis) on Vancouver Island at fish-rearing facilities (hatcheries) and at nearby natural sites where fish were present but less abundant. Snakes of all sizes fed on fish at hatcheries, but fish were rarely eaten at natural sites, where amphibians or earthworms were the major prey types. Any particular characterization of the diet of this species therefore must be site specific. Although snakes exhibited intersite variation in diet, there was no evidence of temporal variation in diet at any site. The proportion of snakes with food in their stomachs varied among sites (perhaps indicating differences in frequency of feeding among sites) and was correlated with mean relative body mass of snakes. This suggests that some sites are more productive than others for snakes, but rigorous tests of whether snake populations are food-limited have not been done.
Distribution of the South American dolphin Sotalia fluviatilis
Authors: Borobia Mônica , Siciliano Salvatore , Lodi Liliane , Hoek Wyb
Published: August 2008

The marine form of the South American dolphin Sotalia fluviatilis has an extensive and possibly continuous distribution, from the Florianópolis region, Brazil (27°35′S, 48°34′W), north to Panama (~9°22′N, 79°54′W). The high number of records from 25–20°S is due to the presence of many observers in those latitudes. The freshwater form of this species inhabits the Amazon and Orinoco drainages. It is commonly seen in the Amazon, and has been found as far inland as southern Peru. The southern limit of the range of the marine form of Sotalia is associated with the confluence zone of the Brazil and Falkland currents, suggesting that low sea-surface temperature is a limiting factor, whereas in fresh water the distribution of Amazonian Sotalia seems more closely related to the movements and concentrated occurrence of prey.
Metal concentrations in crayfish tissues in relation to lake pH and metal concentrations in water and sediments
Authors: Young Leah Bendell , Harvey Harold H.
Published: August 2008

Cambarus bartoni from two acid lakes, Cambarus robustus from one acid lake, and Orconectes virilis from one acid and two circumneutral lakes were analyzed for the following concentrations: Mn, Fe, Al, Zn, Cu, and Cd in gill; Mn, Fe, Al, Zn, and Cu in muscle; and Mn, Al, Fe, Zn, Cu, Ca, Mg, Ba, and S in carapace tissue. Analysis of covariance and canonical variates analysis were used to illustrate differences in the six crayfish populations, based on the elemental content of the three tissues. Gill Cd was significantly greater in all four crayfish populations from the acid lakes, as compared to crayfish from circumneutral lakes. Subsequent canonical variates analysis separated crayfish from acid lakes from those sampled from two circumneutral lakes, based on gill Cd concentrations and to a lesser extent on gill Mn concentrations. Carapace elemental composition was also significantly different among the six crayfish populations, with the canonical variates analysis separating crayfish of acid-lake origin from those captured in circumneutral lakes, based on differences in Mg and Mn content of the carapace; carapaces of crayfish from acid lakes had more Mn and less Mg relative to crayfish carapaces from circumneutral lakes. The elemental composition of crayfish muscle was the least variable and the least indicative of differences in elemental content among the six populations. Conditions of low pH may be preventing the normal mineralization of crayfish carapaces, as evidenced by crayfish from acid lakes having carapaces with lower Mg concentrations relative to crayfish from circumneutral lakes. More importantly, however, increases in gill Cd in crayfish from low-pH lakes appear to be a pH-related effect rather than being attributable to differences in Cd accumulation among species or to abiotic factors such as concentrations of Cd in the sediments, dissolved organic carbon, or water-borne Ca concentrations. As crayfish are an important food resource for many fish and semiaquatic animals, they could be a key vector in the trophic transfer of Cd from the aquatic to the terrestrial environment.
Biliverdin in the serum of ammocoetes of Lampetra lamottenii (Le Sueur)
Authors: Eng F. , Youson J. H.
Published: August 2008

Green sera collected from larval lampreys of Lampetra lamottenii were assayed and were shown to contain biliverdin at a concentration ranging from 141.5 to 305.0 μmol/L (mean 231.0 ± 27.4). These levels of serum biliverdin are compared with those of other lower vertebrates and with those observed during several human pathological conditions and are discussed with regard to the location of larval nematodes of Truttaedacnitis stelmioides within the bile ducts of these lampreys.
Environmental and physiological factors controlling the reproductive cycles of pinnipeds
Authors: Boyd I. L.
Published: August 2008

The reproductive pattern of pinnipeds is characterised by embryonic diapause, annual reproduction, and synchronous breeding cycles. Active gestation lasts about 8 months in most species, but the duration of embryonic diapause varies indirectly with the length of the postpartum oestrous cycle. Data on reproductive endocrinology are limited to a few species, owing to difficulties involved in obtaining serial samples from individuals. The postpartum oestrus is marked by elevated oestradiol concentrations followed by a rise in progesterone levels after ovulation. An infertile cycle may lead to pseudo-pregnancy, although on rare occasions there may be a further period of oestrus. Progesterone concentrations remain elevated for the duration of pregnancy and chorionic gonadotrophin concentration in the placenta increases early in postimplantation. Sex steroids do not appear to be directly involved in blastocyst reactivation. The environmental factors influencing implantation appear to be the most significant proximate factors in timing pinniped reproductive cycles. In most species, implantation occurs when day length is declining, and a photoperiod of about 12 h may provide the signal for implantation in some species. Other proximate factors may include sea temperature, at least for grey seals. Pinnipeds have reproductive cycles with an active and an inactive phase. The inactive phase may be equivalent to the period of embryonic diapause. Transition from the inactive to the active phase and reactivation of embryonic growth are probably controlled by the same environmental cues.
Patterns of mass gain and sexual dimorphism in adult dragonflies (Insecta: Odonata)
Authors: Anholt B. R. , Marden J. H. , Jenkins D. M.
Published: August 2008

We present data on mass gain and sexual dimorphism from 61 collections of 54 species in eight families of Odonata. Males and females emerge at similar mass in most species (14 of 17 measured). However, females are significantly heavier than males when mature in 37 species. Males are heavier in only four species (though none significantly so). Females increase in thoracic mass as well as abdominal mass (presumably for egg maturation). Males allocate most additional mass to the thorax. Females increase in mass by an average of 125% between emergence and sexual maturity. The average increase for males is only 84%, and in some species males lose mass. Sexual dimorphism in mass at maturity is most striking in the nonterritorial Coenagrionidae, where females average > 60% heavier than males. In species known to be territorial, male and female masses are more similar; female mass does not exceed that of males by more than 32%. We propose that mass gain as an adult is beneficial to females regardless of mating system because it increases fecundity. In territorial species, heavier males are more likely to acquire and hold territories and thereby gain access to mates. In nonterritorial species, heavy males do not have the same advantage in access to mates. Because acquiring resources for mass gain has costs in time and mortality, and there are metabolic costs of maintaining additional mass, males of species with nonterritorial mating systems gain less mass. As a result, the mass of males and females in species with territorial mating systems are more similar than in species with nonterritorial mating systems.
A comparison of the male genitalia of three Calopteryx species (Odonata: Calopterygidae)
Authors: Adams John A. , Herman Thomas B.
Published: August 2008

We compared the morphology of male genitalia in the damselflies Calopteryx maculata (P. de Beauvois), C. aequabilis Say, and C. amata Hagen in Nova Scotia. Differences were most pronounced between C. maculata and the other two species. The number of spines and the arrangement and density of spinulae on the ventrolateral surface of the penis shaft varied among species; the largest species, C. amata, had three times as many spines as did the smallest, C. maculata. Scanning electron micrographs of penes revealed structures in C. aequabilis and C. amata similar to those in C. maculata. Males of both C. amata and C. aequabilis can likely remove sperm from the reproductive storage organs of females, as previously shown in C. maculata and C. dimidiata.
Parasites of carabid beetles: prevalence depends on habitat selection of the host
Authors: Andersen Johan , Skorping Arne
Published: August 2008

The prevalence of endoparasitic nematodes (Mermithoidea and Heterotylenchus sp.) and the ectoparasitic fungi Laboulbenia spp. was examined in 14 riparian species of carabid beetles of the genus Bembidion. The values for Laboulbenia spp. and nematodes (Heterotylenchus sp) were 41.1 and 11.4%, respectively, in host species living in protected microhabitats (silty, more or less vegetated, often shady sites). In Bembidion species living in open microhabitats (open silty, sandy, or gravelly–stony sites with little or no vegetation) the prevalence of both parasites was less than 1%. The open microhabitats are more subject to floodwater scouring and erosion than the protected ones. This may explain the observed difference in prevalence, since the beetles are infected with the parasites through contact with contaminated soil.
Effect of temperature and inoculum size on reproduction and development of Heterorhabditis heliothidis and Steinernema glaseri (Nematoda: Rhabditoidea) in Galleria mellonella
Authors: Zervos S. , Johnson S. C. , Webster J. M.
Published: August 2008

Larvae of Galleria mellonella were kept at temperatures of 5, 10, 15, 20, 25, and 30 °C, and exposed to six levels of inocula (5, 10, 25, 50, 100, and 500 infective juveniles/larva) of Heterorhabditis heliothidis and Steinernema glaseri. Temperature and inoculum level significantly affected time to first emergence, duration of emergence, and yield of juveniles. All parameters except emergence of H. heliothidis showed significant interactions between temperature and inoculum level. No juveniles emerged at 5 or 10 °C and development time was most rapid at 25 °C. No juvenile H. heliothidis emerged at 30 °C or with 500 infective juveniles/host, but duration of emergence was shortest at high temperatures with large inocula; yield per host and yield per inoculum were greatest at 20 °C with small inocula. Yields of S. glaseri were half those of H. heliothidis; duration of emergence was shortest at low temperatures; yield per host was greatest at 20 and 25 °C from large inocula; and yield per inoculum level was greatest when the numbers inoculated were small (5–50/host).
Seasonal variation in temperature preference of juvenile Atlantic cod (Gadus morhua), with evidence supporting an energetic basis for their diel vertical migration
Authors: Clark Donald S. , Green John M.
Published: August 2008

Juvenile (3-year-old) Atlantic cod (Gadus morhua) from Broad Cove, Conception Bay, Newfoundland, exhibit seasonal variation in temperature preference. Laboratory studies show that juvenile cod from ambient temperature water prefer temperatures that correlate closely with seasonal changes in the temperature of the inshore waters that they inhabit. A similar pattern is shown by fish held in 10 °C water over winter, indicating that variation in temperature preference is not simply a response to changing ambient temperatures but occurs in an anticipatory manner that allows them to maintain their physiologically optimal temperature at a seasonally appropriate level. The results also support the hypothesis that the diel vertical migration of juvenile cod in summer increases energetic efficiency by reducing metabolic costs in nonfeeding hours.
Gross anatomy, myoarchitecture, and ultrastructure of the heart ventricle in the haemoglobinless icefish Chaenocephalus aceratus
Authors: Harrison P. , Zummo G. , Farina F. , Tota B. , Johnston I. A.
Published: August 2008

The gross and microscopic anatomy of the heart ventricle in the haemoglobinless icefish Chaenocephalus aceratus is described. The ventricle is saclike in shape and has a relative mass approximately three times greater than that of related "red-blooded" Antarctic fish. The myocardium in C. aceratus is entirely trabecular and consists of myocytes, granulated noncontractile cells, and electron-dense interstitial spaces. Blood supply is through the venous lacunary circuit. In addition, two size classes of channels occur in the subepicardium, with mean diameters of 15 and 50 μm. The larger channels are connected directly with the intertrabecular spaces. The volume density of mitochondria is 0.47 in icefish myocytes, 0.15 in those of a tropical fish (Astronotus ocellatus) with a myoglobin-rich ventricle, and 0.27 in a cold-temperate fish (Cyclopterus lumpus) with a myoglobin-poor ventricle. The volume density of myofibrils in C. aceratus (0.25) is significantly less than in A. ocellatus (0.45) and C. lumpus (0.42). The data obtained are discussed in relation to present knowledge about the function of the heart in C aceratus as a low-speed, large-volume pump.
Response of young female prairie voles (Microtus ochrogaster) to nonresident males: implications for population regulation
Authors: McGuire Betty , Getz Lowell L.
Published: August 2008

We measured behavioral and physiological responses to nonresident males of young female prairie voles (Microtus ochrogaster) living in family groups. Although substantial variation both among families and among littermates was noted, females generally exhibited investigative and affiliative behavior toward nonresident males, and many were reproductive at the end of a 10-day period. Approximately 31 and 56% of females exposed to sexually inexperienced and experienced males, respectively, had uterine weights greater than or equal to 30 mg. Females exposed in the absence of their fathers to sexually experienced males displayed the highest levels of interaction with nonresident males, and 71% were classified as reproductive. Control females, exposed either to castrated nonresident males or not exposed to nonresident males, remained nonreproductive. Frequent interactions with nonresident males can thus override the reproductive suppression experienced by young female prairie voles at natal nests. The resultant increase in proportion of reproductive females within each family group may contribute to dramatic increases in population density. By limiting interactions between their daughters and nonresident males, resident males play a role in population regulation.
The influence of temperature on the survival, development, growth, and chromosome preparation quality of the EFG/C, ACD, and AA cytotypes of the Simulium venustum–verecundum complex (Diptera: Simuliidae)
Authors: McCreadie John W. , Colbo Murray H.
Published: August 2008

The influence of temperature on survival, development, and growth of simuliid larvae of the EFG/C cytotype and of a mixed population of ACD–AA cytotypes was examined, employing a stir bar rearing system. The EFG/C type completed larval development from 5 to 30 °C, with maximum survival between 15 and 20 °C (68.0–73.5%). The ACD–AA types completed development between 5 and 25 °C, with maximum survival between 15 and 25 °C (55.3–61.0%). The temperature–survivorship curve of EFG/C was significantly different from the ACD–AA one. Using regression analysis, threshold temperature was determined to be 0 °C. Mean degree-days required to complete larval development varied depending on temperature, cytotype, and sex. Degree-day determination in the laboratory agreed well with field data. Final larval instars of EFG/C and ACD were largest at 10–15 °C. The results are compared with those of previous studies and discussed in relation to "optimal temperature" and fitness. The size and band discrimination of the salivary gland polytene chromosomes used to identify the above cytotypes were found to vary with rearing conditions. We suggest that larvae reared at 15 °C and fed Tetra, at a dosage of ≥ 0.3 mg/larva per day, will provide good-quality chromosome preparations.
Facultative estivation in the water strider Gerris remigis
Authors: Wilcox R. Stimson , Maier Hilmar A.
Published: August 2008

Marked individuals of the water strider Gerris remigis estivated facultatively during summer in damp areas underneath stream-bed rocks when a pool in a small stream in New York twice went dry.
Lepeophtheirus cuneifer Kabata, 1974 (Copepoda: Caligidae) from seawater-reared rainbow trout, Oncorhynchus mykiss, and Atlantic salmon, Salmo salar, in the Strait of Georgia, British Columbia, Canada
Authors: Johnson S. C. , Albright L. J.
Published: August 2008

Adults, preadults, and chalimus larvae of Lepeophtheirus cuneifer were recovered from rainbow trout, Oncorhynchus mykiss, and Atlantic salmon, Salmo salar, cultured in seawater in the southern Strait of Georgia, British Columbia. This species has not been reported previously from these hosts or in Canadian waters. It was found only in low abundance and is not an economically important parasite of farmed salmonids in British Columbia.
Phylogeny of parasitic Platyhelminthes: a critical study of synapomorphies proposed on the basis of the ultrastructure of spermiogenesis and spermatozoa
Authors: Justine Jean-Lou
Published: August 2008

Recent cladistic phylogenies of the Platyhelminthes, especially the parasitic species, use for synapomorphies several characters of the spermatozoa, together with other characters. This paper reinvestigates synapomorphies based on sperm characteristics. The outgroup usually chosen for such studies on the parasitic Platyhelminthes (Cercomeria) is the "Dalyelliida" or "Dalyellioida," generally considered a paraphyletic group, but sperm structure in this group shows great variation. In this paper, the Typhloplanoida, which have a plesiomorphic structure (two free axonemes), are considered the outgroup. One of the synapomorphies recently proposed for the Neodermata is "spermatozoon with axonemes incorporated in the cytoplasm." This definition introduces convergences with several other groups of nonparasitic Platyhelminthes. A more precise definition of spermiogenesis, based on a detailed description, is proposed in this paper and avoids homoplasies: "proximodistal fusion of the axonemes." This implies the presence of dorsal and ventral microtubules in the nuclear region of the spermatozoon. This synapomorphy characterizes the Cercomeridea but not the Neodermata (= Udonellidea + Cercomeridea). The character "absence of dense granules in the spermatozoon" should be considered a synapomorphy for the Neodermata and has almost no homoplasies. For the Temnocephalidea, the spiral pattern of the peripheral microtubule row is proposed as a synapomorphy. This character is present in Didymorchis; however, Didymorchis lacks tentacles, which are present in the other genera, and thus the ultrastructural synapomorphy is in conflict with a recently proposed morphological synapomorphy for this group: the presence of tentacles. No synapomorphy of the spermatozoon can be proposed for the Monogenea, but the presence of lateral microtubules lining the axonemes is proposed as a synapomorphy for the polyopisthocotylean Monogenea, and the absence of dorsal and lateral microtubules is proposed as a synapomorphy for the monopisthocotylean Monogenea (this is a reversal of the synapomorphy for the Cercomeridea defined above). The cyclophyllidean Eucestoda show a twisting of the peripheral microtubules of the spermatozoon, which is proposed as a synapomorphy.
A comparison of scolex morphology between the plerocercoid and the adult of Calliobothrium verticillatum (Tetraphyllidea: Onchobothriidae)
Authors: Caira J. N. , Ruhnke T. R.
Published: August 2008

The morphological changes associated with the ontogenetic transformation of the scolex from larva to adult were investigated in the tapeworm Calliobothrium verticillatum (Rudolphi, 1819) van Beneden, 1850 by comparing the morphology of plerocercoids collected from the hermit crab Pagurus pollicaris Say, 1817 with that of adult worms collected from the shark Mustelus canis (Mitchell, 1815), using scanning electron microscopy. The apex of the scolex in young plerocercoids bore a conspicuous sucker. Each bothridium was flat and divided into four regions: an anterior oval region with two marginal bumps, and three posterior loculi clearly marked by two costae. The microthrix pattern was not determined for very young plerocercoids. The most conspicuous feature of older plerocercoids was the sucker on the apex of the scolex. The bothridia were concave, and each bore an apical region subdivided into three shallow suckers and three conspicuous loculi. Densely packed blade-like microtriches intermingled with filiform microtriches were visible on all surfaces of the scolex except the surface directly adjacent to the opening of the apical sucker of the scolex, which was entirely devoid of microtriches, and the proximal surfaces of the bothridia, which had only blade-like microtriches. The apical sucker was absent from the scolex adult specimens. The only remnant of this structure was a small knob on the apex of the scolex. The bothridia were concave and bore, from anterior to posterior, three conspicuous apical suckers arranged in a horizontal row adjacent to one another, two pairs of single-pronged hooks, and three conspicuous loculi. Densely packed blade-like microtriches were present on all proximal surfaces of the scolex. Microtriches were not present on the distal surfaces of the apical suckers of the bothridia, on the hooks, or on the distal surfaces of the loculi of the bothridia. The latter regions were covered with very small, round structures. The differences in the microthrix components of the various surfaces of the scolex between the plerocercoid and the adult suggest that complex surface changes occur during this phase of ontogeny. Comparison of the development of this species with that of other onchobothriids suggests that, in general, the number of loculi to be expected in the plerocercoid of an onchobothriid is one plus the number of posthook loculi in the adult.
Maternal adjustment of sex ratio in response to host size in the aphid parasitoid Ephedrus californicus
Authors: Cloutier C. , Lévesque C. A. , Eaves D. M. , Mackauer M.
Published: August 2008

It has been suggested that sex ratios dependent on host size are unlikely to evolve in parasitoid wasps developing in growing hosts because future host quality would not be predictable at the time of oviposition by the female. We used logistic regression to estimate the primary sex ratio of a solitary parasitoid of aphid nymphs, using data on offspring sex at the time of adult eclosion. The method corrects for any differential preadult mortality between male and female offspring. Male preadult mortality is estimated separately from data on male-only offspring produced by unmated females. This information is built into the statistical analysis of data on offspring sex at the time of eclosion of progeny of mated females to estimate female preadult mortality and the primary sex ratio. The method was used to demonstrate manipulation of offspring sex by females of the parasitoid Ephedrus californicus parasitizing large (third-instar) and small (first-instar) pea aphids, Acyrthosiphon pisum. Mated E. californicus females fertilized nearly 50% of their eggs laid in large host aphids but only about 20% of those laid in small hosts, the difference being highly significant. Parasitoid survival from oviposition to adult eclosion was about 10% higher in small hosts than in large hosts, but for a given host size, the incidence of survival did not differ significantly between the sexes. Therefore, differential preadult mortality had no effect on modifying the primary sex ratio under the experimental conditions. The results also indicated that female decisions about the sex of offspring were affected by previous experience with the range of host sizes available and were more flexible with large than with small hosts, which were allocated male progeny almost invariably. We discuss the evolution of sex-ratio manipulation in solitary hymenopterous parasitoids of the koinobiotic type, which develop in growing host stages, such as aphid nymphs, as opposed to eggs and pupae. Our data indicate that a growing host can represent a reliable resource that is predictable from its initial size, even though it has not reached its potential size at the time of parasitoid oviposition. At least in species such as E. californicus that attack a range of host instars differing widely in size and thus in potential for parasite growth, the ability to effect sex-ratio adjustments based on host size at the time of oviposition may help to maximize female reproductive success, despite any uncertainty about future host quality.
Calcium carbonate and calcium oxalate as cuticular hardening agents in oribatid mites (Acari: Oribatida)
Authors: Norton Roy A. , Behan-Pelletier Valerie M.
Published: August 2008

Hardening of adult oribatid mite cuticle by the deposition of crystalline calcium salts is demonstrated by a combination of X-ray diffraction and X-ray dispersion methods, in conjunction with experimental acid decalcification. Calcite (calcium carbonate) is the mineral deposited by mites representating the Ptyctima, but three species of Enarthronota (Eniochthonius minutissimus, Archoplophora rostralis, and Prototritia major) deposit whewellite, a form of calcium oxalate. The latter is deposited even in individuals living in base-poor environments such as sphagnum bogs, and probably derives from crystals originally precipitated by the fungal food of these mites. Our observations provide the first strong evidence of cuticular hardening by mineralization in the Arachnida, and the only known instance of the use of whewellite as a general intracuticular hardening agent in arthropods. A brief survey of representative oribatid mites, examined for strong birefringence under polarized light, suggested that each of the three ptychoid lineages (Ptyctima, Mesoplophoridae, Protoplophoridae) evolved cuticular mineralization independently.
Development and infectivity of Trypanosoma phaleri in leech and fish hosts
Authors: Jones Simon R. M. , Woo Patrick T. K.
Published: August 2008

Trypanosoma phaleri underwent cyclopropagative development in the gut of the leech Desserobdella phalera. Dividing sphaeromastigotes and epimastigotes preceded nondividing, elongate, slender trypomastigotes. The latter forms migrated from the crop to the proboscis sheath, shortened, and acquired infectivity. Metatrypanosomes from the proboscis sheath but not those from the crop were infective. The flagellum of short metatrypanosomes penetrated the cuticular lining of the proboscis sheath. Proboscis-sheath infections were first detected 9 days after an infective blood meal in 2 of 10 leeches incubated at 13 °C and after 2 days in 1 of 10 leeches incubated at 20 °C. In the former group, 3 of 10 leeches had proboscis-sheath infections after 11 days whereas in the latter group, 9 of 10 leeches had proboscis-sheath infections after 5 days. Metatrypanosomes did not reinvade the proboscis sheath when infected leeches fed on uninfected Amia calva but did so if the subsequent blood meal was infective. Developmental stages were not detected in 49 leeches that fed on A. calva with infections of 24 and 48 h but were detected in 4 of 27 leeches that fed on A. calva with 72-h infections.
Size-related foraging behaviour of the leaf-cutting ant Atta colombica
Authors: Shutler Dave , Mullie Adele
Published: August 2008

In a Costa Rican forest adjacent to cattle pasture, larger individuals of the leaf-cutting ant Atta colombica carried heavier loads and foraged farther from the colony, as predicted by foraging theory. Counter to foraging theory, individual ants did not increase their load mass if they foraged farther from the colony. However, the colony avoided this apparent inefficiency by sending larger ants to more distant trees. The colony harvested simultaneously from several individuals of the same tree species, even though distant trees were twice as far from the colony as nearby trees. The reasons for this behaviour require further investigation. In a wide foraging trail, larger ants travelled faster than their smaller counterparts. In addition, ant velocity was reduced when loads were experimentally supplemented, and increased when loads were experimentally reduced. Ants using narrow trails in the leaf litter may all be constrained to travel at the same speed, irrespective of load or body size, simply because they get in each other's way.
In vitro effects of implanted spinal ganglia on cartilage cells in Xenopus laevis forelimb regenerates
Authors: Tsilfidis Catherine , Liversage Richard A.
Published: August 2008

Following forelimb amputation in Xenopus laevis froglets a heteromorphic cartilaginous spike regenerate develops. It has been shown that the peripheral innervation of a forelimb is essential throughout the regeneration process; in its absence a regenerate undergoes resorption and subsequent stumping. This study examined the in vitro effects of spinal ganglion implants from siblings on forelimb regenerates of froglets. Perichondrial cells and chondroblasts of the regenerates incorporated tritiated thymidine, which suggests a causal relationship between the presence of implanted sensory nerves and cell proliferation. Presumably, a neurotropic factor(s) of low molecular weight is produced which can diffuse through the extracellular and cartilage matrices and exert its effect on the perichondrium and the developing cartilage within the spike regenerate. From our histological observations it appears that the innervated explants underwent appositional (perichondrial) as well as interstitial (cartilaginous) growth.
Spatial distribution patterns in freshwater macrozooplankton: variation with scale
Authors: Pinel-Alloul Bernadette , Pont Didier
Published: August 2008

The spatial heterogeneity of four macrozooplankton species (Skistodiaptomus oregonensis, Mesocyclops edax, Diaphanosoma brachyurum, and Daphnia sp.) was investigated over different scales, (fine and coarse scales: 2–40 m; lake-size scale: 10–380 m) in a small Canadian Shield lake. Values for the log s2: log [Formula: see text] relationships were established for the different scales and compared. Spatial analysis methods (space-constrained clustering analysis, spatial autocorrelation, and variogram modelling) were used for describing the surface distribution patterns observed on the whole-lake transect. The study demonstrated that spatial heterogeneity occurs on both the fine and coarse scales. Maximal spatial heterogeneity was observed on the vertical axis (depth) rather than on the horizontal axis. Macrozooplankton patchiness scales in Lake Cromwell correspond to whole-lake scale patterns for M. edax and D. brachyurum, and to fine-scale patterns for S. oregonensis and Daphnia spp. Our results confirm the general trend of interspecific variations in patch sizes of freshwater macrozooplankton. Distribution of the invertebrate predators Chaoborus spp. is inversely related to the large-scale gradient of D. brachyurum. Multiple regression analysis showed that several physical (water temperature, oxygen, wind direction) and biological (chlorophyll a) factors, in addition to mean population abundance, were correlated with macrozooplankton heterogeneity on the fine scale.
Response of the crayfish Cambarus bartonii bartonii to acid exposure in southern Appalachian streams
Authors: Distefano Robert J. , Neves Richard J. , Helfrich Louis A. , Lewis Mark C.
Published: August 2008

Intermolt adult and juvenile Cambarus bartonii bartonii (Fabricius) from southern Appalachian Mountains streams tolerated considerable acidity when acutely exposed to greatly reduced pH levels in laboratory bioassays. Tolerance increased with increasing size or age of crayfish. Ninety-six-hour exposures yielded LC50 values of pH 2.43, 2.56, and 2.85 for adults, advanced juveniles, and early juveniles, respectively. Lowering the water temperature increased the acid tolerance and survival time of intermolt adults during severe acidification (temperatures ranged from 20.2 to 13.3 °C). Acid exposure of intermolt adults in soft water up to 96 h caused a linear decrease in hemolymph [Na]. Hemolymph [Ca] increased through 48 h and then returned to near pre-exposure levels. An initial increase in [K] was followed by a decrease to slightly below pre-exposure levels. Hemolymph [Mg] remained unchanged. No Ca was lost from carapaces. These observations indicate that occasional episodes of higher than normal acidity in southern Appalachian streams are not necessarily a threat to intermolt adult and juvenile C. b. bartonii. Nevertheless, gradually increasing acidity and loss of watershed buffering capacity could produce sublethal effects such as altered reproductive activity, or changes in early life history stages and more sensitive molt cycle stages, that could damage these populations.
Group size and activity patterns of belugas (Delphinapterus leucas) and narwhals (Monodon monoceros) during spring migration in Lancaster Sound
Authors: Cosens Susan E. , Dueck Larry P.
Published: August 2008

Aerial surveys of belugas (Delphinapterus leucas) and narwhals (Monodon monoceros) were conducted in Lancaster Sound and northern Admiralty Inlet, N.W.T., during spring migration in 1987. Interspecific differences in grouping patterns and associated behaviour were observed. Group size and behaviour varied with ice type and state of breakup but patterns of variation differed between species. Behaviour of narwhals but not of belugas varied significantly with group size. Variation in group size and activity suggests that aggregation patterns are not related to predator avoidance strategies. Additional data are needed to test hypotheses about grouping patterns and behaviour in relation to prey distribution.
Early life stages, growth, and reproduction of spring-spawning ciscoes (Coregonus artedii) in Lac des Écorces, Quebec
Authors: Hénault Michel , Fortin Réjean
Published: August 2008

The biological characteristics of an allopatric population of spring-spawning ciscoes, an extremely rare ecotype, were studied at Lac des Écorces (southwestern Quebec). Environmental conditions during the early life stages are marginal for the species; the eggs are deposited in the deeper section (>20 m) of the lake and the first larva was caught on 30 July. Epilimnetic temperatures were then near the upper lethal threshold for fall cisco larvae. Lac des Écorces ciscoes are very small at the end of their 1st year of life (mean total length 58 mm). They more than double in length during their 2nd year (mean total length 161 mm). Growth thereafter, longevity, fecundity, and egg diameter are within the observed ranges for the species. Spawning occurs from mid-May to early June. Males and females spawn for the first time at age 3. The best predictor of fecundity is liver weight. Gametogenesis occurs under environmental conditions different from those encountered by fall-spawning salmonids. Seasonal changes in the gonadosomatic and hepatosomatic indexes are discussed in terms of temperature, photoperiod, and hormonal influences.
Population biology and conservation of Hector's dolphin
Authors: Slooten Elisabeth , Lad Frank
Published: August 2008

During the past decade, Hector's dolphins, Cephalorhynchus hectori, have suffered an alarming level of mortality due to entanglement in commercial and amateur gill nets. In this paper we study two Leslie matrix population models that incorporate known features of dolphin fertility and mortality, focussing on the information they provide regarding age distributions and maximum population growth rates. The simplest model specifies constant survival rates over many age-classes. The second model uses more realistic curves of age-specific survival rates. The results indicate that Hector's dolphin, like most other small cetaceans, has a low potential for population growth. Growth rates of 1.8–4.9% per year are likely to be the maximum possible for Hector's dolphin populations, and C. hectori (and C. commersonii) populations are likely to be declining under recent levels of net entanglement. Survival rate estimates from free-living populations, subject to natural and net-entanglement mortality, showed decreasing populations. Even with the most optimistic reproductive parameters, survival rates would need to be some 5–10% higher than those observed in populations subject to gill-net entanglement before population growth could occur. The likely consequences of a reduction in entanglement mortality through conservation management are explored using the survivorship curve model. These simulations show that the age structure of the population can have an important effect on changes in the size and growth rate of the population during the recovery phase following a reduction in entanglement mortality.
Seasonal variation in muscle fatigue in the sartorius muscle of the frog Rana pipiens
Authors: Renaud Jean Marc
Published: August 2008

The goal of this study was to determine whether seasonal variation occurs in the rates of fatigue development and force recovery in the frog sartorius muscle. The data were gathered from different experiments performed during a 6-year period (1983–1989). All frog sartorius muscles were stimulated to fatigue with tetanic contractions at the rate of 1/s for 3 min. The decrease in tetanic force after 1.5 and 3 min of stimulation was relatively consistent throughout the year. The only significant difference occurred in the muscles tested in September and October, which were less fatigue resistant than those tested in December. Following fatigue, muscles were stimulated at the rate of one contraction every 100 s, so that the recovery of tetanic force could be followed. A large and significant seasonal variation was observed in the recovery period. Frog sartorius muscles tested between March and July recovered their tetanic force at a faster rate than those tested between August and October. It was shown that the highest capacity to recover force coincides with the time of the year when frogs are the most active.
Anthelmintic activity of mitomycins A, C, and F against hymenolepidid larvae in Tribolium confusum
Authors: Novak Marie , Kornovski Barbara , Kunz Kenneth R.
Published: August 2008

Mitomycin analogues were tested against metacestode stages of Hymenolepis microstoma and H. nana developing in Tribolium confusum. The effects of the mitomycins varied according to both the drug and the species of the parasite. In general, the most effective compound was mitomycin C, followed by mitomycin A and then by mitomycin F. The efficacy of drugs improved further when sodium bicarbonate was added to the diet.
Xiphyropronia gen.nov., a new genus of the Roproniidae (Hymenoptera: Proctotrupoidea) from China
Authors: Junhua He , Xuexin Chen
Published: August 2008

Xiphyropronia tianmushanensis gen. et sp.nov., belonging to the Roproniidae, is described from China.
Analyse expérimentale de l'isolement reproductif entre deux espèces jumelles et sympatriques d'araignées : le Lycosa thorelli (Keyserling) et le Lycosa carbonelli Costa et Capocasale
Authors: Costa Fernando G. , Francescoli Gabriel
Published: August 2008

Four experimental groups were used: (A) males Lycosa thorelli × female L. thorelli; (B) male Lycosa carbonelli × female L. carbonelli; (C) Male L. thorelli × female L. carbonelli; (D) male L. carbonelli × female L. thorelli. Males were placed in a field with conspecific sexual pheromone and confronted to anesthetized virgin females. Male L. thorelli showed a greater tenacity than male L. carbonelli in the maintenance of the copulatory position. The typical copulation pattern (intraspecific groups) became atypical in interspecific groups. Only one typical interspecific copulation was observed in group C. Male L. carbonelli showed a good specific discrimination when mounting the female, while male L. thorelli showed a low discrimination level. The maintenance of the copulatory position could be determined by a modal number of ejaculations in the case of male L. carbonelli and by a modal duration in the case of male L. thorelli. Atypical copulations might indicate a mechanical incompatibility between the genitalia of the two species. Typical copulations produced offspring, indicating the absence of postcopulatory isolation mechanisms.
Otolith microstructure and growth patterns during the early life history of lanternfishes (family Myctophidae)
Authors: Linkowski Tomasz B.
Published: August 2008

The microstructure of the central part of the sagittal otoliths of 55 myctophid species belonging to 27 genera of lanternfishes was compared by means of light and scanning electron microscopy. Multiple primordia were found in the nuclei of all otoliths. In most species and genera a symmetrical pattern of accessory primordia (AP) was observed: they were located along the same growth increment, which indicates simultaneous formation. A clustered pattern of AP was found only in species belonging to the tribe Gymnoscopelini: AP occurred at several growth increments, which indicates that they developed sequentially. The growth increments formed after the formation of clustered AP revealed a sectorial otolith structure, i.e., growth increments were not continuous but separated by radial discontinuities. The pattern and time of formation of AP were found to influence the relationship between otolith diameter and fish length in the Myctophidae. The formation of numerous AP concurrently with transformation of the larva led to a dissociation of fish growth from otolith growth. When AP appeared simultaneously but before transformation, the allometric relationship between otolith size and fish length was not disrupted by this process. Sequential formation of AP considerably before transformation, which occurred only in the Gymnoscopelini, led to an isometric relationship between fish size and otolith size. The potential importance of the AP pattern as a distinguishing character for myctophid larvae is considered to be greatest in the Gymnoscopelini, as these growth centers, in the form of external protrusions, were evident over a wide range of sizes from small larvae to early juveniles.
Effects of open- and closed-system temperature changes on blood oxygen dissociation curves of skipjack tuna, Katsuwonus pelamis, and yellowfin tuna, Thunnus albacares
Authors: Brill Richard W. , Bushnell Peter G.
Published: August 2008

Tunas often experience rapid temperature changes of 10 °C or more during their daily vertical movements. Their blood is therefore subjected to open-system (i.e., constant O2 and CO2 partial pressure, variable O2 and CO2 content) temperature changes during passage through the gills. In addition, tunas possess vascular countercurrent heat exchangers and can have deep red muscle temperatures as much as 20 °C above ambient. Their blood also experiences closed-system (i.e., constant O2 and CO2 content, variable O2 and CO2 partial pressure) temperature changes during passage through the heat exchangers. Temperature-independent blood O2 binding could be expected. We found blood oxygen dissociation curves of skipjack tuna (Katsuwonus pelamis) and yellowfin tuna (Thunnus albacares) to be temperature independent during open-system temperature changes. Although blood from both species showed unsually large Bohr effects (−0.986 and −0.865 Δlog P50∙ΔpH−1 for skipjack and yellowfin tuna, respectively) when subjected to CO2 partial pressure alterations in the open system, the oxygen dissociation curves of skipjack tuna blood were nearly temperature independent during closed-system temperature changes. In other words, blood from skipjack tuna showed a reduced Bohr effect when subjected to the inevitable CO2 partial pressure changes that accompany closed-system temperature shifts. Since skipjack tuna blood shows temperture-independent O2 binding during closed-system temperature changes whereas yellowfin tuna blood does not, this unusual feature is not obligatory in thermoconserving fishes.