Changes in morphological characteristics of an introduced population of the threespine stickleback <Emphasis Type="Italic">Gasterosteus aculeatus</Emphasis> in Lake Towada,northern Japan

A freshwater population of the threespine stickleback Gasterosteus aculeatus occurs at an elevation of 400m in Lake Towada in the mountains of northern Japan. Morphological characteristics of each sex of this population were studied between 1985 and 1992. The 1985 fishes were larger in standard length than even anadromous populations, as well as all other freshwater populations, so the large body size of this population was unusual for the species. The population was also characterized by large ratios of head length, eye diameter, and gill raker length, and a higher ovary volume in 1992 than in 1985, but it was not readily characterized by meristic characters. The population may have been introduced within the last 20 years (probably in the early 1980s). The large body size of the population may not reflect a defense against predators because coexisting fishes were not important predators on threespine stickleback adults. It is supposed that the change of body size was induced by environmental changes in prey abundance in the lake and/or by the longevity of fishes.     

Genetically isolated sympatric forms of threespine stickleback,Gasterosteus aculeatus,in Lake Azabachije (Kamchatka-peninsula,USSR)

Synopsis Two sympatric morphs of threespine stickleback Gasterosteus aculeatus are found in Lake Azabachije (Kamchatka, USSR); resident low-plated leiurus and completely plated trachurus, migrating from the Bering sea into the Lake to spawn. The absence of the intermediate morph semiarmatus and significant differences in a number of characters are indicative of reproductive isolation. The results show that the leiurus morph is common in the regions other than those with mild climate and small seasonal fluctuations of temperature.     

Morphometric and meristic variation in Galician threespine stickleback populations,northwest Spain

Synopsis We evaluated morphological differentiation among populations of threespine stickleback, Gasterosteus aculeatus, from the Limia and Miño basins (Galicia, NW Spain), the river Karup (Denmark) and Aiguamolls de l’Empordà (Girona, northeast Spain), using multivariate analysis of morphometric and meristic characters. Multivariate discriminant analysis and hierarchical cluster analysis uncovered significant differences among the four main groups, between the two groups from Galicia and among populations within the Miño basin. The stickleback from Galicia differed from the Danish group in head and body armour characters. Between the Miño and Limia groups, we found differences in both head and body proportions as well as in number of gill rakers. Within the Miño basin populations varied with respect to head and body armour traits and the number of lower gill rakers. Clustering analysis divided these populations into two groups based on the latter trait: fish from the upper section of river Miño and tributaries (a lower number of lower gill rakers) and fish from the central and lower reaches of the river. Overall, morphometric traits were more useful than meristic ones; however, the two types of data provided congruent information about the morphological differentiation of stickleback populations.     

The ecology of ruffe,Gymnocephalus cernuus (Pisces: Percidae) introduced to Mildevatn,western Norway

Synopsis Diet, habitat use, diel and seasonal activity and a number of population parameters were studied on ruffe,Gymnocephalus cernuus, introduced to Mildevatn, western Norway. This lake is sited outside the natural range of the ruffe and has a lower fish diversity and a different fish species composition than within its native range. From June through September the ruffe was planktivorous and mainly caught at 4 to 6 m depth in the benthic zone. At other times of year ruffe was feeding on zoobenthos and caught deeper in the benthic zone. Ruffe was mainly day active. Zooplankton feeding during summer is the clearest difference compared to ruffe populations living within its natural range. Presence of large zooplankton organisms available for ruffe is suggested as the main reason for the difference found in food choice. The availability of large zooplankton is probably due to community structure caused by a predator and lack of interspecific competition for zooplankton in the deeper parts of the lake. Piscivorous brown trout.Salmo trutta, restrict the habitat of threespined stickleback,Gasterosteus aculeatus, to the zone of littoral vegetation, allowing high densities of larger zooplankton species likeBythotrephes longimanus to be present in the lake. Brown trout is present only in the upper light and well oxygenated parts of the lake, leaving a refuge for the ruffe, where they can feed on the rich zooplankton community.     

Comparative study of the olfactory epithelium of the three-spined stickleback (Gasterosteus aculeatus) and the nine-spined stickleback (Pungitius pungitius)

Summary The olfactory epithelium of the three-spined stickleback (Gasterosteus aculeatus) and the nine-spined stickleback (Pungitius pungitius) has been studied with a conventional histochemical and a novel immunological staining technique. In both species, the sensory epithelium is arranged in folds separated by non-sensory epithelial tissue. In the nine-spined stickleback, intrinsic folds consisting of non-sensory cells are found in the apical part of the sensory epithelium where they divide the surface of the sensory epithelium into small islets. These non-sensory cells are non-ciliated, flattened and piled on top of each other; they contain numerous electron-translucent vesicles. The intrinsic folds are absent from the sensory epithelium of the three-spined stickleback. In both species, axons of receptor cells form a layer of fibers in the sensory epithelium immediately above the basal cells. In the three-spined stickleback, thick branches of the olfactory nerve are frequently found in this layer. These branches are only occasionally observed in the sensory epithelium of the nine-spined stickleback. Thus, the three-spined stickleback and the nine-spined stickleback show considerable differences in the organization of the sensory regions of the olfactory epithelium.     

Possible competitive interactions between overwintering tufted duck (Aythya fuligula (L.)) and fish populations of Lough Neagh,Northern Ireland: evidence from diet studies

The overwintering population of tufted duck (Aythya fuligula) on Lough Neagh, Northern Ireland, has varied over the last three decades, with numbers declining in the early 1980s but then increasing to former levels in the late 1980s. Population fluctuations of recently introduced roach (Rutilus rutilus) mirrored these trends. The present study explores the possibility that competition for benthic food resources is responsible for these changes by examining the diets of tufted duck, roach and other major fish species of the lake. Diet overlaps were generally high due to the common consumption of chironomid larvae. The diet of tufted duck overlapped most with that of roach because these two species were the only significant consumers of molluscs. This evidence provides further support for a tufted duck — roach competition hypothesis.     

Morphological and genetic characteristics of sea bass,Lateolabrax japonicus, from the Ariake Sea, Japan

Sea bass,Lateolabrax japonicus, from the Ariake Sea, characterized by black dots on the lateral body region as in the Chinese sea bass,L. sp., were examined and compared morphologically and genetically withL. japonicus andL. sp. Some meristic characters of the Ariake form tended to fall midway between values for the two former species. Genetic features, evaluated by isozyme analyses, indicated that the Ariake form as represented a simple Mendelian population, there being no significant differences from a Hardy-Weinberg equilibrium according to chi-square tests. Although some extreme differences in allelic frequencies were found at some loci betweenL. japonicus andL. sp., the Ariake form possessed many heterozygotes at thePROT-1 ^* locus, in addition to allelic frequencies at some loci conforming to those ofL. sp. Average allele numbers per locus, rate of polymorphic loci and average heterozygosity of the Ariake form were higher than for eitherL. japonicus orL. sp., indicating high genetic variation in the former. The results suggested that the Ariake population is genetically independent of other populations ofL. japonicus, but might be genetically influenced byL. sp.     

假刺苋——中国大陆一新归化种

报道了广东省潮州市韩江沿岸发现的中国大陆一新归化种——假刺苋(Amaranthus dubius Mart.ex Thell.)。该种原产热带美洲及西印度群岛,已经引入并局部归化于欧洲、热带亚洲地区和非洲,在中国台湾已经归化。通过野外调查,获得该种的详细特征与生境等信息,并讨论了与其他苋属植物的区别及其潜在的入侵性。此外,还提供了用于检索中国苋属植物的分类检索表。     

Cannibalism as the cause of an ontogenetic shift in habitat use by fry of the threespine stickleback

Summary In Crystal Lake, British Columbia, small fry (15 mm SL) of the threespine stickleback (Gasterosteus aculeatus) are concentrated in vegetation while larger fry are not. Because fry in all size classes feed primarily on zooplankton, even when in vegetation, we hypothesized that size-limited predation was responsible for the observed shift in habitat use with size. The major predators on fry in Crystal Lake are adult threespine stickleback, the water scorpion, Ranatra sp. (Hemiptera: Nepidae), backswimmers, Notonecta spp. (Hemiptera: Notonectidae), and dragonfly naiads of the genus Aeshna (Odonata: Aeschnidae). On the basis of distribution and hunting behavior we excluded the insects Ranatra sp., and Notonecta sp. as causal agents for this shift in resource by fry in water >0.25 m deep. Ranatra was found almost exclusively near the shoreline in water <0.25 m deep, and both insects hunted primarily as ambush predators within vegetation. Such predators seemed more likely to drive vulnerable fry from vegetation than to restrict them to it. In contrast, Aeshna naiads and adult stickleback frequently hunted outside of vegetation. In prey preference experiments the naiads did not show the decline in predation efficiency on fry >15 mm SL that would be expected if size-limited predation by this insect was responsible for the observed shift in resource use by fry. Adult stickleback only fed on fry <15 mm SL, and in an experimental situation, consumed fry at a rate 10 times greater than that exhibited by any of the insects. Predation experiments demonstrated that small fry (11–15 mm) spent more time in vegetation in the presence of adult conspecifics than they did in control pools, as would be expected if size-limited cannibalism caused small, vulnerable fry to be restricted to vegetation. Fry >15 mm SL were found outside of vegetation more often than in control treatments. The probable cause of this result is that adults become aggressive toward fry at this size, and often could be seen chasing large fry from vegetation during the experiments. Dragonfly naiads (Aeshna spp.) spent most of their time in vegetation in the experimental pools. Both size classes of fry spent less time in vegetation in the presence of dragonfly naiads than they did in control treatments, an apparent reflection of their similar vulnerabilities to these naiads. The presence of vegetation in pools reduced predation rates by adult stickleback on small fry. Because the experiments presented here indicate that fry are capable of rapidly assessing predation risk and of altering their behavior adaptively, we conclude that small fry occupy vegetation as a refuge from cannibalism. Once fry have reached the size-threshold at which they are no longer vulnerable to adult conspecifics they are able to forage farther from vegetation thereby reducing risk of predation by insects in vegetation and possibly acquiring more abundant food resources.     

Production,population biology and diet ofNeomysis integer (Leach) in a shallow Frisian lake (The Netherlands)

TheNeomysis integer population of a shallow Frisian freshwater lake, situated in the north of the Netherlands, was studied from May until October 1980. The results were compared with observations on populations in other Frisian lakes, and with the results reported by other authors on brackish-water and marine populations of this species.Three generations were observed: one overwintering generation and two summer generations. Reproduction stopped completely during winter. During 1980 population densities ofN. integer were relatively low in all Frisian lakes. In Slotermeer the maximum population density was only 6 individuals m^–2, production amounted to 10 mg dry wt m^–2 yr^–1. The annual P/B ratio was 4.0. The diet ofN. integer consisted, in terms of biomass, of more than 95% detritus and animal food, the latter mainly consisting ofBosmina and cyclopoid copepods. Feeding intensity reached a maximum at sunset. It was still high during first part of the night and was low in the morning just after sunrise.     

Chloroplast and nuclear DNA variation among homozygous plants in a population of the autogamous annualMicroseris douglasii (Asteraceae,Lactuceae)

The autogamous diploid annualMicroseris douglasii of California occurs in many isolated populations. The populations consist of one to many highly inbred biotypes. Morphological variation among populations usually is greater than within populations. In spite of the virtual absence of gene flow even within populations, genetically determined character differences are randomly distributed and associated throughout the range of the species. Recent evidence even suggests introgression of chloroplasts from the relatedM. bigelovii. Offspring families from 25 plants of a very variable population were raised and examined for segregation of morphological and molecular (RAPD) markers. All 25 original plants were completely homozygous for all markers, but each differed from all others at least in some markers. The population consisted of two genetically isolated groups of plants: a distinct inbred line (3 plants) and 22 plants with random associations of a common set of markers and characters, possibly recombinant inbreds from a past hybridization event. One of these 22 plants contained a chloroplast genome found inM. bigelovii, the other 24 plants a chloroplast genome found only inM. douglasii.     

The Response of Prolactin,ACTH, and Growth Hormone Cells in the Pituitary Gland of the Three-Spined Stickleback,: Gasterosteus aculeatus L. form leiurus,to Increased Environmental Salinities

Benjamin, M. 1980. The response of prolactin, ACTH, and growth hormone cells in the pituitary gland of the three-spined stickleback, Gasterosteus aculeatus L. form leiurus, to increased environmental salinities. (Department of Anatomy, University College, Cardiff, Wales, U.K.) — Acta zool. (Stockh.) 61(1): 1–7. The time-sequence of response of the prolactin, ACTH and growth hormone cells in the pituitary gland of the leiurus form of the three-spined stickleback, Gasterosteus aculeatus L., to a transfer from freshwater to seawater, was studied by light microscopy. The appearance of the pituitary was compared with that of animals caught in brackish or sea water. The prolactin cells respond only slowly to seawater by cytological changes interpreted as signs of decreased secretory activity. It is thus suggested that prolactin is unlikely to be important for osmoregulation in this stickleback. The growth hormone cells are more active in all seawater-adapted animals, while the ACTH cells are less active—although only in laboratory experiments. The differing responses of the pituitaries of the leiurus and trachurus forms of G. aculeatus and Pungitius pungitius to high salinities are compared. Even in species whose pituitaries are virtually identical, the response to high salinites may differ widely.     

Behavioural and morphological changes in polymorphic Daphnia related to different predation regimes

Morphology and behaviour of Daphnia galeata in Lake Lille Lungegårdsvann, Bergen, Norway, were studied in two consecutive years. A portion of the population showed helmet cyclomorphosis in 1992, but no helmets developed in 1993. The non-helmeted individuals in 1992 were found in the littoral habitat during summer, whereas the helmeted morph stayed mainly in the pelagial. These differences in morphology and behaviour within and between years are likely to be caused by changes in predation regimes. Larvae of the predacious phantom midge, Chaoborus flavicans, were observed only in 1992, whereas the three-spined stickleback, Gasterosteus aculeatus, was present both years.     

Invasive pike establishment in Cook Inlet Basin lakes,Alaska: diet,native fish abundance and lake environment

Northern pike (Esox lucius) were introduced to the northern Susitna Basin of south-central Alaska in the 1950’s, and have since spread throughout the upper Cook Inlet Basin. Extirpations of several native fish populations have been documented in this area. It is hypothesized here that invasive pike remodel the ecology of lakes by removing vulnerable prey types and that these changes are reflected in the diet of invasive pike. Trends in pike diet suggest that pike switch to less desirable but more abundant macroinvertebrate prey as preferred fish prey are eliminated. The impacts of pike introduction were studied in detail for one species of resident fish, the threespine stickleback (Gasterosteus aculeatus). Stickleback abundance decreases as pike invasion progresses. Conductivity is a significant environmental predictor of stickleback abundance, with higher conductivity apparently mitigating population reduction. Higher conductivity water may lessen the physiological costs of developing more robust armor, which reduces vulnerability to predation. Maximum lake depth also appears to predict stickleback abundance, though this trend was only marginally significant. Deeper lakes may provide an open-water refuge from pike predation by allowing stickleback to exist outside of the pike inhabited littoral zone. These findings indicate the importance of diverse habitat types and certain chemical and physical characteristics to the outcome of invasion by fish predators.     

Fathead Minnows, Pimephales promelas, Learn to Recognize Chemical Alarm Cues of Introduced Brook Stickleback, Culaea inconstans

In four experiments conducted over a 6-year period, we investigated whether fathead minnows, Pimephales promelas, could acquire the ability to recognize chemical alarm cues of introduced brook stickleback, Culaea inconstans. A laboratory experiment documented that stickleback-naïve minnows did not exhibit an anti-predator response when exposed to the chemical alarm cues of stickleback. In a laboratory experiment conducted 5 years after the introduction of stickleback to the pond, minnows exhibited an antipredator response to stickleback cues. Moreover, in a field experiment the minnows exhibited avoidance of areas labelled with stickleback alarm cues. Minnows raised from eggs taken from the test pond did not exhibit an anti-predator response to stickleback cues while minnows from the test pond that had experience with stickleback cues did respond to stickleback cues. Our results provide clear evidence that cross-species responses to chemical alarm cues of fishes can be learned. Learned recognition of alarm cues has important implications for predator/prey interactions.     

New records and distributions of two North American branchiobdellidan species (Annelida: Clitellata) from introduced signal crayfish, <Emphasis Type="Italic">Pacifastacus leniusculus,</Emphasis> in Japan

This is the first report of two North American branchiobdellidans, Sathodrilus attenuatus Holt, 1981, and Xironogiton victoriensis Gelder and Hall, 1990, on the signal crayfish, Pacifastacus leniusculus (Dana, 1852) introduced into Japan from the Columbia River system, northwestern North America. Signal crayfish from 12 localities in eastern and northern Hokkaido, Japan, were examined and each supported S. attenuatus. In addition, an individual of this species was found on preserved material from Ishikawa Prefecture, central Honshu. All of these branchiobdellidans reported in Hokkaido most probably came from the original population of signal crayfish introduced into Lake Mashu, Hokkaido, Japan, in 1930. It is suggested that the use of non-pathogenic branchiobdellidans, when present, provides an easy method for tracing the spread of crayfishes around Japan and could also be applied in other countries and continents. Specimens of X. victoriensis were only found on crayfish in a stream at Akashina in Nagano Prefecture, central Honshu, Japan. Although the signal crayfish appears to be displacing the endemic Japanese crayfish, C. japonicus, no native branchiobdellidans were found on any of the introduced signal crayfish examined.     

Molecular and morphological differences between two geographic populations of Salanx ariakensis (Salangidae) from Korea and Japan

Geographic variations of a salangid, Salanx ariakensis, from Korea and Japan, based on partial mtDNA cyt b gene sequences and morphometric data, are presented and compared with Salanx cuvieri from China. Analyses of molecular variance (AMOVA) suggested that the two populations of S. ariakensis differed significantly from each other in pairwise fixation index (F _ST = 0.43), although their reciprocal monophyly was not constructed in the phylogenetic analysis. The phylogenetic analysis, however, supported the reciprocal monophyly of S. ariakensis (Korean population + Japanese population) and S. cuvieri. Differences in genetic structure between the two populations of S. ariakensis were suggested by diversity indices, mismatch distribution shape, and minimum spanning network. In particular, diversity indices indicated that the Korean population was historically larger and more stable than the Japanese population. In addition, both the principal component analysis (PCA) and canonical discriminant analysis (CDA) for morphometric characters, and the Kruskal–Wallis test for some meristic characters, showed that the two populations of S. ariakensis differed from each other, although morphological differences between the two populations of S. ariakensis were smaller than those between S. ariakensis and S. cuvieri. Such morphological differences were consistent with the differences in mtDNA.     

中国凤仙花科植物叶表皮特征及其分类学意义

利用光学显微镜观察凤仙花科106份样本材料、36种代表植物的叶表皮微形态特征。结果表明:该科植物叶表皮微形态特征种内稳定,对于种间及属间关系的界定具有重要的分类学价值。上表皮细胞的形状及垂周壁的式样种间差异明显,各分类群间有明显的界限,是种间界定的重要依据,因此上表皮微形态特征具有重要的的分类学价值,基于上表皮的微形态特征将研究的36种代表植物划分为5个类型。下表皮的微形态特征虽更为多样,种间差异显著,可用于种间界定,但对于属下划分难以提供有价值的性状。该科植物叶表皮微形态特征与宏观形态特征的相关性较弱,与地理分布格局的相关性较强,关系更为密切。同一地理分布区域内的种类宏观形态特征虽然差别明显,但叶表皮微形态特征却表现出较强的一致性,这似乎也反映了叶表皮微形态这一性状受环境饰变的影响比较明显。综上所述,叶表皮微形态特征可为凤仙花科的系统发育,尤其是凤仙花属种间界定提供有价值的分类学佐证     

Translocation and Spread of Piscivorous Fishes in the Burdekin River, North-eastern Australia

The distribution of the biogeographically distinctive fish fauna of the Burdekin River, north-eastern Australia, is largely determined by the presence of a large waterfall located at the lower quarter of the river’s length. Downstream of the falls, assemblages are characterised by the presence of piscivorous fishes whereas such species are largely absent from upstream reaches. Sleepy cod (Oxyeleotris lineolatus), a large piscivorous gudgeon, was first introduced into the upper reaches of the Burdekin River in 1980 and other releases, both official and unofficial, have occurred subsequently. The population remained small and restricted to the site of introduction for a decade, but expanded in size and distribution after the occurrence of a large flood and entry into a prolonged period of drought. This gudgeon is now present in every tributary system of the Burdekin Basin. Despite the occurrence of substantial temporal variation in fish abundance due to a highly variable flow regime, negative impacts on one species, a small gudgeon (Mogurnda adspersa), are evident. Both deliberate and accidental releases of other species into the upper Burdekin River have also occurred, often to satisfy recreational fishing demand. Such species are typified by large size and piscivorous habit, characteristics alien and inimical to the native fish fauna. It is hypothesised that these piscivorous species may have even greater impact than O. lineolatus in some tributary systems of the upper Burdekin River.     

Evolution,pollination, and systematics of the tribeNeottieae (Orchidaceae)

The various classifications of the orchid tribeNeottieae are reviewed and a new classification is proposed that divides the tribe into three subtribes,Neottiinae, Limodorinae, andCephalantherinae, based primarily on characters of the column (gynostemium). A cladistic analysis illustrates that these three subtribes are more closely related to one another than either is to any other group in subfam.Neottioideae, although there are very few apomorphic characters for the tribe. Pollination biology is also discussed showing links between breeding systems and distribution. There is also a possible role between column and labellum morphology and the emergence of a deceptive pollination syndrome from one of reward.