Deep water stratification in deep caldera lakes Ikeda, Towada, Tazawa, Kuttara, Toya and Shikotsu

From six deep caldera lakes in Japan, namely lakes Ikeda, Towada, Tazawa, Toya, Kuttara and Shikotsu (in Japanese referred to as Ikedako, Towadako, Tazawako, Toyako, Kuttarako and Shikotsuko), fine resolution profiles of temperature, electrical conductivity, dissolved oxygen and pH have been measured. Measurements were conducted just after deep circulation from the end of March to the end of May 2005. Lake Ikeda and Lake Towada did not undergo a complete turnover. Both showed meromictic features with a clear interface separating the recirculated mixolimnion from the deeper monimolimnion. Lake Tazawa and Lake Toya showed a complete turnover in winter 2004/05, while in Lake Kuttara and Lake Shikotsu, a deep water body remained throughout winter due to pressure effects on the temperature of maximum density. Although these deep waters were never fully recycled into the mixolimnion, they presented themselves as well supplied with oxygen and well circulated within themselves. Where overturn had not been complete small gradients in the oxygen profile, pH profiles and electrical conductivity profiles could be detected. However only in Lake Towada were concentrations of dissolved substances and gradients high enough to have decisive impact on the circulation pattern.     

Amino acids dissolved in stream water as possible home stream odorants for masu salmon

It is well established that salmon return to their home stream by sensing the odors of the stream water. In this study we have attempted to identify the home stream odorants used by masu salmon in Lake Toya. The salmon in Lake Toya return to the home stream which flows into the lake after lake life for 2-3 years. Besides water from the home stream, waters from two other streams which flow into Lake Toya were also used in the experiments. We analyzed the compositions of amino acids, inorganic cations and bile acids in waters from the three streams. Application of mixtures of inorganic cations or bile acids, reconstituted based on the compositions of the stream waters, to the olfactory epithelium induced only very small responses. On the other hand, application of mixtures of amino acids induced large responses. The response to artificial stream water reconstituted based on the compositions of amino acids and salts closely resembles that to the corresponding stream water. Cross-adaptation experiments with three combinations of the mixtures were carried out. The response pattern for each combination closely resembled that to the corresponding combination of stream waters. Based on the results obtained, we concluded that amino acids dissolved in the home stream water are possible home stream odorants.     

Strelkovimermis amphidis n. sp. from chironomid adults emerging from Lake Itasca and Long Lake, Minnesota

Mermithid nematodes, Strelkovimermis amphidis n. sp., emerged from chironomid imagos from Lake Itasca in Minnesota in the fall of 1996, 1997 and from Long Lake in the fall of 1998. The species is distinguished from the other 11 members of the genus by the long cephalic papillae, absence of an excretory pore, pointed termini in both sexes, large amphids, body diameter decrease at the vulva, long vagina, and the absence of lateral genital papillae. Strelkovimermis amphidis n. sp. is the fifth member of this genus recorded from Lake Itasca. The presence of and nature of the bursal sleeve is suggested as a useful distinguishing characteristic. The ratios involving spicule axis length, diameter of the body at the genital pore, and the length of the tail are also discussed in distinguishing species of Strelkovimermis. An expanded key to the species of Strelkovimermis is included.     

Olfactory discriminating ability of lacustrine sockeye and masu salmon in various freshwaters

In order to study the olfactory discriminating ability of lacustrine sockeye salmon (Oncorhynchus nerka) and masu salmon (O. masou), the integrated olfactory nerve response to various freshwaters was recorded by electrophysiological techniques. In both species independent of sex and gonadal maturity, each freshwater caused a different olfactory response. Source and effluent waters of the culture pond at Toya Lake Station (the source and culture pond waters) evoked the minimum and maximum response magnitude, respectively. In cross-adaptation experiments, the culture pond water abolished all secondary responses to other freshwaters, and no freshwater abolished the secondary response to the culture pond water. The concentration response study revealed that the minimum concentration (threshold) to induce response to the culture pond water after adaptation to Lake Toya water was between 0.1 and 1.0%. The present study indicates that the olfactory organ of lacustrine salmonids may discriminate different intensities of various freshwater odors.     

Arctodiaptomus (Rhabdodiaptomus) michaeli n.sp. (Copepoda,Calanoida) from Kashmir,India

Arctodiaptomus (Rhabdodiaptomus) michaeli n.sp. is described from the material collected in Alapathar Lake and Marsar Lake of Kashmir, India.     

The description of Paralongicollum nemacheili n. gen., n. sp. (Acanthocephala: Pomphorhynchidae) from freshwater fishes in Kazakh S.S.R

Paralongicollum nemacheili n. gen., n. sp. is described from Salmo gairdneri Richardson and Nemacheilus stoliczkai Steindacher in Lake Kul'say in the basin of Lake Balkhash, Kazakh S.S.R. Its long uniformly cylindrical neck and nonfiliform proboscis distinguish it from the other 3 genera of the family. Tenuiproboscis Yamaguti, 1935, has a filiform proboscis. The neck of Pomphorhynchus Monticelli, 1905, has a bulb anteriorly, and that of Longicollum Yamaguti, 1935, is spirally twisted with expansions. A key to the genera of Pomphorhynchidae is provided. The relatively longer necks in juveniles than in larger worms probably enhance the establishment of new infections. A large proportion of worms had extensive body wall deformities. Longicollum sergenti (Choquette and Gayot, 1952) Golvan, 1969, is relegated to the new genus Paralongicollum.     

Tanganyikacypridopsis gen.n. (Crustacea, Ostracoda) from Lake Tanganyika

A new genus of freshwater ostracods, Tanganyikacypridopsis gen.n., is established to include the species Potamocypris depressa Kiss, 1959, Cypridopsis calcarata Rome, 1962 and Cypridopsis anomala Rome, 1962, all from Lake Tanganyika. The genus is related to Sarscypridopsis McKenzie, 1977 and Plesiocypridopsis (Rome, 1965), mainly because of its hemipenis anatomy, and is believed to be endemic to Lake Tanganyika.     

Lepidotrachelophyllum fornicis,n. g., n. sp., a Ciliate with an External Layer of Organic Scales (Ciliophora,Litostomatea, Haptoria)1

Lepidotrachelophyllum fornicis n. g., n. sp. was discovered in White Lake, Ontario, Canada, under winter ice. The genus is Trachelophyllum-like, being highly flattened, elongate, and very extensible. The major feature that separates it from other genera in the family Trachelophyllidae is the presence of a dense layer of organic scales which covers the exterior of the cell and through which the cilia emerge. The scales are composed of filamentous material which is organized as an ovoid structure. The “rim” of the baseplate is formed of interwoven filaments. The baseplate is broken by circular or polygonal apertures. The same filaments form an arched superstructure broken by even larger, less regular apertures.     

Physiological mechanisms of imprinting and homing migration in Pacific salmon Oncorhynchus spp

After several years of feeding at sea, salmonids have an amazing ability to migrate long distances from the open ocean to their natal stream to spawn. Three different research approaches from behavioural to molecular biological studies have been used to elucidate the physiological mechanisms underpinning salmonid imprinting and homing migration. The study was based on four anadromous Pacific salmon Oncorhynchus spp., pink salmon Oncorhynchus gorbuscha, chum salmon Oncorhynchus keta, sockeye salmon Oncorhynchus nerka and masu salmon Oncorhynchus masou, migrating from the North Pacific Ocean to the coast of Hokkaido, Japan, as well as lacustrine O. nerka and O. masou in Lake Toya, Hokkaido, where the lake serves as the model oceanic system. Behavioural studies using biotelemetry techniques showed swimming profiles from the Bering Sea to the coast of Hokkaido in O. keta as well as homing behaviours of lacustrine O. nerka and O. masou in Lake Toya. Endocrinological studies on hormone profiles in the brain-pituitary-gonad axis of O. keta, and lacustrine O. nerka identified the hormonal changes during homing migration. Neurophysiological studies revealed crucial roles of olfactory functions on imprinting and homing during downstream and upstream migration, respectively. These findings are discussed in relation to the physiological mechanisms of imprinting and homing migration in anadromous and lacustrine salmonids.     

Cochliopodium arabianum n. sp. (Amorphea,Amoebozoa)

A new species of Cochliopodium isolated from freshwater at Arabia Lake in Lithonia, GA, USA is described based on light microscopic morphology, fine structure, and molecular genetic evidence. Cochliopodium arabianum n. sp., previously labeled as “isolate Con1” in prior publications, has been shown to group within the genus Cochliopodium in our molecular phylogenetic analysis. Light microscopy and fine structure evidence indicates the new isolate not only shares characters of the genus but also unique distinctive features. Cochliopodium arabianum n. sp. is typically round when stationary; or oval to sometimes broadly flabellate or triangular in shape during locomotion, with average length of 35 μm and breadth of 51 μm. Fine structure evidence indicates C. arabianum n. sp. has tower‐like scales, lacking a terminal spine, sharing high similarity with its closest relative C. actinophorum. However, the scales of C. arabianum n. sp. are unique in height and the breadth of the base plate. Both morphological and molecular data, including SSU‐rDNA and COI, indicate that this new species falls in a clade sufficiently different from other species to suggest that it is a valid new species.     

Lanceimermis palustris n. sp. and Telomermis palustris n. sp. (Nematoda: Mermithidae) parasites of chironomid (Insecta: Diptera) adults from Lake Alice Bog in northern Minnesota

In the summer of 2003, chironomid imagoes eclosing from Lake Alice Bog in Minnesota yielded mermithid nematodes of 2 new species. Lanceimermis palustris n. sp. is distinguished from the other 14 species of the genus by the subventral mouth position, thinness of the hook-shaped spicule, body index, and structure of the male tail muscles. Telomermis palustris n. sp. is distinguished from the only other species of the genus by the structure of the amphids, body length, maximum body width, length of the esophagus, and the presence of a minute larval terminal horn. Lanceimermis palustris n. sp. hosts were Chironomus maturus Johannsen and T. palustris n. sp. hosts were Tanytarsus mendax Kieffer, Paratanytarsus nr. dissimilis n. sp., and Micropsectra polita (Malloch). In both mermithid species, the percent of mermithid males per host increased with the intensity of the infection.     

Hydromermis contorta (Kohn) and Hydromermis pseudocontorta n. sp. from chironomids of Lake Itasca and Long Lake, Minnesota

Hydromermis contorta (Kohn) and Hydromermis pseudocontorta n. sp. are described from chironomids in Lake Itasca and Long Lake, Minnesota, respectively. The former was recovered from adult females of Glyptotendipes paripes (Edwards) and the latter from fourth-instar larvae of Chironomus sp. Hydromermis pseudocontorta n. sp. resembles H. contorta in cephalic structures, overall size, and the presence of a restricted trophosome in the female. The terminal mouth, long uterine and vulvar limbs of the vagina, and the strongly chitinized brownish spicule of H. contorta contrast with the subventral mouth, short vaginal limbs, and the light yellow spicule of H. pseudocontorta n. sp. Both nematode species emerge from the host as sexually mature adults and both species give evidence of mating while in the host. The H. contorta described by Welch is designated as a new species, Hydromermis albionis n. sp.     

Dentiphilometra monopteri n. gen., n. sp. (Nematoda: Philometridae) from the abdominal cavity of the ricefield eel Monopterus albus in China

A new genus and species of philometrid nematode Dentiphilometra monopteri n. gen., n. sp., are described on the basis of the specimens found in the abdominal cavity of the ricefield eel (swamp-eel) Monopterus albus (Zouiev) from Liangzi Lake (the Yangtze River drainage system), Hubei Province, in central China. Dentiphilometra, assigned to the Philometrinae, differs from other genera of this subfamily mainly in the presence of a sclerotized oral ring armed on its inner surface by numerous small peribuccal teeth in the gravid female. The new species is characterized by minute cephalic papillae, a greatly developed anterior esophageal bulb separated from the cylindrical part of the esophagus, anterior extention of the esophageal gland anterior to the nerve ring, and by large caudal projections in females and equal spicules 0.051-0.096 mm long in males. This is the second philometrid species recorded from fishes of the Synbranchiformes.     

Morphology and gene sequence of Levicoleps biwae n. gen., n. sp. (Ciliophora, Prostomatida), a proposed endemic from the ancient Lake Biwa, Japan

Levicoleps biwae n. gen., n. sp. was discovered in organic mud on the shore of Lake Biwa, Japan. Its morphology and small subunit rRNA gene sequence were studied with standard methods. Further, we established a terminology for the colepid armour and selected four features for genus recognition: the number of armour tiers, the structure of the tier plates, the presence/absence of armour spines, and the number of adoral organelles (three or five). The Japanese colepid, a barrel-shaped ciliate with an average size of 75 x 45 microm, has six armour tiers and hirtus-type tier plates, but lacks armour spines, both in the environment and in laboratory culture. Thus, it is considered to represent a new genus. This rank is supported by the considerable genetic distance (7%) from the common Coleps hirtus. Although L. biwae looks quite similar to C. hirtus in vivo, it is very likely most closely related to Coleps amphacanthus, a species with conspicuous armour spines, as indicated by body size, the number of ciliary rows and, especially, the multiple caudal cilia. Lake Biwa is about four million years old and inhabited by many endemic organisms, ranging from algae to large fish. Thus, we suspect that L. biwae is restricted to Lake Biwa or, at least, to Asia. Based on literature data and the generic features established, we also propose the new genus Reticoleps for Coleps remanei Kahl, 1933, and resurrect the genus Pinacocoleps Diesing, 1865 to include Coleps incurvus Ehrenberg, 1833, Coleps pulcher Spiegel, 1926, Coleps tessalatus Kahl, 1930 and, probably, Baikalocoleps quadratus Obolkina, 1995a. Nine colepid genera are diagnosed and dichotomously keyed.     

Reconstruction of Holocene lake-level changes in Lake Kalvsjön, southern Sweden, with a contribution to the local palaeohydrology at the Elm Decline

Past lake-level changes in Lake Kalvsjön are reconstructed and compared with the changes recorded in nearby Lake Bysjön. The two major lowerings of lake level noted in Lake Bysjön are also recorded in Lake Kalvsjön, the older lowering taking place between ca. 9500–9200 B.P. and the younger occurring between ca. 6500–3000 B.P. A distinct decrease in the frequency ofUlmus, corresponding to the classical Elm Decline, is recorded in the pollen diagram from Lake Kalvsjön. The high rapidity of the decline strongly suggests that a pathogenic attack was primarily responsible. However, both human interference and palaeohydrological change may have interacted by disturbing the surrounding forests and increasing the susceptibility of elm to pathogenic attack. In the Lake Kalvsjön area, the disturbance resulting from palaeohydrological change is assumed to have been more influential in pre-disposing the forest to an outbreak of elm disease than any human interference.     

Thysanotaenia congolensis n. sp. (Cestoda: Anoplocephalidae) in the lesser savanna cane rat, Thryonomys gregorianus from Democratic Republic of Congo, Africa

Ten (100%) lesser savanna cane rats, Thryonomys gregorianus, collected from the Lake Kivv area of the Democratic Republic of Congo, Africa were found to be infected with an undescribed anoplocephalid tapeworm, Thysanotaenia congolensis n. sp. Like other species of Thysanotaenia, T. congolensis n. sp. has the ovary and vitellarium centrally located, and the egg capsules and testes are intervascular. The new species differs from the 2 existing species, Thysanotaenia lemuris in lemurs and Thysanotaenia cubensis in humans, in being smaller (34-50 mm long) and in having a smaller scolex (260-410 microns in diameter), a shorter cirrus sac (115 microns long), and smaller eggs (40 microns in diameter). Anastomoses of the excretory system and formation of egg capsules in the new species are also described.     

Description of a new species of Proteocephalus pronini sp.n. (Cestoda: proteocephalidae)--a parasite of grayling from lake Hovsgol

A new cestode species, Proteocephalus pronini sp. n., is described from the Lake Hovsgol Grayling Thymallus arcticus nigrescens (Mongolia, Hovsgol Lake). The new species differs from P. thymalli from the Baikal Lake by the length of strobile, number of proglottids, form of mature proglottids, and number of diverticles of uterus.     

Spinitectus osorioi n. sp. (Nematoda: Cystidicolidae) from Chirostoma spp. (Osteichthyes: Atherinidae) in Lake Pátzcuaro, Michoacán, México.

Spinitectus osorioi (Nematoda: Cystidicolidae) is described from the freshwater atherinids Chirostoma estor and Chirostoma attenuatum from Lake Pátzcuaro in the Mesa Central, Michoacán State, México. This nematode is characterized by a conspicuous protuberance on the ventral surface of the distal end of the long spicule that distinguishes it from its congeners in North America and in the neotropics. In addition, the species can be readily distinguished from 4 of the 5 nominal species of North American freshwater Spinitectus by the absence of either a terminal barb or heel on the short spicule and from Spinitectus mexicanus by the spination. Previous records of Spinitectus carolini from Chirostoma spp. in México (Lakes Pátzcuaro and Zirahuén) refer to S. osorioi, and the species appears to be specific to Chirostoma spp. The geological history of the Mesa Central drainages and the historical biogeography of freshwater atherinids in this region suggest that the origin of S. osorioi may be associated with either the marine history of their hosts or with host-switching from more distantly related freshwater hosts after colonization of freshwater environments by atherinids.     

Facieplatycauda pratti gen. n., sp. n. and Two New Species of Myxobolus (Myxosporida)*

Synopsis. Facieplatycauda pratti gen. n., sp. n. and Myxobolus kozloffi sp. n., from the Klamath Lake sucker, Catostomus luxatus (Cope), are described. The new genus is placed in the family Myxobolidae between Henneguya and Myxobolus. The spore valves beyond the sporoplasmic space are broad and long but not attenuated as an inverted triangle as in certain species of Myxobolus with tails, or of Henneguya with sometimes bifurcated tails. An organism resembling Myxobolus insidiosus (Wyatt & Pratt) was found in the muscle of the body of Salmo clarki (Richardson). Differences in spore structure and site of infection suggest this is a subspecies of the previous form which should be designated Myxobolus insidiosus clarki. A previously unreported species of Myxobolus from Cottus aleuticus (Gilbert) is also described.