Comparative studies on scanning electron microscopy of trophi of the genus Filinia Bory De St. Vincent (Rotifera)

Trophi of Filinia species from 16 South Island lakes and three North Island lakes of New Zealand were examined and compared with specimens from Australia, Austria, Belgium, and Turkey. Five species of Filinia (brachiata, longiseta, cf. pejleri, novaezealandiae, and terminalis) were positively identified from the New Zealand samples. Numbers of unci teeth are considered to be the most reliable features for identification within the genus. Numbers obtained from SEM for other species of Filinia (australiensis, grandis, and hofmanni) are also listed for the first time.     

The ultrastructure of the mastax of Filinia longiseta (Flosculariaceae, Rotifera): Informational value of the trophi structure and mastax musculature

The study contributes to the discussion of mastax evolution within Rotifera by giving an insight into the ultrastructure of the mastax in the rotifer species Filinia longiseta (Flosculariacea) and additionally into the bdelloid rotifer species Adineta vaga and Zelinkiella synaptae. The existence of cuticularized jaw elements (trophi) in the mastax, a muscular pharynx, is one of the defining rotiferan characters and the basis on which the monophyletic taxon Gnathifera Ahlrichs 1995a, comprising Rotifera, Gnathostomulida, Micrognathozoa and Acanthocephala, was erected. By means of SEM observations of the trophi and ultrathin serial sections (TEM) of the mastax, the internal and external organization of the jaw elements of F. longiseta is reconstructed. TEM sections of the incus of Filinia demonstrate that the fulcrum and the rami are built up by multitudes of tiny cuticular tubes. While tubular substructures in the rotiferan fulcrum have been described previously, distinct cuticular tubes as a substructure of the ramus have only been described for species belonging to the taxa Seisonidea and Bdelloidea so far ( [Koehler and Hayes, 1969] and [Ahlrichs, 1995b]). By comparing the appearance and arrangement of the cuticular tubes in the rami of F. longiseta to those found in species of Seisonidea and Bdelloidea, a higher degree of resemblance between the structures in F. longiseta and Bdelloidea can be reported. The occurrence of the ramus substructures in species of Seisonidea (Paraseison annulatus and Seison nebaliae) is given consideration to represent an intermediate between the ramus substructure of Bdelloidea/Flosculariacea and Ploima. Additionally, the mastax musculature of F. longiseta, being associated with the trophi, is described: A total of seven muscles are found that directly insert the jaw elements or are indirectly associated with them via muscle-to-muscle connections.     

New records of rotifers from the South Island lakes,New Zealand

Thirty-five lakes in the South Island of New Zealand were surveyed for rotifers during 1988–1991. Of 85 taxa identified, 31 are first records for New Zealand, bringing the rotifers recorded from the country to 331. Four species (Keratella australis, K. slacki, Lecane herzigi and L. tasmaniensis), previously recorded as endemic forms only in Australia, are now added to the New Zealand checklist. Several of the new records are photographed, and scanning electron micrographs of the trophi are shown. Comments are made on the Australasian endemics and rotifer biogeography in New Zealand.     

<Emphasis Type="Italic">Rhinoglena kutikovae</Emphasis> n.sp. (Rotifera: Monogononta: Epiphanidae) from the Bunger Hills,East Antarctica: a probable relict species that survived Quaternary glaciations on the continent

A new species of rotifer, Rhinoglena kutikovae n.sp. (Monogononta: Epiphanidae), is described from a freshwater lake in the Bunger Hills, East Antarctica. The new taxon is characterized by the following combination of characters: body conical to vase-shaped; a single toe; distal foot pseudosegment bulged; tail prominent, semi-circular; two small spherical pedal glands with common duct, forming a complex with caudal ganglion; trophi with seven major teeth with offset head and two smaller teeth without offset head. The new species is compared with R. fertoeensis, R. frontalis and R. tokioensis, of which scanning electron microscopic information is presented of the trophi. R. kutikovae n.sp. is probably a relict species that survived Quaternary glaciations in glacial lacustrine refugia on the Antarctic continent.     

A simplified method for preparing rotifer trophi for scanning electron microscopy

A simple, quick technique for the preparation of rotifer trophi for scanning electron microscopy is described. The method permits visual monitoring of the extraction process and does not require critical point drying of the specimens. Micrographs showing fine, structural detail of the hard parts of the mastax of representatives of the following genera are presented:Asplanchna, Conochilus, Filinia, Hexarthra, Keratella, Proalides, Synchaeta, andTrichocerca.     

Disentangling the morphological stasis in two rotifer species of the <Emphasis Type="Italic">Brachionus plicatilis</Emphasis> species complex

The taxonomic uncertainty surrounding cryptic species complexes has traditionally been resolved using lengthy experimental approaches, while, since the advent of PCR based techniques the number of cryptic species described in a variety of taxa is increasing steadily. Here we formally describe a new rotifer species of the Brachionus plicatilis complex: Brachionus manjavacas n.sp., disentangling what was known as a morphological stasis. Detailed morphological analyses demonstrated significant differences in body shape and size between B. manjavacas and B. plicatilis s.s., analysed by geometric morphometrics; unfortunately these statistical differences are not taxonomically reliable because of wide overlaps. Size and asymmetry of masticatory apparatus, named trophi, observed by SEM, gave similar results, with taxonomic ambiguity. Only the shape of small pieces of the trophi, named satellites, were consistently different between the species. On a strictly classical taxonomical basis it is absolutely useful to name new species on morphological bases, as we did, and to assess their status as distinct entities. Nevertheless, the two species are broadly similar; therefore, we do not suggest using the small differences in shape of satellites of trophi to identify the species for further ecological studies, but to continue discriminating them on genetic marker bases. Handling editor: K. Martens     

Preliminary remarks on the characteristics of the rotifer fauna of Australia (Notogaea)

Unusually large forms of Asplanchna sieboldi, Brachionus plicatilis, B. calycijlorus, Filinia pejleri, Trichocerca similis and Keratella slacki were collected from waters of south-eastern Australia. These giant forms are figured, and brief location and ecological data are given. Although the rotifer fauna of the Murray riversystem contains pan-tropical and pan-subtropical species, there exists a greater degree of endemicity than previously considered.     

Rotifer vertical distributions in a meromictic basin of Lake Banyoles (Spain)

The vertical distribution of rotifer populations has been analyzed in a meromictic basin (III) of the karstic Lake Banyoles. This basin had, at the time of the study, an anaerobic monimolimnion from around 17 m in summer or 21 in winter to 25 m, its maximum depth. However, below this layer a warmer microaerophilic zone with suspended marls is found in a chimney to a depth of 130 m.The rotifer distributions of several years are compared. The presence of large populations of rotifers at the oxic-anoxic interface is constant through the years, but highly variable regarding the total abundance and relative proportions of the species, depending on the importance of the vertical mixing in winter and the posterior segregation of water layers as a function of production and decomposition processes. Filinia hofmanni, Filinia longiseta longiseta are species with a restricted occurrence at the oxycline and are not present in the other non meromictic basins of the lake. Filinia terminalis, more broadly distributed, also has dense populations in summer at the oxycline in basin III, but disappears from the plankton during this season in the other basins. Other species, such as Polyarthra dolichoptera, Anuraeopsis fissa, Keratella cochlearis and Kellicottia longispina, also showed maxima at the oxycline in summer, as well as other maxima in the metalimnion. Populations at the oxycline are probably different ecotypes adapted to low oxygen conditions, but having the advantage of high food availability.     

Study of the Trophi of <Emphasis Type="Italic">Testudinella</Emphasis> Bory de St. Vincent and <Emphasis Type="Italic">Pompholyx</Emphasis> Gosse (Rotifera: Testudinellidae) by Scanning Electron Microscopy

The fine morphology of the trophi of Pompholyx sulcata and nine species of Testudinella (Rotifera, Monogononta, Flosculariacea, Testudinellidae) was studied by scanning electron microscopy. The number of unci teeth and arched rami scleropili, and the shape of the major unci teeth and fulcrum are considered to be reliable additional characters for identification.     

Revisiting the Cephalodella trophi types

The six trophi types proposed by Wulfert (Archiv für Hydrobiologie 31:592–636, 1937) are used as one main character to identify Cephalodella species, although these trophi types were just based on the trophi of 31 species described after light microscopy findings. Given the 160 species nowadays valid and the possibility of examining trophi with scanning electron microscopy it is questionable if the definitions of the six types might or rather have to be improved in order to facilitate species identification. Here, a new even simpler definition scheme is proposed to identify the six trophi types.     

Plankton composition, abundance and dynamics in a severely stressed cooling reservoir

The effects of severe thermal stress imposed by the intermittentoperation of a nuclear reactor on plankton abundance and dynamicswere investigated in Pond C, a cooling reservoir on the SavannahRiver Site in South Carolina, USA. Temperatures in Pond C rangedup to 58°C during reactor operation. The thermal effluenteliminated zooplankton from regions where the temperature exceeded45°C, reduced zooplankton abundance by 1–3 ordersof magnitude and typically halved the number of taxa. Reactoroperation also reduced phytoplankton biovolume, often by >70%.During intermittent reactor operation, the rotifer Filinia longisetadominated the zooplankton and two cladocerans of the genus Moinawere abundant. These species were not abundant during extendedreactor shutdowns. The success of Filinia and Moina was dueprimarily to their tolerance of high temperatures. Sparse phytoplanktonprobably limited some zooplankton taxa, although other taxa,such as Filinia may have utilized bacterial resources. Reactoroperation may have intensified predation on crustacean zooplanktonwhen fish were concentrated in refuge areas with zooplankton.Processes by which zooplankton repopulated the reservoir afterreactor shutdown were inferred from zooplankton distributionpatterns, and population growth and birth rates. Repopulationtypically occurred within a few days due to rapid growth ofpopulations from refuge areas within the reservoir and colonistsbrought in through a tributary canal. Mechanisms of zooplanktonrepopulation in Pond C suggest that refuges or colonizationcorridors should be maintained when the re-establishment ofcommunities following cessation of stresses is desired.     

Feeding responses of Asplanchna brightwelli (rotifera): laboratory and field studies

Laboratory-reared A. brightwelli were offered 16 different prey rotifer species from the genera Anuraeopsis, Brachionus, Epiphanes, Filinia, Hexarthra, Lecane, Lepadella, Pompholyx, Proalides and Trichocerca. Feeding responses (prey encounter, escape, capture, rejection and ingestion) were recorded. In general, the predator's ingestion time was positively correlated with prey length. B. falcatus and H. intermedia were never captured. Once captured, smaller rotifer species were ingested. Gut contents of field-collected A. brightwelli revealed increased occurrence of prey numbers when concentrated plankton samples were preserved after some delay.     

Two new species of the family Dicranophoridae (Rotifera, Ploima) from the littoral psammon, with notes on other brackish water rotifers in Denmark

The rotifer fauna has been investigated at three littoral brackish water localities in the Öresund, Denmark. Samples taken from plankton, periphyton and psammon yielded 14 rotifer species. Two of these are new to science and are described herein. Both species were found in psammon at the same locality. Erignatha longidentata n. sp. is characterised by having toes with swollen bases, convex outer margins and concave inner margins. The trophi have a pair of large subunci and relatively large unci. The other new species, Paradicranophorus wesenberglundi n. sp., is characterised by having two large red pigmented eyespots and large conical toes. The rami are lyrate, and intramallei and supramanubria are present in the mallei.     

Do Rotifer Jaws Grow After Hatching?

The hard articulated jaws of some pseudocoelomate metazoans were recently used in reconstructing their phylogenetic relationships, but we still do not know if these structures could change in size and shape during the life of individuals, and experimental data are lacking on their post-embryonic development. Rotifers are one of the groups in which hard articulated jaws, called trophi, are well known, and are widely used taxonomically. Here we report on SEM study of trophi of rotifers of different ages, to determine if the trophi structures change in shape and/or in size during post-embryonic development. We used linear measurements and geometric morphometrics analyses from scanning electron microscopic pictures of trophi of Cupelopagis vorax, Dicranophorus forcipatus, Macrotrachela quadricornifera, Notommata glyphura, Rotaria macrura, R. neptunoida, and R. tardigrada. Results for these species show that trophi do not change after hatching, either in size or in shape. In contrast, data on Asplanchna priodonta reveal trophi growth after hatching.     

Systematics of AustralianLepidium species (Brassicaceae) and implications for their origin: Evidence from IEF analysis of Rubisco

Variation in subunit polypeptide composition of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) from native AustralianLepidium taxa was analyzed by isoelectric focusing (IEF). Species of grexMonoplocoidea on the one hand, and species of gregesPseudoruderalia andPapillosa on the other, were well separated by Rubisco IEF patterns. The protein data suggest grexMonoplocoidea to be placed in sect.Monoploca whereas gregesPseudoruderalia andPapillosa should be integrated into sect.Dileptium. We suggest that the Rubisco type of American and/or AsianLepidium species was contained in those plants migrating to Australia and evolving into the recent native Australian species. Fossil pollen records and vegetation history indicate that the origin ofLepidium in Australia was restricted to the late Tertiary of Quaternary. Data presented in this study fit best with an immigration by long-distance dispersal of seeds by birds from Asia and/or from South America.     

Scanning Electron Microscopy of Mouth Appendages in Six Species of Barnacles (Crustacea Cirripedia Thoracica)

The morphology and setation of mouth appendages (trophi) are investigated with scanning electron microscopy in the balanomorph barnacles Semibalanus balanoides, Balanus balanusand B. nubilusand in the pedunculate barnacles Pollicipes polymerus, P. cornucopiaand Lepas anatifera.It is difficult to uphold a clearcut distinction between denticles and setae and several types of setae also intergrade with each other. The trophi of Pollicipes polymerusand P. cornucopiahave the most ‘generalized’ morphology. The palps of Pollicipesand L. anatiferaare simpler than those in balanomorphs and carry a single type of seta. In L. anatiferathe mandibles and maxillules are adapted to a semi-predatory feeding habit by carrying large, pointed teeth, but this species lacks the foliate-serrate setae which populate the palps in the other species studied. Compared with Pollicipesand Lepas, the three balanomorphs have palps with a complex setation. The trophi in S. balanoidesdiffer from the two species of Balanusin numerous features of setation and denticulation, notably in having the palps populated by plumodenticulate setae homologous to purely denticulated types in Balanus.It is suggested that SEM studies of barnacle trophi will provide characters of use in estimating phylogeny.     

Phylogeny, biogeography, and species boundaries within the Alexandrium minutum group

The geographic range and bloom frequency of the toxic dinoflagellate Alexandrium minutum and other members of the A. minutum group have been increasing over the past few decades. Some of these species are responsible for paralytic shellfish poisoning (PSP) outbreaks throughout the world. The origins of new toxic populations found in previously unaffected areas are typically not known due to a lack of reliable plankton records with sound species identifications and to the lack of a global genetic database. This paper provides the first comprehensive study of minutum-group morphology and phylogeny on a global scale, including 45 isolates from northern Europe, the Mediterranean, Asia, Australia and New Zealand.Neither the morphospecies Alexandrium lusitanicum nor A. angustitabulatum was recoverable morphologically, due to large variation within and among all minutum-group clonal strains in characters previously used to distinguish these species: the length:width of the anterior sulcal plate, shape of the 1′ plate, connection between the 1′ plate and the apical pore complex, and the presence of a ventral pore. DNA sequence data from the D1 to D2 region of the LSU rDNA also fail to recognize these species. Therefore, we recommend that all isolates previously designated as A. lusitanicum or A. angustitabulatum be redesignated as A. minutum. A. tamutum, A. insuetum, and A. andersonii are clearly different from A. minutum on the basis of both genetic and morphological data.A. minutum strains from Europe and Australia are closely related to one another, which may indicate an introduction from Europe to Australia given the long history of PSP in Europe and its recent occurrence in Australia. A minutum from New Zealand and Taiwan form a separate phylogenetic group. Most strains of A. minutum fit into one of these two groups, although there are a few outlying strains that merit further study and may represent new species. The results of this paper have greatly improved our ability to track the spread of A. minutum species and to understand the evolutionary relationships within the A. minutum group by correcting inaccurate taxonomy and providing a global genetic database.     

Caractères taxinomiques et spécificité dans le genreAsplanchna (Rotifère)

A comparative analysis of eight characters in two clones ofA. brightwelli and a clone ofA. intermedia, fed withParamecium orBrachionus, is made to determine the intraclonal, interclonal and interspecific variations in this complex of species.The trophi morphology appears the most species specific criterium whereas the other features (size of males, diameter and ornamentation of resting eggs, nuclear number in syncytial glands) show variability, either genetic or related to environmental conditions. The variation observed in the ornamentation of resting eggs and in the nuclear number of vitellogen was distributed along a continuous gradient.