Freshwater Nemerteans Research Articles

A re-examination of the taxonomic status of Prostoma jenningsi-a Freshwater Nemertean.

Prostoma jenningsi was first recorded at the Clay 'Ole pond in Lancashire, UK, in 1969 and was distinguished histologically from other Prostoma by the presence of 11 proboscidial nerves (with all other Prostoma species thought to have 9-10). P. jenningsi was considered to be the only species endemic to Lancashire and listed in the British Red Data Book as 'Insufficiently Known' as well as a 'Species of Principal Importance' under the UK Natural Environment and Rural Communities Act (2006). A limited number of Prostoma spp were recovered from the Clay 'Ole in 2011 (the first confirmation of the presence of Prostoma spp. since 1999). In 2015, further sampling was undertaken and expanded to other ponds in Lancashire resulting in the discovery of Prostoma spp. at a further 3 locations. Thereafter, DNA sequencing of nuclear 18S ribosomal RNA and mitochondrial Cytochrome Oxidase I (COI) genes were undertaken and phylogenetic analyses performed to establish the taxonomic status of recovered specimens. All available Prostoma sequences (Prostoma eilhardi and Prostoma graecense) were downloaded from GenBank® and Barcode of Life Data System (BOLD) databases for comparison. All 18S sequences from samples in Lancashire were identical to each other and to all downloaded Prostoma sequences, allowing no further analyses. With COI, 50 individuals were collected from 4 locations across Lancashire and sequenced, comparing a total of 480 base pairs. Average uncorrected p-distances between UK and European samples were low, although some more geographically distant samples from California, USA, displayed higher uncorrected p-distance values. Results suggest that the Prostoma recovered from the Clay 'Ole (and all other sampled locations in Lancashire) are not distinct from P. eilhardi and P. graecense (as downloaded from GenBank® and BOLD) suggesting that there is a strong case for the species status of P. jenningsi to be revoked. Further regional and national sampling is required to obtain a clearer evaluation of the distribution of Prostoma and the levels of genetic diversity present in the UK. In addition, results from this study indicate that thorough taxonomical re-evaluation of species within the Prostoma genus is required.

Rediscovery of the nemertean Prostoma graecense from Xochimilco, 75 years after its first and only record

The identity of the freshwater nemertean Prostoma graecense (Bohming, 1892) from Lake Xochimilco is solved 75 years after its first recording. Identification of the specimens was accomplished via both morphological and molecular means, the latter employing the mitochondrial cytochrome c oxidase subunit I. Recent literature and our results suggest that this species has a cosmopolitan distribution and has, presumably, been recently introduced to areas well removed from its original distribution, which is unknown. The current study provides a background for continuing the work with freshwater and marine nemerteans and underscores the importance of including molecular data in future studies of the group.

The first finding of freshwater nemerteans in Ohrid Lake (Macedonia) with some comments on the taxonomy of the genus Prostoma (Nemertea, Monostilifera)

The first finding of freshwater nemerteans from the genus Prostoma (Duges 1828) from the relic Ohrid Lake is described in the article. Genetic analysis of the gene fragment CO1 was performed, according to which Prostoma of Ohrid Lake should be considered as conspecific with the widespread species P. graecense (Bohmig 1892). It has been assumed that P. graecense and P. eilhardi (Montgomery 1894) belong to the same species, which should be called Prostoma clepsinoides Duges 1828 (the type species of the genus Prostoma). Data from the molecular and phylogenetic analysis prove that the family Prostomatidae is independent.

A new genus and species of freshwater monostiliferous hoplonemertean (Nemertea, Enopla) from the People's Republic of China

A new genus and species of freshwater monostiliferous hoplonemertean, Limnemertes poyangensis gen. et sp. nov., from Poyang Lake, People's Republic of China, is described and illustrated. The taxon is compared and contrasted with previously described freshwater hoplonemerteans. This is the fourth species of freshwater nemertean to be described from China and the first recorded from Poyang Lake.

Further studies on the evolution of land and freshwater nemerteans: generic relationships among the paramonostiliferous taxa

Morphological characteristics of the terrestrial (Acteonemertes, Antiponemertes, Argonemertes, Katechonemertes, Leptonemertes) and freshwater (Campbellonemertes, Potamonemertes) paramonostiliferous nemerteans, all of which are at present unplaced at the family level, are compared and contrasted with those of the marine genera Plectonemertes (Plectonemertidae), Cratene‐mertes, Korolkevilschia and Nippormemertes (Cratenemertidae). It is concluded that whilst Acteonemertes, Antiponemertes, Argonemertes, Campbellonemertes and Potamonemertes can with certainty be placed in the family Plectonemertidae, the unspecialized and geographically isolated genera Katechonemertes and Leptonemertes, although lacking positive grounds for their exclusion, are only questionably included in this taxon. The possible evolutionary relationships of the plectonemertid genera are discussed and a diagnosis of the family is provided.

THE EVOLUTION AND COMPARATIVE PHYSIOLOGY OF TERRESTRIAL AND FRESHWATER NEMERTEANS

Summary(1) Parallel evolution from separate marine ancestors has given rise to two groups of genera of terrestrial nemerteans, representative of at least two different family stocks. They have colonized land by the direct route, moving up the shore on widely separated oceanic islands. The relationships between the known terrestrial and semi‐terrestrial nemerteans, comprising seven genera and 15 species, are defined and their geographic distribution is discussed.(2) In fresh water, three heteronemertean and nine hoplonemertean species are known. The hoplonemerteans arise from two different families representing two different evolutionary routes to fresh water, one by way of estuaries and the other via land. The distribution of freshwater nemerteans and the characters common to all species are discussed.(3) Very little is known about the comparative physiology of land and freshwater nemerteans. However, information about the physiology of marine forms is combined with morphological differences from them found in terrestrial and freshwater species to suggest profitable lines of future research.(4) Water relations pose a major problem for both terrestrial and freshwater nemerteans. The role of the cerebral organs, the blood and the excretory system in the osmotic physiology of some littoral nemerteans is beginning to be understood. These systems in land and freshwater forms have clearly distinctive features which need to be thoroughly investigated.(5) Suggestions are given for valuable lines of investigation of the mucous glands, digestive physiology and general behaviour of terrestrial and freshwater nemerteans.

Oxygen consumption and the occurrence of a haemoprotein within the central nervous tissue of the hoplonemertean Amphiporus lactifloreus (Johnston) (Nemertea: Enopla: Monostilifera)

The red pigment occurring intracellularly within the cerebral ganglia and lateral nerve cords of Amphiporus lactifloreus (Johnston) has been investigated by histochemical, cytochemical, and microdensitometric means. A non-enzymic peroxidase activity distributed homogeneously throughout the cytoplasm of certain glial cells is demonstrated. Specific histochemical results and characteristic absorption spectra confirm that the pigment is a haemoprotein. Rapid de-oxygenation and subsequent re-oxygenation of the pigment in conditions of fluctuating oxygen tension indicates that the haemoprotein is physiologically active.Respiratory data have been obtained for A. lactifloreus and these are compared with the results published for the freshwater nemertean Prostoma graecense (Bohmig). Carbon monoxide interferes with the neuro-pigment and treatment with this gas results in a 50% reduction in respiratory rate and oxygen consumption. Graphs of oxygen consumption and body weight, both on a log10 basis, are depicted and discussed.The possible rôle of the pigment in facilitative diffusion of oxygen within the nemertean central nervous system is discussed.

Observations on the Fresh-water Nemertean, Prostoma rubrum (Leidy), in Alabama

Observations on the Fresh-water Nemertean, Prostoma rubrum (Leidy), in Alabama

Oxygen consumption and the respiratory pigment in the fresh-water nemertean, Prostoma rubrum

1. 1. The oxygen consumption and respiratory rate of the freshwater nemertean, Prostoma rubrum, were determined at 20°C. 2. 2. The mean respiratory rate for forty-nine specimens was 0·700 μl O 2/mg dry wt. per hour (±0·071). 3. 3. Oxygen consumption varied with the 0·478 power of the body weight. 4. 4. A heme-containing pigments is present which may assist in the respiratory process.

Benthic Macroinvertebrates of the Otter Creek Drainage Basin, Northcentral, Oklahoma

Distribution, seasonal abundance, and ecological notes on 122 taxa of benthic macroinvertebrates collected in the Otter Creek Drainage system are discussed. The freshwater nemertean, Prostoma rubrum (Leidy), and the oligochaetes, Tubifex templetoni Southern, Dero digitata (Muller), Nais variabilis Piguet, Pristina breviseta Bourne, P. longiseta Leidyi Smith, P. longidentata Harman, and two species of Pristina new to science are reported from Oklahoma for the first time. Benthic macroinvertebrate studies have recently become of increased importance to aquatic biologists because of their use in evaluating effects of pollutional effluents, and recognition of their central position in aquatic food chains. Benthic macroinvertebrates of southwestern lotic waters are poorly known. The only major contributions in this area are by Hornuff (1957) and Wilhm and Dorris (1966). This situation is further complicated by the draeth of taxonomic studies on immature stages of many aquatic invertebrates. These points can be emphasized by pointing out that eight of the 11 species of oligochaetes collected during this study represent new state records, two of these are new to science. Furthermore, only 65 of the 122 taxa collected could be identified to species. This report consists of information concerning distribution, seasonal abundance, and ecological notes on species collected during a one year study of the Otter Creek Drainage system. Distribution is discussed in terms of Horton's (1945) stream order classification, as modified by Strahler (1954; 1957) and redescribed by Kuehne (1962) and Leopold (1962). Kuehne (1962), Harrel et al., (1967) and Harrel and Dorris (1968) showed the usefulness of stream order classification in successional studies. Detailed evaluations of drainage basin geomorphology, physicochemical conditions, and species diversity of benthic macroinvertebrates and fishes have been published elsewhere (Harrel et al., 1967;

On a Fresh-water Nemertean from Hokkaido

On a Fresh-water Nemertean from Hokkaido

Note on the Occurrence of a Freshwater Nemertine in England

A FEW days after reading M. de Guerne's “History of Freshwater Nemerteans,” published in the August number of the Annals, I happened upon a specimen of the group amongst the roots of some water plants, which I collected in the river Cherwell, close to Oxford. I was, at the time, searching for the cocoons of a new Rhinodrilid worm, of which a description will shortly appear. The gathered roots, with the cocoons, were placed in a bottle of water, in order that the worms might hatch out. On examining the bottle two days later, namely, on September 5, I noticed a small bright orange animal, about half an inch long when extended, creeping amongst the cocoons. Further observation with the microscope showed that it was a species of Tetrastemma. Unfortunately the animal was crushed before I had done more than sketch the general appearance and make some few observations, and I have not yet succeeded in finding more specimens; so that I am unable to state how far it agrees with or differs from the previously known freshwater forms enumerated by M. de Guerne, most of which are included by Silliman and later authors under the title Tetrastemma aquarum dulcium.

The history of the freshwater Nemerteans; their geographical distribution and their origin

The history of the freshwater Nemerteans; their geographical distribution and their origin