Freshwater nemerteans

The freshwater hoplonemertean genus Prostoma is critically reviewed and revised and a new species Prostoma kolasai sp. nov., is described. All the freshwater nemerteans of the world are compared and contrasted, with reference to those common morphological characters which may be related to the colonization of freshwater habitats. A key to the world freshwater nemerteans is provided.     

On a new genus of freshwater hoplonemertean from Campbell Island

A new freshwater hoplonemertean from Campbell Island, to the south of New Zealand, i s described and named Campbellonemertes jolinsi gen. et sp. nov. The morphology of this tiemertean relates it with the family Prosorhochmidae and the occurrence of this form, the second freshwater prosorhochmid genus from the Antipodes, strongly supports an earlier hypothesis on the evolution of freshwater hoplonemerteans.     

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.     

On the hoplonemertean, Kameginemertes parmiornatus (Iwata, 1957) gen. n., comb. n. from Sagami Bay, Japan

The hoplonemertean Amphiporus parmiornatus Iwata,1957, from Sagami Bay, Japan, has beenredescribed and named Kameginemertes gen. n. asa member of the reptantic Polystilifera. Anatomicallythe new genus shows affinity to the genus Drepanophorus belonging to the EureptantiaAequifurcata, but because of differences in thecerebral sensory organs, nervous system,blood-vascular system, and rhynchodaeal wall, a newgenus is proposed for it.     

A new semi-terrestrial nemertean from California

A new species of semi-terrestrial monostiliferous hoplonemertean from California, Pantinonemertes californiensis sp. nov., is described and illustrated. The genus Pantinonemertes, transitional between marine and terrestrial habitats, provides evidence for one evolutionary line towards the colonization of land by nemerteans.     

A New Polystiliferous Hoplonemertean, Curranemertes natans gen. et sp.n., from the Caribbean Sea (Nemertina, Polystilifera Reptantia)

A polystiliferous hoplonemertean, Curranemertes natans gen. et sp.n., is described from Venezuela where it was found on corals in shallow water. It is the third species of reptantic Polystilifera known from the Caribbean Sea. Anatomically the new species shows affinities to the genera Punnettia, Polyschista , and Drepanophorina , but because of differences in the nervous system, cerebral organs, and alimentary tract, a new genus is proposed for it.     

Genus Tetrastemma Ehrenberg, 1831 (Phylum Nemertea)--a natural group? Phylogenetic relationships inferred from partial 18S rRNA sequences

We investigated the monophyletic status of the hoplonemertean taxon Tetrastemma by reconstructing the phylogeny for 22 specimens assigned to this genus, together with another 25 specimens from closely related hoplonemertean genera. The phylogeny was based on partial 18S rRNA sequences using Bayesian and maximum likelihood analyses. The included Tetrastemma-species formed a well-supported clade, although the within-taxon relationships were unsettled. We conclude that the name Tetrastemma refers to a monophyletic taxon, but that it cannot be defined by morphological synapomorphies, and our results do not imply that all the over 100 species assigned to this genus belong to it. The results furthermore indicate that the genera Amphiporus and Emplectonema are non-monophyletic.     

Evolutionary relationships between mono- and polystiliferous hoplonemerteans: Nipponnemertes (Cratenemertidae), a “missing link” genus?

Histological studies on several species of the monostiliferous hoplonemertean genus Nipponnemertes show that they share certain significant features with reptantic Polystilifera. A brief survey of these features provides a basis for an analysis of possible evolutionary relationships between mono- and polystiliferous Hoplonemertea. It is suggested that ancestral enoplans possessed a rhynchocoel wall containing two muscle layers and a simple protopolystiliferous type of proboscis armature, and that this ancestral pool gave rise to two distinct evolutionary lineages, one leading to cratenemertid, group 2 terrestrial and freshwater, and polystiliferous hoplonemerteans, the other to the typical modern monostiliferous forms. A reclassification of the Enopla is proposed.     

A new genus and species of monostiliferous hoplonemertean (Nemertea: Enopla: Monostilifera) from Japan

A new genus and species of monostiliferous hoplonemertean, Diopsonemertes acanthocephala gen. et sp. nov., is described from Otsuchi Bay, Japan. Significant anatomical features of the new form include a body wall longitudinal musculature anteriorly divided into inner and outer layers by connective tissue, no pre-cerebral septum, the presence of a thin coat of diagonal muscle fibres between the body wall longitudinal and circular muscle layers in the foregut body region, cephalic retractor muscles derived only from the inner portion of the divided longitudinal muscles and a rhynchocoel more than half the body length.     

THE EVOLUTION AND COMPARATIVE PHYSIOLOGY OF TERRESTRIAL AND FRESHWATER NEMERTEANS

(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.     

Description of Conticribra tricircularis,a new genus and species of Thalassiosirales,with a discussion on its relationship to other continuous cribra species of Thalassiosira Cleve (Bacillariophyta) and its freshwater origin

A new diatom genus Conticribra is erected to accommodate C. tricircularis, described from a freshwater Pliocene deposit in Trout Creek, Oregon (USA). The genus accommodates species possessing: (i) loculate areolae with (semi-) continuous cribra; (ii) non-plicated valve face; (iii) rimoportula located on the valve mantle, replacing a fultoportula. Conticribra tricircularis has no valve face fultoportulae and can easily be distinguished by its marginal fultoportulae with four satellite pores arranged in three rings. Three species are transferred to the new genus from Thalassiosira sensu lato. Using evidence from the fossil record and recent molecular data, a hypothesis concerning the freshwater origin of Conticribra is discussed.     

Freshwater triclads (Turbellaria, Tricladida) from the oriental region

Two new freshwater triclad species of the genus Dugesia Girard, 1850 are described from the oriental region. The first is the only species of freshwater triclad described from Ceylon and the second, a cavernicolous form, is the only one known from Malaya. A synopsis, in tabular form, of the oriental Dugesia species is also given and some aspects of their distribution are discussed. It is intended that the tabular synopsis should provide diagnostic characters for the delimitation of the new and previously described species, and act as a basis for a future revision of the oriental representatives of the genus, many of which are poorly described or poorly known. Apreliminary dichotomous key to the valid species is also provided.     

A new species of commensal hoplonemertean from Australia

A new series of hoplonemertean from Australia is described and named Gononemertes australiensis. The morphology of this nemertean, which lives commensally in the ascidian Pyura pachydermatina (Herdman) variety intermedia Herdman, is described and illustrated and its taxonomic placing discussed.     

MICROFISSURATA GEN. NOV. (BACILLARIOPHYTA), A NEW DIATOM GENUS FROM DYSTROPHIC AND INTERMITTENTLY WET TERRESTRIAL HABITATS1

A new freshwater benthic diatom genus, Microfissurata gen. nov., was identified from light and scanning electron micrographs. The most characteristic morphological feature (referred to also by the name of the new genus) is the structure of the striae/alveoli, which are simple, mostly uninterrupted, transapical slits. The combination of characteristics of the new genus is unique. It includes two new species: Microfissurata paludosa Cantonati et Lange‐Bert. sp. nov. and M. australis Van de Vijver et Lange‐Bert. sp. nov., distributed in Europe and on an austral island, respectively. The new genus occurs in freshwater dystrophic lakes, pools, seepage springs, mires, and in intermittently wet terrestrial habitats. It is not abundant but widespread wherever these habitat types are well developed, in Nordic‐alpine and sub‐Antarctic areas. Overall, the new genus appears to be mostly epiphytic (bryophilous) and capable of tolerating a wide range of moisture conditions (xerotolerant). The finding of the type species (M. paludosa) in a well‐investigated area like central Europe highlights the diatom species richness of dystrophic habitats and their importance for diatom biodiversity conservation.     

The Morphology of Paranemertes sanjuanensis sp.n. (Nemertea, Monostilifera) from Washington, U.S.A.

The morphology of Paranemertes sanjuanensis sp.n., a new monostiliferous hoplonemertean from San Juan Island, Washington, is described. As in other members of the genus, P. sanjuanensis has numerous eyespots, a proboscis sheath that extends one-half to two-thirds the length of the body, well-developed cephalic and subepidermal glands, and two distinct layers of longitudinal muscles in the body wall of the cerebral region. A precerebral septum is absent, as only fibers from the inner longitudinal layer extend into the proboscis. The cerebral sense organs are well developed and lie just anterior to the brain. The esophagus opens into the rhynchodaeum and leads posteriad, into a highly folded stomach. The intestinal caecum is short and lacks anteriorly directed pouches. Gravid females have numerous ovaries in the posterior two-thirds of their bodies. The proboscis is relatively large and contains an average of 5 reserve stylet sacs, each of which contains 2 to 3 stylets. The stylets are stout and have prominent, helically-arranged grooves.     

A new freshwater heteronemertean from the Zhujiang (Pearl River), People's Republic of China

A new genus and species of freshwater heteronemertean, Amniclineus zhujiangensis, from the Zhujiang (Pearl River), People's Republic of China, is described and illustrated. The species is placed in the family Lineidae along with the existing freshwater heteronemertean taxa, with which its anatomy is compared.