XV.—Information respecting botanical travellers

Summary

A new species of mysid, Parvimysis pisciscibus, is described from leaf litter banks in the Igarapé Tarumazinho, a freshwater side stream of the Rio Negro, Brazil. This small species is the first freshwater mysid to be described from the Amazon basin.     

New bariliin cyprinid fishes from West Africa,with a consideration of their biogeography

Five new species of bariliin cyprinid fishes are described from West Africa. Three belong to the genus Leptocypris and two to Raiamas. One species of each genus is from Guinea (Konkoure river) and from Sierra Leone (Taia and Little Scarcies rivers), the other, a Leptocypris, is from Cameroon (Cross River). A taxon of indeterminate generic identity from Guinea is also described. The phylogenetic relationships of the bariliins are hypothesized and in this light their geographical distribution is compared with that of other cladistically analysed African freshwater fish groups. The significance to West African fish distribution of the Togo-Benin (Dahomey) Gap is discussed.     

Generic status and redescription of the Mediterranean fish Gobius liechtensteini Kolombatovic, 1891 (Teleostei: Gobioidea), and its affinities with certain American and Indo-Pacific gobies

Summary

A new monotypic genus, Corcyrogobius, is proposed for the gobiid fish, Gobius liechtensteini Kolombatovic 1891, known only from its Adriatic typelocality of Kor?ula, Yugoslavia. The species is redescribed and a lectotype designated from probable syntype material, which also includes examples of Odondebuenia balearica (Pellegrin & Fage, 1907), supposed by Kolombatovic to be adults of G. liechtensteini. The affinities of C. liechtensteini and the related genus Odondebuenia are discussed with reference to American seven-spined gobies, the Indo-Pacific Gladiogobius, and the subfamily Lioterinae, currently placed in the Eleotridae. Overall similarities between these gobies are described, their possible phylogeny outlined, and the Lioterinae transferred to the family Gobiidae.     

Discovery of the freshwater genus Sicyopus (Teleostei: Gobioidei: Sicydiinae) in Madagascar,with a description of a new species and comments on regional dispersal

In the Indo-Pacific area, insular rivers are mainly colonized by gobiids of the Sicydiinae subfamily. These species spawn in freshwater, where the free embryos drift downstream to the sea before returning to rivers to reproduce; they are amphidromous. These gobies are the greatest contributors to the fish diversity and have the highest levels of endemism. Among the nine known genera of Sicydiinae, only two have been found in the West Indian Ocean, and only one (Sicyopterus) is known from Madagascar. Recently, two surveys discovered a new species in the genus Sicyopus. Sicyopus lord sp. nov. differs from other species by a combination of characters that includes a particular colour pattern, similar in both sexes; more scales than its congeners in lateral series (35–43), transverse back series (12–18) and a shorter caudal fin length in male fish. This paper describes the new species and discusses the presence of this genus in Madagascar.     

First record of a freshwater Pisionidae (Polychaeta): description of a new species from Panama with a key to the species of Pisione

A new species of Pisione Grube, 1857, Pisione garciavaldecasasi n. sp. (Polychaeta: Pisionidae) is described from several small rivers in Cobia Is., Pacific, off Panama. This is the first report of a freshwater Pisionidae and it is one of very few known species of true freshwater polychaetes. The species is characterized by large size, by dorsal cirri of setiger 2 and ventral cirri of setiger 1 only slightly elongated, by non-successive male copulatory organs, and by parapodia each with one compound seta with long blade and three others with short blades.     

Revision of the millipede genus Xystodesmus,with reference to the status of the tribe Xystodesmini (Diplopoda: Xystodesmidae)

On the basis of morphometrics and geographic distribution, we revise Xystodesmus martensii Peters and its related forms in Japan, which had been recognized as ten species belonging to five genera. In delimitation of species, first we sought the biggest pheno-geographic units based on the dendrogram from a cluster analysis and geographic distribution; a pheno-geographic unit is defined as an aggregation of populations being phenetically closely similar and geographically closely distributed to each other. Then, we decided whether each unit was warranted as a species. As a result, we propose that these forms constitute a single genus Xystodesmus comprising six species including one new species. The newly defined Xystodesmus is characterized by high variation in gonopod morphology and conservative coloration, body form and size. The status of some populations is still uncertain because of lack of material. The tribe Xystodesmini, to which Xystodesmus belongs, and the tribe Harpaphini are so similar that we could not warrant their separation. We propose the following new synonymies: the tribe Harpaphini with the tribe Xystodesmini; Phrurodesmus Takakuwa and Nikkonus Chamberlin and Wang with Xystodesmus; Xystodesmus scabra Verhoeff, Rhysodesmus tuberculatus Takakuwa, Rh. ikaoensis Takakuwa, and Rh. kitazawai Miyosi, with X. martensii; Phrurodesmus kinshaensis Murakami with X. gracilipes (Takakuwa). Riukiaria shirozui Takakuwa, Rh. serrulatus Miyosi, and P. gracilipes Takakuwa, are transferred to Xystodesmus. We describe X. tokaiensis as a new species.     

Identification and characterization of Biomphalaria peregrina (Orbignyi, 1835) from Agua Escondida in northern Patagonia,Argentina

During a general malacological survey for freshwater gastropods in northern Patagonia, a population of Biomphalaria was encountered at Agua Escondida. Biomphalaria spp. are freshwater pulmonates of biomedical importance, uncommon in Mendoza Province, and often act as intermediate hosts for Schistosoma mansoni. By looking at both morphological and molecular characters, we describe a detailed process of identification and characterization of Biomphalaria peregrina from a location towards the extremity of its species range. A reference DNA ‘barcode’ is presented. As B. peregrina has been shown to be a permissive experimental host of S. mansoni, snails were also screened in the field for schistosomiasis and later in the laboratory using a novel polymerase chain reaction-based assay but no infections were found. Considering the transmission potential of this species, increased vigilance for intestinal schistosomiasis is recommended, especially if local environmental conditions become favourable for disease transmission, for example, through future climate change and intensification of irrigation.     

Study of the external morphology of Leptodora kindtii Focke, 1844 (Crustacea: Branchiopoda: Haplopoda), with notes on its relation to Cladocera and on conspecificity of populations of the species over the Eurasian range

Leptodora kindtii is a peculiar carnivorous crustacean widely distributed and occupying a prominent position in the freshwater planktonic communities. This species was originally found and described in the 1840–1860s and since then it has been a subject of numerous studies, morphological, embryological, behavioural, and ecological, which elucidated various aspects of its body structure and mode of life. Nevertheless, analysis of the literature and personal investigation of material on the species have led to the conclusion that the morphology of the species was not studied properly and the previous data might be incorrect and inconsistent, which obstructed proper understanding of its phylogeny, taxonomic position, and habits. In the present investigation, the external morphology of L. kindtii is described and analysed in detail, from comparative morphological and eco‐morphological aspects. Also, the morphological features of representatives of the species from different populations over the vast area of its Eurasian range have been studied with respect to their intra‐ and interpopulational variability and taxonomic significance. It has been shown that the majority of populations of L. kindtii from Europe to the Far East of Russia do not display any significant morphological differences, which testifies to their conspecificity. Only a small set of adult specimens from Lake Bolon (the Amur River basin, Far East of Russia) differed considerably from others in their small size and body proportions which implies the occurrence of another species of the genus in this region to be studied and validated in the future together with the enigmatic cave species L. pellucida Josef. In spite of high morphological peculiarity, L. kindtii possesses a number of “core” characteristics, which undoubtedly show its close relationship with other mostly small branchiopods (Ctenopoda, Anomopoda, Onychopoda) traditionally united in the taxon Cladocera whose validity has also been supported by modern molecular‐genetic studies.     

What is the matter with Corbicula fluminea (Mollusca: Bivalvia: Cyrenidiae)? Occurrence of unusual shell erosion in Northern Italy

ABSTRACT

Corbicula fluminea is a bivalve considered to be among the 100 worst invasive species in Europe due to its economic and ecological impacts in freshwater ecosystems. Here, we report for the first time a phenomenon of shell erosion observed in two distinct populations of C. fluminea collected in 2015 from two semi-natural small streams of the River Ticino hydrographic basin (Northern Italy). We measured several biometric variables in order to quantify the shell damage: length and thickness of the right valve and the shell free dry weight of each specimen and compared results with those of ‘normal’ populations from another stream of the same area. Our results confirmed that there was abnormal shell erosion and a reduction in shell thickness in both populations. We hypothesised several potential causes for the observed erosion, but none of them could provide sufficient explanation: neither the pH of the water, nor the level of calcium or total hardness of the water or granulometry of the substrates differed among streams. Similarly, predation pressure cannot be considered a reasonable explanation, since in the study area only a few animals actively prey on these bivalves and the marks they leave on the shells are completely different from the ones observed on our specimens. Lastly, we hypothesised that the bivalves may have been affected by a disease or parasitic infestation that had weakened their shells or prevented them from self-repairing and identified a fungal parasite that could possibly cause a disease to C. fluminea, namely the Ascomycota Geotrichum candidum. However, this species occurred only in one of the two abnormally eroded populations. In conclusion, a valid explanation for the morphological alteration that our study revealed has yet to be found.     

The influence of environment and competition on the distribution of Bdellocephala punctata (Turbellaria,Tricladida) in Britain

Summary

Bdellocephala punctata (Pallas), the largest British freshwater triclad, has been recorded from thirty-four, widely distributed sites in the British Isles. This distribution does not appear to be associated with any chemical or physical characteristics of the habitats. Although B. punctata has a simple pattern of population dynamics, which normally enables it to avoid competition for food with other triclads, it is suggested that this strategy is sensitive to environmental fluctuations. A decrease in relative food supply, particularly if this is due to increased breeding overlap with a confamilial, would lead to drastic reductions or extinctions of local populations and produce the observed disjunct distribution. The possibility that it may be a comparatively recent immigrant to Britain cannot be excluded.     

Mapping aquatic faunal exchanges across the Sunda shelf,South-East Asia,using distributional and genetic data sets from the cyprinid fish Barbodes gonionotus (Bleeker, 1850)

The islands of Sumatra, Java and Borneo and mainland South-East Asia are encompassed by a shallow marine shelf, the Sunda shelf. The striking faunal similarities between countries bordering the Sunda shelf have been attributed to faunal exchanges across the shelf during Pleistocene glacial maxima when sea levels fell by up to 120 m and the shelf was exposed and drained by large river systems which connected many of today's rivers. The widespread distribution of fish species reflecting extensive faunal exchange across the area is predicted to be observed within species through the broad geographic distribution of genetic lineages. Here I report a discontinuous species distribution across the region for the cyprinid fish, Barbodes gonionotus. Mitochondrial DNA control region sequence and nuclear locus data from populations sampled across the species range, suggest that the present species distribution largely reflects faunal exchanges early in the Pleistocene and that these two regional population groupings have subsequently diverged in isolation. However, the mtDNA data present some evidence for limited genetic dispersal during more recent Pleistocene low sea levels. These results broadly confirm previous work from a catfish species and suggest that freshwater faunal exchanges may have been limited across the region during the Pleistocene despite extended periods during which the Sunda shelf was exposed.     

News from a small island – first record of a freshwater shrimp (Decapoda,Atyidae, Caridina) from Peleng,Banggai Islands,Indonesia

The Indonesian island Sulawesi is well known for its fascinating fauna. Among the atyid and palaemonid freshwater shrimps described from Sulawesi are also a number of endemic species. In contrast, freshwater shrimps have never been reported from the nearby and smaller Peleng Island. Here we describe Caridina thomasi sp. nov. as a first record of an atyid freshwater shrimp from Peleng and compare it with atyids from Sulawesi and other localities. The new species is probably endemic to the island and shows some characters never described in the genus Caridina before. However, a molecular phylogeny of atyid shrimps from the Indo‐West Pacific based on mitochondrial DNA (16S) places C. thomasi within a clade of typical species of Caridina. We tentatively assign the new species to the genus Caridina and discuss the possibility of future changes in the classification of species in this genus.     

A new species of the genus Aspidisca (Ciliophora,Hypotrichida)

The morphology and taxonomy of a new freshwater species of ciliate, Aspidisca jugensis, are described. Special reference is given to the infraciliature of the organism, the variability of 16 morphological characteristics and quantitative data regarding 29 other structural characteristics of this ciliate.     

Freshwater sponges of the West Indies: Discovery of Spongillidae (Haplosclerida,Spongillina) from Cuba with biogeographic notes and a checklist for the Caribbean area

The paper reports the first finding of freshwater sponges from the Greater Antilles. Spongillidae belonging to four species of the genera Ephydatia, Anheteromeyenia, and Radiospongilla were found in a variety of freshwater habitats in western Cuba. Anheteromeyenia cheguevarai nov. sp. is described. Morphological traits of sponges from West Cuba were characterized by light microscopy and scanning electron microscopy and compared to the spongillofauna of the Nearctic and Neotropical regions and the pan‐Caribbean area. The specific richness and the discovery of a new species suggest a high diversity of the Antillean freshwater sponges although the investigated area of Cuba is relatively small.     

The reproductive cycle of Mothocya epimerica (Isopoda: Cymothoidae) a parasite of the sand smelt,Atherina boyeri (Osteichthyes: Atherinidae), in the Lesina Lagoon,Italy

The population of sand smelt, Atherina boyeri, living in the Lesina lagoon (Italy, south-western Adriatic Sea) is infested by the cymothoid isopod Mothoyca epimerica. Monthly samples of sand smelt were taken from July 1990 to May 1991. Male hosts were more infested than females. No relationship was found between the prevalence of infestation and the gonadosomatic and hepatosomatic indices of sand smelt. Mothocya epimerica is a protandric hermaphrodite. Reproduction occurs about four times from early summer to early winter, at 2 month intervals. Females produce multiple broods and their life span is at least 6 months during the reproductive season. From February to May reproduction is considerably reduced.