Lecane segersi n.sp. (Rotifera, Lecanidae) from Thailand

Lecane segersi n.sp. collected from a swamp in Udornthani province, northeastern part of Thailand, is described and figured. It is closely related to the common, warm-stenotherm Lecane papuana (Murray), but distinguished by the presence of inwardly directed antero-lateral spines.     

Comments on the morphology of Nicsmirnovius eximius (Kiser, 1948) (Aloninae,Anomopoda, Cladocera) in Thailand,with description of its male

The density, diet and habitat use of brown trout (Salmo trutta) and Siberian sculpin (Cottus poecilopus) were studied in the subalpine River Atna in southeastern Norway in the autumn during a six year period (1986–1991). There was an inverse relationship between the density of brown trout and Siberian sculpin. Diet overlap, as indicated by the Schoener index, was high between the two species, ranging between 0.48 and 0.86. Chironomid larvae and other aquatic insects were the most common food items for both species. Brown trout also consumed substantive amounts of surface insects. Siberian sculpin typically occupied sites with finer substrates and greater water depths than brown trout, even though there was considerable overlap in habitat use between the two species. Because the two species shared similar habitats, we suggest that the potential for species interactions exists, particularly at sites where density of sculpin is high.     

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.     

Trans-Tasman variation in Australasian Filinia populations

Morphological comparisons of populations of Filinia from New Zealand and Australia established the presence of an undescribed species in Lake Okaro, N.Z. Filinia novaezealandiae n. sp. is described. SEM micrographs of trophi were used to distinguish closely allied Filinia species. Filinia grandis comb. nov. is redescribed from Australia on the basis of trophi differences from F. pejleri. It is suggested that Filinia species may be more restricted than global records indicate; these records reflect the distribution of authoritative taxonomic references, not necessarily the animals they depict.     

Additions to the rotifer fauna of south-east Asia: new and rare species from north-east Thailand

Ninety-three freshwater habitats in the north-eastern part of Thailand were surveyed for rotifers during March–October 1993. Two hundred species were identified, 120 of which are new to Thailand. Brachionus africanuss Segers, B. lyratus Shephard and Trichocerca hollaerti De Smet are new to Asia. Brachionus niwati n.sp. is described and figured. Brachionus donneri Brehm, Keratella edmondsoni (Ahlstrom) and Lecane blachei Berzi, endemic to south and southeast Asia, were found also.Comments are presented on some insufficiently known taxa. Of special zoogeographic interest is the record of several species previously considered endemic to Australia. An attempt is made to characterise the Thai rotifer fauna in the light of recent developments in rotifer zoogeography.     

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.     

First record of the family Thamnocephalidae (Crustacea: Anostraca) from Southeast Asia and description of a new species of Branchinella

During a two-year investigation of freshwater microcrustaceans in Thailand, an undescribed species of fairy shrimp of the genus Branchinella Sayce, 1903 in the family Thamnocephalidae, was discovered. This is the first record of the genus and the family from Southeast Asia and the second anostracan reported from Thailand. The new species, Branchinella thailandensis n. sp. appears to be morphologically intermediate between B. kugenumaensis (Ishikawa, 1895) from Japan and east China, and B. madurai Raj, 1951 from India and Pakistan. B. thailandensis n. sp. was collected from several temporary ponds in 11 provinces of the northeast and the central Thailand, often co-occurring with Streptocephalus sirindhornae Sanoamuang, Murugan, Weekers & Dumont, 2000.     

The rotifer fauna of Lake Kud-Thing,a shallow lake in Nong Khai Province,northeast Thailand

The species composition of the rotifer fauna of Lake Kud-Thing, Nong Khai Province, northeast Thailand was investigated in a monthly sampling program from January to December 1998. A remarkably rich rotifer community consisting of 183 taxa was recorded, including 32 new records to the Thai fauna. The most diverse genera were Lecane (23.5%), followed by Trichocerca (16.9%) and Lepadella (11.5%). Lecane isanensis n. sp. is described and figured. Thirteen species (Aspelta circinator, Collotheca tenuilobata, Lecane nelsoni, Lepadella benjamini, Lepadella eurysterna, Sinantherina ariprepes, Testudinella cf. insinuata, Trichocerca abilioi, Trichocerca inermis, Trichocerca montana, Trichocerca orca, Trichocerca rosea and Trichocerca simonei) are new to the Oriental region. Notably, the record of Trichocerca orca is the first since its discovery in New Zealand in 1913. The rotifers can be classified into three groups based on duration of appearance; (1) common, perennial; (2) uncommon, perennial; and (3) uncommon, sporadic species. The high species richness of rotifers, particularly members of the genera Lecane and Trichocerca, but low diversity of Brachionus together suggest that the lake is probably not eutrophicated.     

Comparative reproductive study of two <Emphasis Type="Italic">Streptocephalus sirindhornae</Emphasis> (Branchiopoda: Anostraca) populations and F1 hybrids: a laboratory study

We investigated the effects of inbreeding and crossbreeding on the reproductive biology of two populations of fairy shrimp Streptocephalus sirindhornae from Maha Sarakham (M) and Suphan Buri (S) provinces of Thailand. Four groups of the mature fairy shrimp were experimentally mated; S × S, M × M, M × S and S × M. The data on life span, age at first spawning, number of eggs per brood and total number of eggs per female of the inbred and crossbred parent generations (P) were not significantly different. The spawning frequency and capacity of the crossbred P were significantly more productive than those of the inbred. In both populations, the majority of P had the greatest egg numbers in the 8th to 14th broods. The hatching percentages of eggs and the survival percentages of nauplii from the 10th brood of the F ₁ populations were significantly higher than those of the 20th and 1st broods. The inbreeding in F ₁ had no effect on hatching and survival percentages, sex ratios of males to females, average weight, body length and specific growth percentages. Our findings suggest that the inbred populations in P and F ₁ were able to yield eggs similar to the crossbred populations, with similar growth, hatching and survival percentages.