Transitions in functional morphology from “large branchiopods” to Cladocera: Video and confocal microscopic studies of Cyclestheria hislopi (Cyclestherida) and Sida crystallina (Cladocera: Ctenopoda)

Great diversity is found in morphology and functionality of arthropod appendages, both along the body axis of individual animals and between different life-cycle stages. Despite many branchiopod crustaceans being well known for displaying a relatively simple arrangement of many serially post-maxillary appendages (trunk limbs), this taxon also shows an often unappreciated large variation in appendage morphology. Diplostracan branchiopods exhibit generally a division of labor into locomotory antennae and feeding/filtratory post-maxillary appendages (trunk limbs). We here study the functionality and morphology of the swimming antennae and feeding appendages in clam shrimps and cladocerans and analyze the findings in an evolutionary context (e.g., possible progenetic origin of Cladocera). We focus on Cyclestheria hislopi (Cyclestherida), sister species to Cladocera and exhibiting many “large” branchiopod characters (e.g., many serially similar appendages), and Sida crystallina (Cladocera, Ctenopoda), which likely exhibits plesiomorphic cladoceran traits (e.g., six pairs of serially similar appendages). We combine (semi-)high-speed recordings of behavior with confocal laser scanning microscopy analyses of musculature to infer functionality and homologies of locomotory and filtratory appendages in the two groups. Our morphological study shows that the musculature in all trunk limbs (irrespective of limb size) of both C. hislopi and S. crystallina comprises overall similar muscle groups in largely corresponding arrangements. Some differences between C. hislopi and S. crystallina, such as fewer trunk limbs and antennal segments in the latter, may reflect a progenetic origin of Cladocera. Other differences seem related to the appearance of a specialized type of swimming and feeding in Cladocera, where the anterior locomotory system (antennae) and the posterior feeding system (trunk limbs) have become fully separated functionally from each other. This separation is likely one explanation for the omnipresence of cladocerans, which have conquered both freshwater and marine free water masses and a number of other habitats.     

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.     

Generic revision of Cypricercinae McKenzie, 1971 (Crustacea,Ostracoda), with the description of three new genera and one new species and a phylogenetic analysis of the subfamily

The Cypricercinae are one of the most speciose subfamilies of non-marine ostracods, with more than 170 described species, mostly from the tropics. Although the identity of the subfamily as such is clear, because of the presence of unifying characters such as the Triebel’s loop in the attachment of the caudal ramus, the supra-specific taxonomy of this group has long been confused because of lack of good generic and tribal characters. Here, the generic characters of the Cypricercinae are revised. Eleven genera are retained in this subfamily, including three new genera: Bradleytriebella n. gen., Nealecypris n. gen. and Pseudostrandesia n. gen. Tanycypris siamensis n. sp. is described from Thailand. In addition, five species [Bradleystrandesia fuscata (Jurine, 1820), Bradleytriebella tuberculata (Hartmann, 1964), Nealecypris obtusa (Klie, 1933), Pseudostrandesia striatoreticulata (Klie, 1932), Spirocypris horrida (Sars, 1926)] are redescribed. A key to the genera is given. We propose three tribes: the nominal tribe Cypricercini McKenzie, 1971, as well as two new tribes, Bradleystrandesiini n. trib. and Nealecypridini n. trib. To evaluate the systematic relationships within this subfamily, phylogenetic analyses, based on morphological characters of valves and soft parts, were conducted. The Neighbour Joining (NJ) tree strongly supports the classification into three independent tribes, whereas the Maximum Parsimony (MP) tree shows that Bradleystrandesiini n. trib is actually a subgroup of the Cypricercini. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Handling editor: Luigi Naselli-Flores