Karyotypic stasis and its implications for extensive hybridization events in corallivores species of butterflyfishes (Chaetodontidae).

The butterflyfishes (Chaetodontidae), emblematic inhabitants of coral reef environments, encompass the majority of known coralivorous species and show one of the highest hybridization rates known among vertebrates, making them an important evolutionary model. The vast knowledge about their life history and phylogenetic relationships contrasts with scarce information on their karyotype evolution. Aiming to expand the cytogenetic data of butterflyfishes and evaluate their karyotype evolution in association with evolutionary aspects, we conducted an extensive cytogenetic analysis in 20 species (Heniochus pleurotaenia and 19 Chaetodon spp.) from the Atlantic and Indo-Pacific regions, comparing the karyotype macrostructure and the arrangement of the 18S and 5S rDNA repetitive DNA classes in their chromosomes. The results demonstrate that butterflyfishes underwent a period of karyotypic stasis, as evidenced by their homoploid and structurally identical basal karyotype, which has 2n = 48 acrocentric chromosomes and is shared by 90% of species. Only C. trifascialis (2n = 48; FN = 50) and C. andamanensis (2n = 48; FN = 52) stood out because they both had karyotypes that diverged due to pericentric inversions. The microstructural arrays of 18S rDNA and 5S rDNA sequences were primarily comprised by single and independent loci on homologous chromosomes, indicating that there was little reshuffling among sets of orthologue chromosomes of species. Geographical comparisons revealed similar karyotypes between individuals of C. striatus from the Greater Caribbean and those of the coast of Brazil, corroborating previous data of gene flow through Amazon/Orinoco plume. The conservative chromosomal patterns in the butterflyfishes, likely overcome the limitations related to segregation and pairing of heterospecific complements and reinforce their contribution to the high degree of hybrid viability and introgression in Chaetodon species.

Chromosomes of Asian cyprinid fishes: Novel insight into the chromosomal evolution of Labeoninae (Teleostei, Cyprinidae).

The Labeoninae subfamily is a highly diversified but demonstrably monophyletic lineage of cyprinid fishes comprising five tribes and six incertae sedis genera. This widely distributed assemblage contains some 48 genera and around 480 recognized species distributed in freshwaters of Africa and Asia. In this study, the karyotypes and other chromosomal properties of five Labeoninae species found in Thailand Labeo chrysophekadion (Labeonini) and Epalzeorhynchos bicolor, Epalzeorhynchos munense, Henicorhynchus siamensis, Thynnichthys thynnoides (´Osteochilini´) were examined using conventional and molecular cytogenetic protocols. Our results confirmed a diploid chromosome number (2n) invariably 2n = 50, but the ratio of uni- and bi-armed chromosomes was highly variable among their karyotypes, indicating extensive structural chromosomal rearrangements. Karyotype of L. chrysophekadion contained 10m+6sm+20st+14a, 32m+10sm+8st for H. siamensis, 20m+12sm+10st+8a in E. bicolor, 20m+8sm+8st+14a in E. munense, and 18m+24sm+8st in T. thynnoides. Except for H. siamensis, which had four sites of 5S rDNA sites, other species under study had only one chromosome pair with those sites. In contrast, only one pair containing 18S rDNA sites were found in the karyotypes of three species, whereas two sites were found in that of E. bicolor. These cytogenetic patterns indicated that the cytogenomic divergence patterns of these labeonine species largely corresponded to the inferred phylogenetic tree. In spite of the 2n stability, diverse patterns of rDNA and microsatellite distribution as well as their various karyotype structures demonstrated significant evolutionary differentiation of Labeoninae genomes as exemplified in examined species. Labeoninae offers a traditional point of view on the evolutionary forces fostering biological diversity, and the recent findings add new pieces to comprehend the function of structural chromosomal rearrangements in adaption and speciation.

A comparative cytogenetic study of Hypsibarbusmalcolmi and H.wetmorei (Cyprinidae, Poropuntiini).

Cyprininae are a highly diversified but demonstrably monophyletic lineage of cypriniform fishes. Here, the karyotype and chromosomal characteristics of Hypsibarbusmalcolmi (Smith, 1945) and H.wetmorei (Smith, 1931) were examined using conventional, nucleolus organizing regions (NORs) and molecular cytogenetic protocols. The diploid chromosome number (2n) of H.malcolmi was 50, the fundamental number (FN) was equal to 62, and the karyotype displayed 8m + 4sm + 38a with NORs located at the centromeric and telomeric positions of the short arms of chromosome pairs 1 and 2, respectively. 2n of H.wetmorei was 50, FN 78, karyotype 14m + 14sm + 22a with the NORs at the telomeric position of the short arm of chromosome pair 2. 2n and FN in males and females were identical. Fluorescence in situ hybridization using different microsatellite motifs as probes also showed substantial genomic divergence between both studied species. In H.wetmorei, (CAG)n and (CAC)n microsatellites accumulated in the telomeric regions of all chromosomes, while in H.malcolmi, they had scattered signals on all chromosomes. Besides, the (GAA)n microsatellites were distributed along all chromosomes of H.malcolmi, but there was a strong hybridization pattern in the centromeric region of a single pair in H.wetmorei. These cytogenomic difference across the genomes of these Hypsibarbus Rainboth, 1996 species are markers for specific evolutionary differentiation within these two species.

Chromosomes of Asian Cyprinid Fishes: Genomic Differences in Conserved Karyotypes of 'Poropuntiinae' (Teleostei, Cyprinidae).

The representatives of cyprinid lineage 'Poropuntiinae' with 16 recognized genera and around 100 species form a significant part of Southeast Asian ichthyofauna. Cytogenetics are valuable when studying fish evolution, especially the dynamics of repetitive DNAs, such as ribosomal DNAs (5S and 18S) and microsatellites, that can vary between species. Here, karyotypes of seven 'poropuntiin' species, namely Cosmochilus harmandi, Cyclocheilichthys apogon, Hypsibarbus malcomi, H. wetmorei, Mystacoleucus chilopterus, M. ectypus, and Puntioplties proctozysron occurring in Thailand were examined using conventional and molecular cytogenetic protocols. Variable numbers of uni- and bi-armed chromosomes indicated widespread chromosome rearrangements with a stable diploid chromosome number (2n) of 50. Examination with fluorescence in situ hybridization using major and minor ribosomal probes showed that Cosmochilus harmandi, Cyclocheilichthys apogon, and Puntioplites proctozystron all had one chromosomal pair with 5S rDNA sites. However, more than two sites were found in Hypsibarbus malcolmi, H. wetmorei, Mystacoleucus chilopterus, and M. ectypus. The number of chromosomes with 18S rDNA sites varied amongst their karyotypes from one to three; additionally, comparative genomic hybridization and microsatellite patterns varied among species. Our results reinforce the trend of chromosomal evolution in cyprinifom fishes, with major chromosomal rearrangements, while conserving their 2n.

Distribution of Ecnomus McLachlan, 1864 (Trichoptera, Ecnomidae) from the Lower Mekong River with a description of Ecnomusstungtrengensis new species.

Background: Trichoptera were surveyed from four different physiographic regions of the Lower Mekong River, including the Northern Highlands, the Khorat Plateau, the Tonle Sap Basin and the Mekong Delta in Myanmar, Laos, Thailand, Cambodia and Vietnam. New information: Twenty-three species of the genus Ecnomus, including a new species, were identified and mapped. Ecnomusmammus Malicky & Chantaramongkol, 1993 is a common species which is found from Tonle Sab Basin and Mekong Delta. Ecnomusalkmene Malicky & Chantaramongkol, 1997, E.volovicus Malicky & Chantaramongkol, 1993 and Ecnomusquordaio Malicky, 1993 are the common species in the area of the Northern Highlands and the Khorat Plateau. Ecnomusplotin Malicky & Laudee 2010 is found in the Mekong Delta. Ecnomustriangularis Sun, 1997 is a new species record for Southeast Asia. In addition, E.stungtrengensis sp. n. is described and illustrated. The male genitalia of E.stungtrengensis sp. n. are clearly different from those of other species in the genus Ecnomus by the shape of superior appendages which are slender and bent downwards distally in lateral view.

The larvae of caddisfly species (Insecta, Trichoptera) in northern Thai streams and their relationships to environmental variables.

There have been few systematic studies on Trichoptera larvae in Thailand. The larval stages of the endemic species remain mostly unknown. Continued work on describing the larval stages of species will improve the precision of water quality monitoring metrics and enable ecological studies of species. This paper describes the unknown larvae of Hydropsyche pallipenne Banks 1938 and Hydropsyche askalaphos Malicky & Chantaramongkol 2000, with their identities deduced from the fact that both the larvae described here and identifiable adult specimens were sampled at the same location. Also, the effects of environmental variables on the distribution of caddisfly larvae in northern Thai streams were investigated. In total, 41 taxa from seven streams were identified, representing twenty-four genera and thirteen families. The Hydropsychidae were the most numerous family collected, accounting for 1,487 specimens (54%). Trichopteran abundance (for Triaenodes sp., Marilia sumatrana, Amphipsyche meridiana, Hydropsyche askalaphos, Leptocerus sp., Ganonema sp., Chimarra cf. akkaorum, Cheumatopsyche cf. dubitans, Macrostemum sp., and Leptocerus sp.) is influenced by environmental factors such as water temperature, dissolved oxygen, total dissolved solids, ammonia nitrogen, nitrate nitrogen, and pH. Because of their significant responses to environmental fluctuations, the caddisfly assemblage proved useful in identifying variations in water quality conditions in northern Thai streams.

New species of caddisflies (Trichoptera, Ecnomidae, Polycentropodidae, Psychomyiidae) from Mekong tributaries, Laos.

Four new species of caddisflies are added to the fauna of Mekong River, Laos. Described and illustrated are Ecnomus petchanaae sp. nov. and E. boonsawaengae sp. nov. (Ecnomidae), Polyplectropus proukaewi sp. nov. (Polycentropodidae), and Psychomyia srichanai sp. nov. (Psychomyiidae) from tributaries of the Mekong River, Laos. Ecnomus petchanaae sp. nov. can be distinguished by the characters of the superior appendages, which are slender and club-shaped in lateral view. In E. boonsawaengae sp. nov., the inferior appendages are tubular with a concave incision subapically and truncated apex. Polyplectropus proukaewi sp. nov. has the distal process of the dorsal branch of the inferior appendage close to the base of the inferior appendages and the length of the process is half of inferior appendages. Psychomyia srichanai sp. nov. can be distinguished by the structure of the dorsal branches of the harpagones and apical sclerite. The outer branches of the harpago in the latter species are bifurcated and bent 90° degrees outward, and the inner dorsal branches of harpago are curved outward. The apical sclerite is indiscernible.

Karyotype diversity and evolutionary trends in the Asian swamp eel Monopterus albus (Synbranchiformes, Synbranchidae): a case of chromosomal speciation?

BACKGROUND: Synbranchidae or swamp eels are fishes belonging to the order Synbranchiformes that occur in both freshwater and occasionally in brackish. They are worldwide distributed in tropical and subtropical rivers of four different continents. A large degree of chromosomal variation has been found in this family, mainly through the use of conventional cytogenetic investigations. Inside this group, a still almost unexplored species under the cytogenetic point of view is the Asian swamp eel Monopterus albus, a widely distributed species throughout Asia. Here, we tested the hypothesis of chromosomal speciation, where a case of sympatric speciation may occur as the primary consequence of chromosomal rearrangements. We performed a comparative chromosomal analysis of M. albus from 22 different localities in Thailand, using distinct staining methods (C-banding, Ag-NO3, and Chromomycin A3), and FISH with repetitive DNA probes (5S rDNA, 18S rDNA, Rex1 element and microsatellite repeats). RESULTS: This approach evidenced two contrasting karyotypes (named karyomorphs A and B) that varied concerning their 2n and repetitive DNAs distribution, where chromosomal fusions and pericentric inversions were involved in such differentiation. While the karyomorph A has 2n = 24 chromosomes, the karyomorph B has only 2n = 18, both with NF = 24. In addition, karyomorph A contains only acrocentric chromosomes, while karyomorph B contains three unique metacentric pairs. These features highlight that M. albus has already gone through a significant genomic divergence, and may include at least two cryptic species. CONCLUSIONS: This marked chromosomal differentiation, likely linked to the lifestyle of these fishes, point to the occurrence of a chromosomal speciation scenario, in which fusions and inversions had a prominent role. This highlights the biodiversity of M. albus and justifies its taxonomic revision, since this nominal species may constitute a species complex.

Three new species of Ceraclea Stephens 1829 (Trichoptera: Leptoceridae) from Southeast Asia.

Three new species of Ceraclea (Leptoceridae) from Southeast Asia are described and illustrated: Ceraclea (Athripsodina) trisdikooni n. sp. from Myanmar, C. (A.) thongnooi n. sp. from Thailand and Myanmar and C. (A.) thongpongi n. sp. from Laos. Ceraclea trisdikooni n. sp. is distinguished from other species by its inferior appendages recurved ventrad nearly 180° apically. The apex of the basal segment of each inferior appendage is more pointed. In ventral view, each inferior appendage of the new species has an obvious basoventral lobe with numerous long setae. Ceraclea thongnooi n. sp. is distinguished from those by inferior appendages that are each shaped like a seahorse head both in lateral view and ventral view. Ceraclea thongpongi n. sp. is distinguished from other species by the rectangular preanal appendages. In dorsal view, the apical end of segment X is oval and notched apically; in ventral view, the subapicodorsal lobe of each inferior appendage is rounded and straight.