Robert B. Angus

Relationship between macroinvertebrate fauna and environmental variables in small streams of the Dominican Republic

Field assessment methods for freshwater macroinvertebrates and water quality in tropical small-island states were assessed in the Dominican Republic. Macroinvertebrate samples were collected from 26 river sites within the Dominican Republics Yaque del Norte river catchment. Environmental data on geographical, physical and chemical variables were also collected from each site. The Biological Monitoring Working Party score and total numbers of Ephemeroptera and Trichoptera were calculated for each site. Physico-chemical and biological data sets were ordinated by principal components analysis and non-parametric multi-dimensional scaling, and the biotic and abiotic data sets were correlated to determine the most influential factors determining site similarities. Macroinvertebrate assemblage structure was correlated with declining water quality: however, a high correlation between water quality and altitude confounded an unqualified interpretation of impairment.

A reciassification of the Deronectes-group of genera (Coleoptera: Dytiscidae) based on a phylogenetic study

Within the Hydroporini, the Deronectes-group of genera are characterised by having the mesosternal fork and metasternal keel separated (or secondarily fused), the ventral elytral ridge posteriorly elevated but without ligula, and the male protarsus ventrally without adhesive discs. The genera of the group, viz. Deronectes Sharp, 1882, Stictotarsus Zimmermann, 1919, Scarodytes Gozis, 1914, and Nebrioporus Regimbart, 1906, are reclassified and a hypothesis of their phylogenetic relationships is presented. Karyotypes of 14 European species of Hydroporinae are discussed. Nebrioporus is extended to include most species with parameres with apex hook-like and sclerotised, with Potamonectes Zimmermann, 1921, as a junior synonym, syn. n. Nebrioporus s. str. and Zimmermannius Guignot, 1941 are recognized as subgenera of Nebrioporus. Scarodytes is kept as a separate genus because of its characteristic ventral sculpture and seemingly higher number of autosomes than in Nebrioporus. The species with simple parameres previously placed in Potamonectes are transferred to Stictotarsus together with S. bertrandi (Legros, 1956), previously in Deronectes. Consequently, Trichonectes Guignot, 1941, is a junior subjective synonym of Stictotarsus, syn.n. In an appendix, a check-list is provided for the species of the Deronectes-group. The subgenus Nebrioporus s. str. is divided into three species-groups: the kilimandjarensis-, the abyssinicus-, and the depressus-groups.

A chromosomal investigation of five European species of Anacaena Thomson (Coleoptera: Hydrophilidae)

Chromosomal data are given for five European species of Anacaena. A. bipustulata, A. limbata and A. lutescens have the diploid number 16 + XY (male), 16 + XX (female). A. globulus has the number 14 + XY/XX, while in A. rufipes the number is 10 + neo-XY (male). Chromosomal data from various Hydrobiinae suggest that a diploid number of 16 + XY or XX is normal in this subfamily, and that the karyotypes of A. globulus and A. rufipes result from reductions in number. In A. globulus the sizes and shapes of the chromosomes suggest that there may have been loss of the centromere from one of the smaller chromosome pairs, with the two arms fusing with two different autosomes. In A. rufipes the process appears to have gone further, with the original sex chromosomes fusing with a pair of autosomes to give a neo-XY. The karyotypes of all five species are distinctive, confirming the recognition of A. lutescens as a distinct species. In populations of A. lutescens comprising only females, all specimens were heterozygous for a deletion polymorphism in one pair of autosomes. This deletion was not found in bisexual populations. Two of the females-only populations included a proportion of triploid individuals, and this, in conjunction with the deletion polymorphism, is taken as evidence that these populations are parthenogenetic. Present evidence is not considered sufficient to show whether the parthenogenesis has a single origin in A. lutescens or whether it is polyphyletic, though the discovery of consistent small differences in the relative length of two autosomes, between parthenogenetic and bisexual populations, suggests a single origin. The triploid karyotypes show small differences between the two populations in which they are known, and this suggests that triploidy has arisen after the establishment of parthenogenesis, and is of multiple origins. In most cases the only tissue available for chromosome preparations was mid-gut of adult beetles, and the methods used are described.

Suphrodytes Des Gozis a valid genus, not a subgenus of Hydroporus Clairville (Coleoptera: Dytiscidae)

Suphrodytes Des Gozis is shown, on the basis of the morphology of the prosternal process and the arrangement of the fertilisation tract of the female, to be a valid genus, with one species, Dytiscus dorsalis Fabricius, 1787. The northern Palaearctic species, Hydroporus arcticus Thomson, 1854, H. tomentosus Poppius, 1905, H. submuticus Thomson, 1875 and H. lapponurn Gyllenhal, 1808, formerly placcd together with S. dorsalis in Hydroporus (Suphrodytes) are shown to be good Hydroporus. Hydroporus arcticus and H. tomentosus are sunk as subspecies of the Nearctic H. notabilis LeConte, 1850.

Taxonomy and chromosomal analysis of Egyptian Synchortus imbricatus (Klug) (Coleoptera: Noteridae)

Synchortus imbricatus (Klug) is recorded for the first time in Egypt. Egyptian specimens are much smaller than the type series from Mozambique, but Sudanese material described by Omer‐Cooper shows features linking the two extremes. A lectotype is designated for S. imbricatus (Klug). Regimbarts types of S. simplex var. echinatus have been studied, as well as males from the same locality. They are shown to be S. imbricatus and a lectotype is designated. Sharps types of S. sparsus and S. aciculatus have been studied and found to be conspecific with S. simplex Sharp, as suggested by Omer‐Cooper (1972). The chromosomes of Egyptian S. imbricatus are shown to comprise 12 pairs of autosomes plus sex chromosomes which are X1X2Y in the male and X1X1X2X2 in the female, as in Noterus (Bilton, 1992). Unlike Noterus in S. imbricatus the Y‐chromosome is the largest in the nucleus and is largely heterochromatic.

A new Siberian Agabus Leach, with notes on the other species with clubbed male antennae (Coleoptera: Dytiscidae)

Agabus vereschaginae sp. n. is described and its systematic position discussed in the light of revisional notes on A. serricornis (Paykull), A. clavicornis Sharp and A. antennatus Leech. The synonymy of A. clavicornis and A. verus Brown is confirmed. A British Pleistocene fossil, formerly identified as A. clavicornis, is shown to belong to A. serricornis, but its pronotal sculpture resembles that found in Siberian rather than Scandinavian specimens.

Further karyosystematic studies of the Boreonectesgriseostriatus (De Geer) group of sibling species (Coleoptera, Dytiscidae)-characterisation of B.emmerichi (Falkenström, 1936) and additional European data.

Abstract A lectotype is designated for the Tibetan species Deronectes emmerichi Falkenström, 1936 (Currently Boreonectes emmerichi (Falkenström)), and its habitus, as well as the median lobe and parameres of its aedeagus, are figured along with additional comparative material. Material of Boreonectes emmerichi from Sikkim (BMNH) represents the first record of a Boreonectes Angus, 2010 species from India. The karyotype of Boreonectes emmerichi is described as having 26 pairs of autosomes plus sex chromosomes which are X0 (♂), XX (♀). The karyotype is most like that of Boreonectes macedonicus (Géuorguiev, 1959), but with slight differences. Additional chromosomal information is given for Boreonectes griseostriatus griseostriatus (De Geer, 1774) in the French Alps, Boreonectes griseostriatus strandi (Brinck, 1943) on the Kola Peninsula, Boreonectes multilineatus (Falkenström, 1922) in the Pyrenees and Boreonectes ibericus (Dutton & Angus, 2007) in the Spanish Picos de Europa.

A further chromosomally distinct sibling species of the Helophorus minutus complex from Morocco, with additional notes on Spanish H. calpensis Angus, 1988 (Coleoptera: Helophoridae)

Helophorus atlantis sp. n. is described from the Moyen Atlas region of Morocco (Ifrane and Fes). Morphologically it appears indistinguishable from the more lightly built species of the H. minutus group (H. minutus Fabricius, 1775 and H. calpensis Angus, 1988), and its karyotype is most similar to that of H. calpensis, but with important differences, especially in the sex chromosomes. An additional karyotype of H. calpensis, from the Coto Doñana, Provincia de Huelva, Spain provides a major extension to the known distribution of this species, hitherto known only from its type locality (Tarifa, Provincia de Cádiz) and also confirms the chromosomal distinction between H. calpensis and H. atlantis.

Chromosomal Analysis of Neohydrocoptus jaechi (Wewalka) and Canthydrus diophthalmus (Reiche & Saulcy) (Coleoptera: Noteridae)

Neohydrocoptus jaechi (Wewalka) is recorded for the first time in Egypt. It is very similar to N. angolensis (Peschet), but there are aedeagal differences. The karyotype consists of 6 pairs of autosomes and sex chromosomes which are neo-XY (♂) and neo-XX (♀). C-banding shows that the sex chromosomes of Canthydrus diophthalmus (Reiche & Saulcy) are not the small pair suggested by Bilton (1992), but are one of the largest pairs, with the Y-chromosome totally heterochromatic. The implications of these findings are considered in the light of Belkacemes (1991) work on the phylogeny of Noteridae. Neohydrocoptus is placed among the group of more primitive genera, outside the closely-knit group of higher Noteridae, while Canthydrus is placed right at the top of the higher Noteridae. The neo-XY sex chromosomes of Neohydrocoptus could be a primitive condition for the family, while the system found in Canthydrus is derivable from that of Synchortus Sharp (Saleh Ahmed et al., 1997) (one of Belkacemes basal genera of the higher Noteridae) by loss of the mainly heterochromatic X2-chromosome, leaving the more normal X1-chromosome and the Y, which is almost entirely heterochromatic in Synchortus and completely so in Canthydrus.

A chromosomal analysis of Nepa cinerea Linnaeus, 1758 and Ranatra linearis (Linnaeus, 1758) (Heteroptera, Nepidae)

Abstract An account is given of the karyotypes and male meiosis of the Water Scorpion Nepa cinerea Linnaeus, 1758 and the Water Stick Insect Ranatra linearis (Linnaeus, 1758) (Heteroptera, Nepomorpha, Nepidae). A number of different approaches and techniques were tried: the employment of both male and female gonads and mid-guts as the sources of chromosomes, squash and air-drying methods for chromosome preparations, C-banding and fluorescence in situ hybridization (FISH) for chromosome study. We found that N. cinerea had a karyotype comprising 14 pairs of autosomes and a multiple sex chromosome system, which is X1X2X3X4Y (♂) / X1X1X2X2X3X3X4X4 (♀), whereas R. linearis had a karyotype comprising 19 pairs of autosomes and a multiple sex chromosome system X1X2X3X4Y (♂) / X1X1X2X2X3X3X4X4 (♀). In both N. cinerea and R. linearis, the autosomes formed chiasmate bivalents in spermatogenesis, and the sex chromosome univalents divided during the first meiotic division and segregated during the second one suggesting thus a post-reductional type of behaviour. These results confirm and amplify those of Steopoe (1925, 1927, 1931, 1932) but are inconsistent with those of other researchers. C-banding appeared helpful in pairing up the autosomes for karyotype assembly; however in R. linearis the chromosomes were much more uniform in size and general appearance than in N. cinerea. FISH for 18S ribosomal DNA (major rDNA) revealed hybridization signals on two of the five sex chromosomes in N. cinerea. In R. linearis, rDNA location was less obvious than in N. cinerea; however it is suggested to be similar. We have detected the presence of the canonical “insect” (TTAGG)n telomeric repeat in chromosomes of these species. This is the first application of C-banding and FISH in the family Nepidae.