The sex ratios of Trichoniscus pusillus Brandt (Crustacea: Oniscoidea)

Summary

The frequency of males in the bisexual and parthenogenetic forms of T. pusillus is assumed to be 0·5 and 0·03 respectively. This assumption for the bisexual form is tested with culturing, which demonstrates a numerical equality of the sexes and produces no evidence of differential survivorship of the sexes, and by field sampling of a suspected bisexual population. A statistical technique using the difference in male frequency in the two forms to determine the composition of T. pusillus agg. is presented. Other work on sex ratio in isopods is reviewed.     

Occurrence of sexual morphs in Trama troglodytes von Heyden, 1837 (Hemiptera,Aphididae)

The root-feeding aphids of the tribe Tramini have been cited as a possible case of ancient apomixis, as there are no substantiated records in the literature of a functional bisexual generation, even in common and well-known European species. The karyotypic variation found in this group, involving considerable structural heterozygosity within species, also pointed to the decay of diploidy that would be an expected consequence of loss of sexuality and absence of meiosis. However, we have now found a small number of oviparae (mating females) and males in populations of the common species Trama troglodytes. Fertilized eggs were not obtained, but adult oviparae contained large, yolky eggs. The single adult male was apterous, small and blind, but had fully developed mouthparts and genitalia, and contained mature sperm. Both sexual morphs are described, and the karyotrypic variation is reassessed in the light of these findings. Occasional sexual reproduction is in concordance with recent molecular evidence that some recombination occurs in T. troglodytes and related species.     

Distribution of bisexual and unisexual species in the aphid genus Colopha Monell (Aphididae: Eriosomatinae), with the description of a new species in Japan

Aphids of the genus Colopha are represented by three bisexual and three unisexual species. The bisexual species are associated with two Ulmus species that are most closely related, being distributed disjunctively in Europe and eastern North America on the host plants. A new unisexual species of Colopha, collected from Setaria chondrachne (Poaceae) in Japan, is described under the name Colopha setaricola sp. nov. The distribution of the three unisexual species is discussed in relation to aphid‐plant associations and historical changes in the distribution of the host plants. It is suggested that these unisexual species have persisted on the secondary hosts through parthenogenetic reproduction since the extinction of the primary host plants, Ulmus species section Blepharocarpus. Therefore, the unisexual species in Colopha exemplify Mordvilko's hypothesis that unisexual species on the secondary host plants have remained as relics in the region where the primary host was once distributed but then became extinct.     

Parthenogenetic Darevskia lizards mate frequently if they have the chance: a quantitative analysis of copulation marks in a sympatric zone

Several Caucasian rock lizards of the genus Darevskia of hybrid origin are known to reproduce parthenogenetically. Local communities can be composed exclusively of parthenogens, though syntopy with bisexual members of the genus may occur. In some localities, reproduction between bisexual and parthenogenetic Darevskia has been previously reported based on lizard intermediate morphology and karyology (3n, 4n). However, the frequency of such heterospecific matings remains unknown. We indirectly quantified the reproductive interactions through the inspection of copulation marks in females in a mixed Darevskia community from Kuchak (Armenia) composed of two hybrid parthenogens (D. armeniaca and D. unisexualis), one bisexual species (D. valentini) and their putative backcrosses. A total of 139 adults were randomly collected and photographed. Females were later measured (SVL), inspected for inguinal marks and ranked from 0 (no scars) to 3 (≥ 3 scars). The lizard species and ploidy determination was ensured by a parallel microsatellite analysis. Sex-ratio in the community was extremely biased due to the high abundance of parthenogenetic females. All female types displayed copulation marks with frequencies varying from 80% in D. valentini to 64% in D. armeniaca. Remarkably, 7 out of 11 (64%) backcross females also showed marks. In the most abundant D. armeniaca, the prevalence and intensity of copulation marks increased with body size, just as predicted for polygynous female lacertids. These results indicate that copulation between parthenogenetic and bisexual species in Darevskia mixed communities is common and driven by sexual selection, thus reinforcing previous suggestions of reproductive interaction in syntopy. Evolutionary implications of these findings are discussed.     

Taxonomic revision of Steganacarus (Steganacarus) magnus (Nicolet, 1855) (Acarida,Oribatida)

The classical taxon, Steganacarus (Steganacarus) magnus (Nicolet, 1855) is redescribed on the basis of topotypic material. The study and the comparison of many European and North African populations reveals a variation in the size of the anterior notogastral tectum and consequently enables another classic entity, S. (Steganacarus) anomalus (Berlese, 1883), to be put into synonymy. These two different ecophenotypes, in the authors' opinion, seem to be linked to the presence of xeric low-altitude southern environments (S. (S.) magnus f. anomala) or cool higher-altitude mid-northern environments (S. (S.) magnus f. magna).     

The juvenile stages of Parastacus brasiliensis (von Martens, 1869) (Crustacea,Decapoda, Parastacidae)

The family Parastacidae consists of the freshwater crustaceans popularly known as crayfishes or crawfishes. Only the genus Parastacus occurs in Brazil, with P. brasiliensis (von Martens, 1869) endemic to the state of Rio Grande do Sul in southern Brazil. Parastacids have direct development, ecloding as juveniles. In laboratory‐reared specimens, juvenile I stage is similar in morphology to the adult, with no setae on most appendages, absence of uropods and presence of a hook on the dactyl of pereiopods 4 and 5. The juvenile II retains juvenile I characteristics but has more setae, which are more varied in morphology. The juvenile III possesses setae as the adults, fully formed uropods and the hooks on pereiopods 4 and 5 are substituted by an apical rectilinear dactylus.     

Foraminiferan (Protozoa) epizoites on the anthuridean (Crustacea,Isopoda) Calathura brachiata (Stimpson)

Foraminiferan epizoites were studied on the isopod Calathura brachiata (Stimpson). Most individuals found belonged to the genus Cibicides. The foraminiferans were either rare or quite frequent on Calathura brachiata, indicating patchy occurrence of living foraminiferans. They were most frequent on the anterior part of the body (head, first pereonites) and the first two pairs of legs (pereopods). This pattern, which is unusual among foraminiferan epizoites on isopods, is explained by habitat selection of the foraminiferans and the behaviour of the isopod, which presumably rests between feeding with the anterior part of the body held in an upward position, allowing foraminiferans to settle on mouthparts and on the legs (first two pereopods) used in grasping prey. The size range of the foraminiferans indicates that settling of foraminiferans from the water column is more important for the development of foraminiferan epibiosis on Calathura than migration of individuals from the bottom and this may be the general pattern for most isopod species.     

Postmarsupial development of Atlantoscia floridana (van Name, 1940) (Crustacea,Isopoda, Oniscidea): the manca stages

In this paper we describe the postmarsupial development of the manca stages of Atlantoscia floridana (van Name, 1940). Ovigerous females were collected in Reserva Biológica do Lami, Porto Alegre, RS, Brazil and separately reared in small containers at 20°C (±1°C). After birth each newborn (manca I) was reared separately in order to observe the subsequent moults. In a period of about 12 h the animals underwent the first moult. The manca II stage lasts 9.16±1.57 days while manca III takes up a period of 9.96±1.05 days. Growth was observed through measurements of cephalothorax width. The three manca stages are described, illustrated and compared with the adults. The main distinguishing characteristics among mancas I, II and III are presented as well as the b/c and d/c co-ordinates of the noduli laterales.     

Some European Processidae (Crustacea,Decapoda, Caridea)

Summary

The name Processa canaliculata Leach has been applied to a species other than that to which the holotype belongs. The species P. canaliculata Nouvel & Holthuis non Leach has no valid name; it is re-named P. nouveli, with type material from Monaco.

P. nouveli and P. canaliculata have been considered to be conspecific by one recent author. New characters for their separation are described from Irish Sea material.

The northern form of P. nouveli differs from the Mediterranean form sufficiently to be placed in a separate subspecies. The name P. nouveli holthuisi is proposed for it, with type material from the Irish Sea.

The distribution of the four species and subspecies of Processa known to occur in northern Europe is reviewed.     

Biology of a tropical intertidal population of Cerithium atratum (Born, 1778) (Mollusca,Gastropoda)

The spatial distribution, population structure and secondary production of the gastropod Cerithium atratum were studied in the intertidal region of Engenho d'Água Beach in São Sebastião Channel on the northern coast of the state of São Paulo, Brazil, from May 1998 to April 1999. Twenty monthly samples were taken using a 0.25×0.25?m quadrat in each of two areas. Individuals showed a clustered dispersion pattern in both areas throughout the sampling period. Abundance and mean shell size were related to period of the year and to intertidal level, although no consistent pattern could be described when comparing the two sampling areas due to significant interaction between time and locality. Migratory events were evidenced by marked year-round variations in the frequency of individuals in the largest size classes. Thus, the size structure of this population could not be explained by recruitment and growth alone. Almost 90% of the intertidal population was represented by small individuals that recruited at the beginning of the sampling period (May to August 1998). The intertidal population was composed of annual cohorts formed by individuals recruited in different years. Each annual cohort could be divided into sub-cohorts with closely spaced recruitment periods in the same breeding season. The growth and annual P/B ¯ ratio (where P is the annual somatic production and B ¯ is the mean annual biomass) was estimated for the first year of life of recruits from 1998 occupying the intertidal region. Individuals may have an increment of up to 15?mm in shell length during the first year of life, but the growth was more pronounced in summer months. The high value of P/B ¯ (3.902) was a consequence of the dominance of small-sized individuals, which have a higher weight-specific increment than large-sized ones.     

Rediscovery of Gastrostyla setifera (Engelmann, 1862) Kent, 1882: morphology and divisional morphogenesis (Ciliophora,Hypotrichida)

The morphology and morphogenesis of the poorly known hypotrichous ciliate Gastrostyla setifera, isolated from a freshwater pond near Harbin, China, are described from both living and protargol silver-impregnated specimens. The Harbin population of this species is characterized thus: medium-sized freshwater Gastrostyla, 150-205 × 70-95 μm in vivo, ellipsoid in shape but somewhat narrowed posteriorly. Contractile vacuole located in left half of mid-body region. On average 48-56 (mean 52) adoral membranelles; 10 frontal and 9-11 ventral cirri; 23-26 left and 30-34 right marginal cirri; usually with four complete dorsal kineties and two dorsomarginal kineties; three caudal cirri present at posterior margin; invariably two macronuclear nodules and two micronuclei. Its morphogenesis reveals the following characteristics: (1) adoral zone of membranelles (AZM) in the opisthe arises from the new oral primordium while the proter inherits the entire parental structure; (2) 10 frontal, 9-11 ventral and five transverse cirri are derived from five frontoventral transverse cirral anlagen together with the undulating membrane anlage; (3) left and right marginal cirri are derived from new anlagen which originate within the old marginal rows; (4) the generation of the dorsal kineties is of the 'two-group-mode'; three left primary dorsal anlagen and two dorsomarginal anlagen appear as two groups in both dividers from which all dorsal kineties are derived (the fourth kinety is formed due to the fragmentation of the third anlage); (5) one caudal cirrus is formed at the ends of each of the first, second and fourth dorsal anlagen.     

Taxonomy of Sphaeromeria, Artemisia , and Tanacetum (Compositae, Anthemideae) based on randomly amplified polymorphic DNA (RAPD)

Relationships within, between, and among the Anthemideae genera Sphaeromeria, Artemisia , and Tanacetum were investigated using 238 randomly amplified polymorphic DNA (RAPD) markers obtained from twenty 10-mer primers amplified on genomic DNA. Forty-one populations from 16 taxa (15 species) were studied. Jaccard's coefficient of similarity and UPGMA clustering analysis were used to construct phenograms. T tests were used to make comparisons between samples at various systematic levels. DNA markers were 75% similar for conspecific populations. Sixteen Sphaeromeria populations (5 species) showed an average interspecific similarity of 21%. Interspecific similarity among 23 Artemisia populations (8 species with 2 subspecies of A. tridentata included) averaged 27%. Two Tanacetum species (1 population each) were 89% similar. The high similarity of Tanacetum species was in the range of observed values for conspecific populations; indeed those 2 species ( T. vulgare and T. boreale ) have been considered conspecific by some authors. The 3 subgenera of Artemisia studied ( Artemisia, Dracunculus , and Tridentatae ) formed separate groups. In comparison among the genera, Sphaeromeria was 18% similar to Artemisia (more similar to subgenus Tridentatae than the other Artemisia subgenera); intergeneric comparisons of Sphaeromeria and Artemisia and Tanacetum , which supports previously established morphological distinctions. Sphaeromeria potentilloides may be misplaced in the genus Sphaeromeria based on DNA marker results. It is likely that North American Anthemideae are circumboreal derivatives of ancestral Eurasian stock and that Sphaeromeria is derived from an Artemisia -like ancestor.     

Epibiontic communities on the freshwater shrimp Caridina ensifera (Crustacea,Decapoda, Atyidae) from Lake Poso (Sulawesi,Indonesia)

The epibiont communities of the freshwater shrimp Caridina ensifera, endemic to Lake Poso (Sulawesi, Indonesia), were analysed for the first time based on their morphological and biometrical characteristics and taxonomic position. Seven ciliated protozoans and a rotifer were examined: three suctorian ciliate protozoan species (Acineta sulawesiensis, Podophrya maupasi, and Spelaeophrya polypoides), three peritrichs (Zoothamnium intermedium, Vorticella globosa, and Cothurnia compressa), a haptorid (Amphileptus fusidens), and the rotifer species Embata laticeps. A mean number of 314.6 epibionts was found per shrimp specimen. The distribution of the epibiont species on the surface of the basibiont was recorded, to allow calculation of the density on the different colonized individuals of C. ensifera and on each anatomical unit of the shrimp. The most abundant species, Zoothamnium intermedium and Acineta sulawesiensis, were also the ones most widely distributed. The statistical analysis showed that Zoothamnium, Acineta, Podophrya, and Embata were the epibiont genera most widely distributed on the basibiont, and the pairs of epibiont genera Zoothamnium–Embata, Podophrya–Acineta, Spelaeophrya–Amphileptus, and Cothurnia–Vorticella followed a similar pattern of distribution. There was a significant difference between the distribution patterns of the different epibiont species on the shrimp. The analysis of the densities of the epibionts throughout the longitudinal axis of the shrimp showed a gradient from the anterior to the posterior end of the body, and a significantly different distribution of each epibiont species. Their colonization follows a certain pattern of behaviour, the species occupying the available substratum, with particular requirements of each functional group, but with a trend resulting in equilibrium among species and groups, compensating for diversity and density. The possible adaptations of the epibionts, as well as the colonization patterns are discussed.     

Anatomy of the alimentary canal of Parandania boecki (Stebbing, 1888) (Crustacea,Amphipoda, Stegocephalidae) from the Antarctic Ocean

The alimentary canal of Parandania boecki (Stebbing, 1888) has been investigated. Examination of gut contents shows that this species feeds on Cnidaria. The oesophagus, stomach and midgut are adapted to ingest and store large masses of soft food. The opening of the oesophagus is closed by a labral operculum and ‘double gate’ — like narrowings at the stomach entrance. The foregut is extremely enlarged and the funnel region is reduced. The midgut very probably is not connected to the foregut, and the resorption of food takes place only in the midgut caeca. The midgut forms a shallow, crescentic cavity over the midgut caeca.     

The systematics of Microtus (Terricola) savii group: an odonthometrical perspective (Mammalia,Rodentia, Cricetidae)

ABSTRACT

The morphology of the first lower molar of Microtus savii group (M. brachycercus, M. nebrodensis, M. savii) is complex and highly variable. A morphometrical analysis done by grouping the samples into large geographical sets reveals the differentiation between northern, central and southern populations. The specific status of M. nebrodensis is confirmed while it is not possible to separate M. brachycercus. The subspecies M. savii tolfetanus and M. brachycercus niethammericus are, respectively, not well and moderate distinguished from the other populations. Finally, the distinction of M. savii group from other species of European voles is also confirmed.     

A new species of Protocladorchis (Paramphistomidae,Dadaytrematinae) from Pangasius nasutus (Bleeker, 1863) in Thailand

Protocladorchis chinabutae sp. nov. from Pangasius nasutus in Thailand differs from Protocladorchis burmanicus mainly in the size, shape and position of the testes and from P. pangasii in body shape, egg size and the shape of the pharyngeal sacs. The genus has not previously been reported from Thailand.     

The identity of Alcyonidium gelatinosum (Linnaeus, 1761) (Bryozoa: Ctenostomatida)

Since 1984, when Alcyonidium gelatinosum (Linnaeus, 1761) was shown not to be the free-growing species hitherto known by that name, it was assumed to be the valid name for A. polyoum (Hassall, 1841). We have established that its neotype is not a specimen of A. polyoum but of A. reticulum Ryland and Porter (2000) introduced for A. mytili auctt. non Dalyell (1848). A. reticulum must accordingly be relegated to the synonymy of A. gelatinosum. A. polyoum is a valid but different species and the provenance of Hassall's specimens is discussed. We deliberate the identity of the nominate species in Linnaeus' Fauna svecica (1761). While the occurrence of A. polyoum in the Kattegat-Mecklenburg Bight sea area cannot wholly be ruled out, the common species is A. reticulum (i.e. A. gelatinosum). The neotype does therefore represent the Swedish specimen(s) used by Linnaeus, and the identity of A. gelatinosum is at last correctly established.     

Description of the immature stages of Sigara (Tropocorixa) santiagiensis (Hungerford, 1928) (Insecta: Heteroptera: Corixidae)

The immature stages of Sigara santiagiensis are described and illustrated for the first time. The eggs of Sigara can be distinguished by the chorionic surface. The main characters separating the five nymphal instars of S. santiagiensis are: body and head lengths; body, head and eye widths; ocular index; numbers of transverse sulcations of the rostrum, setae on the inner surface of protibiotarsus, campaniform sensilla on posterior surface of protrochanter, spines on posteroventral surface of mesotibia and on tibial comb of metaleg, long, slender setae on posterodorsal surface of mesotarsus, spines and swimming hairs on anteroventral and posterodorsal surfaces of metatarsus; and grade of development of the wing pads. The body length, the chaetotaxy of the mesonotum, profemora and metafemora, protibiotarsus, metatibia, metatarsus and urosternites distinguish species or group of species of instars I and V of some of the species of the genus Sigara described up to now.