Moulting,ontogeny and sexual dimorphism in the Cambrian ptychopariid trilobite Strenuaeva inflata from the northern Swedish Caledonides

Abstract: Three thousand seven hundred disarticulated remains together with several articulated specimens of the Cambrian Series 2 ptychopariid trilobite Strenuaeva inflata Ahlberg and Bergström, 1978 have been collected from the Torneträsk area, northern Sweden. The material provides significant new data on the morphology, ontogeny, moulting and enrolment of the species. Two distinct morphotypes, possibly an expression of sexual dimorphism, are recognized. The morph with a pair of bulbs in the frontal area, interpreted as brood pouches, is considered to represent females. Statistical treatment of the length/width ratio in cranidia reveals isometric growth during ontogeny for both morphotypes. The transition from the meraspid to holaspid ontogenetic period has been established through recognition of the successive development of the number of thoracic segments in articulated late meraspides. Throughout its life cycle, S. inflata went through 11 meraspid degrees and at least 17 holaspid growth stages. Inferred moult ensembles and exuviae reveal the successive opening of cephalic sutures and the function of the rostral plate during exuviation. As in other ellipsocephalid trilobites in which enrolment is known, the pygidium and two or three thoracic segments of S. inflata are concealed beneath the cephalon (spiral enrolment) during complete enrolment.     

A NEW TRISTICHOPTERID (SARCOPTERYGII, TETRAPODOMORPHA) FROM THE UPPER FAMENNIAN EVIEUX FORMATION (UPPER DEVONIAN) OF BELGIUM

Abstract:  Additional material of a large specimen of tristichopterid fish from the Upper Famennian Evieux Formation of Belgium is described. This large fish was previously assigned to Tristichopteridae gen. et sp. indet. due to the lack of diagnostic anatomical data. New available material consists of the internal surface of the parietal shield, vomers and anterior part of the parasphenoid, subopercular and submandibulo-branchiostegal bones, and an internal view of the anterior part of the mandible. A possible autapomorphy of the new form from Belgium, Langlieria socqueti gen. nov. et sp. nov., is the absence of marginal teeth on the vomer except on its most lateral part. Apart from these features, it only differs from the genus Mandageria from Australia in the absence of marginal teeth between the dentary fang and the mandibular symphysis, in the presence of a raised marginal crest lateral to the anterior coronoid fang, and in the presence of numerous small marginal teeth on the premaxilla. It differs from the cosmopolitan genus Eusthenodon in a number of respects: the supratemporal, tabular, and postparietal bones are superficially fused, as are the intertemporal and parietal bones, the dermal ornament is proportionally very fine, and the denticulated field of the parasphenoid stands proud rather than being recessed into the body of the bone.     

Dynamic micro-geographic and temporal genetic diversity in vertebrates: the case of lake-spawning populations of brown trout (Salmo trutta)

Conservation of species should be based on knowledge of effective population sizes and understanding of how breeding tactics and selection of recruitment habitats lead to genetic structuring. In the stream‐spawning and genetically diverse brown trout, spawning and rearing areas may be restricted source habitats. Spatio–temporal genetic variability patterns were studied in brown trout occupying three lakes characterized by restricted stream habitat but high recruitment levels. This suggested non‐typical lake‐spawning, potentially representing additional spatio–temporal genetic variation in continuous habitats. Three years of sampling documented presence of young‐of‐the‐year cohorts in littoral lake areas with groundwater inflow, confirming lake‐spawning trout in all three lakes. Nine microsatellite markers assayed across 901 young‐of‐the‐year individuals indicated overall substantial genetic differentiation in space and time. Nested gene diversity analyses revealed highly significant (≤P = 0.002) differentiation on all hierarchical levels, represented by regional lakes (F_LT = 0.281), stream vs. lake habitat within regional lakes (F_HL = 0.045), sample site within habitats (F_SH = 0.010), and cohorts within sample sites (F_CS = 0.016). Genetic structuring was, however, different among lakes. It was more pronounced in a natural lake, which exhibited temporally stable structuring both between two lake‐spawning populations and between lake‐ and stream spawners. Hence, it is demonstrated that lake‐spawning brown trout form genetically distinct populations and may significantly contribute to genetic diversity. In another lake, differentiation was substantial between stream‐ and lake‐spawning populations but not within habitat. In the third lake, there was less apparent spatial or temporal genetic structuring. Calculation of effective population sizes suggested small spawning populations in general, both within streams and lakes, and indicates that the presence of lake‐spawning populations tended to reduce genetic drift in the total (meta‐) population of the lake.     

Deficiency in African plant distribution data – missing pieces of the puzzle

Biodiversity is spatially unevenly distributed and so is the information on its spatial patterns. This uneven distribution of information on species occurrences is an important impediment to the conservation of biodiversity. Based on 185 427 collection records of 5873 plant species in sub-Saharan Africa, we analyse the availability of distribution data suitable for the GIS-based mapping of plant diversity patterns at a one-degree resolution. Using the bioclimatic model GARP, distribution ranges for each species were modelled. In order to identify data-deficient areas, the documented and modelled diversity patterns were compared. Only for a few, well-known centres of plant diversity are there comparatively many data collection records available. For several of the areas with very few collection records, such as the Guinean montane forests, the north-western Congolian lowland forests, and the southern Albertine Rift montane forests, the model predicts a species richness much higher than currently documented. In many of the data deficient areas, difficult conditions for scientific research appear to have limited collection activities for decades. Only strategic field collections can fill these gaps. Another cause of data deficiency is that data collected and digitized do not match the quality requirements for GIS-based work at the super-regional scale. In particular, regional databases documenting partial ranges of species are rarely connected. One challenge for the Global Strategy for Plant Conservation is therefore to establish international collaborative structures and technical standards that will allow analysis of biogeographical patterns across political boundaries.  © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 150 , 355–368.     

Morphological, vocal and genetic divergence in the Cettia acanthizoides complex (Aves: Cettiidae)

We used morphological, vocal and molecular (one mitochondrial and two nuclear loci) data to re-evaluate the taxonomic status of the taxa acanthizoides , concolor , and brunnescens in the Cettia acanthizoides (J. Verreaux, 1871) complex. We conclude that all three are valid taxa, and that acanthizoides of China and concolor of Taiwan are best treated as conspecific, whereas brunnescens of the Himalayas is better considered as a separate species. The degree of morphological, vocal, and genetic differentiation is variably congruent among all taxa; the recently separated acanthizoides and concolor differ slightly in plumage and structure but are indistinguishable in vocalizations, whereas the earlier diverged brunnescens and acanthizoides/concolor differ only slightly more in morphology but to a much greater degree in vocalizations. We stress the essential nature of taxonomic revisions as a prerequisite for the biodiversity estimates required for conservation planning.  © 2007 The Linnean Society of London, Zoological Journal of the Linnean Society , 2007, 149 , 437–452.     

Ocular structures in an Ordovician agnostid trilobite

Ocular structures have recently been discovered on the cephalon of an Ordovician agnostid trilobite, Oculagnostus frici (Holub, 1908). They are represented mainly by obvious palpebral lobes situated at the postero-lateral part of the genae. In addition, in one specimen there is a dome-shaped structure below the palpebral lobe. This may well be the remains of an eye, but details of its structure are indeterminate. In the other two cephala to hand there is a notch or cavity beneath the palpebral lobe, indicating that the visual surface may have been encompassed by a circum-ocular suture such that the lentiferous region normally dropped out during ecdysis. The origin of the ocular structures in Oculagnostus frici is briefly discussed. Oculagnostus n. gen. is described.     

Spatial patterns of photobiont diversity in some Nostoc-containing lichens

Patterns of photobiont diversity were examined in some Nostoc -containing lichens using the nucleotide sequence of the cyanobacterial tRNA^Leu (UAA) intron. Lichen specimens collected in northwestern USA were analysed and the sequence data were compared with tRNA^Leu(UAA) intron sequences previously obtained from lichens in northern Europe. Generally, it is the species identity of a lichen rather than the geographical origin of the specimen that determines the identity of the cyanobiont. Identical intron sequences were found in Peltigera membranacea specimens collected in Oregon (USA) and in Sweden, and very similar sequences were also found in Nephroma resupinatum thalli collected in Oregon and Finland. Furthermore, in mixed assemblages where two Peltigera species grew in physical contact with each other, the different lichen species housed different photobiont strains. There is however not a one-to-one relation between mycobiont and photobiont as some intron sequences were found in more than one lichen species, and different intron sequences were found in different samples of some lichen taxa. Peltigera venosa exhibited a higher level of photobiont diversity than any other lichen species studied, and several intron sequences could for the first time be obtained from a single thallus. It is not clear whether this is evidence of lower cyanobiont specificity, or reflects an ability to exhibit different degrees of lichenization with different Nostoc strains. In one specimen of P. venosa , which contained bipartite cyanosymbiodemes and tripartite, cephalodiate thalli, both thallus types contained the same intron sequence.     

Multiple α2-Adrenoceptor Signalling Pathways Mediate Pigment Aggregation Within Melanophores

It has previously been shown that α₂-adrenoceptors (α₂-ARs) mediate pigment granule (melanosome) aggregation in melanophores of the teleost fish Labrus ossifagus. The present investigation scrutinized the signalling mechanisms of melanosome aggregation induced by sympathetic nerve stimulation or by exogenous addition of α-AR agonists and cAMP analogues. The following was observed: i) nerve-induced melanosome aggregation was associated with a rapid decrease in the cAMP level; ii) noradrenaline or medetomidine (an α₂-AR agonist) caused melanosome aggregation and reduced the cAMP content; iii) RP-S-CI-cAMP, a membrane-permeating inhibitor of protein kinase A induced melanosome aggregation; and iv) B-HT 920 (an α₂-AR agonist) and methoxamine (an α₁-AR agonist) induced melanosome aggregation, although they did not reduce cAMP. It has been suggested that in some teleost species α₁-ARs mediate melanosome aggregation by increasing the level of intracellular calcium. However, we found that the effect of methoxamine in melanophores from Labrus ossifagus could be blocked by yohimbine (an α₂-AR antagonist) but not by equimolar concentration of prazosin (an α₁-AR antagonist). Furthermore, 1 μM ionomycin (a calcium ionophore) did not induce melanosome aggregation. Our findings therefore do not indicate that α₁-ARs and/or an increase in intracellular calcium mediate melanosome aggregation in Labrus ossifagus. Our results suggest that α₂-AR-mediated melanosome aggregation is induced by multiple signalling pathways. One of these involves a reduction in cAMP, but none involves an increase in intracellular calcium.     

Grazing by a native and an exotic crayfish on aquatic macrophytes

1. We compared grazing by native noble crayfish ( Astacus astacus ) and the exotic signal crayfish ( Pacifastacus leniusculus ) on seedling or well-established macrophytes.
2. In a pool experiment, seedlings of emergent Scirpus lacustris and floating-leaved Potamogeton natans were heavily grazed by adult signal crayfish, whereas established plants of the same species sustained only minor damage.
3. In a preference experiment two submerged macrophytes ( Chara vulgaris and Elodea canadensis ), and both seedlings and established plants of S. lacustris and P. natans , were presented pairwise to signal and noble crayfish. There was no significant difference in preference by the two crayfish species. Chara vulgaris was preferred to all other plants presented, established plants of S. lacustris and P. natans were never preferred, and seedlings of P. natans were preferred to established P. natans .
4. An aquarium experiment was conducted in which the consumption of Chara by signal and noble crayfish was measured in relation to water temperature. Signal crayfish consumed significantly more Chara than noble crayfish, especially at higher temperatures.
5. Our results indicate that the signal crayfish is the more voracious grazer especially at higher temperatures. There may be negative effects on vegetation (emergents and floating-leaved, as well as submerged species) when the signal crayfish is introduced. Chara species are particularly susceptible, since they are preferred by crayfish and the genus includes a large number of rare species. Stocking of crayfish therefore could lead to the decline or removal of submerged species in order of crayfish feeding preferences and could prevent the spread or cause a decline of emergent and floating-leaved vegetation.