Historical influences on genital morphology among sympatric species: gonopod evolution and reproductive isolation in the crayfish genus Orconectes (Cambaridae)

Freshwater crayfishes represent an incredibly diverse component of temperate aquatic ecosystems. The genus Orconectes (Cambaridae) comprises approximately 17% of total global crayfish diversity and is native to central and eastern North America. Using both Bayesian and parsimony-based phylogenetic hypotheses from complete cytochrome c oxidase subunit I (COI) mtDNA sequence data (1545 bp) along with information on male gonopod shape and species distribution patterns, we examined the evolution of male genital morphology and its potential influence on species co-occurrence. We found that sympatric species exhibited similar male genital morphology more often than expected based on the frequency of genital shapes within the genus. When evolutionary history was incorporated into this analysis, the result was no longer significant, suggesting that species co-occurrence and the associated genital shapes of sympatric congeners cannot be explained solely by interspecific ecological interactions. Our results also do not support the current subgeneric classifications within Orconectes or the monophyly of the genus, both of which have been based previously on male genital morphology.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 89 , 1–12.     

Primers for amplifying the hypervariable,male‐transmitted COII‐COI junction region in amblemine freshwater mussels (Bivalvia: Unionoidea: Ambleminae)

Freshwater bivalves in the superfamily Unionoidea possess distinct male (M)‐ and female (F)‐transmitted mitochondrial DNA (mtDNA). The former evolves independently of and at a significantly faster rate than the latter. Thus, population genetic and phylogenetic analyses of M sequences facilitate the generation of independent estimates of genetic variation and evolutionary relationships which are often more robust than those provided by analyses of F sequences alone. However, M mtDNA's rapid substitution rate often renders polymerase chain reaction (PCR) amplification difficult with ‘universal’ primers. Herein, we report on three pairs of PCR primers that consistently amplify the hypervariable M COII‐COI gene junction region in 25 bivalve genera (Unionoidea: Ambleminae).     

Cross‐species amplification at microsatellite loci in Australian quolls including the description of five new markers from the Chuditch (Dasyurus geoffroii)

The quolls are the largest native predators remaining on mainland Australia. We describe the cross‐species testing of all available microsatellite loci for representative across the entire distribution of quolls, with the additional characterization of five new microsatellite loci from the Chuditch. All primers produced clear and polymorphic amplification patterns containing between nine and 17 alleles and with high levels of diagnostic variability. These highly polymorphic primers make them useful additional tools in planning conservation strategies across related conspecifics, many of which are under threat.     

Response properties of the prothoracic AN2 auditory interneurone to model calling songs in the cricket Gryllus bimaculatus

Sound processing properties for calling song (CS) models, as described for the prothoracic L3 auditory neurone in Acheta domesticus, are investigated for the homologous auditory neurone 2 (AN2) in female Gryllus bimaculatus De Geer. AN2 of G. bimaculatus responds selectively to the syllable period (SP) of models of a male CS. The selectiveness of this response parallels the selectivity of phonotaxis females perform in response to the same SPs. Both, the responses of AN2 and female behaviour show clear interindividual variability. The SP‐selective responses of AN2 result from an SP‐dependent reduction in the spiking to subsequent syllables of the model CSs, measured as the percentage decrement. This SP‐dependent response does not primarily result from inbuilt properties of the AN2 membrane. Rather, it is dependent on inhibitory input to the AN2. However, clear inhibitory postsynaptic potentials in dendritic recordings of the AN2 are not encountered. This immediate response of AN2 to CSs is followed by an increased rate of tonic firing between stimulus CSs, which is termed the prolonged response, and is dependent on the carrier frequencies that make up the male CSs. With stimulation on the contralateral side of the soma of AN2s, more than 50% of AN2s exhibit a prolonged response. However, with stimulation from the ipsilateral side of the soma, most AN2s exhibit a prolonged response. The prolonged response of AN2 at 5 kHz may be even more sensitive than the immediate response. Thus, the AN2 neurone could provide a basis for phonotaxis that is selective for both the SPs and the carrier frequencies of potentially attractive calling songs.     

Long-Term Maintenance of Tetrahymena Spp.

SYNOPSIS. Simple media for Tetrahymena, using rat gut or soybean as the nutrient source are described. Cultures can be maintained in these media up to one year at room temperature.     

Fertile pinnules of Danaeites rigida Gu and Zhi (Marattiales) from the Upper Permian of south China

Recently collected specimens of Danaeites rigida Gu and Zhi from the Upper Permian of south China have been subjected to detailed morphological investigations in order to reveal features of their fertile pinnules. The specimens are preserved as compression/impressions and possess pecopteroid-type pinnules with a single row of synangia on either side of the pinnule midvien. Individual synangia are bilaterally symmetrical, sessile, and their bases are embedded in the tissues of the pinnules. Synangia possess 18–24 sporangia that are laterally fused to one another throughout their entire length. Sporangial dehiscence is through a longitudinal slit and sporangia contain trilete spores with a granular ornamentation, referable to the dispersed spore Cyclogranisporites. This combination of characters is unique in specimens preserved by compression/impression although they are similar to those known in permineralized marattialean fertile fronds. However, anatomical details salient to the identification of these permineralized taxa are not identifiable in impression/compression fossils such as Danaeites. The taxonomic and phylogenetic implications of these findings are considered in detail and we conclude that Danaeites has closer links with Marattia than with Danaea.     

Insect-repelling behaviour in bovids: role of mass, tail length, and group size

Biting insects are costly to hosts, and insect-repelling movements of the tail, ears, head, and feet are widespread in mammals and effective in reducing bites. We investigate whether the 'peripheral stimulation model' can explain the regulation of this widespread behaviour pattern in a comparative study of bovids. The peripheral stimulation hypothesis predicts: (1) a positive association between insect-repelling rates and body size because larger hosts produce more of the sensory cues that attract biting insects; (2) that individuals in larger groups will exhibit a higher rate of insect defense behaviour if group size and insect attraction follows a linear function; and (3) larger species will evolve proportionately longer tails in response to higher rates of insect attack. To test these predictions, we observed insect-repelling behaviour in 26 species of bovids at a zoological park, and controlled for common ancestry with formal phylogenetic analyses (independent contrasts). Consistent with the peripheral stimulation hypothesis, rates of tail-switching and all insect-repelling behaviours combined were positively associated with body mass, whereas ear-flicking was positively associated with proportional tail length. Larger bovids had proportionately longer tails for more effective fly swatting. There was no significant association between insect-repelling rate and group size, suggesting that a nonlinear relationship exists between group size and insect attacks whereby individuals in larger groups do not experience an increased attack rate.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 91 , 383–392.