Bdelloid rotifers and nematodes in a small Italian stream

SUMMARY. The bdelloid rotifers and nematodes of a small clean watercourse in the area surrounding the Po river near Parma have been studied. The samples were collected at two sites 400 m apart. The species found in twelve collections of benthos between May 1977 and June 1978 were eighteen belonging to Bdelloidea and forty-seven to Nematoda (Tylenchida have not been considered). Nearly all the bdelloid species were oligosaprobic or beta-mesosaprobic; the Shannon index of diversity was 3.0 at the first site and 2.4 at the second. Among the Nematoda the dominant species were Paraplectonema pedunculatum and Paraphanolaimus anisitsi which were not previously recorded for Italy. Nearly all nematodes are microphagous; predators represent only 10% of collected specimens. Polluted water indicator species (Secernentia group) were only 3.5% of the total nematodes recorded. Most rotifers and nematodes did not show seasonal fluctuations in numbers. The two sampling sites do not seem to have substantial differences in the taxocoenosis of Rotifera and Nematoda; their percentage of similarity is 69% and 79% for the two classes respectively.     

Exploring the history of Serapias politisii (Orchidaceae), a narrow endemic on the opposite coasts of the Otranto channel: insights from molecular investigations

Knowledge of genetic spatial structure may provide insights into the causes of population disjunctions in plants. Serapias politisii is a narrow endemic with only a few populations scattered along the opposite coasts of the Otranto strait (southern Adriatic Sea). It was originally considered to be of hybrid origin between S. vomeracea ssp. laxiflora and S. parviflora, a possibility suggested also by a DNA phylogenetic study that grouped Italian and Greek populations in two distinct clades. In this study we have carried out additional plastid DNA sequencing and an AFLP analysis of the three taxa. Whereas the geographical distribution of four plastid DNA haplotypes supports the likelihood of a double hybrid origin or of a plastid capture, AFLP data do not support such a hypothesis, because S. politisii shows several private alleles, some of which are shared by Italian and Greek populations. In light of the floristic specificity of the coasts bordering the Otranto strait, we consider that the present‐day disjunction of S. politisii could have originated either by a long‐distance seed dispersal or by a fragmentation of an old polymorphic population. The pairwise mismatch distribution excludes a recent expansion of the populations examined. In light of recent evidence concerning the Mediterranean Lago‐Mare period and the westward haplotype evolution detected in some Euro‐Mediterranean trees, we argue that fragmentation of a previously continuous population could be an intriguing possibility. © 2010 The Linnean Society of London, Botanical Journal of the Linnean Society, 2010, 162 , 572–580.     

Crossing barriers between the unrewarding Mediterranean orchids Serapias vomeracea and Serapias cordigera

Understanding the genetic architecture of admixed hybridizing populations helps in evaluating the nature of species boundaries and the levels of gene exchange between co-occurring species. In the present study, we examined a contact zone between Serapias vomeracea and Serapias cordigera , two unrewarding Mediterranean orchid species with a non-specific pollination strategy. Fruit production and seed viability from interspecific hand-pollination treatments pointed out the weaknesses of post-pollination barriers. The occurrence of hybridization was molecularly confirmed in the genus Serapias for the first time, as parts of plants with a transitional morphology were observed in both alleles of the parental LEAFY intron. Amplified fragment length polymorphism analysis revealed that plants with uncertain morphology and classified as one of the other parental species are actually backcrosses, attesting to an extensive interspecific gene exchange. Overall, the contact zone is more similar to a hybrid zone of Ophrys species, well known for their highly specialized pollination, than to a hybrid zone of unspecialized food-deceptive orchids. Therefore, species boundaries in Serapias are maintained by pre-pollination mechanisms that need to be better investigated. In light of the intriguing similarities between Serapias and Ophrys underlined by the present study, we hypothesize that the emission of floral scents could be involved in the maintenance of species boundaries in Serapias .     

Managing invasive crayfish: use of X-ray sterilisation of males

1. In the last decade, many attempts have been made to contain the spread of the North American crayfish Procambarus clarkii , an invader of many European water bodies, but none has been successful.
2. This study investigates the effects that ionising irradiation has on the reproduction of P. clarkii males by analysing the behaviour of the treated individuals, their reproductive output, the vitality and survival of their offspring and the damages induced to their gonads.
3. We found that a dose of 20 Gy X-rays did not compromise either the survival or the mating ability of males, but reduced the size of their testes and significantly altered spermatogenesis. The number of aborted eggs was larger in clutches sired by treated males, with a consequent reduction (by 43%) in the number of offspring.
4. These results foster hopes in our efforts to control invasive crayfish, showing the potential effectiveness of ionising irradiation to reduce male fertility in the perspective of adopting the Sterile Male Release Technique to control P. clarkii populations.     

Walking in skates (Chondrichthyes, Rajidae): anatomy, behaviour and analogies to tetrapod locomotion

Pelvic fin walking in skates is common. However, the structure and function of pelvic fins have not been analysed. Pelvic fins of skates of the genus Psammobatis and Rioraja agassizi are externally divided into an anterior leg-like lobe and a posterior fin-like lobe. Internally, the anterior lobes are supported by a compound radial, a proximal radial and distal radials that resemble a thigh, a calf and a foot, respectively, and three associated radials arising from the pelvic girdle. A highly developed radial condyle on the pelvic girdle enables broad 'limb' movements. The muscular arrangement of the anterior lobes is formed by protractor, retractor, flexor and extensor muscles, clearly departing from the generalized fin muscle arrangement of elasmobranchs. Walking is composed of propulsion and recovery phases. A backward movement of the compound radial in the horizontal plane characterizes the propulsive phase. The proximal radial connects vertically the compoundradial with the foot-like distal radials, which are anchored on the bottom. During the recovery phase, the foot-like structure is lifted off the bottom and the entire limb-like anterior lobe is moved forwards for starting a new cycle. Walking in skates resembles the ancestral tetrapod sprawling locomotion seen in many salamanders and lizards. Pelvic fin anatomy and walking behaviour in skates and hemiscylliid sharksare compared. Ecological and evolutionary implications of walking locomotion in skates are also discussed.  © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 77 , 35–41.