In vitro effect of isotocin on ovarian tunica albuginea contractility of gilthead seabream (Sparus aurata L.) in different reproductive conditions

Contractions of ovarian tunica albuginea, the teleostean cystovary wall layer containing smooth muscle fibres, facilitate oocytes and fluids movements within the ovary, oocytes ovulation and spawning. Fish isotocin, the homologue hormone of mammalian oxytocin, plays a significant role in ovulation, oviduct contraction and spawning. In the present study, ovarian wall spontaneous contraction, as well as isotocin in vitro effect on tunica albuginea contractility, was analysed in female seabream in different reproductive conditions: vitellogenesis, regressing (post-spawning) and extensive atresia. Tunica albuginea spontaneous contractility was recorded using ovary wall strips mounted in an organ bath containing modified Ringer’s solution. The strips were then exposed to cumulative doses of isotocin (6, 30, 60 μg/ml). Female seabream in regressing condition exhibited the highest level of tunica albuginea spontaneous contraction amplitude compared with the other two groups. Only fish in vitellogenesis state showed a significant increase in contraction amplitude after isotocin administration at the dose of 30 μg/ml. The same group exhibited also a significant isotocin dose-dependent decrease in the contractile frequency. These results confirm the involvement of isotocin in stimulating tunica albuginea contractile activity during the oestrogen-regulated phase of vitellogenesis, whereas the absence of significant effects of isotocin on ovarian contractility in fish at the regressing state might be ascribed to the occurrence of a contractile activity autonomously regulated by the internal pacemaker system. The absence of exposed isotocin receptors could explain the lack of effects of the isotocin administration in seabream showed extensive atresia of the follicular cells.     

A comparison of soil- and canopy temperature-based methods for the early detection of water stress in a simulated patch of pasture

This paper evaluates the sensitivity of two different methods of water stress detection in a simulated patch of pasture grown in a greenhouse. The performance of two indices, based respectively on canopy temperature and soil water content values — the latter gauged by means of a time domain reflectometry (TDR) system, was assessed against actual evapotranspiration, measured by a very accurate weighing system. Both methods were able to detect water shortage by the time transpiration was reduced to some 80% of its potential value. The soil-based index, however, relied on the estimate of root water extraction rate, which may not be known. It is concluded that detection of water shortage by means of a canopy temperature-based stress index is to be preferred to measuring soil water deficits by time domain reflectometry, despite the accuracy of the TDR-based soil water content estimate.     

Conserving indigenous crayfish: stock assessment and habitat requirements in the threatened Austropotamobius italicus

• 1. As part of the Austropotamobius pallipes species complex, the crayfish Austropotamobius italicus is a species of community interest whose preservation requires the designation of Special Areas of Conservation (SACs) (Annex II, EU Habitats Directive). This study aimed at (1) assessing the conservation status of this threatened indigenous species by stock assessment in central Italy and (2) identifying some aspects of its elective habitat.
• 2. Surveys were conducted in nine streams harbouring A. italicus (streams WI) and in 10 streams where crayfish populations became extinct at least 5 years before the study (streams WO).
• 3. The results confirmed that A. italicus is a K‐selected species, with a relatively slow growth rate (males: 0.34; females: 0.37) and a long life expectancy (males: 8.2 years; females: 7.8 years). The extant populations are healthy, showing balanced sex‐ratios and well structured age‐class compositions. Mortality is mainly due to fishing, which is illegal in Tuscany.
• 4. Principal Components Analyses showed that the streams WI and WO differ in the abundance of allochthonous plant detritus but not in the taxonomic composition of their macroinvertebrate communities. Age classes were found to be spatially segregated, juveniles mainly using cobbles as substrates and adults seemingly avoiding them.
• 5. The loss of the pristine riverine landscape seems to have been responsible, together with illegal fishing, for the local extinction of the species. As a consequence, retaining, enhancing, and restoring the habitat and its complexity are required for the preservation of A. italicus.
• 6. The designation of SACs might help in this endeavour if accompanied by programmes aimed at publicizing the need for conservation of this species. Unfortunately, crayfish‐focused projects supported by LIFE in Italy since 1992 (4%) and the SACs involved (1.4%) have been relatively few, despite the poor conservation status of this species and its well recognized ecological role.

Copyright © 2008 John Wiley & Sons, Ltd.     

Feline leishmaniosis due to Leishmania infantum in Italy

A case of leishmaniosis in domestic cats (Felis catus domesticus) is described. The subject showed a nodular lesion on the eyelid. The diagnosis was achieved by serological, parasitological, and light and electron microscopic investigations. By molecular techniques the aetiological agent was identified as belonging to Leishmania infantum, the species implicated in human and canine leishmaniosis in southern Europe. A preliminary study on the prevalence of asymptomatic feline leishmaniosis, performed in the areas where the infected cat was identified, revealed a low seroprevalence of infection: only 1 (0.9%) of the 110 cat sera examined by indirect fluorescent antibody test was positive for anti-Leishmania antibodies. Because clinical signs in feline leishmaniosis are unspecific and similar to those observed in other diseases commonly found in this species, leishmaniosis must be added to the differential diagnosis by feline veterinary practitioners and adequate serologic and histopathologic investigations must be performed in endemic areas.