Resi Mencacci

The 7000-km oceanic journey of a leatherback turtle tracked by satellite

A leatherback turtle nesting on a KwaZulu-Natal beach was tracked by satellite for nearly 7000 km during internesting movements, rapid straight transfers and feeding-related movements in the Southern Ocean. Some parts of the track reveal the ability to maintain a straight course in the absence of cues deriving from the coastline or shallow bottoms. Swimming speed and diving behaviour varied in different segments of the journey. The value of satellite telemetry for planning conservation strategies is emphasized.

Long-Term Tracking of Adult Loggerhead Turtles (Caretta caretta) in the Mediterranean Sea

Abstract Three adult-sized Loggerhead Turtles (Caretta caretta), captured incidentally by bottom trawlers, were tracked by satellite in the Mediterranean Sea for a substantial part of their annual cycle, including the period preceding nesting. The three turtles performed long-distance movements that were variable between individuals but shared common features such as seasonal migration. Very prolonged dives (up to over 300 min) were associated with temperature drops to below 18°C , likely an overwintering strategy. Our findings integrate recent tracking data on the postnesting migrations of Mediterranean Loggerhead Turtles, documenting the movement patterns made during the poorly known nonreproductive phase.

Differential magnetic field effects on heart rate and nociception in anosmic pigeons

Several studies have shown that exposure to altered magnetic fields affects nociception by suppressing stress-induced hypoalgesia, and that this effect is reduced or abolished if the treatment is performed in the absence of light. This raises the question as to whether other sources of sensory stimuli may also modulate these magnetic effects. We investigated the possible role of olfaction in the magnetically induced effects on sensitivity to nociceptive stimuli and heart rate (HR) in restraint-stressed homing pigeons exposed to an Earth-strength, irregularly varying (<1 Hz) magnetic field. The magnetic treatment decreased the nociceptive threshold in normally smelling birds and an opposite effect was observed in birds made anosmic by nostril plugging. Conversely, no differential effect of olfactory deprivation was observed on HR, which was reduced by the magnetic treatment both in smelling and anosmic pigeons. The findings highlight an important role of olfactory environmental information in the mediation of magnetic effects on nociception, although the data cannot be interpreted unambiguously because of the lack of an additional control group of olfactory-deprived, non-magnetically exposed pigeons. The differential effects on a pigeons sensitivity to nociceptive stimulus and HR additionally indicate that the magnetic stimuli affect nociception and the cardiovascular system in different ways.

The Green Turtles of Ascension Island: a paradigm of long-distance navigational ability

Sea turtles are a favourite object of investigations aimed at understanding the mysterious mechanisms of navigation that guide migrating animals across the ocean. According to the results of tagging and mtDNA studies, sea turtles that migrate for the first reproductive cycle to the natal beach rely on navigational information acquired as hatchlings on the natal beach and/or while wandering in the ocean before settling in the chosen residential quarters. The case of green turtles (Chelonia mydas) which migrate from Brazil to the remote Ascension Island is the real test of hypotheses about the guidance mechanism(s) and nature of the navigational cues that allow successful migration. Two hypotheses are currently the focus of attention, one based on the idea of a chemical trace between Ascension and Brazil, the other assuming the use of features of the earth’s magnetic field. A recent satellite tracking experiment allowed reconstruction of the course of five turtles returning from Ascension to Brazil. The orientation of the first leg appears to be influenced by the current, but afterwards turtles correct their course, presumably on the basis of external information. This first experiment draws attention to the role of the currents and to a possible involvement of the chemical sense in directing migratory journeys. Satellite tracking will be of paramount importance for the success of future experiments on navigational mechanisms.RiassuntoLe tartarughe marine sono uno dei modelli animali favoriti per le ricerche sui meccanismi di navigazione, tuttora sconosciuti, che guidano gli animali nelle migrazioni oceaniche. Dalle ricerche su esemplari contrassegnati e sul mtDNA si deduce che nelle tartarughe marine la prima migrazione dell’adulto, che va a riprodursi sulla spiaggia natale, è guidata da informazioni che i giovani hanno memorizzato in fase perinatale e/o durante i loro movimenti in oceano prima della scelta dell’area di residenza. Il caso delle tartarughe verdi (Chelonia mydas), che dal Brasile raggiungono la remota isola di Ascensione, è il banco di prova delle ipotesi sui meccanismi di guida e sulla natura degli stimoli orientanti che consentono il successo della migrazione. Sono attualmente al centro dell’attenzione due ipotesi, una basata sull’idea di una guida chimica tra Ascensione e il Brasile, l’altra sull’uso di parametri del campo magnetico terrestre. Un recente esperimento di ricostruzione delle rotte a mezzo satellite ha permesso di ricostruire il percorso di cinque tartarughe nel ritorno da Ascensione al Brasile. La direzione scelta nel primo tratto sembra influenzata dalla corrente, ma successivamente le tartarughe dimostrano capacità di correzione della rotta in base ad informazioni esterne. Questo primo esperimento, che richiama l’attenzione sul ruolo delle correnti e su un possibile coinvolgimento del senso chimico nelle scelte direzionali, mostra il ruolo decisivo della telemetria satellitare per il successo delle future indagini sui meccanismi di navigazione.