RESUMO
Hundreds of years ago, sailors were terrified by the Kraken, a dreadful sea monster capable of sinking ships and with a taste for human flesh. Today we know the legends of this monster were based on sightings of giant squids. This animal belongs to the genus Architeuthis and was the subject of many scientific studies. Despite its enormous size (up to 18m), the giant squid is astoundingly elusive and much of its biology remains unknown. Thus shrouded in mystery, Architeuthis is almost a mythological creature and has a place both in science and in myth: the very last of the legends to persist to this day.
Assuntos
Biologia Marinha , Mitologia , Animais , Decapodiformes , História do Século XVI , História do Século XVII , História do Século XVIII , História do Século XIX , História MedievalRESUMO
Hundreds of years ago, sailors were terrified by the Kraken, a dreadful sea monster capable of sinking ships and with a taste for human flesh. Today we know the legends of this monster were based on sightings of giant squids. This animal belongs to the genus Architeuthis and was the subject of many scientific studies. Despite its enormous size (up to 18m), the giant squid is astoundingly elusive and much of its biology remains unknown. Thus shrouded in mystery, Architeuthis is almost a mythological creature and has a place both in science and in myth: the very last of the legends to persist to this day.
Séculos atrás, marinheiros se amedrontavam com histórias do Kraken, um terrível monstro marinho capaz de afundar embarcações e devorar suas tripulações. Atualmente, sabemos que a lenda desse monstro foi baseada em encontros com lulas-gigantes. Esse animal pertence ao gênero Architeuthis e foi alvo de muitos estudos científicos. Apesar de seu enorme tamanho (pode chegar a 18m), a lula-gigante é incrivelmente elusiva e muito de sua biologia permanece desconhecida. Assim, envolto em mistério, Architeuthis é quase um ser mitológico, ocupando um lugar tanto na ciência como no mito: a última das lendas a persistir nos dias de hoje.
Assuntos
Animais , História do Século XVI , História do Século XVII , História do Século XVIII , História do Século XIX , Biologia Marinha , Mitologia , Decapodiformes , História MedievalRESUMO
Subterranean rodents spend most of the day inside underground tunnels, where there is little daily change in environmental variables. Our observations of tuco-tucos (Ctenomys aff. knighti) in a field enclosure indicated that these animals perceive the aboveground light-dark cycle by several bouts of light-exposure at irregular times during the light hours of the day. To assess whether such light-dark pattern acts as an entraining agent of the circadian clock, we first constructed in laboratory the Phase Response Curve for 1 h light-pulses (1000lux). Its shape is qualitatively similar to other curves reported in the literature and to our knowledge it is the first Phase Response Curve of a subterranean rodent. Computer simulations were performed with a non-linear limit-cycle oscillator subjected to a simple model of the light regimen experienced by tuco-tucos. Results showed that synchronization is achieved even by a simple regimen of a single daily light pulse scattered uniformly along the light hours of the day. Natural entrainment studies benefit from integrated laboratory, field and computational approaches.
Assuntos
Adaptação Fisiológica/fisiologia , Luz , Modelos Biológicos , Fotoperíodo , Roedores/fisiologia , Animais , Ritmo Circadiano/fisiologia , Simulação por Computador , Ecossistema , Abrigo para Animais , Comportamento de Nidação/fisiologiaRESUMO
South American subterranean rodents (Ctenomys aff. knighti), commonly known as tuco-tucos, display nocturnal, wheel-running behavior under light-dark (LD) conditions, and free-running periods >24 h in constant darkness (DD). However, several reports in the field suggested that a substantial amount of activity occurs during daylight hours, leading us to question whether circadian entrainment in the laboratory accurately reflects behavior in natural conditions. We compared circadian patterns of locomotor activity in DD of animals previously entrained to full laboratory LD cycles (LD12:12) with those of animals that were trapped directly from the field. In both cases, activity onsets in DD immediately reflected the previous dark onset or sundown. Furthermore, freerunning periods upon release into DD were close to 24 h indicating aftereffects of prior entrainment, similarly in both conditions. No difference was detected in the phase of activity measured with and without access to a running wheel. However, when individuals were observed continuously during daylight hours in a semi-natural enclosure, they emerged above-ground on a daily basis. These day-time activities consisted of foraging and burrow maintenance, suggesting that the designation of this species as nocturnal might be inaccurate in the field. Our study of a solitary subterranean species suggests that the circadian clock is entrained similarly under field and laboratory conditions and that day-time activity expressed only in the field is required for foraging and may not be time-dictated by the circadian pacemaker.