Banca de QUALIFICAÇÃO: SYLVIA LIMA DE SOUZA MEDEIROS

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
STUDENT : SYLVIA LIMA DE SOUZA MEDEIROS
DATE: 16/05/2024
TIME: 09:00
LOCAL: meet.google.com/zfw-rwqk-jst
TITLE:

Cyclic alternation between quiet and active sleep states in octopuses observed under controlled laboratory conditions and in the wild

KEY WORDS:

Cephalopods; Active sleep; Quiet sleep; Reaction time; Octopus insularis; Wild.

PAGES: 102
BIG AREA: Ciências Biológicas
AREA: Fisiologia
SUMMARY:

The alternation of long episodes of quiet sleep rhythmically interrupted by short episodes of active sleep, a pattern once thought to be exclusive of amniotes, has recently been reported in some invertebrates, such as in drosophila, jumping spider and in cuttlefish. However, these studies that shows the sleep cyclic pattern have been developed in animals kept in captivity within laboratory conditions. This leaves open questions with regard to the natural sleep cycle of invertebrates, and how it is affected by environmental factors. To investigate in detail the behavioral structure of cephalopod sleep, we recorded uninterrupted videos (12h in 4 consecutive days) of the behavior in laboratory of four adult specimens of Octopus insularis, a common benthic octopus in the tropical western Atlantic. The animals were captured in Pirangi (6°0’14.29”S, 35° 6’21.01”W) and kept in tanks measuring 1.0 x 0.7 x 0.6 meters, Natal/RN. Then, we quantified several variables during each of the behavioral states, as well as during transitions between states. Changes in skin color and texture, eye and mantle movements were assessed using automated image processing tools developed for this purpose. To measure the arousal threshold in each state, the latency of the behavioral response to sensory stimuli was measured. Two distinct behavioral states of lack of reactivity to stimulation were identified. The first was a quiet sleep state characterized by uniformly pale skin, closed pupils, and long episode durations (median 415.2 s). The second was an active sleep state characterized by dynamic skin patterns of color and texture, rapid eye movements, and short episode durations (median 40.8 s). Active sleep was periodic (60% of recurrences between 26-39 min) and occurred mostly after quiet sleep (82% of transitions). These results suggest that cephalopods presents an ultradian sleep cycle analogous to that of amniotes. To compare these results with data obtained in the wild, we made a collaboration to analyze existing data on the behavior of Octopus insularis, recorded in a minimally invasive way by remote cameras positioned at the dens entrances, on the Caribbean islands of Turks and Caicos (21.5112°N , 71.5190°W). 10 adult specimens were recorded during the day and night (total of 240 hours). The results show that all animals presented a cyclical sleep pattern surprisingly similar to the pattern observed in the laboratory, with a periodic alternation of episodes of quiet sleep (median 643.2 s) and active sleep (37.8 s median), with episodes of quiet sleep preceding episodes of active sleep 98% of the time. We also observed that the animals were sleeping (both quiet and active sleep) for 44% of the sampled period, which demonstrates that sleep occupies a substantial fraction of adult lifespan in O. insularis. Documenting and quantifying cyclic sleep pattern in specimens of O. insularis, investigated both in the laboratory and in the natural environment, helps to understand the selective pressures that drove the evolution of the sleep cycle in cephalopods.

COMMITTEE MEMBERS:
Externo ao Programa - 1216466 - JOHN FONTENELE ARAUJO - nullInterno - 1698305 - RODRIGO NEVES ROMCY PEREIRA
Presidente - 1660044 - SIDARTA TOLLENDAL GOMES RIBEIRO
Externa à Instituição - TATIANA SILVA LEITE - UFSC