Literatura científica selecionada sobre o tema "Haliclystus auricula"

The diet of Haliclystus auricula was studied from the gut contents of Stauromedusae collected every two months in southern Chile between November 2001 and November 2002. A total of 3790 medusae were collected and examined. Stauromedusae prey consisted primarily of harpacticoid copepods (68·4%), followed by gammarid amphipods (15·4%), chironomid fly larvae (9·2%) and podocopid ostracods (5·9%). The remaining 1·1% of the diet was made up of empidid fly larvae, polychaete worms, isopods, juvenile decapod crustaceans and gastropods. Gut content was observed in 31% of the stauromedusae collected and only in medusae with an umbrella height greater than 0·4 mm. Frequency of medusae with prey items in their gut content increased with stauromedusae size. The type of prey most frequently found in the smallest medusae were copepods, whilst larger individuals contained mainly amphipods. A strong tendency for the length of prey consumed to increase with medusae size was found.

The population biology and habitat of Haliclystus auricula was studied from samples taken every two months in southern Chile between November 2001 and November 2002. A total of 3790 medusae were collected and examined. The abundance of H. auricula varied seasonally. Maximum densities occurred in summer (1405/m2) and minimum densities during the winter, when the population gradually disappeared. Gonads were observed in medusae starting from a size of 2·0 mm. Stauromedusae were found most often on the red filamentous alga Ceramium rubrum (69%), followed by Gymnogongrus furcellatus (12%) and Ulva sp. (10%). There were highly significant differences in mean abundance of medusae on these three algae (P<0·05). The remaining 9% of medusae were found on other seaweeds. The smallest medusae (0·08–0·9 mm umbrella height) were found exclusively on C. rubrum. The highest densities were recorded in the midlittoral zone.

Morphological abnormalities were observed in a population of the stauromedusa Haliclystus auricula in southern Chile. A total of 144 abnormal specimens was observed out of 3790 Stauromedusae sampled. The following abnormalities are described: individuals lacking arms (73%), with more than eight anchors (11%), more than eight arms (8%), lacking anchors (4%) and one individual with tentacles in abnormal locations. An individual with two peduncles, one with two mouths and one twin-like individual are recorded for the first time in this species. Their possible causes are discussed.

Traditional underwater rigid robots have some shortcomings that limit their applications in the ocean. In contrast, because of their inherent flexibility, soft robots, which have gained popularity recently, offer greater adaptability, efficiency, and safety than rigid robots. Among them, the soft actuator is the core component to power the soft robot. Here, we propose a class of soft electrohydraulic bending actuators suitable for underwater robots, which realize the bending motion of the actuator by squeezing the working liquid with an electric field. The actuator consists of a silicone rubber film, polydimethylsiloxane (PDMS) films, soft electrodes, silicone oils, an acrylic frame, and a soft flipper. When a square wave voltage is applied, the actuator can generate continuous flapping motions. By mimicking Haliclystus auricula, we designed an underwater robot based on six soft electrohydraulic bending actuators and constructed a mechanical model of the robot. Additionally, a high-voltage square wave circuit board was created to achieve the robot’s untethered motions and remote control using a smart phone via WiFi. The test results show that 1 Hz was the robot’s ideal driving frequency, and the maximum horizontal swimming speed of the robot was 7.3 mm/s.

AbstractStaurozoa is a small group of marine stalked jellyfish, some of which have specialized attachment organs — rhopalioids, or so‐called anchors. The adhesive function of these organs was mentioned in numerous studies; however, the mechanism of their temporary attachment is still unknown. Moreover, it is assumed that rhopalioids may be homologous to rhopalia of scypho‐ and cubozoans and provide sensory and integrative functions. Nevertheless, nervous elements associated with rhopalioids are poorly investigated. Thus, we focused on morphological features of rhopalioids in staurozoan Haliclystus auricula James‐Clark, 1863 using histological and semithin sections, and also confocal laser scanning microscopy. We described histological organization of rhopalioids and observed four types of epidermal gland cell, which presumably provide the attachment and reattachment to the substrate. Supposedly, the musculature of rhopalioids can also play a role in the attachment and reattachment. We have studied organization of the nervous system in rhopalioids, which includes FMRFamide‐, tubulin‐ and neurotensin‐positive nerve clusters and FMRFamide‐positive presumptive sensory cells. Based on our results, we assume that rhopalioids, besides the complex attachment, may act like sensory organs and play a role of integrative centres.