IndexIntroductionDiscussionConclusionIntroductionMany desert-dwelling creatures rely on some sort of special adaptations, and mist beetles have one of the strangest ways of finding water. Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an original essayThe Namib Desert where these beetles live, is located on the southwestern coast of Africa (21°07´S 14°33´E) This is one of the driest areas in the world, receiving only 1.4 centimeters (0.55 inches) of rain per year. The cold Benguela Current runs across the desert creating the driest habitats on earth. Water is essential for all living organisms and this hostile environment represents a major challenge for all life forms. However, the cold coastal current not only suppresses precipitation over the desert, but is also the source of fog that can reach up to 100 km inland from the coast. But some species of tenebrinoid beetles living in the Namib Desert obtain water by drinking water that condenses from fogs. They can simply pick up condensation from any surface, but some species show behavioral adaptations for collecting condensation. (Insects, structure and function; RF Chapman; page 577). The benefit of fog harvesting for water intake in an extremely arid desert is obvious and critical when precipitation is absent for prolonged periods of time. Long-term studies of the population density of darkling beetles in the Namib Desert clearly show that fog-harvesting beetles are still present in large numbers during periods of low rainfall, while the vast majority of darkling beetles that lack these adaptations disappear or decline at lower levels. less than 1% of their average abundance (Norgaard and Dacke, Frontiers of Zoology, 20 July 2010). Four Darkling beetles have been discussed here: Onymacris unguicularis, Onymacris laeviceps, Stenocara gracilipes, and Physasterna cribripes. Some characteristics of fog beetles: Dimensions: length up to 2 cm. Habitat: Namib Desert in southwestern Africa. Food: any plant and animal substance. Food is often difficult to find in the harsh desert, so fog beetles have adapted to eating whatever they can find. Their sharp jaws can slice through plants and dead animal bodies, and the tiny hairs in their mouths absorb moisture from food. Long Legs: Long legs are essential for the existence of these beetles. Their legs keep their bodies above the scorching desert sands. They also allow them to run at speeds of up to 3 feet per second and cover a lot of ground in their daily search for food. Shelter: Mist beetles occasionally need a way to shelter from the scorching sun. Without natural shelter in the desert, they hide in the sand with their front legs and can disappear in seconds. Marathon Mate: Male beetles chase females during mating season, but the females manage to defeat them. If a male loses sight of a female after she has burrowed in the sand for the night, he will wait and headbutt any other males who approach to distance them from his female. Distribution of fog basking on desert beetles. Dark Beetle Life Cycle: Beetles, like other insects, go through a complete process of metamorphosis in which they go through four stages of development. Eggs: Starts with the female roach laying tiny, oval, white or yellow eggs. It usually takes 4-7 days for the eggs to hatch. Then they enter the"larval stage". Larvae: In this stage, they will eat a huge amount of food and continue to grow, losing their exoskeleton many times as they grow. It takes about 3-7 weeks. It then enters the pupal stage. Pupa: It then enters the pupal stage which can take up to 7-11 days. After the pupa an adult emerges. Adult: This beetle will feed, mate, and if it is a female, lay eggs to start another generation. Usually their lifespan is up to 2 years. Fig: Dusky beetle life cycle What is mist basking behavior? Basking in the fog is adapting to a characteristic head-down position on the dune crests, facing the fog-laden wind; the water from the fog condenses on the back and then drips towards the mouth where the condensation is absorbed (Hamilton & Seely, 1976; Seely, 1979). Surprisingly, fog basking often occurs outside of this species' normal activity period, at ambient temperatures and wind speeds far from their preferences, and they are not known to forage for food during these periods (Seely et al., 1983; Louw et al., 1986). Mist basking position of Onymacris unguicularis. Photograph of an O. unguicularis basking in the fog inside the fog chamber showing a characteristic mount on the head basking in the fog. This posture allows misty water collected on the beetle's dorsal surface to drip into its mouth. Mechanism of basking in the fog: · After a long night, when the air is refreshed by the sea breeze, the sun rises to warm the Namib Desert. Turning towards the shore, the fog beetle uses its long hind legs to prop its rear end in the air. The fog begins to form after a few minutes and a few drops of moisture appear on the cockroach's body. After an hour of perfect immobility, the cockroach's body is covered in dew and drops of water drip into its mouth. The mechanism by which fog water forms into large droplets on a pearly surface has been described from the study of the elytra of beetles of the genus Stenocara [Parker A Lawrence CR]. The structures underlying this process are believed to be hydrophilic peaks surrounded by hydrophobic areas; The water carried by the fog settles on the hydrophilic tips of the smooth protuberances of the beetle's elytra and forms fast-growing droplets that - once large enough to move against the wind - roll down towards the head. Here systematic location of four darkling tenebrinoids Beetles are given: Comparative fog basking behavior and water collection efficiency in these four darkling beetles Namib Desert Darkling: Fog collection behavior of four species of tenebrionid beetles was compared : Onymacris unguicularis (Figure 1A) is known to bask in fog and has a smooth dorsal surface with broad grooves [7]. Onymacris laeviceps (Figure 1B) has a similar surface structure, albeit with finer grooves, and inhabits the same sand dune habitat as O. unguicularis. However, it is not known to fogbask, but drinks from fog-moistened surfaces [Seely et al., 2005]. Stenocara gracilipes (Figure 1C) and Physterna cribripes (Figure 1D) are found outside the sand dune habitat and have elytra with a more or less regular series of smooth protuberances. It is a matter of debate whether either of these two species or genera basks in the fog or not []. Size differences: Figure 1 Size difference between the four model beetles. Examples of specimens of each beetle species placed next to each other for size comparison. A: O. unguicularis, B: O. laeviceps, C:S.gracilipes and D: P. cribripes. The dorsal surface of P. cribripes was found to be 1.39 times larger than O. unguicularis, 1.56 times larger than O. laeviceps, and 2.52 times larger than S. gracilipes. Surface structure of the elytra: SEM images and photos taken through a dissecting microscope show details of the pronounced differences in the structure of the elytra between the four beetle species). While in all beetles the pronotum is rather smooth, it is the elytra that have different structures. The elytra of O. unguicularis are almost completely smooth except for the posterior half which has large distinct grooves, about 0.5 mm wide, divided by narrow ridges. The elytra of O. laeviceps have much finer grooves (Figure 2B1), approximately 0.1 mm wide, covering almost the entire elytra. The valleys of the fine furrows are not as smooth as those of O. unguicularis but rather have a rougher surface. In living animals the posterior half of O. laeviceps has a blue-gray color. The elytra of small S. gracilipes are covered in jagged bumps that form irregular lines, although bumps between the lines are also present. The elytraEven large P. cribripes have bumps that form irregular rows with additional bumps in between. The bumps are slightly rounder than those of S. gracilipes and are found on all elytra, with a smooth stripe on either side of the suture of the beetles' fused elytra. Structures of the elytra.A) Onymacris unguicularisB) Onymacris laevicepsC) Stenocara gracilipesD) Physasterna cribripes.A1-D1) Extended depth focus images of examples of experimental animals obtained with a dissecting microscope. Scanning electron microscope images of the apex of the elytra. Figure: Hydrophobic dorsal surface of Physasterna cribripes Fog basking behavior: Of the four beetles in the Namib Desert during a fog event, only O. unguicularis was observed actively collecting water from fog. In an experimental chamber these beetles positioned themselves on the top of a sand ridge and assumed a basking position in the fog after 114.5±9.28 seconds. The starting point of this behavior was defined as the moment when O. unguicularis oriented itself with its back towards the fog and subsequently remained in this static position with its head tilted downwards for a minimum of 2 minutes. During these events the ventral side of the cockroach was held at an angle of approximately 23° from the horizontal. In contrast, the other three beetle species continued to walk around the arena during the 20 minutes they were observed in the cloud chamber. These three species were therefore excluded from further behavioral experiments in the cloud chamber. THE. unguicularis basking in fog was again tested in the cloud chamber at temperatures equivalent to those existing during natural fog events, this time without fog in the chamber. In the absence of fog, O. unguicularis showed no fog accumulation behavior during the 20 minutes they were observed in the chamber. However, if the temperature was raised to room temperature and the chamber was filled with fog, six out of twelve beetles assumed a fog-basking position after 175 ± 21.65 seconds. The other six beetles remained active and moving for the 20 minutes they were there. observed, but never adopted a static standing head position. High humidity, rather than low temperature, is therefore the critical condition in which fog-basking cockroaches will assume their characteristic water-collecting head position. However, a combination of fog and low temperatures is the factorstrongest trigger for this behavior. Fog water collection efficiency: Regardless of whether or not their ability to actively collect water from fog in the fog chamber, the ability of the four beetle species to passively collect water from fog has been tested by scientists from specimens dead. Mount upside down at an angle of approximately 23°. After two hours in the cloud chamber, Onymacris unguicularis and O. laeviceps, which have smooth grooved elytra, had collected 0.16 ± 0.03 and 0.11 ± 0.01 ml of water, respectively. Stenocara gracilipes and P. cribripes, which have elytra with a series of protuberances, collected, in the same time, 0.11 ± 0.01 ml and 0.14 ± 0.03 ml, respectively. Onymacris unguicularis and P. cribripes showed a tendency to collect more misty water than O. laeviceps and S. gracilipes, but not significantly so. Despite markedly different elytra structures and behaviors, the four beetles collected the same amount of water over a 2-hour period in the fog chamber. The four beetle species, however, vary in size. The relative sizes of the dorsal surface of the beetles (the dorsal part of the head, the pronotum, and the elytra) were established from colored latex casts of the different beetles used in the water collection efficiency experiments. The scientists found that the dorsal surface of the large P. cribripes on average is 1.39 times larger than the same region of O. unguicularis, 1.56 times larger than that of O. laeviceps, and 2.52 times larger than that of the smaller beetle S. gracilipes. By applying these relative differences in dorsal surface areas as conversion factors on the absolute amount of water harvested per species, an estimate of each species' water harvesting efficiency was obtained that is independent of their size. Despite the fact that O. unguicularis is the only beetle in this study that actively collects fog water, it does not appear to have superior surface structures for the purpose compared to those of other beetles. In fact, it is not possible to find any significant difference in water collection per unit of dorsal surface area between O. unguicularis (0.22 ± 0.04 ml) and O. laeviceps (0.18 ± 0.01 ml), or O. unguicularis and S. gracilipes (0.27 ± 0.02ml). The water collection efficiency of large P. cribripes (0.14 ± 0.03 ml) is, however, significantly lower than that of O. unguicularis basking in the fog. The small (S. gracilipes) and large (P. cribripes) both have elytra with distinct protuberances, but the water collection efficiency of these two beetles is at the high and low end of the spectrum, respectively, with a significant difference between the two. Indeed, S. gracilipes collected almost double the water per unit surface area (0.27 ± 0.02 ml) during the two hours in the cloud chamber compared to P. cribripes (0.14 ± 0.03 ml). Figure 5 Fog collection efficiency. The freeze-killed beetles had their legs and antennae removed and were placed upside down at a 23° angle in a cloud chamber. An Eppendorf tube was placed under the head of each beetle to collect water. After two hours in the chamber, the total amount of water captured by each of the four beetle species (blue) was measured. The relative dorsal surface area of ​​each beetle was determined and normalized to the larger beetle. This conversion factor was used to obtain the relative amount of water captured per dorsal surface area (red). Columns show mean ± SE. The columns marked above with corresponding lowercase letters are not significantly different at p < 0.05 (test ofKruskal-Wallis and Dunn's multiple comparisons test). Discussion Fog basking behavior in an experimental fog chamber: When the four dusky beetles from the Namib Desert were exposed to fog in a small chamber, (the temperature is about 10-12°, which is a similar temperature range to that of a fog event in the Namib Desert), the fog-basking beetle O.unguicularis promptly assumed its characteristic fog-basking position after a little more than 2 minutes in the chamber. The static head position assumed by O.unguicularis while basking in the fog in the chamber was very similar for the same species while basking in the fog on the crest of a sand dune during a fog event in the Namib Desert. The other three beetles remained active but never assumed a similar position during the 20 minutes they spent in the cloud chamber. The lack of fog-basking behavior in these three beetle species is in agreement with long-term observations of Darkling beetles in the Namib Desert, [5], where only two of the approximately 200 beetle species inhabit this area have been observed. fog-bask - both of the genus Onymacris. O. unguicularis readily and predictably basking in fog in the same artificial environment supports the validity of the experimental setup. However, P. cribripes and many other tenebrionid beetles also assume a tilted posture as a common response to alarm [9]. The beetle then sticks its head into the ground, spreads its legs and lifts the back of its body. This posture resembles that of basking in the fog and may have been confused with it in Parker and Lawrence's study [10]. Fog was found to be the trigger for O. unguicularis to assume the position of basking in the fog. None of the twelve beetles assumed this position at low temperatures without fog, but half of the O. unguicularis tested engaged in fog basking when exposed to fog at around 23°C. In contrast, all O. unguicularis placed in a fog-filled chamber at temperatures similar to those of a natural fog event in the Namib Desert [9] assumed a fog-basking position. This indicates that temperature is a contributing, but not critical, factor in eliciting this behavior. The recorded tolerance for variability in factors triggering fog harvesting further supports our finding that other beetle species do not engage in this behavior. Even if the temperature in the chamber was not set to the absolute critical temperature to elicit the fog-basking behavior in O. laeviceps, S. gracilipes, or P. cribripes, the fog-basking posture was never observed. Efficiency of water capture by beetle elytra: Experimental results reveal that the small beetle S. gracilipes is as efficient at collecting misty water, when measured per square unit of dorsal surface area, as the larger O. unguicularis , although it has never been observed actively basking in fog in the wild [5] or in our cloud chamber. The high water collection efficiency recorded for S. gracilipes is most likely a result of its relatively smaller size. Other organisms in the Namib Desert use fog as an important water source, and small leaves have been shown to be an important factor for plants when harvesting water from fog [12]. This is because small or narrow leaves have only thin boundary layers (a slowly moving envelope of air around the object) that allow water mist to collect on the surface.