jmalloldiaz's blog

A study on COM motion in three fish species with different morphologies discovered that the surge fluctuated at twice frequency of the tail for eels and sunfish, while the sway resulted at the same frequency as the tail beat. Despite surge oscillations not changing significantly with increasing speed, sway oscillations did increase. Other study using particle image velocimetry discovered that the water flow of fish with homocercal tails produces vortex rings in a linked-chain pattern, while fish with heterocercal tails like sharks produce dual linked-ring vortexes. Regarding the effect of skin denticles on performance, a study discovered that intact shark skin provides 12.3% more speed than membranes with removed denticles. Lastly, a study using robotic models found that small length changes in swimming bodies can alter speed by a factor of three to five times.

The goal of this review was to examine new ways of analyzing fish locomotion. The author explored recent advances in the center of mass (COM) motion in undulatory fish, water flow patterns produced during swimming, the role of skin denticles in performance, and aquatic propulsion studies using robot models.

Fish locomotion involves the transfer of momentum to water, and is accompanied by changes in the shape of the body and surface structures like fins or scales. Despite the great diversity of fish morphologies and swimming patterns, recent advances in research have shed light on the kinematics of swimming. The motion created by fish can be analyzed in a three-dimensional space to study their center of mass and water flow patterns, and robotic models of fish can provide greater experimental control for such purposes.

This species has developed a series of adaptations for navigating underwater during short periods of time. Its nostrils and reduced ears close underwater, and due to having its eyes protected by a full nictating membrane it mostly relies on its highly sensitive long whiskers for detecting its prey or other obstacles. Nonetheless, this species has good vision on land and uses it for detecting potential prey instead of echolocation, which has been lost in favor of smaller ears that provide better streamlining.

This species has developed certain adaptations that allow it to succesfully enter the water at a high speed when diving. Its unusual beak-shaped mouth provides streamlining, which minimizes the impact against the surface and increases the chances of a successful hunt by avoiding excessive splashing that may scare away fish. Unlike most mammals, which have seven cervical vertebrae, this species has five cervical vertebrae and they are surrounded by thick layers of soft tissue. This gives the bat a shorter neck with a shock absorbing mechanism that greatly reduces the risk of injury when penetrating the water.

Crab spiders are ambush hunters that prey on pollinator insects by lurking in the flowers they visit. Due to the nature of their hunting strategies, we hypothesized that crab spiders prefer to hide in flowers that more closely resemble their body coloration. In order to test this, we set up an arena divided into two colors and recorded the location of the spider prior to being displaced and after being moved to the center of the stage.
The data for the cyan versus green trials suggests that Mecaphesa celer shows an initial preference towards cyan, but when placed in the center of the arena it will move towards the green background. Meanwhile, in the white and yellow trials Mecaphesa initially shows no particular preference between the backgrounds, but when placed in the center of the arena it will move towards the white side. The results agree with our hypothesis that crab spiders prefer backgrounds that match their current body coloration, although further trials with a larger sample size and a refined protocol should be performed in the future to confirm these findings. Despite being a pilot study, this line of investigation could shed light on multiple aspects of the ecology and evolution of cryptic coloration in predator-prey relationships.

Geckos are able to adhere to surfaces thanks to a combination of their physical structures and behaviors. The fingertips of a gecko's hand are made up of lamellae, which are modified scales that contain special hairs called setae. These hairs are tiny, which allow for making better contact with surfaces via Van der Waals forces. As well, geckos have tendons in their hands that allow them to "peel off" their fingers when climbing, and their motions follow a complex set of behaviors that maximize their grip to surfaces.

Sea lampreys are anadromous. From their lake or sea habitats, they migrate up rivers to spawn (followed by
the death of the spawning adults); females deposit a large number of eggs in nests made by males in the
substrate of streams with moderately strong current. Larvae (ammocoete larvae) burrow in sand and silt
bottom in quiet water downstream from spawning areas and filter-feed on plankton and detritus.
After 7 years in freshwater habitats, the ammoecoete larvae undergo a metamorphosis that allows young
post metamorphic lampreys to migrate to the sea or lakes and start feeding on blood.
The lamprey uses its suction cup-like mouth to attach itself to the skin of a fish and rasps away tissue with
its sharp, probing tongue and keratinized teeth. After one year of hematophagous feeding, lampreys return
to the river to spawn and die, a year and a half after the completion of metamorphosis.

Like other crab spiders, Mecaphesa celer is an ambush hunter and it preys on pollinator insects by lurking in the flowers they visit. We hypothesized that in order to successfully capture its prey, Mecaphesa would choose to hide in flowers that more closely resemble its actual body coloration. In order to test our hypothesis, we designed an arena split into two different colors based in the RGB color model, and recorded to which side the spider moved after being placed in the center.

The data for the cyan versus green trials suggests that Mecaphesa celer shows an initial preference towards cyan, but when placed in the center of the arena it will move towards the green background. Meanwhile, in the white and yellow trials Mecaphesa initially shows no particular preference between the backgrounds, but when placed in the center of the arena it will move towards the white side.

The results agree with our hypothesis that crab spiders prefer backgrounds that match their current body coloration, although further trials with a larger sample size and a refined protocol should be performed in the future to confirm these findings. Despite being a pilot study, this line of investigation could shed light on multiple aspects of the ecology and evolution of cryptic coloration in predator-prey relationships.