Arthropod Roundup: Callinectes in the UK, horny females, artificial arthropod hair, and genetic mosquito control

Brief blurbs about recent arthropod news and research:

• The blue crab, Callinectes sapidus, has been found in England for the second time ever. These ill-tempered, but delicious, swimming crabs are native to North America; where they represent a major marine fishery despite serious conservation concerns. Previously, blue crabs have turned up in Japan and the Mediterranean. It is conventionally thought that these crabs were brought in as larvae in ship ballast water and have since gained a foothold in their new homes. It is possible that this blue crab in Cornwall also came over from America in ballast water, or it could have been carried on ocean currents up from the Mediterranean population. It is unclear weather this is an isolated individual or a representative of a new invasive population.
• You will be disappointed to learn that the horny females I referred to in the title are dung beetles. One usually associates the growth of horns and antlers with males who use them to battle for dominance in a social hierarchy or for their pick of the choicest females. However, female dung beetles, Onthophagus sagittarius, are known to have much more impressive horns than their male counterparts. A new study suggests that these horns are used by the females to compete over reproductive resources (i.e. poop). Size matched females with larger horns were found to achieve greater reproductive fitness, making horn size a positively selected female secondary sex characteristic in these beetles. (Via 80Beats)
  
  

  Horned Onthophagus sagittarius females square off. Photo: Sean Stankowski

• New research reports the development of synthetic superhydrophobic materials inspired by tiny, water repellent hairs in insects. These hairs are found on the legs of water walkers and the backs of Stenocarid beetles, which use the hairs to channel water droplets to their mouth.
• The genomes of the malaria mosquito, Anopheles gambiae, and the yellow fever mosquito, Aedes aegypti, were published in 2002 and 2006, respectively. These sequencing efforts appear to be bearing a lot of fruit as of late; as several genetic approaches to controlling the spread of mosquito vectored diseases have been proposed. These include; increasing the immunity of mosquitoes to the dengue fever virus, weakening mosquitoes by preventing waste secretion, and preventing female mosquitoes from developing functioning flight structures. Some of these ideas are pretty far from real-world application unfortunately, and the buzz surrounding them seems to be the result of overly-excitable university PR departments.

Bees can learn to discriminate human faces

New research published in the Journal of Experimental Biology sheds light onto visual stimuli processing in arthropods. Researchers (Avargues-Weber et al., 2010) have shown that honeybees, Apis mellifera, are capable of complex visual processing and learning tasks that are commonly reserved for primates. With a small fraction of mammalian neural complexity, honeybees are capable of discriminating face-like visual stimuli; both between face-like and non-face-like stimuli and between variations of face like stimuli. That is, the honeybees are capable of visually discriminating and remembering one human face from another.

Of course, there is no ecological reasoning for honeybees to discriminate human faces, but the behavior is a clue about the bee’s underlying visual processing capacities. This research tells us that honeybees are able to perceive and learn, not just the individual components of a visual stimulus, but the interrelationships between them. This is the first demonstrated instance of configural processing in an arthropod.

Members of this research team first suggested that bees were capable of discriminating human faces in 2005. However, their work was criticized because it did not control for low-level stimuli (individual cues, center of gravity, symmetry, spacial frequency, and background cues) in the faces. That is, the researchers did not clearly show that the bees were actually carrying out configural processing; perceiving the interrelationships of multiple facial components processed together.

In their new paper, the researchers preformed a variety of behavioral experiments to control for low-level visual cues. They primarily used a Y-maze chamber with a choice of two visual stimuli at the end of the two branches. The bees were trained to associate a sugar reward with one of the stimuli. Afterwords, in the absence of a reward, the researchers recorded the percentage of correct choices by the bees.

First, the researchers showed that the bees could distinguish face-like and non-face-like arrangements of dashes and dots. Furthermore, they confirmed that the bees were discriminating based on the combined relationship of the eyes, nose, and mouth components of the face-like arrangements; and not just the orientation of individual components. A series of additional controls showed that the bees were not using symmetry, center of gravity, or spatial frequency cues to distinguish the stimuli. Finally, the researchers showed that the honeybees could also distinguish photos of human faces.
Some of the choices that the honeybees were able to distinguish.

This research concludes that honeybees are capable of high-level cue integration and configural visual processing. Such a capacity in honeybees is likely used for navigation and identifying flowers. The neurobiology responsible for configural visual processing is only partially understood in humans, and completely undescribed in arthropods. By working out this processing system in comparatively simple insect brains, researchers can hope to eventually apply this finding to synthetic facial recognition systems.

References:

• Avargues-Weber, A., Portelli, G., Benard, J., Dyer, A., & Giurfa, M. (2010). Configural processing enables discrimination and categorization of face-like stimuli in honeybees Journal of Experimental Biology, 213 (4), 593-601 DOI: 10.1242/jeb.039263
• Dyer, A.G., Neumeyer, C. & Chittka, L., 2005. Honeybee (Apis mellifera) vision can discriminate between and recognise images of human faces. J Exp Biol, 208(24), 4709-4714.