The Ecological Significance of Aphid Cornicles and Their Secretions

Aphid cornicles are abdominal appendages that secrete an array of volatile and nonvolatile compounds with diverse ecological functions. The emission of alarm pheromones yields altruistic benefits for clone-mates in the aphid colony, which is essentially a superorganism with a collective fate. Secreted droplets also contain unsaturated triglycerides, fast-drying adhesives that can be lethal when smeared on natural enemies but more often impede their foraging efficiency. The longest cornicles have evolved in aphids that feed in exposed locations and are likely used to scent-mark colony intruders. Reduced cornicles are associated with reliance on alternative defenses, such as the secretion of protective waxes or myrmecophily. Root-feeding and gall-forming lifestyles provide protected feeding sites and are associated with an absence of cornicles. In some eusocial gall-formers, soldier morphs become repositories of cornicle secretion used to defend the gall, either as menopausal apterae that defend dispersing alatae or as sterile first instars that dispatch predators with their stylets and use cornicle secretions as a construction material for gall repair. Collectively, the evidence is consistent with an adaptive radiation of derived cornicle functions molded by the ecological lifestyle of the aphid lineage.

Turning defence into offence? Intrusion of cladoceran brood chambers by a green alga leads to reproductive failure

Microalgae are the foundation of aquatic food webs. Their ability to defend against grazers is paramount to their survival, and modulates their ecological functions. Here, we report a novel anti-grazer strategy in the common green alga Chlorella vulgaris against two grazers, Daphnia magna and Simocephalus sp. The algal cells entered the brood chamber of both grazers, presumably using the brood current generated by the grazer's abdominal appendages. Once inside, the alga densely colonized the eggs, significantly reducing reproductive success. The effect was apparent under continuous light or higher light intensity. The algal cells remained viable following removal from the brood chamber, continuing to grow when inoculated in fresh medium. No brood chamber colonization was found when the grazers were fed the reference diet Raphidocelis subcapitata under the same experimental conditions, despite the fact that both algal species were readily ingested by the grazers and were small enough to enter their brood chambers. These observations suggest that C. vulgaris can directly inflict harm on the grazers' reproductive structure. There is no known prior example of brood chamber colonization by a microalgal prey; our results point to a new type of grazer–algae interaction in the plankton that fundamentally differs from other antagonistic ecological interactions.

STUDIEN AN KARIBISCHEN CIRRIPEDIEN I. ERGANZENDE BESCHREIBUNG VON SCALPELLUM REGINA PILSBRY, 1907

A supplementary description of Scalpellum regina is given, based on the morphology of mouth parts, cirri, abdominal appendages and penis. Also for the first time are described and illustrated the cypris larva and complemental males of this species. There are given some remarks on the substrata of the specimens found in Colombian waters, and briefly discussed the intrageneric relationships of Scalpellum.

Model Development and Analysis of a Cricket Filiform Hair Socket Under Low Velocity Air Currents

Cricket filiform hairs are very sensitive to air currents in the animal’s immediate environment generated by movement of other animals or objects. When an air current is experienced by the animal, filiform hairs located on a pair of abdominal appendages called cerci deflect from their original position, activating the sensing mechanism. Though the flow sensing mechanism of the hair has been studied previously and flow sensors have been fabricated based on the same principle, the socket structure in which the hair base sits and which encompasses the hair below the skin of the cricket has not been characterized in terms of deformation and stress transfers. This paper presents a preliminary study on the response of the socket under a given loading or displacement the hair experiences. If the socket is characterized well, the mechanical principles can be applied in the design of a highly-responsive MEMS senor.