Chapter 2 - Morphological Adaptations of Parasitic Arthropods

Abstract

Many morphological features of parasitic insects and arachnids are modified for feeding on vertebrate blood, attaching to and clinging to hosts, and dispersal to new hosts. The body shape of ectoparasitic arthropods is commonly flattened, either dorsally or ventrally, to facilitate movement on the host, to enable hiding in tight spaces when off the host, and as protection against host grooming. Wings of parasites with ephemeral host contact are of the normal form, while those that have extended host contact have become secondarily reduced, or even completely lost, as in fleas, lice, and bed bugs. The mouthparts of parasitic arthropods are typically adapted for feeding on host tissue or body fluids. Many blood-feeding groups possess highly modified and specialized mouthparts that pierce host flesh, then consume blood from individual capillaries, often leaving little or no evidence of an actual puncture of the skin at the bite site. Parasitic insects and arachnids that are on their vertebrate hosts for extended periods of time often possess highly modified legs with strong claws and spines to accommodate attachment to the host, as well as movement amid the host hair or feathers that lessen removal by host grooming. Various sensory structures of parasitic arthropods function to detect motion, vibrations, temperature, moisture, carbon dioxide, and a plethora of chemical substances produced by potential hosts. These serve as cues that may be specific for a single host species or group of closely related host animals. Each particular modification and adaptation has allowed parasitic arthropods to more efficiently exploit their vertebrate hosts.