Morphological diversity of the skeletal structures of fleas (Siphonaptera). Part 2: The general characteristic and features of the thorax

Abstract

Analysis of a considerable amount of data on the anatomy of 27 structures of the thorax in 96 genera of fleas (over 90% of the genera in the world fauna) shows that different flea taxa can be described based on 48 universal and specific characters, whose 203 states reflect the entire known diversity of the flea morphology. Of them, 26 characters with 96 states can be formulated based on universal terms; 22 universal characters with 88 states describe the proportions of the segments and their parts, and also proportions and shapes of their sclerites; 23 specific characters with 107 states describe the structure of the thoracic sclerites and ridges as well as the patterns of their junctions. Judging by the number of characters and their states, the most evolutionarily flexible structures in fleas are the mesosternite and its apodeme together with the upper part of the mesopleural rod. Homoplasies at various levels comprise less than half (40%) of all the character states in the thorax structure. The character states reflecting the phylogenetic closeness of taxa make up about 15%.