Mid-Mesozoic flea-like ectoparasites of feathered or haired vertebrates

Parasite-host associations among insects and mammals or birds are well attended by neontological studies [1]. An Eocene bird louse compression fossil [2, 3] and several flea specimens from Eocene and Oligocene ambers [4-8], reported to date, are exceptionally similar to living louse and flea taxa. But the origin, morphology, and early evolution of parasites and their associations with hosts are poorly known [9, 10] due to sparse records of putative ectoparasites with uncertain classification in the Mesozoic, most lacking mouthpart information and other critical details of the head morphology [11-15]. Here we present two primitive flea-like species assigned to the Pseudopulicidae Gao, Shih et Ren familia nova (fam. nov.), Pseudopulex jurassicus Gao, Shih et Ren genus novum et species nova (gen. et sp. nov) from the Middle Jurassic [16] and P. magnus Gao, Shih et Ren sp. nov. from the Early Cretaceous in China [17]. They exhibit many features of ectoparasitic insects. Large body size and long serrated stylets for piercing tough and thick skin or hides of hosts suggest that these primitive ectoparasites might have lived on and sucked the blood of relatively large hosts, such as contemporaneous feathered dinosaurs and/or pterosaurs or medium-sized mammals (found in the Early Cretaceous, but not the Middle Jurassic).     

Growth and microvascular development of the uterus during early pregnancy in ewes.

Growth and microvascular development of the uterus were evaluated for ewes on Days 12, 18, 24, and 30 after mating (3-4 ewes/day; Day 0 = day of mating) in two experiments. In experiment 1, fresh weight and dry weight of gravid uterine horns were increased on Days 24 and 30 after mating, whereas those of nongravid uterine horns were elevated only on Day 30. The increased fresh and dry weights of gravid uterine horns on Day 24 were associated with uterine hyperplasia (increased DNA content). Increased fresh and dry weights of gravid uterine horns on Day 30, however, were associated with hypertrophy (increased RNA:DNA and protein:DNA ratios) of uterine tissues. In experiment 2, vascularity of endometrial tissues was elevated on Days 24 and 30 after mating. In addition, dramatic changes in uterine architecture (increased lumenal diameter and decreased endometrial thickness) and in uterine microvascular development (increased abundance of large microvessels and development of a subepithelial capillary plexus) were observed by Day 24 after mating. Characterization of the patterns of uterine growth and microvascular development will enable us to further define the role of previously reported uterine and conceptus-derived growth and angiogenic factors during early pregnancy.     

Comparison of the respiratory transition at birth or hatching in viviparous and oviparous amniote vertebrates

Regardless of the mode of reproduction, three things must occur at birth or hatching in amniote vertebrates: initiation of breathing, pulmonary fluid elimination and reabsorption, and adequate perfusion of pulmonary circulation. Although data on these events are few, there appears to be no fundamental difference in them that can be associated with the oviparity to viviparity transition. There are, however, differences in the timing of these events in oviparous and viviparous amniotes. The transition to neonatal respiration tends to be very quick in viviparous species because the vascular support for oxygen uptake provided by the mother is rapidly disassociated from the mechanism for uptake by the embryo. By contrast, hatching often is a slow process, taking 24 h or more in some species, as chorioallantoic blood flow slowly gives way to clearing of the lungs and pulmonary gas exchange. Little is known of the mechanisms of pulmonary fluid elimination and reabsorption or lung inflation in reptiles, but the cellular structures and surfactant systems are similar in all amniote vertebrates. Nevertheless, there are differences, particularly of timing and maturation of various systems, but there has been no exploration of the functional (or phylogenetic) bases of these differences. Perfusion of the neonatal pulmonary system to support respiration in reptiles remains to be investigated. In mammals and birds, closure of the ductus arteriosus is important, but the role played by the ductus arterioisus in reptilian hatching or birth is not known.     

Comparison of the respiratory transition at birth or hatching in viviparous and oviparous amniote vertebrates.

Regardless of the mode of reproduction, three things must occur at birth or hatching in amniote vertebrates: initiation of breathing, pulmonary fluid elimination and reabsorption, and adequate perfusion of pulmonary circulation. Although data on these events are few, there appears to be no fundamental difference in them that can be associated with the oviparity to viviparity transition. There are, however, differences in the timing of these events in oviparous and viviparous amniotes. The transition to neonatal respiration tends to be very quick in viviparous species because the vascular support for oxygen uptake provided by the mother is rapidly disassociated from the mechanism for uptake by the embryo. By contrast, hatching often is a slow process, taking 24 h or more in some species, as chorioallantoic blood flow slowly gives way to clearing of the lungs and pulmonary gas exchange. Little is known of the mechanisms of pulmonary fluid elimination and reabsorption or lung inflation in reptiles, but the cellular structures and surfactant systems are similar in all amniote vertebrates. Nevertheless, there are differences, particularly of timing and maturation of various systems, but there has been no exploration of the functional (or phylogenetic) bases of these differences. Perfusion of the neonatal pulmonary system to support respiration in reptiles remains to be investigated. In mammals and birds, closure of the ductus arteriosus is important, but the role played by the ductus arterioisus in reptilian hatching or birth is not known.