Search

Recent fossil finds in China and Argentina have provided startling new insights into the reproductive biology and embryology of pterosaurs, Mesozoic flying reptiles. Nineteen embryos distributed among four species representing three distinct clades have been described and all are assumed to be at, or near, term. We show here how the application of four contrasting quantitative approaches allows a more precise identification of the developmental status of embryos revealing, for the first time to our knowledge, the presence of middle and late developmental stages as well as individuals that were at term. We also identify a predicted relationship between egg size and shape and the developmental stage of embryos contained within. Small elongate eggs contain embryos at an earlier stage of development than larger rounder eggs which contain more fully developed embryos. Changes in egg shape and size probably reflect the uptake of water, consistent with a pliable shell reported for several pterosaurs. Early ossification of the vertebral column, limb girdles and principal limb bones involved some heterochronic shifts in appearance times, most notably of manus digit IV, and facilitated full development of the flight apparatus prior to hatching. This is consistent with a super-precocial flight ability and, while not excluding the possibility of parental care in pterosaurs, suggests that it was not an absolute requirement. [ABSTRACT FROM AUTHOR]

We examine the internal morphology of the female genitalia of representatives of the three subfamilies of the spider family Ochyroceratidae (Ochyroceratinae, Psilodercinae and Theotiminae) by means of scanning electron microscope. Ochyroceratines have the uterus externus constricted into a narrow neck at its connection with the uterus internus, which, after comparison with other spider families, is proposed as a synapomorphy of the subfamily. We describe Ochyrocera diablo sp. nov. from Misiones province in northeastern Argentina. The measurements of their eggs and uterus externus indicate that the eggs must squeeze through a small duct 40 times smaller in diameter. We also propose that another synapomorphy for Ochyroceratinae is the insertion of the male palpal copulatory organ in a projecting pedestal at the base of the cymbium, and update the differential diagnosis of the subfamily. Finally, we recognize that Psilodercinae Deeleman-Reinhold, 1995 is a junior objective synonym and homonym of Psilodercinae Machado, 1951 . [ABSTRACT FROM AUTHOR]

The immature stages of Rachiplusia nu (Guenée) are redescribed and illustrated, according to current standards of descriptive patterns. The immature stages of R. nu were obtained from laboratory cultures under controlled conditions of temperature at 27 ± 2°C, 14:10 (light/darkness) artificial photoperiod and 70-75% of relative humidity. For the first time, the larval instars previous to the larvae mature are described. All immature stages were compared with those of Pseudoplusia incluens (Walker), with which they can often be confused in the field. The estimation of the larval age allowed to determine that the highest rate of growth takes place in the fourth larval instar and then decreases gradually to mature larva. [ABSTRACT FROM AUTHOR]

The rote of environmental factors on the hatching response of O. albifasciatus (Macquart) eggs is studied by simulating winter conditions in the laboratory. The hypothesis tested was that hatching response is affected by: (1) time that eggs remain at low temperature, (2) storage conditions, and (3) acclimatization time. Eggs were stored at 5°C in drought and immersion conditions during 7, 21, 35, 90 and 146 days, immediately after, they were acclimatized at 22°C during 24, 72, and 168 hours, and then eggs were flooded to induce hatching. Percent of hatched eggs was analyzed with a Generalized Lineal Model with a binomial distribution. Results show that: (1) a long storage period at cold temperature and long acclimatization periods improve the hatching response; (2) storage conditions have a moderate effect on hatching, being more evident in eggs stored dry; (3) a long time of acclimatization favors the hatching response in submerged eggs more than in eggs stored dry; (4) long time at cold favors the hatching response in eggs stored dry more than in submerged eggs; (5) the hatching response of eggs that remain for a long time at low temperature is higher when the time of acclimatization is long. [ABSTRACT FROM AUTHOR]

The first dinosaur embryos found inside megaloolithid eggs from Auca Mahuevo, Patagonia, were assigned to sauropod dinosaurs that lived approximately 80 million years ago. Discovered some 25 years ago, these considerably flattened specimens still remain the only unquestionable embryonic remains of a sauropod dinosaur providing an initial glimpse into titanosaurian in ovo ontogeny. Here we describe an almost intact embryonic skull, which indicates the early development of stereoscopic vision, and an unusual monocerotic face for a sauropod. The new fossil also reveals a neurovascular sensory system in the premaxilla and a partly calcified braincase, which potentially refines estimates of its prenatal stage. The embryo was found in an egg with thicker eggshell and a partly different geochemical signature than those from the egg-bearing layers described in Auca Mahuevo. The cranial bones are comparably ossified as in previously described specimens but differ in facial anatomy and size. The new specimen reveals significant heterochrony in cranial ossifications when compared with non-sauropod sauropodomorph embryos, and demonstrates that the specialized craniofacial morphology preceded the postnatal transformation of the skull anatomy in adults of related titanosaurians. • The first 3D preserved embryonic skull of a sauropod sauropodomorph • It differs in facial anatomy and size from the sauropod embryos of Auca Mahuevo • It exhibits an unusual monocerotic and stereoscopic face for a sauropod • Heterochronies in cranial ossifications occurred in the evolution of sauropods Kundrát et al. report the first 3D preserved embryo representing a sauropod sauropodomorph. The analyses indicate an unusual monocerotic face and the early development of stereoscopic vision for a sauropod. It reveals significant heterochrony in prenatal cranial ossification when compared with non-sauropod sauropodomorphs. [ABSTRACT FROM AUTHOR]

In temperate and subtropical regions, populations of Aedes (Stegomyia) aegypti (L.) survive unfavorable winter conditions in the egg stage. Knowing their survival rates can be of great interest for the health authorities in charge of control activities. In this study, we analyzed the mortality of Ae. aegypti eggs exposed to the cold season as well as their hatching patterns under laboratory conditions in the city of Resistencia, Chaco, Argentina. The mortality rate was 48.6%. No statistically significant differences were observed in the mortality of eggs exposed at different sites. Hatching response differed significantly among the successive postexposure immersions, with the highest proportion of hatched eggs during the first immersion. These results show that the mortality rate of Ae. aegypti eggs exposed to the cold season in a subtropical city of Argentina was higher than those from temperate climate region. The additional mortality of eggs in our study might be related to fungal development (an unexpected event), which was not observed in research in temperate climate. The hatching pattern observed in this study ensures a rapid increase of the population at the beginning of the favorable breeding season, but it also maintains a batch with delayed hatching eggs, posing a risk for the community., (© The Authors 2015. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Chagas disease is a zoonosis transmitted to man by blood-sucking triatomine bugs found in the Americas. Triatoma infestans (Klug, 1834) is the main vector of Chagas' disease in Argentina. The control of this illness relies heavily on vector control through the use of insecticide. However, resistance to pyrethroid insecticides associated with ineffective field treatments has been increasingly reported in T. infestans from Argentina and Bolivia. There are few reports on the expression and causes of resistance in eggs of resistant populations, and even fewer studies on insecticide resistance throughout embryonic development. In this study, we explore the biochemical and molecular mechanisms potentially associated with the deltamethrin resistance assessed in the developing eggs of the Argentinean (Campo Largo) and Bolivian (Entre Ríos) T. infestans populations.We found measurable activity of monooxigenases and pyrethroid esterases throughout embryonic development. The pyrethroid esterase activity grew steadily throughout development in all the studied populations and was highest in eggs 12 d old. Mean enzyme activity increased from 13.6 to 16.3 and 22.2 picomol 7-hydroxycoumarin/min (7-OHC) in eggs of 4-, 7-, and 12 d old from the susceptible reference bug colony. Mean activity of resistant populations increased from 16.0 to 25.9 picomol 7-OHC/min in eggs of 4- to 12 d old in Entre Ríos population, and from 15.9 to 28.9 picomol 7-OHC/min in Campo Largo population. Molecular analysis of susceptible and resistant developing eggs detected L1014F mutation in both resistant populations, but no L925I mutation was found in any of the studied populations.Higher esterase activity and L1014F presence justify the resistance to pyrethroid throughout developing eggs of both studied T. infestans populations. The description of resistance profiles including resistance mechanisms involved will allow a rational design of campaigns for the control of Chagas disease transmission., (© The Authors 2015. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Descriptions of the last three nymphal instars of the water boatman Sigara (Aphelosigara) tucma Bachmann (Hemiptera: Heteroptera: Corixidae) are provided, for the first time, for specimens collected in northern Argentina; the egg is redescribed. Adults and nymphs were collected in the field. The eggs were obtained by dissection from females. The immature stages were fixed for microscopic examination and illustration and were described with an emphasis on morphometry and chaetotaxy of selected structures. The last three nymphal instars of S. tucma can be easily recognized by the body and head lengths and widths; the number of transverse sulcations of the rostrum; the chaetotaxy of trochanters, protibiotarsus, midlegs, metatibia, and metatarsus; and the grade of development of the wing pads. The eggs of the genus Sigara can be distinguished by the size and the chorionic surface. The chaetotaxy of the mesonotum, metafemur, and metatibia distinguish groups of species belonging to the last nymphal instar of the genus Sigara. A key to the last three nymphal instars of the species of Sigara from Argentina is provided., (© The Author 2014. Published by Oxford University Press on behalf of the Entomological Society of America.)