Project description:Spermatogenesis leads to the formation of functional sperm cells. Here we have applied high-pressure freezing in combination with transmission electron microscopy (TEM) to study the ultrastructure of sperm development in subadult males of the praying mantid Hierodula membranacea, a species in which spermatogenesis had not previously been studied. We show the ultrastructure of different stages of sperm development in this species. Thorough examination of TEM data and electron tomographic reconstructions revealed interesting structural features of the nebenkern, an organelle composed of fused mitochondria that has been studied in spermatids of other insect species. We have applied serial-section electron tomography of the nebenkern to demonstrate in three dimensions (3D) that this organelle in H. membranacea is composed of two interwoven mitochondrial derivatives, and that the mitochondrial derivatives are connected by a zipper-like structure at opposing positions. Our approach will enable further ultrastructural analyses of the nebenkern in other organisms.
Project description:Praying mantids are important models for studying a wide range of chromosome behaviors, yet few species of mantids have been characterized chromosomally. Here we show that the praying mantid Hierodula membranacea has a chromosome number of 2n = 27, and X1X1X2X2 (female): X1X2Y (male) sex determination. In male meiosis I, the X1, X2, and Y chromosomes of H. membranacea form a sex trivalent, with the Y chromosome associating with one spindle pole and the X1 and X2 chromosomes facing the opposite spindle pole. While it is possible that such a sex trivalent could experience different spindle forces on each side of the trivalent, in H. membranacea the sex trivalent aligns at the spindle equator with all of the autosomes, and then the sex chromosomes separate in anaphase I simultaneously with the autosomes. With this observation, H. membranacea can be used as a model system to study the balance of forces acting on a trivalent during meiosis I and analyze the functional importance of chromosome alignment in metaphase as a preparatory step for subsequent correct chromosome segregation.
Project description:The presence of the Indochina mantis Hierodula patellifera (Mantidae, Mantinae) as a new alien species in Italy is reported, with the description of the first stable macro-population in Europe. This macro-population shows a wide distribution, comprising several fragmented and reproducing sub-populations in Northern Italy and one in Southern France. Specimens and individuals were collected or observed on trees and ornamentals in urban ecosystems with the help of citizen science. A spatial analysis (Average Nearest Neighbour) was undertaken to characterise the present distribution pattern, evidencing the hot spots of arrival and the local spreading process. The random pattern of presence in the local urban textures and the resistance of this species to the challenging North Italian climate, are here discussed in the perspective of a future expansion to central and Northern Europe, using probably the main railways to arrive at depots and cities, travelling with Asian goods. Identification characters are also presented to separate this alien species from the other species of the subfamily Mantinae, native or introduced, present in Europe.