Comparative cytogenetic study of three Macrolophus species (Heteroptera, Miridae.)

Macrolophus pygmaeus (Rambur, 1839) (Insecta, Heteroptera, Miridae) is a predator of key vegetable crop pests applied as a biocontrol agent in the Mediterranean region. M. pygmaeus and M. melanotoma (A. Costa, 1853) are cryptic species with great morphological similarity which results in their misidentification and negative consequences for the conservation of their populations on greenhouse and outdoor crops. In order to find out specific markers for their separation we studied the karyotype, male meiosis and heterochromatin composition of these species and additionally of a third species (as a reference one), M. costalis Fieber, 1858. We demonstrate here that all the three species share achiasmate male meiosis and sex chromosome pre-reduction. On the other hand, the species differ in karyotype, with 2n=28 (26+XY) in M. pygmaeus, 2n=27 (24+X1X2Y) in M. costalis, and 2n=34 (32+XY) in M. melanotoma, and heterochromatin distribution and composition. In addition, the species differ in sperm morphology: sperm cells of M. costalis are significantly longer with longer head and tail than those of M. melanotoma and M. pygmaeus, whereas sperm cells of M. melanotoma have a longer tail than those of M. pygmaeus. All these characters can be used as markers to identify the species, in particular the cryptic species M. melanotoma and M. pygmaeus.This study has been funded by the Spanish Ministry of Economy and Competitiveness (MINECO) (Project AGL2011-24349), and by a travel grant from the University of Lleida - Fundació “La Caixa” to Dr Grozeva. The chromosome analysis was performed using microscope Axio Scope A1 – Carl Zeiss Microscopy upgraded by the project WETLANET (FP7 CSA – SUPPORT ACTION, GA 229802). We thank cordially Prof. Dr V. Kuznetsova for the valuable advices to improve the manuscrip

Elliptic Fourier analysis in the study of the male genitalia to discriminate three Macrolophus species (Hemiptera:Miridae)

Within the genus Macrolophus (Heteroptera: Miridae), the species M. costalis (Fieber), M. melanotoma (Costa) and M. pygmaeus (Rambur) are present in the Mediterranean region on a wide variety of plant species. While M. costalis can easily be separated from the other two by the black tip at the scutellum, M. pygmaeus and M. melanotoma are cryptic species, extremely similar to one another in external traits, which has resulted in misidentifications. M. pygmaeus is an efficient biological control agent, both in greenhouse and field crops. The misidentification of these cryptic species could limit the effectiveness of biological control programs. Although the morphology of the left paramere of the male genitalia has been used as a character for identification of these two cryptic species, there is controversy surrounding the reliability of this character as a taxonomic tool for these species. Using geometric morphometric techniques, which are a powerful approach in detecting slight shape variations, the left parameres from these three Macrolophus species were compared. The paramere of M. costalis was larger and had a different shape to that of M. melanotoma and M. pygmaeus; however, no differences in size or shape were found between the left paramere of M. melanotoma and that of M. pygmaeus. Therefore, our results confirm that this character is too similar and it cannot be used to discriminate between these two cryptic species.This study has been funded by the Spanish Ministry of Economy and Competitiveness (MINECO) (Project AGL2011-24349 and AGL2014-53970-C2-2-R)

Pre-planting inoculation for early establishment of Dicyphus bolivari and D. errans on tomatoes

Slow establishment and risks of plant damage are major constraints for the use of the predatory mirid bugs that are commercially available for release in greenhouse crops. Therefore, a new interest has turned towards two predatory Dicyphus species (Heteroptera: Miridae) that have been investigated in the past but have not been used commercially in augmentative biological control. We assessed their development duration and survival at temperature and day length of summer and winter conditions and assessed the feasibility of pre-planting predator establishment on plant seedlings under those conditions. Dicyphus bolivari (Lindberg) and D. errans (Wolff) nymphs reached the adult stage in 47.4 (winter conditions) and 18.6 days (summer conditions) and 46.0 (winter) and 16.3 days (summer) respectively. They showed more than 90% survival when provided with food (Ephestia eggs). Provision of food allowed females to lay more eggs and to distribute them more evenly among tomato seedlings. No injuries or other negative effects on tomato seedling development were observed. Nymph development time of the two mirid species studied were slightly higher than other commercial mirid predators. The results show great potential of these predatory bugs, which are now being tested under field conditions

Comparative cytogenetic study of three Macrolophus species (Heteroptera, Miridae.)

Macrolophus pygmaeus (Rambur, 1839) (Insecta, Heteroptera, Miridae) is a predator of key vegetable crop pests applied as a biocontrol agent in the Mediterranean region. M. pygmaeus and M. melanotoma (A. Costa, 1853) are cryptic species with great morphological similarity which results in their misidentification and negative consequences for the conservation of their populations on greenhouse and outdoor crops. In order to find out specific markers for their separation we studied the karyotype, male meiosis and heterochromatin composition of these species and additionally of a third species (as a reference one), M. costalis Fieber, 1858. We demonstrate here that all the three species share achiasmate male meiosis and sex chromosome pre-reduction. On the other hand, the species differ in karyotype, with 2n=28 (26+XY) in M. pygmaeus, 2n=27 (24+X1X2Y) in M. costalis, and 2n=34 (32+XY) in M. melanotoma, and heterochromatin distribution and composition. In addition, the species differ in sperm morphology: sperm cells of M. costalis are significantly longer with longer head and tail than those of M. melanotoma and M. pygmaeus, whereas sperm cells of M. melanotoma have a longer tail than those of M. pygmaeus. All these characters can be used as markers to identify the species, in particular the cryptic species M. melanotoma and M. pygmaeus