Spontaneous centric fusions affecting chiasma conditions in Dichroplus elongatus (Orthoptera)

Spontaneous centric fusions were detected in two natural populations, Raco (RA) and Tafi Viejo (TV), of Dichroplus elongatus from Tucumán Province (Argentina). In TV one male carried centric fusion between autosomes L3 and M4 (3/4 fusion). One male from RA showed two centric fusions, one between the X and M5 (X/5) and the other between autosomes L1 and M4 (1/4) (in homozygous condition). A significant reduction in the number of chiasmata in the fused bivalents or trivalents with respect to standard karyotypes was observed in all cases except the M4 arm of the 1/4 fusion. Significant chiasma redistribution towards more distal positions was observed in the L1 arm of the 1/4 fusion, the L3 arm of the 3/4 fusion and the L5 arm of the X/5 fusion. These results revealed that a) some fusions per se may affect chiasma conditions, b) the intensity of such effect varies among chromosome pairs.