In this paper we describe a new species of Luzarinae cricket collected from the cave "Gruta de Ubajara, municipality of Ubajara, State of Ceará, Brazil, highlighting phallic sclerites morphology and chromosome complement as diagnostic characters. We presented meiotic and mitotic characterization in order to define the karyotype with 2n = 12 + X1X2♂/12 + X1X1X2X2♀. This represents the first record of X1X20 chromosomal sex system in Gryllidae.
Karyotypes in the worldwide subfamily Oecanthinae show variations in diploid number, chromosome morphology, and sex-chromosome system. This study described the chromosome set and phylogenetic relationships of four Neotropical species,
Oecanthus lineolatus, O. valensis
,
O. pallidus
, and
O. pictus
. We used classical cytogenetics and Bayesian Inference for phylogenetic reconstruction, using the mitochondrial genes
COI
,
12S rRNA
, and
16S rRNA
; and analyzed the phylogenetic patterns of changes in chromosome numbers, using ChromEvol. We observed differences in chromosome number among species and two different sex-chromosome systems.
Oecanthus pictus
showed 2n = 21, X0♂/22, XX♀;
O. lineolatus
, 2n = 20, XY♂/XX♀; and
O. valensis
and
O. pallidus
, 2n = 18, XY♂/XX♀. The karyotype of
Oecanthus
was asymmetric, one group with large chromosomes and variation in heterochromatin distribution, and another with small acrocentric chromosomes. The phylogenetic tree recovered two main groups: one with the Palearctic species and another with species from different bioregions, but with low posterior probability. The Neotropical species grouped separately,
O. valensis
and
O. pictus
with Nearctic and Ethiopian species, and
O. pallidus
and
O. lineolatus
in another, well-supported clade. Together, the phylogenic and chromosome data suggest descending dysploidy events during the evolution of the group.
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