Individuals of gonochoric animal species that exhibit anomalous sexual phenotypes are generally classified as either intersexes or gynandromorphs, although these terms are often used inconsistently or interchangeably (Fusco and Minelli 2023). From a strictly descriptive standpoint, gynandromorphs display a mosaic condition in which distinctly male and female structures occur in clearly delimited body parts, whereas intersexes typically lack such discrete boundaries and instead present intermediate sexual traits (Narita et al. 2010, Fusco and Minelli 2023). These categories have also been differentiated based on their presumed underlying mechanisms: Gynandromorphs are usually interpreted as genotypic chimeras composed of both male and female cell lineages, while intersexes are genetically uniform individuals whose atypical phenotypes arise from developmental perturbations driven by genetic or environmental factors (Narita et al. 2010).

Despite these conceptual distinctions, broad definitions of intersexuality and gynandromorphism remain insufficient to capture the diversity and complexity of mechanisms and phenotypic expressions associated with sex anomalies (Fusco and Minelli 2023). Nevertheless, regardless of the classificatory framework adopted, the documentation and analysis of such anomalies provide valuable insights into the ontogeny, homology, and evolution of sexual characters (Rafael et al. 2017, Germani et al. 2018).

Reports of gynandromorphism and intersexuality span at least 15 insect orders, including Blattodea, Coleoptera, Diptera, Ephemeroptera, Hemiptera, Hymenoptera, Lepidoptera, Mantodea, Odonata, Orthoptera, Phasmatodea, Plecoptera, Siphonaptera, Trichoptera, and Zoraptera. Within Orthoptera, such anomalies have been recorded in Acrididae, Gryllidae, Rhaphidophoridae, Tetrigidae, Tettigoniidae (Narita et al. 2010), Chorotypidae (Benediktov 2010), and Trigonidiidae (Taniyama et al. 2018).

Here, we document the first case of gynandromorphism in a phalangopsid cricket, Endecous (Notendecous) potiguar Castro-Souza, Zefa & Ferreira, 2017. We provide photographic documentation and a detailed description of the mixed male and female morphological traits exhibited by the specimen. In addition, we compare the gynandromorph with conspecific males and females collected concurrently from the same cave in which the anomalous specimen was discovered.

The gynandromorph (ISLA151621; Fig. 1B) of E. potiguar was collected by active search in Dos Dois Cave (5°34'06.5"S, 37°40'50.4"W; Fig. 1D), located in the municipality of Felipe Guerra, Rio Grande do Norte, Brazil, on 20 April 2025. The specimen was preserved in 70% ethanol and deposited in the Collection of Subterranean Invertebrates of Lavras (ISLA), housed at the Federal University of Lavras, Minas Gerais, Brazil, alongside seven males (ISLA151615, ISLA151616, ISLA151617, ISLA151618, ISLA151622, ISLA151623, ISLA151631; Fig. 1C) and two females (ISLA151619, ISLA151620; Fig. 1A) collected from the same cave during the same sampling event.

Three adult males were dissected, and their phallic complexes were treated with a pancreatin enzymatic solution for 24 h, following Álvarez-Padilla and Hormiga (2007), to remove associated muscle tissue. The cleared phallic complexes were subsequently compared with conspecific specimens deposited in ISLA. In addition, the right tegmina of the gynandromorph and of six males (ISLA151615, ISLA151616, ISLA151617, ISLA151618, ISLA151622, ISLA151623) were removed to assess the venation and number of stridulatory teeth under an Axio Lab.A1 microscope (Zeiss). The gynandromorph was not dissected in order to preserve the natural arrangement and spatial organization of its internal organs for future comparative anatomical analyses.

The anomalous specimen, together with four males and two females, was measured and photographed using an Axiocam 506 color camera (Zeiss) mounted on an Axio Zoom V16 stereomicroscope (Zeiss). The following body regions and appendages were measured: body length, compound eye length and width, pronotum length and width, right tegmen length and width, left and right hind femur length and width, hind leg length, and ovipositor length. Detailed examination and characterization of the gynandromorph were further conducted using a Stemi 2000 stereomicroscope (Zeiss).

The specimens of E. potiguar collected in Dos Dois Cave represent a new geographical record for the species. The anomalous individual constitutes the first documented case of gynandromorphism in a phalangopsid cricket and exhibits a conspicuous mosaic of sexually derived morphological traits, a condition typically associated with gynandromorphism rather than intersexuality (Narita et al. 2010).

Adult males of E. (N.) potiguar possess a pair of superposed tegmina covering approximately half of the abdomen (Fig. 1C), as well as a laterally symmetrical phallic complex, characterized, among other features, by a markedly elongated endophallic sclerite (Fig. 3G, H). Adult females, in contrast, are apterous and bear an elongated, spear-shaped ovipositor composed of four valves (two dorsal and two ventral) (Figs 1A, 3A, 3B). The right side of the body of the gynandromorph displays predominantly male characteristics, including a well-developed tegmen (Fig. 2B, C) (a feature present in all Endecous species except E. apterus Bolfarini & Souza-Dias, 2014) as well as an underdeveloped and malformed phallic complex (Fig. 3C–F). In contrast, the left side lacks a tegmen (Fig. 2A, C), as observed in females of the genus, and bears an ovipositor that is likewise malformed and reduced, measuring approximately two-thirds the length of a typical ovipositor. No additional external traits could be unequivocally assigned to either sex. Body measurements of the gynandromorph and of adult males and females are presented in Table 1.

The right tegmen of the gynandromorph presents a mirror with three bifurcated, interconnected, arched crossveins and a harp with three weakly defined, irregular crossveins (Fig. 2C). This venation pattern falls within the range of intraspecific variation observed in E. potiguar specimens collected from the same cave (Fig. 2D–G) and in populations from other caves within the Apodi speleological group (Castro-Souza et al. 2017). In contrast, the number of stridulatory teeth recorded in males from Dos Dois Cave (x̄ = 59; SD = 6.39; n = 6; range = 50–70) is lower than previously reported for the species by Castro-Souza et al. (2017). The pars stridens of the gynandromorph bears 53 stridulatory teeth, a value that falls within the range observed in males from Dos Dois Cave.

The ovipositor of the gynandromorph is markedly shorter than that of typical females (Fig. 3A, B) and exhibits pronounced curvature and malformation. It consists of two left valves (upper (Luv) and lower (Llv)) and a single right valve (Ruv), which is shorter than the left and only slightly exceeds the paraprocts in lateral view (Fig. 3E).

Similarly, the phallic complex (already everted at the time of collection; Fig. 1B) is represented solely by the right side of a typical E. potiguar male structure (Ps.p., pseudepiphallic parameres; Ps.arm, pseudepiphallic arm, or dorsal branch sensuCastro-Souza et al. 2017; A, pseudepiphallic A sclerite; Fig. 3C–F). These sclerites are comparable in shape and length to those of adult males (Fig. 3G, H). However, the endophallic sclerite (End.s) (or endophallic duct sensuCastro-Souza et al. 2017) is distinctly sinuous along its entire length (Fig. 3F), indicating structural deformation. The subgenital plate, which is sexually dimorphic in the species, is also malformed (Fig. 3F).

Males and females of E. potiguar are similar in morphology, differing primarily in their reproductive structures and associated traits, as well as in the presence of developed tegmina in males. As previously noted by Castro-Souza et al. (2017), both sexes exhibit comparable body sizes, a pattern also observed in the specimens from Dos Dois Cave, including the gynandromorph (Table 1).

From a strictly descriptive standpoint, we classify this individual as a gynandromorph. The specimen displays discrete external body regions that can be unambiguously assigned to either male or female conditions, in contrast to intersex individuals, which typically exhibit intermediate phenotypes (Narita et al. 2010, Fusco and Minelli 2023). Following the approach advocated by Fusco and Minelli (2023), a morphology-based classification avoids uncertainties associated with inferring the underlying developmental mechanisms.

At first inspection, the distribution of sexual traits in the analyzed specimen suggests a bilateral pattern, with the right side expressing male features and the left side expressing female features. However, closer examination of the terminal abdominal region reveals the presence of ovipositor valves on both sides of the body, indicating a more complex chimeric arrangement of male and female tissues. This configuration is consistent with the “mosaic” or “patchy” types of gynandromorphism described by Michez et al. (2009) and Fusco and Minelli (2023), respectively.

In this context, the anomalous specimen reported herein is noteworthy, as most gynandromorphic Orthoptera are classified as bilateral (Hewitt 1979, Barrientos-Lozano et al. 2015), with multiple cases reported in Acrididae (e.g., Friauf 1947, White 1968, Aldini 2017) and Tettigoniidae (e.g., Agar 1939, Nickle 1983, Robert 2008, Massa 2010). Barranco et al. (1995) discussed two cytogenetic theories that could explain the rise of bilateral gynandromorphic specimens in Orthoptera: one involving the loss of an X chromosome in an XX zygote during the first cleavage division, and the other involving the fertilization of a binucleate egg by two spermatozoa, one carrying an X chromosome and the other lacking it. The development of mosaic patterns of gynandromorphism, however, remains less well understood. Accordingly, further genetic, ontogenetic, and anatomical investigations are necessary to elucidate the processes of sex determination and cellular differentiation in Orthoptera, particularly in phalangopsid crickets.

The occurrence of E. potiguar in an additional cave within the Apodi speleological group further reinforces the broad distribution of this species across subterranean environments in western Rio Grande do Norte. Such a wide distribution may reflect dispersal through interconnected subterranean voids or, alternatively, episodic surface movements during the rainy season when the otherwise harsh conditions of the surrounding semiarid landscape are temporarily attenuated (Castro-Souza et al. 2017).

The species is abundant in Dos Dois Cave as well as in other caves throughout the region (Castro-Souza et al. 2017). Moreover, adults exhibit conspicuous sexual dimorphism, allowing for straightforward discrimination between males and females, an attribute that facilitates the detection of anomalous individuals (Narita et al. 2010). Together, these factors likely increase the probability of encountering rare phenotypes, such as the gynandromorph described herein. Consequently, this record alone should not be considered as an estimate of the frequency of gynandromorphism in natural populations of this phalangopsid cricket. Nevertheless, it is important to emphasize that this condition appears to be exceedingly rare in the species, as sampling efforts conducted in caves of this region over the past two decades have yielded only a single gynandromorph to date.