taxonID	type	description	language	source
901087E4BA1FFFDAFE53F98ACDCDFD82.taxon	description	We compiled 125 papers that included cytogenetic data on Loricariidae species. These studies comprised a diversity of 234 species, here included those identified as “ sp. ”, prope, “ aff. ”, “ cf. ”, “ n. sp. ”, and “ L ” as distinct species, from 48 genus. Hypostominae was the subfamily most represented with 142 species karyotyped, followed by Loricariinae (54 spp.), Hypoptopomatinae (34 spp.), and Delturinae and Rhinelepinae with 2 spp. each, with absence of data for Lithogeninae. The Hypostomus genus was the most represented with 26 valid species karyotyped, in a total of 159 records when including all populational data and those identified as “ sp. ”, prope, “ aff. ”, “ cf. ”, “ n. sp. ”, and “ L ”. The geographical coordinates plotted into maps show a distribution of species cytogenetically investigated in Brazil, Argentina, and Paraguay, comprising six distinct river basins (Fig. 2). Although species from Ecuador and Venezuela were also compiled, those papers do not present geographical coordinates of the sample sites. Diploid number varied from 2 n = 33 in males of Rineloricaria teffeana (Steindachner, 1879) (Marajó et al., 2022) to 2 n = 96 in Hemipsilichthys sp. (Kavalco et al., 2004, 2005). The fundamental number ranged from 34 in R. teffeana (Marajó et al., 2022) to 142 in Hypostomus topavae (Godoy, 1969) (Kamei et al., 2017), and the simple distribution of Ag-NOR / 18 S rDNA was the most common with 269 records, against 110 records of multiple sites. Seven sex chromosomes systems were described for 31 Loricariidae species, the simple XX / XY, XX / X 0, and ZZ / ZW, and the multiples X 1 X 1 X 2 X 2 / X 1 X 2 Y, XX / XY 1 Y 2, ZZ / ZW 1 W 2, and Z 1 Z 1 Z 2 Z 2 / Z 1 Z 2 W 1 W 2. B chromosomes were found in five species, varying from 1 B (e. g., de Souza et al., 2009) to 3 B chromosomes (e. g., Porto et al., 2010). Complete results were compiled in Tab. 1.	en	Sassi, Francisco de Menezes Cavalcante, Cioffi, Marcelo de Bello, Moreira-Filho, Orlando (2024): A state-of-art review of Loricariidae (Ostariophysi: Siluriformes) cytogenetics. Neotropical Ichthyology 22 (4): e 240050, DOI: 10.1590/1982-0224-2024-0050, URL: https://doi.org/10.1590/1982-0224-2024-0050
901087E4BA1FFFDAFE53F98ACDCDFD82.taxon	discussion	DISCUSSION The origin of the chromosomal diversity of Loricariidae is attributed to both ecological and molecular factors. Small and isolated populations, in addition to the low vagility, are the main ecological characteristics that have allowed the fixation of chromosomal rearrangements in Loricariidae, as suggested for Farlowella (Marajó et al., 2018), Harttia (Sassi et al., 2023), and Rineloricaria (Rosa et al., 2012). The diploid number 2 n = 54 is often considered the ancestral diploid number for the family, since it is observed in most Loricariidae subfamilies and present in other Siluriformes (Artoni, Bertollo, 2001). However, there is no consensus on the matter particularly considering the new karyotypic description of basal taxa within subfamilies. Takagui et al. (2020) in a review of Loricariinae karyotypes argue that although predominant, 2 n = 54 should not be considered the basal diploid number for the family because multiple divergences in the microstructure of karyotypes within the same 2 n are recurrently seen throughout the family. Notably, the 2 n range in Loricarioidei suggest that other numbers rather than 2 n = 54 can be considered the plesiomorphic ones, as Astroblepidae presents 2 n = 52 – 54, Scoloplacidae 2 n = 50, Callichthyidae 2 n = 40 – 134, and Trichomycteridae 2 n = 32 – 62 (reviewed by Conde-Saldaña et al., 2018). Beyond that, the Diplomystidae (Siluroidei) presents 2 n = 56 chromosomes (Campos et al., 1997; Oliveira, Gosztonyi, 2000), which might also suggest that as the ancestral 2 n. We plotted the 2 n range per subfamily into the main molecular phylogenetic reconstructions of Loricariidae (Fig. 3) and 2 n = 54 is the most widespread, being conserved in Rhinelepinae and present in all other subfamilies. Regardless matter whether 2 n = 54 or 2 n = 56 is the ancestral diploid number, it is noteworthy that chromosomal evolution in Loricariidae is complex. Considering the lower number of karyotyped species when compared to the valid richness, 234 spp. with cytogenetic data against 1,051 valid species (Fricke et al., 2023), it is difficult to establish the evolutionary pathways that led to the observed variability. Notably, while the stability is restricted to 2 n in some genera, with high divergence in karyotype structure, as the 2 n = 58 in Farlowella, 2 n = 54 in Corumbataia, and 2 n = 52 in Pterygoplichthys, stable 2 n and karyotype is also observed, as the 2 n = 52 (26 m + 20 sm + 6 st / a) in two species of Panaque. Our compilation reveals that processes of ascending and descending dysploidy (i. e., the increase or decrease of 2 n while preserving the genomic content) were frequent in most subfamilies but Rhinelepinae, which may exhibit the constant 2 n = 54 as a symplesiomorphic trait. Despite the 2 n conservation in Rhinelepinae, variations in the karyotype structure are observed within and between species. Populations of Rhinelepis aspera Spix & Agassiz, 1829 from the same river differ in the karyotype formula (Artoni, Bertollo, 2001; Endo et al., 2012), suggesting that pericentric inversions played an important role in the chromosomal evolution of the species. Such mechanism is not restricted to Rhinelepinae but also observed in other loricariids, such as Ancistrus (Mariotto et al., 2009), Loricariichthys (Takagui et al., 2014), and Rineloricaria (Rosa et al., 2012; Primo et al., 2018). In addition, the multiple Ag-NOR observed in Pogonopoma wertheimeri (Steindachner, 1867) (Artoni, Bertollo, 2001) when compared to the simple distribution in other Rhinelepinae species suggest that other mechanisms are also important for the chromosomal evolution in the group. Notably, numeric and structural polymorphisms are frequently observed in loricariids, for example in the multiple karyomorphs of Rineloricaria pentamaculata Langeani & de Araujo, 1994 (Glugoski et al., 2023), and the presence of B chromosomes in Harttia longipinna Langeani, Oyakawa & Montoya-Burgos, 2001 (Blanco et al., 2012). This chromosomal diversity was probably generated by a combination of rearrangements that include Robertsonian fusions and fissions, paracentric and pericentric inversions, and translocations (Artoni, Bertollo, 2001; Kavalco et al., 2004; Ziemniczak et al., 2012). Although rare in most fish species, being observed in only about 5 % of Teleostei species (Arai, 2011; Sember et al., 2021), our compilation shows that Loricariidae species carry seven out of the nine known sex chromosome systems observed among fishes. Ancistrus was demonstrated to harbor the largest diversity of sex chromosomes with six of the seven recognized systems for the family distributed in 18 species, corresponding to about 23 % of the valid species (Neuhaus et al., 2023). The simple XX / XY was the most predominant in the genus, recorded in A. maximus de Oliveira, Zuanon, Zawadzki & Rapp Py-Daniel, 2015 (Oliveira et al., 2010; Favarato et al., 2016), Ancistrus cf. dubius (Mariotto et al., 2011), Ancistrus sp. 1 Quianduba River (Silva et al., 2022, 2023), Ancistrus sp. 1 Maracapucú River (Santos da Silva et al., 2023), Ancistrus sp. 1 Ilha do Capim (Santos da Silva et al., 2023), Ancistrus sp. Catalão (Favarato et al., 2016), Ancistrus sp. L 2 (Prizon et al., 2017), Ancistrus sp. L 3 (Prizon et al., 2017), and Ancistrus sp. Purus (Oliveira et al., 2010; Favarato et al., 2016). Additionally, two multiple sex chromosome systems that were not observed in any other Loricariidae are recorded in Ancistrus: ZZ / ZW 1 W 2 in A. clementinae Rendahl, 1937 (Nirchio et al., 2023), and Z 1 Z 1 Z 2 Z 2 / Z 1 Z 2 W 1 W 2 (Oliveira et al., 2008; Favarato et al., 2016). On other hand, Harttia harbor the highest number of multiple sex chromosome systems when compared to the number of valid species, with six occurrences representing about 25 % of valid species (compiled in Sassi et al., 2021): XX / XY 1 Y 2 in H. carvalhoi Miranda Ribeiro, 1939, H. intermontana Oliveira & Oyakawa, 2019, and Harttia sp. 1 (Centofante et al., 2006; Deon et al., 2020); X 1 X 1 X 2 X 2 / X 1 X 2 Y in H. duriventris Rapp Py-Daniel & Oliveira, 2001, H. punctata Rapp Py-Daniel & Oliveira, 2001, and H. villasboas Oyakawa, Fichberg & Rapp Py-Daniel, 2018 (Blanco et al., 2014; Sassi et al., 2020), in addition to putative simple XX / XY in H. rondoni Oyakawa, Fichberg & Rapp Py-Daniel, 2018 and H. torrenticola Oyakawa, 1993 (Deon et al., 2020; Sassi et al., 2020). The Loricariidae diversity of sex chromosomes was originated by rearrangements that include translocations (Blanco et al., 2014), centric fissions (Sassi et al., 2023); centric fusions (Centofante et al., 2006), and pericentric inversions (Artoni et al., 1998), including the combination of distinct rearrangements especially in the origin of multiple sex chromosome systems (Oliveira et al., 2008; Deon et al., 2022). Sex chromosomes in Loricariidae seems to have independent origins, but further research is required to explore the genomic content of those sex chromosomes and its origin. Indeed, there is a recognized lack of information regarding the effects of environmental cues and molecular / gene mechanisms in sex determination of Neotropical fishes (Fernandino, Hattori, 2019). Most Loricariidae species present a single 18 S rDNA / Ag-NOR site, which is also considered a plesiomorphic character in the group (Artoni, Bertollo, 2001; Kavalco et al., 2004), and the standard distribution in most vertebrates (Sochorová et al., 2018). Notably, such region in loricariids is involved in several chromosomal rearrangements, including the origin and differentiation of sex chromosomes, being considered evolutionary breakpoint regions in Ancistrus, Harttia, and Rineloricaria (Glugoski et al., 2018; Deon et al., 2022). Size heteromorphism in the Ag-NOR site is also common, probably because of unequal crossing-over between homologs (Takagui et al., 2020). According to our review, some genus conserved the simple Ag-NOR locus in all analyzed species to date (here included only those genera with more than one species karyotyped), namely as Baryancistrus, Corumbataia, Farlowella, Harttia, Hisonotus, Lasiancistrus, Loricaria, Loricariichthys, Neoplecostomus, Panaqolus, Panaque, Pareiorhina, Pseudacanthicus, Pterygoplichthys, and Scobinancistrus. On other hand, the multiple distribution of Ag-NOR seems to be conserved only in Hypancistrus, while other genus as Ancistrus, Hypostomus, and Rineloricaria present both simple and multiple distributions on chromosomes. Although distributed throughout the Neotropical region, there is a predominance of cytogenetic studies in Loricariidae species from Brazil (Fig. 2). Few studies were conducted in other countries that includes Argentina, Ecuador, Paraguay, and Venezuela. Notably, those in Argentina and Paraguay were mostly restricted to the frontier region with Brazil. When accounting the Brazilian territory, is also notable that some regions are poorly represented in cytogenetic studies, especially the northeast in which at least nine states have not been included in the cytogenetic samplings. In addition, the Guianas Shield and Western Amazon regions are largely recognized as neglected regions in biogeographical and evolutionary studies (Cassemiro et al., 2023), also with little or absent cytogenetic information for Loricariidae. Despite the regional sampling gap problem, Loricariidae diversity is still insufficiently represented by cytogenetic studies. Our compilation recorded 234 species assessed by cytogenetic studies, that in comparison to the 1,051 valid species (Fricke et al., 2023), represents 22.26 % of the family species richness. The diversity of genus assessed by cytogenetic studies was the highest in Hypoptopomatinae (42.1 %), followed by Rhinelepinae (28.5 %), Hypostominae (27.2 %), Loricariinae (24.4 %), Delturinae (20 %), and Lithogeninae (0 %). Besides Lithogeninae that do not have any species karyotyped to date, the subfamily Delturinae has only one genus and two unidentified species karyotyped: Hemipsilichthys sp. Paraitinga River (Kavalco et al., 2004, 2005), and Hemipsilichthys n. sp. Patos River (Alves et al., 2005). We suggest that further cytogenetic studies focus on expand the sampling in the northeast Brazil, the Western Amazon, the Guianas Shield, and other Neotropical countries, in addition to evaluate a more representative portion of the diversity.	en	Sassi, Francisco de Menezes Cavalcante, Cioffi, Marcelo de Bello, Moreira-Filho, Orlando (2024): A state-of-art review of Loricariidae (Ostariophysi: Siluriformes) cytogenetics. Neotropical Ichthyology 22 (4): e 240050, DOI: 10.1590/1982-0224-2024-0050, URL: https://doi.org/10.1590/1982-0224-2024-0050
