Diversity of white spot patterns in the eagle ray Aetobatus laticeps (Myliobatiformes: Aetobatidae) in the north Pacific coast of Costa Rica

Introduction: The Pacific white-spotted eagle ray Aetobatus laticeps, has recently separated from the Atlantic A. narinari based on both morphological and genetic evidence. This species is characterized by a dark body with numerous white spots all over its dorsal side. Considering the type, shape, number, and distribution of these natural markings as potential identifiers at the individual level, we studied the variation in the spot patterns. Objective: Describe and compare the white spot pattern (type and distribution) of individuals and evaluate their potential use as identifiers at the individual level. Methods: We analyzed 54 videos (105 subsequent extracted photos) and 19 photographic records that were taken at different sites along the Pacific coast of northern Costa Rica. Results: Seventeen distinctive types of white spots were identified across the entire dorsal side of the rays. Significant differences between each major body section (pectoral fins, back, head, and pelvic fins) were found in the type and frequency of white spots. The type 'single spot' was commonly distributed across the entire dorsal side, and the spot pattern on the pelvic fins was informative to identify 72 individuals. Conclusions: The analysis of the type, shape, and distribution of white spots in A. laticeps determined several combinations of white spot patterns that be used for further taxonomic description and provide potential identification of the individual for future population studies along with its distribution.

Introducción: La raya águila de manchas blancas del Pacífico, Aetobatus laticeps, se ha separado recientemente de A. narinari del Atlántico basándose en pruebas tanto morfológicas como genéticas. Esta especie se caracteriza por un cuerpo oscuro con numerosas manchas blancas en toda su parte dorsal. Considerando el tipo, la forma, el número y la distribución de estas marcas naturales como identificadores potenciales a nivel individual, estudiamos la variación en los patrones de manchas. Objetivo: Describir y comparar el patrón de manchas blancas (tipo y distribución) de individuos y evaluar su uso potencial como identificadores a nivel individual en especímenes recapturados. Métodos: Analizamos 54 videos (con 105 fotografías extraídas posteriormente) y 19 registros fotográficos que fueron tomados en diferentes sitios a lo largo de la costa pacífica del norte de Costa Rica. Resultados: Se identificaron diecisiete tipos distintivos de manchas blancas en todo el lado dorsal de los radios. Se encontraron diferencias significativas entre cada sección principal del cuerpo (aletas pectorales, espalda, cabeza y aletas pélvicas) en el tipo y frecuencia de manchas blancas. El tipo 'punto único' se distribuyó comúnmente en todo el lado dorsal, y el patrón de puntos en las aletas pélvicas fue informativo para identificar 72 individuos. Conclusiones: El análisis del tipo, la forma y la distribución de las manchas blancas en A. laticeps determinó varias combinaciones de patrones de manchas blancas que se utilizarán para una descripción taxonómica adicional y brindan una identificación potencial del individuo para futuros estudios de población a lo largo de su distribución.

TopoIIα prevents telomere fragility and formation of ultra thin DNA bridges during mitosis through TRF1-dependent binding to telomeres.

Telomeres are repetitive nucleoprotein structures at the ends of chromosomes. Like most genomic regions consisting of repetitive DNA, telomeres are fragile sites prone to replication fork stalling and generation of chromosomal instability. In particular, abrogation of the TRF1 telomere binding protein leads to stalled replication forks and aberrant telomere structures known as "multitelomeric signals". Here, we report that TRF1 deficiency also leads to the formation of "ultra-fine bridges" (UFB) during mitosis, and to an increased time to complete mitosis mediated by the spindle assembly checkpoint proteins (SAC). We find that topoisomerase IIα (TopoIIα), an enzyme essential for resolution of DNA replication intermediates, binds telomeres in a TRF1-mediated manner. Indeed, similar to TRF1 abrogation, TopoIIα downregulation leads to telomere fragility and UFB, suggesting that these phenotypes are due to decreased TopoIIα at telomeres. We find that SAC proteins bind telomeres in vivo, and that this is disrupted upon TRF1 deletion. These findings suggest that TRF1 links TopoIIα and SAC proteins in a pathway that ensures correct telomere replication and mitotic segregation, unveiling how TRF1 protects from telomere fragility and mitotic defects.