Variación temporal de contribución al agregado marino de Eretmochelys imbricata (Carey) en Jardines del Rey, Cuba atendiendo al sexo y a la condición de maduración

Abstract

El agregado marino de Eretmochelys imbricata en el archipiélago de Jardines del Rey (Cuba), localizado entre las principales poblaciones de anidación del Mar Caribe y el Golfo de México, representa una mezcla heterogénea de diferentes estados de maduración y haplotipos. Por tanto, su caracterización fenotípica y genética es relevante para conocer la dinámica regional de la especie. En este trabajo se determinaron los estados de maduración y la composición genética de E. imbricata en este agregado marino durante los períodos de pesquería legal entre 2004 y 2006, empleando descriptores fenéticos y la región no codificadora del mtDNA para el análisis temporal de la maduración y del origen de este agregado. En Jardines del Rey predominaron los individuos con LRC=70,1-80 cm, seguido de los de LRC=60,1-70 cm, mayoritariamente hembras no adultas. Estos tamaños reflejan el crecimiento demográfico temporal informado para varias fuentes regionales, que usan esta área como un corredor. Se presentaron pocos machos pubescentes y espermatógenos (N=3) que aún no habían completado el desarrollo del pene, lo cual refleja un asincronismo entre la espermatogénesis y el desarrollo de las características sexuales secundarias. Las hembras prepubescentes presentaron hasta el estadio de desarrollo folicular III mientras que las pubescentes el IV, lo cual los ubica como estadios clave para la transición hacia la pubertad y la adultez respectivamente. Las hembras maduras reproductoras carecieron de corpora lutea y albicantia, por lo que esta área marina constituyó un corredor migratorio para hembras primíparas de las poblaciones fuentes regionales. Las contribuciones de las fuentes hacia el agregado marino segregado por década y estados de maduración, indicaron valores mayores para las fuentes de mayor Nc, debido a la reducción de las frecuencias haplotípicas de las fuentes y los agregados marinos al considerar un escenario más realista en el MSA. La distancia marítima más corta entre las fuentes y los agregados marinos calculada con o sin el efecto de las corrientes marinas, se correlacionó significativamente pero con bajos coeficientes para agregados de individuos no adultos, y no hubo correlación con las contribuciones hacia agregados de individuos adultos, debido a la similitud genética presente en fuentes más alejadas entre sí que con las más cercanas. Finalmente, la composición de los estados de maduración y genética en el agregado marino de Jardines del Rey fue temporalmente un reflejo del tamaño censal y la cercanía de las poblaciones fuentes regionales a éste para los estados inmaduros aunque esto no se cumplió en los adultos, y la presencia de adultos migrantes hacia las áreas de reproducción regionales fue congruente con la estacionalidad reproductora de las fuentes del Caribe. Esto indica que esta área marina es un corredor clave para la dinámica poblacional de la región.

The mixed stock of Eretmochelys imbricata of Jardines del Rey (Cuba), located between the main nesting or source populations of the Caribbean Sea and the Gulf of Mexico, represents a heterogeneous mixture of different maturation stages and haplotypes. Therefore, their phenetic and genetic characterization is outstanding to know regionally the hawksbill population dynamics. In this study, the sexual classes and maturation stages of E. imbricata from last periods of legal fishery between 2004 and 2006 (N=249) in Jardines del Rey were established by means of the gonads macroscopic inspection and histological processing. In addition, the genetic composition was determined using the non-codifier region of the mtDNA (380 pb or 740 pb) for the temporal analysis of the maturation and origin of this stock. For the origin (contribution from sources to the marine stock), a mixed stock analysis by means of bayesian inference with MCMC was used, segregating the stock in "non adults" and "adults" individuals and in turn per decades. The correlation between the contribution and the maritime distance among source populations and mixed stock (affected or not by the regional pattern of marine currents) was determined. From a sample of twenty individuals randomly taken, a few pubescent and spermatogenic males were presented (N=3), which had not still completed the penis development. This evidences an asynchrony between the spermatogenesis and the secondary sexual characteristics development. The resting individuals were prepubescent (N=11), pubescent (N=4) and one adult females, which were taken to describe the follicular development stages: four previtellogenic and four vitellogenic ones. The prepubescent females presented as maximum follicular development stage the III one while the pubescent ones the IV, which indicates them as key stages to identify the puberty and the transition to adulthood. In these stages evidences of the previtellogenic growth were observed as well as of the vitellogenesis process. In the Jardines del Rey mixed stock between 2004 and 2006 all the caught individuals moved unidirectionally and those that had straight carapace length (SCL)=70,1-80 cm (class III) prevailed, followed by those of LRC=60,1-70 cm (class II), mainly non mature females. This result differed of the 1986-1995 period, in which after the class III the most represented SCL class was the IV (80,1-90 cm). This temporary investment is evidence of the demographic growth experienced by many regional source populations from the 1980 to 2000 decade, which immature cohorts used this marine area as a corridor. The breeding females were more represented in the class IV followed by class III and they lacked of corpora lutea or albicantia. Thus, Jardines del Rey constituted a migratory corridor of primiparous females moving to the regional source populations. For these females, the combined analysis of the capture date, the displacement speed, the distance to the source populations, the time corresponding to the nesting peaks of these ones and their haplotype, allowed infer the possible source population to which the breeding females went. The genetic composition of the Jardines del Rey mixed stock did not differ between the decade of 1990 and the period 2004-2006 per maturation stage, neither in these years, due to the high haplotype heterogeneity. This diversity ratifies the use of Jardines del Rey marine area as dispersion or migration corridor of individuals coming from many source populations, and its relevance for the Caribbean and the Gulf of Mexico region. The sources contribution to Jardines del Rey marine stock of non adult individuals were temporally higher for the biggest and nearest source (Las Coloradas, Mexico). This evidences the importance of Jardines del Rey for the conservation of the Mexican nesting population. The sources contribution to Jardines del Rey mixed stock of adult individuals showed similar values to Las Coloradas, Mona Island (Puerto Rico) and Leeward beaches (Barbados), which differ in population size (# nesting females/ year) and distances to the marine area. The shortest maritime distance (not affected by marine currents) among the source populations and Jardines del Rey marine area for non adult individuals was correlated significantly with r> 0,65 due to the higher contribution of the nearest Mexican population. In the adult ones this correlation was not significant which indicated an independence of the size of adult individuals due to their highest dispersion capacity.