ABSTRACT
This study describes the microscopic anatomy of the reproductive systems of the keyhole limpets Fissurella latimarginata and Fissurella cumingi to test the existence of a possible isolating reproductive mechanism of morphophysiological type between species, and consequently to determine if the findings provide a valid taxonomic characteristic to distinguish these sympatric species. The results show that in both species the reproductive system is intimately associated with the excretory system. The gonad has a septa organization, and is connected with the distal portion of the right kidney by means of a renopericardial duct which functions as a genital duct. The gametes are evacuated to the mantle cavity through the right kidney opening. Besides transport of the gametes, the genital duct, which connects with the pericardium through the nephrostome, bears a gland attached to its inner wall both in males and females. No marked anatomical differences were noted between the reproductive systems of the two limpets which would allow their unequivocal taxonomic differentiation at the species level.
Este trabajo describe la anatomía microscópica del sistema reproductivo en las lapas Fissurella latimarginata y Fissurella cumingi, para examinar la posible existencia de un mecanismo de aislamiento reproductivo del tipo morfofisiológico y consecuentemente, determinar si el sistema reproductivo presenta algún carácter taxonómico válido que permita distinguir estas especies simpátricas. Los resultados muestran que en ambas especies y sexos el sistema reproductivo se relaciona con el sistema excretor. La gónada, de organización en septos, comunica con la porción distal del riñon derecho distal por medio del canal renopericárdico que funciona como conducto genital. Los gametos son evacuados a la cavidad del manto a través de la apertura renal derecha. Además de transportar los gametos, el conducto genital, que comunica con el pericardio a través del nefrostoma, presenta una glándula adosada a la pared interna en los machos y en las hembras. No se detectaron diferencias anatómicas marcadas del sistema reproductivo que permitan diferenciar las especies inequívocamente por lo que este sistema tiene bajo valor taxonómico a nivel específico.
Subject(s)
Animals , Mollusca/ultrastructure , Mollusca/classification , ReproductionABSTRACT
Spermatogenesis and sperm ultrastructure of the clam Lucina pectinata (Lucinidae) from northern Brazil were studied using light and transmission electron microscopy. The uniflagellate spermatozoa are grouped into characteristic rings within somatic cells (Sertoli-like cells), with the acrosome oriented toward the peripheryof these cells. The spermatozoa are long cells of the primitive type (ect-aquasperm) with a total length of 50.2 ± 2.5 mm, consisting of head (acrosome + nucleus), midpiece and tail. Acrosome is formed by an, acrosomal vesicle with a conical cylinder-like shaped (0.9 ± 0.1 mm length and 0.4 ± 0.1 mm in basal diameter) having a deeply infolded basis occupied by the subacrosomal space, containing flocculent material without axial rod. The acrosomal vesicle is formed by a membrane-bounded containing a broad basal ring of electron-dense material. The nucleus (7.5 ± 0.8 mm long) is an elongated, subcylindrical rod-shaped, slightly and gently curved, with a basal invagination (0.2-0.4 mm). It contains dense chromatin without any electron-lucent lacunae.The midpiece (1.0 ± 0.3 mm long; 1.1 ± 0.2 mm width) consist of four equal mitochondria located at the same level, surrounding two centrioles arranged at right angles. The proximal centriole lies at 90° relative the distal centriole and sperm longitudinal axis. The tail (40.5 ± 2.1 mm long) contains the common 9 + 2 pattern which in tapering end piece is successively reduced and sheated by the plasmalemma.