Observation and establishment of gonad development stages in polyplacophorans (Mollusca): Chiton (Chiton) articulatus a case study |
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Authors: | Quetzalli Yasú Abadia‐Chanona Omar Hernando Avila‐Poveda Marcial Arellano‐Martínez Bertha Patricia Ceballos‐Vázquez |
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Affiliation: | 1. Instituto Politécnico Nacional (IPN), Centro Interdisciplinario de Ciencias Marinas (CICIMAR), La Paz, Baja California Sur, Mexico;2. Facultad de Ciencias del Mar (FACIMAR), Universidad Autónoma de Sinaloa (UAS), Mazatlan, Sinaloa, Mexico;3. Dirección de Cátedras‐CONACYT, CONACYT, Ciudad de México, Mexico |
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Abstract: | Gonad development stages (GDS) and, subsequently, the reproductive cycle are described by performing histology of some gonad portions. In polyplacophorans, gametogenesis is not enough to define GDS; further anatomical gonad features are relevant. In most adult polyplacophorans, the gonad is a simple anatomical structure that resembles and operates as one single gonadal acinus without glandular structure. These features have gone unnoticed causing inaccurate GDS assignment and, consequently, imprecise reproductive season in polyplacophorans. Here, dissection protocols that allow extracting a compact gonad are established. Emphasizing the anatomical structure of the whole gonad and the displacement of gametes, five GDS were assigned to both sexes of Chiton (Chiton) articulatus: I‐goniogenesis, II‐development, III‐ripe, IV‐spawning, V‐rest. Tissue platelets contribute importantly to GDS assignment and even help distinguishing between males and females. Neither a randomly selected portion of gonad nor a longitudinal section are recommended because it leads to misinterpretation higher than 50% in determining GDS and besides ignores displacement of gametes. A panoramic sweep across a complete transverse‐section of each gonad was validated as the best option for establishing GDS. This new methodology was tested on several polyplacophorans species, and seems generally applicable for histological assessment of reproductive cycle and reproductive season in polyplacophorans. |
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Keywords: | gonad anatomical structure displacement of gametes gonadal acinus tissue platelets germinal epithelium histology transverse‐section dissection reproductive cycle reproductive season |
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