Body size structure, biometric relationships and density of Chiton albolineatus (Mollusca: Polyplacophora) on the intertidal rocky zone of three islands of Mazatlan Bay, SE of the Gulf of California

Abstract

Resumen.-Las poblaciones del molusco poliplacóforo Chiton albolineatus fueron estudiadas en 6 sitios con diferente acción del oleaje en el litoral rocoso de 3 islas de la bahía de Mazatlán, en el sureste del golfo de California. Esta especie de quitón es endémico de las costas mexicanas del Pacífico. Para determinar sus patrones demográficos basados en su densidad y tamaño corporal se realizaron muestreos en sitios expuestos y protegidos al oleaje de la zona intermareal de estas islas de enero a diciembre de 2008. La longitud (L), ancho (B) y altura (H) del cuerpo de los quitones osciló entre 8,3 y 55,1 (X = 28,9 ± 6,2), 3,0-30,4 (X = 14,8 ± 3,4) y 0,9-19,1 (X = 5,0 ± 1,8) mm, respectivamente, y su peso húmedo (W) varió de 0,1 a 10,2 g (X = 1,7 ± 0,9). Las relaciones biométricas fueron B = 0,478 (L) + 1,212, H = 0,198 (L) -1,170 y H = 0,389 (B) -1,277, para los tamaños corporales y W = 0,0002 (L) 2,710 , W = 0,0008 (B) 2,743 y W = 0,0792(H) 1,908 para el peso. Los valores de la pendiente de la relación longitud-peso significativamente menores de 3 indican que esta especie tiene un crecimiento alométrico negativo. Su densidad media, entre 0,1 a 2,9 org. m -2 , fue mayor en el lado expuesto al oleaje de cada isla posiblemente por una menor presión de depredación que en el lado protegido, mientras que su tamaño corporal fue mayor en el lado expuesto de 2 islas. Esto podría ser interpretado como resultado de la migración desde los sitios protegidos de la acción del oleaje, donde los individuos más pequeños tienen más probabilidades de supervivencia que en las áreas expuestas. Palabras clave: Dimensiones corporales, quitones, exposición al oleaje, islas del Pacífico MexicanoAbstract.-Populations of the polyplacophoran mollusk Chiton albolineatus were studied at 6 sites with different wave exposure of the rocky shores of 3 islands of Mazatlan Bay (southeastern side of the Gulf of California). This chiton species is endemic to the Mexican Pacific coast. Chitons were sampled on wave-exposed and wave-protected sites in the intertidal zone of these islands from January to December 2008 to determine its demographic patterns based on density and body size. Length (L), breadth (B) and height (H) of chiton body ranged between 8.3 and 55.1 (X = 28.9 ± 6.2), 3.0-30.4 (X = 14.8 ± 3.4) and 0.9-19.1 (X = 5.0 ± 1.8) mm, respectively, and their wet weight (W) varied from 0.1 to 10.2 g (X = 1.7 ± 0.9). The biometric relationships were B = 0. The value of the slope of the length-weight relationship was significantly lower than 3, which indicates negative allometric growth. Average densities ranged from 0.1 to 2.9 org. m -2 and were higher in the exposed sites than in the protected sites of each island, possibly because of a lower predation pressure in areas exposed to high wave energy than in sheltered areas, while its body size were larger in the exposed sites of two islands. This could be interpreted as a result of migration from sites protected from the wave action, where survival of smaller individuals is more likely than in expos...

Emergence, Development, and Maturity of the Gonad of Two Species of Chitons “Sea Cockroach” (Mollusca: Polyplacophora) through the Early Life Stages

“…Perhaps these stages are not adequate for all polyplacophorans, but they are at least for the family Chitonidae, which generally exhibits a common “adult”-size above 40 mm, including the chitons here studied [65], and also shows concordance with the modal size-class exhibited by other Mexican populations of both chitons [44]–[47].…”

“…But just toward the adult stage (TL>40 mm), the b-values move downwards to between 2.9 and 2.2 for C. articulatus [43]–[45], and around 2.7 for C. albolineatus [47]. Therefore, this indicates that these species have first, during the early life stages, an isometric growth and subsequently an allometric growth (i.e., growth whereby parts of the same organism grow at different rates) as they develop into adulthood.…”

“…1). The smallest adult size for both collected chitons was established at 40 mm TL, based on the modal size-class from other Mexican populations of C. articulatus [44]–[46] and C. albolineatus [47].…”

Observation and establishment of gonad development stages in polyplacophorans (Mollusca): Chiton (Chiton) articulatus a case study

“…The central benefits of the relaxation technique, fixation, conservation, and dissection of specimens were successful since relaxed and well-stretched polyplacophorans were obtained. description of ratios by the variations in body shape, 'body outline' (Schwabe 2010), to support separation among species through a curvature index (Mannering 1974), length-weight relationship (Hunter and Brown 1965;Flores-Campaña et al 2012;Avila-Poveda 2013), among many studies requiring a totally relaxed polyplacophoran. Other studies in polyplacophorans describe a relaxation process prior to taking measurements using a solution of magnesium chloride as anaesthetizer (Barnes 1972;Matsumura and Kuwasawa 1996).…”

Species richness and community structure of class Polyplacophora at the intertidal rocky shore on the marine priority region no. 33, Mexico

“…There are global reports concerning Class POLYPLACOPHORA on a taxonomic scope and geographical distribution such as [5][6][7][8] for the American Pacific as [9,10], as well as those made in the Mexican coast zone as [3,4,[11][12][13]; other studies also found Chitons' ecological data as [14][15][16]. With respect to marine priority coastal regions in the State of Guerrero, [17] reported for Marine Priority Region No. 32.…”