Using sagittal otoliths and eye diameter for ecological characterization of deep-sea fish: <i>Aphanopus carbo</i> and <i>A. intermedius</i> from NE Atlantic waters

Abstract

SUMMARY:The sagittal otolith and eye diameter of two sympatric species of the genus Aphanopus, A. carbo and A. intermedius, from North Atlantic waters were investigated. The study objectives were to find morphometric variables of otoliths to identify the two species and relate ecomorphological characters of otolith and eye diameter to the depth distribution of each species. The otoliths of the two species are very similar, although significant differences in shape, otolith height and weight and the sulcus acusticus area were detected. The ratio between eye diameter and cephalic length (ED:CL ratio) was also significantly different. In both analyses A. carbo obtained higher values, which suggests that A. carbo and A. intermedius live in different spatial niches, and that A. carbo inhabits deeper waters. The ratio between the sulcus and otolith areas (S:O) was low compared to other fish species, which suggests that the hearing capacity of Aphanopus spp. is adapted to low frequency sound. This adaptation may be related to the oceanographic conditions in which these species live, and in particular to the characteristics of sound transmission in the "SOFAR channel".Keywords: ecology, morphometry, otolith, Aphanopus carbo, Aphanopus intermedius, teleosts.RESUMEN: Uso del otolito sagitta y el diámetro del ojo para la caracterización ecológica de peces de profundidad: AphAnopus cArbo and A. intermedius del Atlántico nororiental. -El otolito sagitta y el diámetro del ojo de dos especies simpátricas del género Aphanopus, A. carbo y A. intermedius, del Atlántico Norte fueron analizados. Los objetivos del estudio se centraron en encontrar las variables morfométricas del otolito que pudiesen ser empleadas en la diferenciación de ambas especies y en establecer una correspondencia entre la profundidad de distribución de las especies y las características ecomorfológicas del otolito y del diámetro del ojo. Los otolitos de ambas especies resultaron ser parecidos, si bien se detectaron diferencias significativas en la forma, en el peso y la anchura del otolito y en el área del sulcus acusticus. La proporción entre el diámetro del ojo y la longitud cefálica (ED:CL) también puso de manifiesto diferencias significativas entre ambas especies. En ambos análisis, los resultados indicaron que A. carbo alcanza valores mayores. Ello proporciona evidencias para poder afirmar que A. carbo y A. intermedius viven en nichos espaciales diferentes, habitando A. carbo aguas más profundas. La proporción entre al área del sulcus y el área del otolito (S:O) alcanzó valores bajos en comparación con otras especies, lo cual sugiere que la capacidad auditiva de Aphanopus spp. está adaptada a sonidos de baja frecuencia. Dicha adaptación podría estar relacionada con las condiciones oceanográficas donde viven estas especies y, en particular, con las características de la transmisión del sonido dentro del denominado "canal SOFAR".

An approach to unraveling the coexistence of snappers (Lutjanidae) using otolith morphology

“…The S:O ratio and otolith size are related to the hearing capabilities of marine fishes (Gauldie 1988, Montgomery andPankhurst 1997) and ecological factors such as depth distribution, fish mobility and differences in food and spatial niches (Lombarte 1992, Aguirre and Lombarte 1999, Tuset et al 2010. Our results stressed the relevance of the sagittal otolith characteristics to the ecomorphological characteristics, showing otolith shape patterns associated with functional and ecological factors.…”

“…sulcus area, depth of the sulcus, sulcus area:otolith area ratio or shape) vary according to environmental, ontogenetic, phylogenetic and ecological factors (e.g. Nolf 1985, Lombarte 1992, Lombarte and Lleonart 1993, Paxton 2000, Gauldie and Crampton 2002, Volpedo and Echeverria 2003, Lombarte and Cruz 2007, Tuset et al 2010, Reichenbacher et al 2007, Teimori et al 2012. However, it is not known how otolith shape variability affects hearing ability Lu 2000, Popper et al 2005).…”

Relationships between Fish and Otolith Size of the Blackspot Snapper <i>Lutjanus ehrenbergii</i> (Peters, 1869) Collected from the Coast of Muscat City, Sea of Oman

“…Study indicated strong correlation between otolith width and fish head and total lengths. Many researchers reported similar relationships between otolith and somatic measurements (Lombarte and Lleonart, 1993;Lleonart et al, 2000;Metin and Ilkyaz, 2008;Tuset et al, 2010;Jawad et al, 2011a;Jawad and Al-Mamry, 2012;Valinassab et al, 2012).…”

Identification of Lessepsian fish species using the sagittal otolith

“…In fact, many of these invaders belong to families or genera that are not represented in the native fish fauna of the Mediterranean Sea. Neverthless, ecomorphological characters of otoliths are generally related to the ecological niche that the species occupies (Lombarte 1992, Arellano et al 1995, Aguirre and Lombarte 1999, Lombarte and Popper 2004, Ramcharitar et al 2004, Schulz-Mirbach et al 2008, Colmenero et al 2010, Tuset et al 2010. Thus, the highly differentiated otolithic morphology of Lessepsian species could reflect specific adaptations (Schoener 1974, Motta et al 1995, and hence novel opportunities to thrive in the newly colonized habitat.…”