Sensory constraints in temporal segregation in two species of anglerfish, Lophius budegassa and L. piscatorius

Abstract

The temporal segregation of 2 ecologically equivalent and sympatric species, the black anglerfish Lophius budegassa and white anglerfish L. piscatorius, was studied in relation to day-night behaviour and the underlying morphological variation in the sensory organs. Temporally scheduled trawl sampling was conducted on the western Mediterranean shelf, and diel fluctuations in catches were used as a proxy of behavioural rhythms. L. budegassa was more abundant at night than L. piscatorius, which mostly occurred in daytime catches. The observed differences in the timing of maximum activity (i.e. catches) were consistent with differences in otolith sagittae weight, eye/lens sizes and optical sensitivity. L. budegassa presented significantly heavier otolith sagittae than L. piscatorius, indicating that the behaviour of the black anglerfish is mostly acoustically driven (a typical characteristic of species living in dim light conditions). Preference for a dim light environment was also confirmed by the high optical sensitivity observed in this species achieved by enlarging the photoreceptors' diameter. In contrast, L. piscatorius showed larger eyes and lenses than L. budegassa, but only in individuals larger than 50 cm. Large eyes usually improve photon capture and the fineness with which the image is sampled; however, relatively low values of sensitivity and resolution were observed in large L. piscatorius. This indicates that a trade-off might exist between the increase in eye size as an adaptive response to the impending deep meso-and bathypelagic life and a visual constraint imposed by the quality of the water at the bottom level where contrast can be degraded by suspended particles. These results indicate that interspecific competition with sympatric and ecologically equivalent species may result in different adaptations to diurnal/nocturnal behaviour, which are sustained by morphological specialisations in sensory organs.

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

“…Accordingly, we infer that L. argentimaculatus, L. erythropterus, L. malabaricus and L. lemniscatus (all 'red-lined') should be adapted to dim light conditions or nocturnal activity; L. ehrenbergii, L. fulviflamma ('black spot' complex), L. lutjanus ('yellow-lined') and L. rivulatus ('blue-lined') should be more active during the day; whereas L. russellii and L. johnii ('black spot' complex) should show a nocturnal-diurnal dichotomy. Thus, the diel activity rhythm facilitates coexistence between competitors extending beyond the effects of adaptation to different behavioral strategies and feeding habitats (Colmenero et al 2010, Fox and Bellwood 2011, Azzurro et al 2013). …”

“…These findings constitute a novel approach to species discrimination. Finally, discrimination of the activity of fishes will be essential for a better understanding of ecosystem functioning and the ecological roles played by fish species (Pulcini et al 2008, Colmenero et al 2010, Meakin and Qin 2011). …”

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.…”

Reproductive biology of Black Anglerfish (Lophius budegassa) in the northwestern Mediterranean Sea

“…This species co-occurs with White Anglerfi sh over all its bathymetric range, although White Anglerfish has a deeper distribution that reaches to depths >1000 m (Afonso-Dias and Hislop, 1996). Despite the overlapping distributions of these species, Colmenero et al (2010) concluded that no ecological competition exists between these species because of a temporal segregation in their biorhythms; Black Anglerfi sh is more active at nighttime, and White Anglerfi sh is more active during daytime.…”

“…In the Mediterranean Sea, studies have been less numerous and for the most part have focused on biological aspects similar to the ones examined in the studies just described (Carlucci et al, 2009;Colmenero et al, 2010;García-Rodríguez et al, 2005;La Mesa and De Rossi, 2008;Maravelias and Papaconstantinou, 2003;NegzaouiGarali et al, 2008;Tsimenidis, 1984;Tsimenidis and Ondrias, 1980;Ungaro et al, 2002). However, only Tsimenidis (1980) and Carbonara et al (2005) focused on reproductive traits of Black Anglerfi sh.…”