Which way to turn? Effect of direction of body asymmetry on turning and prey strike orientation in starry flounder Platichthys stellatus (Pallas) (Pleuronectidae)

Abstract

Starry flounder Platichthys stellatus, a rare polymorphic flatfish exhibiting a large-scale geographic cline in the frequency of right-eyed (dextral) and left-eyed (sinistral) morphs, was studied to investigate whether foraging behaviour (turning angle and prey strike orientation) differed between dextral and sinistral laboratory-raised juveniles. Platichthys stellatus foraging on brine shrimp Artemia sp. nauplii tended to strike dorsally at prey ('left' to an observer for dextral flounder and 'right' to an observer for sinistral flounder), although this effect was stronger for sinistral fish. This dorsal tendency also increased with body size. Non-strike behaviours (movements between strikes) were ventrally biased for both morphs. Maximum turn angles were larger for both morphs towards the dorsal side than the ventral side during prey strikes but were the same during non-strike behaviours. The positioning of the eyes of the juvenile starry flounder was skewed towards the dorsal midline rather than being symmetrically placed between dorsal and ventral margins on the eyed side of each fish. The migrating eyes of dextral fish, however, were significantly closer to the dorsal midline than in sinistral fish. This, in addition to the more dorsally oriented prey strikes in sinistral fish, suggests that the morphs are not simple behavioural mirror images of one another and therefore may differ ecologically.

Polymorphism and multiple correlated characters: Do flatfish asymmetry morphs also differ in swimming performance and metabolic rate?

“…Sinistral and dextral morphs in both species differ in subtle anatomical traits related to head and caudal tail shape (Bergstrom, 2007;Russo et al, 2012), and show slight shifts in diet (Bergstrom & Reimchen, 2018;Russo et al, 2012). In P. stellatus, there are behavioral differences during prey strikes between morphs in captive-reared juveniles (Bergstrom & Palmer, 2007) and sinistral P. stellatus are slightly but significantly enriched in muscle 15 N: 14 N ratios (an indicator of the average trophic level of their prey) among multiple northeastern Pacific samples (Bergstrom & Reimchen, 2018). Clearly, polymorphism in these flatfish species is associated with divergence of multiple characters in addition to asymmetry direction.…”

The Ecology of Asymmetry in Stickleback Defense Structures

“…Other studies have looked at differences between left‐ and right‐biased individuals, but only for conspicuous asymmetries that are presumably genetically determined (Van Valen 1962). Ecological and functional differences occur between left‐and right‐mouthed scale eating cichlids (Hori 1993), and between left‐eyed and right‐eyed starry flounder (Bergstrom 2007; Bergstrom and Palmer 2007). However, these ecological associations with the direction of bias have not involved subtle asymmetries, which are thought to arise due to errors made during development.…”

Inversion ocular en Paralichthys adspersus (Steindachner, 1867) lenguado de ojos chicos (Pleuronectiformes, Paralichthyidae): un caso del ambiente y un analisis en ejemplares cultivados

“…En P. stellatus existen diferencias morfológicas, donde los morfos diestros tienen un pedúnculo caudal más amplio, hocicos más cortos y un menor número de branquispinas que las formas siniestras, que en conjunto con la posición de los ojos, se manifiestan en una conducta de captura de presas entre ambos morfos, que los capacitaría a consumir presas diferentes (Bergstrom, 2007). Estas diferencias son sutiles, pero sugieren que las formas diestras y siniestras difieren ecológicamente y que estos mecanismos ecológicos pueden mantener estas formas polimórficas (Bergstrom & Palmer, 2007). Esta postura se contrapone con lo que ocurre en Xystreurys liolepis, donde morfos diestros y siniestros no muestran diferencias en la cinemática de captura de presas (Gibb, 1996), situación que podría estar influenciada por el cautiverio y el tipo de alimento.…”

“…Esta postura se contrapone con lo que ocurre en Xystreurys liolepis, donde morfos diestros y siniestros no muestran diferencias en la cinemática de captura de presas (Gibb, 1996), situación que podría estar influenciada por el cautiverio y el tipo de alimento. La inversión ocular sería un fenómeno con base genética, que se comprueba para Platichthys stellatus, donde existe herencia moderada (Policansky, 1982a;Boklage, 1984;Bergstrom & Palmer, 2007). En el caso de Paralichthys olivaceus, la migración del ojo es controlada por el locus rev (Hashimoto et al, 2002).…”

“…En Pleuronectes platessa e Hippoglossus hippoglossus ocasionalmente se encuentran individuos siniestros (Norman, 1934;Gudger, 1935;Gudger & Firth, 1937), mientras que en Platichthys stellatus, es más frecuente la ocurrencia de individuos con inversión ocular (Norman, 1934;Policanski, 1982a), existiendo en esta especie polimorfía con variación clinal, con un 50% de ejemplares siniestros en California, llegando a un 100% en Japón (Bergstrom, 2007;Bergstrom & Palmer, 2007), una situación semejante se encuentra en la especie europea de P. flesus (Fornbacke et al, 2002).…”