Spatial choice is biased by chemical cues from conspecifics in the speckeled worm eel Myrophis punctatus

The speckeld worm eel Myrophis punctatus lives in high-densities assemblages, and usually digs through, or lies on the substrate. These behaviours could lead to chemical marks on the substrate and could modulate the spatial distribution in this species. We tested the hypothesis that the spatial choice of the speckled worm eel is modulated by the presence of conspecific odour on the substrate. Here, we showed that the speckled worm eel avoids the substrate area containing the conspecific odour, indicating that this chemical cue modulates the eel's spatial decision. The eels clearly detected the conspecific's odour. This perception might indicate the presence of conspecifics into the substrate. Since the eels avoided an area containing conspecific odour, we suggest this may be a response that avoids the consequences of invading a resident-animal's territory.

Does eel metamorphosis cause a breakdown in the tenets of otolith applications? A case study using the speckled worm eel (Myrophis punctatus, Ophichthidae)

Several basic tenets of otolith research have been questioned recently with regard to eel metamorphosis. Specifically, some researchers have suggested that otolith increment formation is not daily, and otolith material may be resorped during metamorphosis. We conducted a rearing experiment to test the hypothesis that increment formation is daily and that the otolith continues to grow during eel metamorphosis. We marked the otoliths of wild-caught Myrophis punctatus leptocephali and reared these fish through metamorphosis. Metamorphosis was characterized by a decreasing standard length, pre-anal length, and body depth accompanied by an increase in pigmentation and a change in behavior. Increment formation was daily or near-daily through metamorphosis, and the otolith continued to grow during metamorphosis. Thus, the basic tenets of otolith application apply to eel metamorphosis, and non-daily ring deposition and resorption should not be used as explanations for otolith characteristics of eels (e.g., back-calculated hatch dates) unless demonstrated experimentally.