Abstract
Paedomorphosis describes the retention of larval characters in adult stages and is widespread amongst salamanders. Salamandrid newts exhibit facultative paedomorphosis, where paedomorphic and metamorphic adult forms coexist in the same population. Previous studies have shown that prey capture kinematics do not differ between paedomorphic and metamorphosed ambystomatid salamanders, despite diverging morphology and prey capture performance. It remained unclear, however, whether the stereotypy of prey capture kinematics across morphotypes is restricted to ambystomatids, or can be found in other salamander groups too. Here, we performed biplanar high-speed-recordings of the prey capture behavior in paedomorphic and metamorphic salamandrid newts and only found minor kinematic differences across morphotypes, suggesting that stereotypy across morphotypes is a more general feature within salamanders. We then compared anatomy of skull and hyobranchial skeleton, along with the physiological cross sectional area (PCSA) of the rectus cervicis muscle, the main muscle empowering suction feeding. Besides the overall morphological differences of the feeding apparatus, the PCSA of the rectus cervicis also differs significantly between morphotypes, being twice as large in paedomorphs. Accordingly, paedomorphs can exert more powerful suction strikes, which in turn may be one of the key factors why paedomorphs are more efficient in capturing elusive prey compared to metamorphs.
Highlights
Paedomorphosis is defined as the retention of juvenile characters in sexually mature adults and is common in many salamander groups
Kinematics From a qualitative perspective, the suction strike of metamorphs and paedomorphs are very similar and the following description refers to both forms if not noted otherwise: The prey strike is initiated with fast gape opening by dorsal head rotation and lower jaw depression, followed by hyobranchial depression and prey is accelerated into the gaping mouth (Figs. 2 and 3)
Morphology The morphology of the skull and hyobranchial apparatus of metamorphosed and paedomorphic salamandrids is described in detail elsewhere [16,17,18, 20, 21, 32, 36, 56, 63]; we focus mainly on the overall head morphology of both morphs and center on the hyobranchium and the rectus cervicis muscle system
Summary
Paedomorphosis is defined as the retention of juvenile characters in sexually mature adults and is common in many salamander groups. Larval salamanders create higher intraoral pressure drops and are more efficient in capturing elusive prey, their kinematics and motor pattern show no significant difference to metamorphosed salamanders [41, 65]. It has been suggested that the main factors leading to higher intraoral pressure drop and higher feeding efficiency in larval salamanders are based on the different flow regimes in larval and metamorphosed morphologies. Direct comparison of feeding mechanics between larval and metamorphosed salamanders within the same species is only available for ambystomatids. It is unclear whether the lack in kinematic differences of feeding kinematics between larval and metamorphosed individuals is a general feature in salamanders, or only due to the potentially stereotypical nature of the feeding strike in ambystomatids [40]
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