Figure 4.

Morphological features associated with brood parasitism in cuckoo catfish young. (a) The eggs of the cuckoo catfish (Sm) and the non-parasitic congener S. lucipinnis (Sl) shortly after fertilization. (b) Lateral view of 4 dpf hatchlings shows the terminal position of the mouth in the cuckoo catfish and a subterminal mouth position in S. lucipinnis. White arrowhead indicates mouth position. (c) Ventral view of 6 dpf young stained for cartilage with Alcian Blue shows the wider mouth of the cuckoo catfish compared to S. lucipinnis. Black arrowheads indicate jaw margin. (d) Jaw width plotted against notochord length for 20, 6 dpf cuckoo catfish and S. lucipinnis young. Solid line indicates trendline for cuckoo catfish, and dashed line indicates trendline for S. lucipinnis. (e) Comparison of oral jaw teeth between the cuckoo catfish and S. lucipinnis young at 6, 8 and 10 dpf stained with Alizarin Red to reveal mineralized structures. Scale bars denote 1 mm (a–c) and 0.2 mm (e).