Synodontidae: CH II A1

Includes Trachinocephalus myops (Forster 1801), and Synodus indicus (Day, 1873)


Egg diameter in µm

Number of oil globules

Diameter of oil globule in µm

Yolk texture

Perivitelline space

Position of oil globule at hatch

Gut length   at eye- pigment stage








72% of NL


Egg: The size and distinct “honeycomb” pattern of reticulation on the egg are distinctive. The yolk state cannot be seen through the honeycomb patterned chorion, but is likely to be clear, as is the case for synodontids with a clear chorion (see H II A4). Incubation is about 45 hours; notably slower than similar-sized eggs of other species.

Larva: The newly hatched larva is elongate, with a long gut (arrowed). A set of regular black pigment spots develops along the ventral edge of the notochord (B). B: 5 days.

No attempt was made to rear this egg. This is almost certainly a group of species, as various sizes of reticulation were noted. Shao et. al. (2001) list Synodus variegatus, and several Saurida species as having a reticulated chorion. Eight hatched larvae has been sequenced, of which 5 matched 4 adult Synodus indicus, while the other 3 matched 6 adult Trachinocephalus myops (BOLD ), but T. myops appears to be made up of two clades. All adults were from local waters.

This is the most likely egg to be found in a Park Rynie plankton sample, although the reticulated synodontid only appears 21st in numbers of eggs collected (Introductory notes, Section 7, Table 3), due to low numbers in each sample. This is probably due to the solitary nature of the synodontids (though they are often seen in pairs), which results in their eggs being thinly spread. Eggs were collected all year round (blue graph), but this may, in part, be due to the multi-species contribution. Individual species may have better defined spawning periods. The eggs were only seen on 10 occasions in the DHM samples, and in small numbers (green graph). The presence of this egg off Park Rynie, showed no unusual pattern during the study (white graph). The linked samples from Park Rynie showed an almost equal distribution, with 53% inshore, indicating spawning inshore of kob and geelbek. See Section 7.3 and Table 1 of the Introductory Notes, for more information on the linked samples.

linked samples