Anguilliformes: F I A1


Snake eels

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











75% of NL

Ca 140

Egg: Plate A shows all three types of eel egg commonly seen, without an oil globule, with one clear or amber oil globule and with multiple oil globules. Plate B shows a typical single amber oil globule and the green tint to the yolk. There are two distinct size groups, indicating at least two species, thus two size ranges are given in the above table. The position of the single oil globule in the newly hatched larva is uncertain, as it is virtually used up by that stage. When fresh the yolk has a light green tint, and measures 60-64% of egg diameter, in the smaller egg, and 51-57% of egg diameter in the larger egg, in the above table. Incubation time is uncertain, but probably exceeds 80 hours (24°C)

Larva: Larvae reared from these eggs all have clusters of green or black pigment dotted along the ventral edge of the notochord (C & D). The larva is elongate and blade-like, with pigmented eyes, and a partly developed mouth. C: 1 day, D: 2 days, E: 4 days, F: 6 days.

No attempt was made to rear this larva. They have been tentatively assigned to the  snake eels, based on the description in  Fahay (1983). DNA barcoding of these larvae is the surest way to link larva to adult, and a number of eel adults have been sequenced for this study (BOLD). Thirteen larvae from eggs in this group have been sequenced, indicating 5 species, but no matches have been found in the adult archive in BOLD.


This egg is not common in the Park Rynie samples, but the data shows these eels are summer spawners (blue graph). Due to the solitary nature of eels, the eggs were seldom seen in high numbers in a sample, but on one occasion, in March 1993, 37 eggs were collected in one sample off Park Rynie. To see the trend in other years, this sample was reduced to 3 for plotting the annual trend of eggs in samples from Park Rynie. This revealed a drop in collection of these eggs in the late 1990's, but an increase in recent years (white graph). The egg was seen twice in the DHM samples, in April and October, and only as single eggs, suggesting they had drifted in from elsewhere.  In the Park Rynie linked samples, these eel eggs showed an even distribution between the inshore (52%) and offshore samples, indicating spawning inshore of the 30m contour. See Section 7.3 and Table 1 of the Introductory Notes, for more information on the linked samples.

Linked samples