Eggcases

All skate, all chimaera and some shark species are oviparous: They deposit fertilized eggs onto the sandy bottom or (in the case of sharks) attach them to seaweeds or rocks. The egg capsule contains the embryo, which feeds on yolk until it is ready to hatch. 

 

 You can find eggcases on the shoreline or underwater. If you see a capsule underwater, please

DO NOT remove or disturb it as it is most likely that it still contains a developing embryo.

 

The three major groups of eggcases are easily distinguished:

  • Chimaera eggcases have a very distinct teardrop-like shape and broad lateral keels

 

 

  • Skate eggcases are mostly square in shape and have horns (rather than tendrils) attached to all four corners

 

 

  • Shark eggcases are less square in shape and have curly tendrils (might not be present in damaged eggcases)

Identifying the eggcases to a species level however is little more tricky and requires some practice. We have compiled comprehensive ID guides to make it as easy as possible. 

Preparation

 

An eggcase that you find on the beach has already undergone quite a journey: After releasing the embryo it has sheltered, the capsule withstood untamed waves and currents and finally endured the exposure to dry air and the merciless sun. It might not have exactly kept its looks since the moment it left the uterus. So before you start judging on its shape, give it a good bath. 

 

Eggcases should be soaked in sea- or freshwater overnight to ensure that their shape returns to its original state.

Identification

 

Once the egg capsules have been thoroughly soaked, they are ready for identification. Consider that they might have lost certain parts, such as their tendrils, horns or original colour and surface structure. With our ID key, you should still be able to identify the eggcase through a combination of different characteristics.

 

The most commonly found eggcases on the South African South-East Coast are listed below.

St. Joseph / Cape Elephantfish (Callorhinchus capensis)

Length: 130-180mm, convex structure

Colour: pale yellow to dark brown,

broad laminar frill, which is hairy on one surface and smooth on the other

Leopard catshark (Poroderma pantherinum)

Length: 70mm, Width: 30mm,

Colour: light brown to greenish-brown, anterior and posterior tendrils are thinner than those of P. africanum

Dark shyshark / Pretty Happy (Haploblepharus pictus)

Length: 55mm, Width: 25mm,

Colour: amber to dark brown,

thin anterior tendrils. Currently not distinguishable from H.fuscus eggs.

Puffadder shyshark / Happy Eddie (Haploblepharus edwardsii)

Length: 35-50mm, Width: 15-30mm,

Colour: amber to dark brown, transverse, light-coloured bands, thin anterior tendrils

Pyjama shark / Striped catshark (Poroderma africanum)

Length: 95mm, Width: 45mm,

Colour: dark brown, anterior and posterior tendrils are thicker than those of

P. pantherinum

Brown shyshark / Plain Happy (Haploblepharus fuscus)

Like H.pictus eggcase, currently not distinguishable.

Twineyed skate (Raja miraletus)

Length: <50mm, horns robust, tapering and of even length, distal horns hook-like with acute tips, proximal horns filamentous tips, no lateral keel, finely striated, smooth surface

Spearnose skate / White skate (Rostroraja alba)

Length: 150mm, distal horns are short and tapered with attachment fibres, proximal horns are very long, tapered, flattened towards tips. Surface: coarsely striated, rough.

Lateral keels: Broad

 

Please note: The above list is not complete but depicts the most common eggcases. For more species and details, download our ID key.

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© 2020 by ELMO (South African Elasmobranch Monitoring). 

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