THE EGG-CAPSULE OF RAJA BINOCULATA GIRARD, 1854

The big skate (Raja binoculata Girard, 1854) lays probably the biggest egg-capsules in the Rajidae family. Descriptions and a picture of the egg-capsule of Raja binoculata are given by Cox (1963) and DeLacey & Chapman (1935). The last two authors measured twenty egg-capsules. They found ranges for the length from 265 to 305 mm and for the width from 110 to 140 mm.

Raja binoculata

The egg-capsules of Raja binoculata and Raja pulchra Liu, 1932 are at the moment the only ones known which can contain more than one egg inside. According to DeLacey & Chapman (1935) the egg-capsule of Raja binoculata has usually 3 or 4 eggs, but this can vary from 2 to 7 eggs. Ishiyama (1967:36) reports for Raja pulchra 1 to 5 eggs in an egg-capsule.

The egg-capsule of Raja pulchra is described and pictured by Ishiyama (1950, 1958, 1967). A drawing of the egg-capsules treated in Ishiyama (1950) is given below, the egg-capsule of Raja pulchra being in the lower row, second one on the left.

japanese egg-capsules from Ishiyama (1950)

Ralph Cook sent me some pictures of an egg-capsule of Raja binoculata he found washed ashore on the Oregon coast. In these pictures you can clearly see the different eggs in the egg-capsule.

Raja binoculata with eggs

Raja binoculata with eggs

Ralph also found another egg-capsule of Raja binoculata on the beach on the Cove beach at Seaside (Oregon) on October 13th 2000, full with barnacles.

Raja binoculata with barnacles

And here is a picture of an egg-capsule also found on the Oregon coast, on Januar 17th 2002 at Cannon beach, by Ingrid Bartels.

picture by courtesy of Ingrid Bartels

The egg-capsule was heavy, so Ingrid opened it to look inside:

the dorsal side of the egg-capsule the ventral side of the egg-capsule
making the incision the contents of the egg-capsule



In december 2001 Darla Kellog found an egg-capsule of Raja binoculata on the Oregon containing three eggs inside. Chris Kellog was so kind to send me the following pictures for my website. Egg-capsules of Raja binoculata are not rare on the Oregon coast. Chris mailed me that they had found at least six other ones at Seaside and Gearhart in februar 2002!



Literature
Cox, K.W., 1963. Egg-cases of some elasmobranchs and a cyclostome from californian waters. California fish and game 49 (4): 271-289.
DeLacey, A.C. & W.M. Chapman, 1935. Notes on some elasmobranchs of Puget Sound, with descriptions of their egg cases. Copeia 1935 no. 2: 63-67.
Hitz, C.R., 1964. Observations on egg cases of the big skate (Raja binoculata Girard) found in Oregon coastal waters. J. Fish. Res. Bd. Canada 21 (4): 851-854.
Ishiyama, R., 1950. Studies on the rays and skates belonging to the family Rajidae, found in Japan and adjacent regions. 1. Egg-capsule of ten species. Jap. J. Ichthyol. 1: 30-36.
Ishiyama, R., 1958. Observations on the egg-capsules of skates of the family Rajidae, found in Japan and its adjacent water. Bull. Mus. Comp. Zool. Harvard 118: 1-24.
Ishiyama, R., 1967. Fauna Japonica. Rajidae (Pisces): pp. I-VI, 1-84, plates 1-32.