Spurilla macleayi - eggs & development

February 9, 2004
From: Bill Rudman

PHOTOS: Bungan Head, Sydney, NSW, Australia, intertidal, 29 November 1986. approx 20mm long alive. AM C151992. Photos: Bill Rudman

Here are a number of observations showing that Spurilla macleayi is a direct developer. The accompanying photos are of an egg ribbbon laid by the animal from Bungan Head, Sydney, described earlier [message #12135]. The egg ribbon was not measured but the size of the eggs suggest that it is a direct developer. Unfortunately the date the egg ribbon was laid was not noted but my colleague, Ian Loch, made the following notes on the development of the larvae.
• 17 December - no shell but larvae spinning within capsule, 'velar' lobes visible
• 24 December - egg mass breaking down, larvae crawling rather than spinning
• 30 December - young emerging from egg ribbon as crawling slugs.

I have observed similar egg ribbons on two other occasions.
• Ulverstone, Tasmania, 21 February 1984. 20mm long animal. AM C141294. - Laid an egg ribbon, very similar to the one from Sydney in the accompanying photo, and the larvae developed small non-ciliated velar lobes. The egg ribbon diameter was approximately 6mm.
• WEst Head, Flinders, Westernport Bay, Victoria, 2 May 1986. under rocks at low tide. 6 animals 12-16mm long alive. AM C149499. - One animal laid a single string egg ribbon of very large eggs in a dish.

Bill Rudman

Rudman, W.B., 2004 (Feb 9) Spurilla macleayi - eggs & development. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/12136


Spurilla macleayi

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