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Posted by Merry on April 20, 2015 at 10:35:08:

0. Two egg tangles photo 0. Two egg tangles cr DSC_0536_zpsvpxgsvql.jpg

This year, we’ve had extraordinary luck finding nudibranchs that inhabit the blades of giant kelp or other types of low-growing algae. The adults are very small, well-camouflaged, and easily overlooked, but their eggs give them away.

The egg masses of these diminutive slugs appear in sharp contrast to their habitat and our eyes are easily drawn to the luminous white shapes. Delicate strings, flat whorls, wide ribbons, and glistening orbs contain developing embryos that herald another generation of nudibranchs. During these chance encounters, I imagine that I’ve caught a glimpse into their hidden, ephemeral lives.

During courtship and mating, the black dorid, Polycera atra, periodically gave its mate a nudge or a nip. Or perhaps it was a nuzzle.
1. Polycera atra mid-mating nip photo 1.  Polycera atra mid-mating nuzzle DSC_0080_zpsss4agj5k.jpg

Nudibranchs are hermaphrodites, that is, they possesses both male and female reproductive organs. During copulation, the slugs orient themselves so that their genital apertures meet. After reciprocal insemination, each slug may lay eggs.

Polycera atra mating and their characteristic egg ribbon.
2. Polycera atra egg composite photo 2.  Polycera atra egg composite DSC_0079_zps22yxw10a.jpg

These vivid Trapania velox achieved quite a reach with their male reproductive apparatuses. That’s all I will say.
3. Trapania velox mating photo 3.  Trapania velox mating 800 DSC_0269_zpsbkwpb3qm.jpg

Some species of nudibranchs have a patent on their style of egg mass. One example of this is seen in Corambe pacifica and Corambe steinbergae. The two are closely related, similar in appearance, but produce different egg masses.

Both species competitively feed on the bryozoan, Membranipora membranacea, and they reproduce at the same time.
4. Corambe trio & field photo 4.  Corambe trio amp field  DSC_0217_zps1sygezmz.jpg

Corambe pacifica and its distinctive coiled egg mass.
5. Corambe pacifica& egg composite photo 5.  Corambe pacifica amp egg composite DSC_9945_zpssw8vkfwp.jpg

A pair of Corambe pacifica with egg masses.
6. Corambe pacifica & egg composite photo 6. Corambe pacifica two egg masses DSC_9662_zpsx2nasopu.jpg

The slightly smaller Corambe steinbergae.
7. Corambe steinbergae composite photo 7.  Corambe steinbergae composite DSC_0109_zpst0x1h82z.jpg

Both species serve a useful purpose in that by preying on Membranipora they help keep the encrusting bryozoan in check, which is an advantage to giant kelp.

Corambe steinbergae egg masses on Membranipora, showing the empty zooid compartments where the adults had been feeding. Corambe covers each individual zooid with its mouth, uses its radula to slice open the animal’s protective membrane, and then sucks out the soft parts. Yum.
8. C. steinbergae eggs & zooids photo 8.  C. steinbergae eggs amp zooids DSC_0049_zpsfczg2m59.jpg

A Corambe pacifica adult next to Corambe steinbergae eggs.
9. C. pac & C. stein eggs photo 9. C. pac amp C. stein eggs 2 DSC_9946_zpsumtddtly.jpg

10. C. pacifica and steinbergae eggs with text photo 10. C. pacifica and steinb. eggs text DSC_9158_zps2pqmen7t.jpg

Although Corambe steinbergae larvae settles on Membranipora later than C. pacifica settles, their efficient reproduction makes up for lost time. (P. Yoshioka, 1986).
What a mob of C. steinbergae eggs on decimated bryozoan!
11. C. steinbergae eggs lg field photo 11. C. steinbergae eggs lg field DSC_0052_zps5slxvfc6.jpg

After an egg mass is laid, the embryos of most opisthobranch species develop fairly rapidly, roughly in 1 – 2 weeks. In 91% of 126 west coast benthic species, what hatches from the egg is a larvae that does not resemble the adult. Rather, the embryo develops into a shelled veliger larvae, no larger than 1/10th – 1/20th of a millimeter.

The nearly transparent veliger larvae have protective shells and a ciliated velum, which is used for swimming, food particle collection and concentration. Veligers propel themselves upwards in order to prey on single-cell algae near the surface.
12. Veliger illustration photo 12. Veliger illustration_zpshtykwbfu.jpg

13.  Goddard's veligers photo 13. Goddards veligers_zps7n1a4vqq.jpg

Picture this microscopic traveler as enters the cosmopolitan world of plankton, to drift and to swim upwards for hours, days, or weeks, depending on the species. Although we can’t see them while diving, they’re probably zipping all around us. And they’re not alone. A proportion of zooplankton contains other molluscan veligers as well as opisthobranch veligers.

A planktonic larval veliger is the transition state before becoming a recognizable slug. After developing sufficiently, and when the veliger reaches a state of competence, it responds to a chemical signal from its preferred food source and settles to the bottom. In a day or so, it metamorphoses into a juvenile slug.
14.a. Metamorphosis photo 14. Metamorphosis_zpskm8qo8ty.jpg

During the past two weeks, legions of juvenile Falbellina trilineata have appeared on many different types of algae. They’re almost microscopic and about as easy to spot as an eyelash.
14.b. Juvie trilineatas photo 14.1 Juvie trilineatas DSC_0597_zpsce0n0lvy.jpg

Knowing the journey that a nudibranch undergoes before finally becoming a photo subject, makes it all the more exciting to find its eggs. The lush eggs of Cuthona lagunae take 8 days* to develop and hatch into a planktonic veliger. *J. Goddard and B. Green, 2013.
15. Cuthona lagunae eggs composite photo 15. Cuthona lagunae eggs composite DSC_9178_zpse2niylnz.jpg

These well-developed C. lagunae embryos show the features of veliger larvae.
16. Cuthona lagunae eggs close photo 16. Cuthona lagunae eggs close DSC_9178_zpsvusxodcv.jpg

You’ve probably seen the distinctive flower-shaped egg mass of Melibe leonina, the lion nudi, which is laid on kelp blades. Nearly transparent juveniles feed on minute crustacean larvae and other zooplankton.
17. Meliges in Obelia egg composite photo 17a. Melibes in Obelia egg composite DSC_0398_zpska05rmfx.jpg

Melibe leonina veligers develop and hatch in only 4 days*. The well-developed embryos in this egg mass resemble popcorn kernels. *J. Goddard and B. Green, 2013.
18. Melibe leonina embryos photo 18.  Melibe leonina embryos DSC_9628_zpst6jqtfea.jpg

If I had to guess, I'd say that this tangled egg ribbon probably belongs to Dendronotus venustus (formerly D. frondosus).
19. Egg string photo 19. Egg string DSC_9798_zpsvkdch4na.jpg

This assortment of egg masses comprises at least 3 different nudi species, including Eubranchus rustyus (6 cryptic juveniles in photo) and Doto form A.
20.  Multi eggs photo 20. Multi-eggs DSC_0605_zpstqjmoadg.jpg

A single egg mass of Hermissenda crassicornis yields 7,000 – 1,000,000 veliger larvae, which are planktonic for 30-40 days before metamorphosing. (Avila et al.,1997, J Exp Mar Biol Ecol 218:243). Photo by Phil Garner.
21. Hermissenda & eggs photo 21.   Hermi amp eggs _zpskk6r5oji.jpg

My video of Hermissenda crassicornis veligers; there are three per egg capsule.

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