nudibranch | The Marine Detective

Posts tagged ‘nudibranch’

Zyzzyzus rubusidaeus

One of the services I like to provide here on The Marine Detective, is to share words you can try to randomly drop into conversations and annoy your friends. You’re welcome. It’s a task I take very seriously.

Yes, there really is an animal with the scientific name Zyzzyzus rubusidaeus and to me, they look like they have been designed by Dr. Seuss himself. Their common name is the Raspberry Hydroid and they have beautiful predators too.

The common name for Zyzzyzus rubusidaeus is the Raspberry Hydroid. They were only described as a new species in 2013 by northern Vancouver Island’s own Anita Brinckmann-Voss who lived in Sointula. The research paper is at this link.

Their specific nudibranch prey are Pomegranate Aeolids. To my knowledge, the only documentations for both species, to date, are near Telegraph Cove (Weynton Pass) and Quadra Island (Discovery Passage). I can certainly attest to how fortunate we are to see them so predictably near Telegraph Cove.

*What you see here, in addition to Raspberry Hydroids and a Pomegranate Aeolid nudibranch, are Mushroom Compound Tunicates, and a feeding Giant Acorn Barnacle.*

See below for more information about both species. Oh, and if you ever are able to use the word “Zyzzyzus” in a word game because of this post, I expect a thank you! 😉

Descriptor for the above photo:

Trifecta!

(1) Nudibranch species the Pomegranate Aeolid (Cuthonella punicea to 2.5 cm).

(2)Their only known prey, the stinging celled animals Raspberry Hydroids (Zyzzyzus rubusidaeus to 5 cm tall).

(3) The nudibranchs’ egg masses / strings. As is the way with sea slugs, they most often lay their eggs on their prey. Talk about adding insult to injury. I eat you and I lay my eggs on you so there will be more of my kind to prey on your kind.

*More Pomegranate Aeolids feeding on Raspberry Hydroids. This is a female colony. The round structures are female gonophores which may contain embryos.*

More about hydroids:

Almost all hydroid species are colonial. They are carnivores. Hydroids are related to jellies, anemones, and corals (phylum Cnidarian).

The reproduction of hydroids is remarkable. Colonies are male or female. They start by reproducing asexually by budding off hydromedusa – tiny free-swimming, jellyfish-like versions of themselves. These produce either eggs or sperm. Fertilization of the eggs leads to larvae that may settle on the ocean bottom and form colonies.

Hydroids catch drifting prey with their polyps aided by their nematocysts (stinging cells). None of the hydroid species off our coast deliver a sting that we humans can feel (no matter how sensitive you are 😉).

The food gets distributed throughout their single-sex colony.

And who loves to eat species of hydroids? Nudibranchs! Specifically, the aeolid kinds of nudibranchs – they have those bushy structures on their backs (cerata). Many of these nudibranch species not only rely on the hydroids for nutrition but also make use of their prey’s stinging cells! The nematocysts get incorporated into the ends of the cerata.

Sources:
Brinckmann-Voss, A., & Calder, D. R. 2013. Zyzzyzus rubusidaeus (Cnidaria, Hydrozoa, Tubulariidae), a new species of anthoathecate hydroid from the coast of British Columbia, Canada. Zootaxa 3666: 389-397

Bring in the Clowns

Update September 24, 2020 – Species has been reclassified into two.

Triopha modesta has been determined to be a trans-Pacific species and is far more likely to be off the coast of British Columbia and has both flat and branching tubercles and globular bits on their side (“relatively small and dendritic dorsal tubercles, two rows of arborescent tubercles on the dorso-lateral appendages of larger individuals”).

Triopha catalinae has been determined to be an eastern Pacific species (but there is overlap) and have large, conical or rounded dorsal tubercles.

Source; Jung, D., Gosliner, T.M., Choi, T. et al. The return of the clown: pseudocryptic speciation in the North Pacific clown nudibranch, Triopha catalinae (Cooper, 1863) sensu lato identified by integrative taxonomic approaches. Mar. Biodivers. 50, 84 (2020).

Original post from 2016:
In having noted the recent “Creepy Clown” Halloween-related absurdity in the far off periphery of my life, I thought I would share the beauty of the clowns abundant below the surface at this time of year – Clown Dorids.

Clown Dorids are a species of nudibranch (Triopha modesta to 7 cm).

Nudibranchs are sea slugs with naked gills and those in the dorid suborder most often have their plume of gills on their posterior (around the anus in fact). See the orange frills in the Clown Dorids in these images? Those are their gills.

Clown Dorid; gills on right @Jackie Hildering.

Clown Dorid with gills are on the right. It’s “rhinophores”, by which it smells its way around, are on the left, atop its head.

Many dorid species fully retract their gills when disturbed. Clown Dorids can only partial retract their gills.

That’s all! Clown Dorids cannot fully retract their gills like most other dorid species.

Note too the beautiful “oral veil” with papillae that aid Clown Dorids in finding food.

Image allowing a good look at the Clown Dorid’s oral veil.

Also unlike many dorids, Clown Dorids do not feed on sponges. They feed exclusively on bryozoan species; those crusty colonies of organisms often found on kelp.

Clown Dorid likely feeding on Kelp-Encrusting Bryozoan.

There were a particularly large number of Clown Dorids on my dive this past October weekend with many egg masses.

Sea slugs are reciprocal hermaphrodites. This of course makes good sense as a reproductive strategy when you are a slow slug and your offspring hatch out to be plankton. Reciprocal hermaphrodites have both male and female sex organs whereby both individuals are inseminated and lay eggs = way more eggs!

Clown Dorids that have found one another (relying on smell and touch) and maneuvering into the mating position.

Nudibranchs mate right side to right side. If you look very carefully in the photo below, you can see a bump on the individuals’ right side. This structure is the “gonopore” and is usually retracted. They lock onto one another with their gonopores and both become inseminated.

Clown Dorids extending their mating organs and about to lock on right side to right side. (Ochre Star beside them.).

The gonopore is easier to see in the following image.

Clown Dorid – note the “gonopore” on the right near the nudibranch’s head.

The egg masses of each species of sea slug look different. However, it is very difficult to discern the eggs masses of some closely related dorids. The ideal is to find an individual laying the eggs.

However, in all these years, I have never managed to get a photo of a Clown Dorid laying eggs. Dive buddy Paul Sim has though. See his great image below.

paul-sim-clown_dorid_triophina_catalinae

Clown Dorid laying an egg mass. Note each little dot? That’s an egg! ©Paul Sim.

Summary from my social media post on December 13, 2016: Oh the fabulous way sea slugs ensure their kind survives! Imagine the challenges as a sea slug – you’re slow, you can only sense light and dark . . . . so when you finally find a mate it sure makes sense to be a simultaneous hermaphrodite so you both end up laying eggs. And the beauty of the egg masses! They are species specific i.e. the egg mass of each species of sea slug looks different. AND, wondrously, for almost all nudibranch species (at least in the northern hemisphere), these masses are almost always laid in a counterclockwise direction (sinistral) starting at the centre, with equal space between the whorls (i.e. an Archimedes spiral).

More information:

Reproductive structures of Clown Dorids from the Sea Slug Forum – click here.
Colour and diet in Clown Dorids from A Snail’s Odyssey – click here.

Nudibranchs on an Offshore Whale Survey?!

How does studying whale acoustics lead to increased knowledge about the depth range of nudibranchs?

Just a little more is now known about the orange doto’s depth range. Photo: Hildering.

Let me take you deep and share an experience from my recent time offshore in the eastern North Pacific on a DFO cetacean survey.

This is the Canadian Coast Guard Ship – the J.P. Tully.

CCGS J.P. Tully. Photo: Hildering

Among the offshore science expeditions undertaken upon the Tully, are surveys by DFO’s Cetacean Research Program. These line transect studies provide an estimate of cetacean abundance, as well as an opportunity to ID individual whales and collect feeding and genetic information. The knowledge about abundance and location is of particular importance for the large whales that were hunted so intensely and require protection under Canada’s Species at Risk Act.

These are Autonomous Underwater Recorders for Acoustic Listening (AURAL-M2s).

AURAL-M2s. Photo: Sheila Thornton.

AURALs are hydrophones that can be deployed to 300 m, making time-spaced recordings (e.g. 15 minutes every hour) for up to a year. Such acoustic monitoring is a very important supplement to the cetacean vessel surveys. The AURALs are of course placed very strategically, in remote, offshore locations. By passively recording whale calls, the AURALs can provide information about the location and seasonality of whale species which may aid in determining critical habitat.

The AURALs are a wonder of technology. It is of course no problem to get something to the bottom of the ocean but, getting it back to the surface so you can retrieve your equipment and data is not so simple. It is achieved with an acoustic release (“D” in the diagram below). Once the vessel is positioned so that there is no chance of the device coming up under it, a sound signal is sent to the device and the AURAL releases from its anchor and floats to the surface thanks to the big yellow buoy.

AURAL-M2. Click to see an enlarged, labeled schematic on the Multi-Electronique webpage.

These are two perplexed black-footed albatrosses! A big yellow orb has just popped up to the surface as a result of the acoustic release signal. This AURAL was at 226 m depth at the Bowie Seamount, 180 km west of Haida Gwaii. It had been there for a year.

Black-footed albatross just after the buoy with the AURAL recording device came up from 226 m.

Here, the highly skilled Coast Guard crew get the AURAL back aboard the ship so that the data can be retrieved and, ultimately, analyzed for whale vocals.

Coast Guard deck crew expertly retrieves the AURAL. Photo: Hildering

But, there was also a year’s worth of growth on the buoy and who knows what you might find . . .

Nudibranchs! Three species found and even one species with eggs!

3 nudibranch species on the aural that had been at 226 m. Photo: Hildering.

3 nudibranch species on the AURAL that had been at 226 m. BC aeolid; bushy-backed nudibranch and orange doto. Click to enlarge. Photo: Hildering.

Top: BC aeolid (Catriona columbiana to 1.5 cm); eggs also found.
Left: Bushy-backed nudibranch (Dendronotus venustus to 3 cm; previously Dendronotus frondosus)
Right: Orange doto (Doto amyra to 1.4 cm)

By examining the AURAL that had been at 226 m, it confirms that these 3 species of nudibranch have a range to at least that depth.

Sheila Thornton (marine mammal researcher and fellow nudibranch nut) providing a size comparison for the BC aeolids and their egg masses that were found on the AURAL. Click to enlarge. Photo: Hildering

I shared the find with those who have nudibranch expertise much greater than my own (Dave Behrens via Andy Lamb) and learned that for two of the species, there had been no previous record for them at this depth.

It has long been known that some nudibranch species range to depths of at least 700 m. However, you can imagine what a a challenge it is to get species specific depth information. We camera carrying scuba divers can’t help beyond 40 m depth (deeper if diving with mixed gases).

So it’s not a big scientific discovery. Compared to the data the AURAL will reveal about endangered whales, it’s just a sea-slug-sized discovery.

This is me – back on survey duty looking for much bigger organisms but delighting in how collecting data to help save whales, led to learning a bit more about the little guys.

Spotter duty on the DFO Cetacean Program’s offshore survey. July 2013. Christie McMillan photo.

See the CSAS technical report is by Linda Nichol and Dr. John Ford on the importance of the line transect surveys to the recovery of endangered cetaceans: Information relevant to the assessment of critical habitat for Blue, Fin, Sei and North Pacific Right Whales in British Columbia.

A few more photos from this DFO cetacean survey will soon be posted in this FaceBook album.

Scroll down at this link to hear samples of marine mammal vocals recorded by AURALs.

Hooded Nudibranchs and their eggs

*Hooded Nudibranchs – oral hood open ©Jackie Hildering*

[Last updated on January 2, 2022]

The remarkable-looking animals to the right are Hooded Nudibranchs (Melibe leonina up to 17.5 cm). A nudibranch is subgrouping of sea slugs whose characteristics include having naked (“nudi”) gills (“branchs”).

Typically, starting in the fall, around northeast Vancouver Island, Hooded Nudibranchs come together in the hundreds. It is awe-inspiring to see them clustered together just below the surface, delicate and ghost-like, clinging to kelp. Most are translucent white but some individuals are more green or orange.

Often, you can see them swimming on the surface and many people mistake them for jellyfish. But no, they are sea slugs.

The large oral hood (disc-like head) is used to feed on plankton and small crustaceans. The lobed structures on the animals’ backs are the naked gills (cerata). The cerata can pop off if the Hooded Nudibranch is threatened e.g. pinched by a crab. This “ceretal autonomy” and the ability to swim, are believed to be distractors for predator (Bickell-Page, 1989).

The two structures on the Hooded Nudibranch’s oral hood are their rhinophores by which they smell their way around. Hooded Nudibranchs are believed to signal one another by emitting a fruity scent. My personal experience after having picked up a dead Hooded Nudibranch on the beach, is that the smell is something like a mix of watermelon and grapefruit. The scent stayed on my hand for more than an hour.

Hooded nudibranch swimming. ©Jackie Hildering — *Hooded nudibranch swimming* *©Jackie Hildering*.

The secretion is reported to serve as a repellent for predators but does not deter Northern Kelp Crabs.

After mating, as is the way with sea slugs, both individuals lay eggs and then, they die. You can find additional information about sea slugs being reciprocal hermaphrodites in this past blog posting.

Hooded Nudibranch eggs. ©Jackie Hildering — *Hooded Nudibranch egg ribbons. ©Jackie Hildering*

In the area around northeast Vancouver Island, I have observed that they lay their egg masses between January and April. Each ribbon of eggs is only about one centimetre wide. Every dot is an egg capsule containing 15 to 25 eggs. After about 10 days, depending on temperature, the eggs will hatch into larvae that will be part of the zooplankton soup of the Ocean.

After 1 to 2 months, they settle to the ocean bottom and change body shape and even digestive tract to become small adult Hooded Nudibranchs

Hooded Nudibranchs do not have the rasping mouth structure of many other sea slugs (the radula). They feed by opening their oral hood to capture prey while standing on kelp or Eelgrass.

*Hooded Nudibranch on Eelgrass and yes, those little snails are part of their diet.*

From Invertebrates of the Salish Sea: ” . . . diet includes copepods, amphipods, and ostracods, as well as small post-larval mollusks. The animal stands attached to the substrate and expands the oral hood. It then sweeps the hood left and right or downward. When the ventral surface of the hood contacts a small animal the hood rapidly closes and the fringing tentacles overlap, holding the prey in. The whole animal is then forced into the nudibranch’s mouth.”