Category Archives: Mollusks

Crawling Rainbow

Glossodoris Cincta Nudibranch
Glossodoris Cincta Nudibranch

Glossodoris Cincta – Nudibranch
Feeds on sponges. When crawling, the gills make vibrating movements. When provoked, it discharges a white fluid from mantle dermal formations – in which they store distasteful chemicals from their food sponges to use defensively.

Etymology
Glosso= Greek ‘singular’ + dorís= ‘a nymph’, one of the daughters of Oceanus
cinctus= Greek ‘to put a belt around’

Scrambled Egg nudibranch

Sky Blue Phyllidia Nudibranch - Phyllidia varicosa -
Sky Blue Phyllidia Nudibranch – Phyllidia varicosa –

Sky Blue Phyllidia NudibranchPhyllidia varicosa
Probably the most frequently seen tropical Indo-Pacific nudibranchs. The phyllidiids are a group of firm, tough-bodied dorids in which the usual circlet of gills are replaced by leaf like secondary gills under the mantle skirt. It is sometimes called the “scrambled egg nudibranch.” These sea slugs are masters of chemical defense and contain a chemical mucus poisonous to fish and crustaceans. Scientists named it 9-isocyanopupukeane after the dive site, Pupukea, on O`ahu’s north shore. They are capable of killing all life in the aquarium if stressed in any way. They have no known predators.

Etymology
Phyllidium, from the Greek phyllos = ‘leaf’
verrucosa = from Greek ‘wart-like’

It’s a tentacular spectacular!

Phyllodesmium briareum - Nudibranch
Phyllodesmium briareum – Nudibranch

Phyllodesmium briareum – Nudibranch – There is a lot going on in those wavy arms. The name briareus was apparently given to it because it uses camouflage and looks like the soft coral Briareum violacea with which it is often found. Their specific name briareum comes from Briareos, one of three Greek storm giants who each had one hundred hands and fifty heads. P. briareum spends the day feeding on various kinds of soft coral, but they also have contains zooxanthellae which live in specialized ducts in the digestive gland. They do their photosynthesis thing and provide sugars.

The tentacles are cerata (from the Greek word meaning “horn”, a reference to the shape of these structures) of conventional aeolid shape. Aeolids (a suborder of Nudibranchia)take their name from the Greek god of the winds, Aeolus because of the waving of their cerata resembles streamers in the wind.
All aeolids have these dorsal and lateral outgrowths of the body. They are a blood-filled tube which contains a duct of the digestive gland. At the tip of the ceras in most aeolids is a sac, called the cnidosac which stores stinging nematocysts from the cnidarians (sea anemones, hydroids etc) on which they feed. Aeolids can discharge these nematocysts in their own defense. Some aeolids, such as species of Phyllodesmium which feed on soft-corals, do not have a cnidosac because the nematocysts of soft-corals are of little use in defense. Instead their cerata produce a horrible sticky secretion at the tip of the ceras. The cerata can even drop off and wriggle around, hopefully distracting assailants giving it a chance to escape.

Being an aeolid, P. briareum lacks the gills found in many other nudibranches. Instead, they do all their breathing straight through the skin, but particularly through those wonderful tentacles which are known as cerata.

Painted Shielded Horns

Thecacera picta - Nudibranch
Thecacera picta – Nudibranch

Thecacera picta – Nudibranch –
They are almost clear, you can see its internal organs through the translucent body. A characteristic feature of this genus are the long horns on its back, which can be extended and retracted. Most of the nudibranchs with feathery gills have them near the back of the body, but here they’re closer to the front.

Etymology
Thecacera. From Greek ‘theke’, a receptacle, a scabbard or sheath + ‘kerós’, horn, for the shielded rhinophores.
picta – From Latin ‘pictus’ for painted, colored, decorated

A rhinophore is one of a pair of chemosensory rod-shaped structures which are the most prominent part of the external head anatomy in nudibranchs.

Etymology
Rhinophore – relates to the function as an organ of “smell”. A mixed Latin and Greek word meaning “carrying noses” – “Rhino-” means nose from Ancient Greek ‘rhis’ and from its genitive rhinos. “Phore” means “to bear” from New Latin -‘phorus’ and from Greek -phoros “bearing”, a derivative of phérein.

BigFin Reef Squid

Big Fin Reef Squid
BigFin Reef Squid –
Sepioteuthis lessoniana

Bigfin Reef SquidSepioteuthis lessoniana – BfRS have a large oval fin that extends throughout the margins of its mantle.

  • BfRS adapt to warmer temperatures by laying more eggs, making them a good indicator species for climate change.
  • The babies resemble miniature adults and are remarkable for already having the capability to change body coloration upon hatching.
  • BfRS have the fastest recorded growth rates of any large marine invertebrate, reaching 600 g in only four months. They are a short-lived species, with a maximum recorded lifespan of 315 days.
  • Males have been observed to exhibit mating behaviors with other males. Some males have been found with numerous spermatophores embedded in their mouth funnels. Since BfRS distinguish sex by visual cues, this may be a form of deception. The smaller males (termed “female mimics” or “sneaker males”) might have assumed body patterning typical of females in order to trick larger males. Believing they are females, they will then waste their spermatophores on them.
  • BfRS are one of the most commercially important squid species, and are widely consumed as human food.

Coloration

  • Large chromatophores densely cover the upper surfaces of the head, mantle and arms with fewer on the sides.
  • BfRS are capable of metachrosis – rapidly changing body coloration and patterns through voluntary control of chromatophores.
  • They also possess iridophores that produces iridescent metallic greens and red when illuminated.
  • They are also one of two squid species with leucophores that are a reflector-type structural coloration that reflects ambient light, such that they are white in white light, green in green light, and so on.
  • BfRS are remarkable for having the ability to produce complex body patterns from the moment they hatch.

Etymology:
Sepioteuthis – Greek for “cuttlefish squid”
lessoniana: Named after René Primevère Lesson who was a 19th century French botanist and surgeon who collected it off the coast of New Guinea during the circumnavigational voyage of the French corvette La Coquille (1822–1825).

Dwarf Cuttlefish

Stumpy Cuttlefish
Stumpy Cuttlefish

Stumpy CuttlefishDwarf CuttlefishSepia bandensis
This weird and wonderful cuttlefish is not actually a fish but is in fact a mollusk. They have an internal shell (cuttlebone), amazing large W-shaped pupils, eight arms and two tentacles which they use for feeding.

This little fellow was smooth a few moments before and then bumped himself up changed color from almost white to this tan, a true ‘chameleon of the sea’.

On the Right Side…

Side-gilled slug - Pleurobranchus forskalii
Side Gilled Slug – Pleurobranchus forskalii

Oooh! A Side-gilled slug Pleurobranchus forskalii – gills are found on the right side of the body in the gap between the mantle and the foot. This relatively large pleurobranch is often found in quite large populations in shallow lagoons, reef crests and pools and sea grass beds.

Funeral Nudibranch

The Funeral Nudibranch - Jorunna funebris
Funeral Nudibranch

The Funeral NudibranchJorunna funebris, gets is name from the black and white coloration. It feeds on a blue sponges (Neopetrosia sp.), which makes it poisonous, and able to secrete chemicals that make them distasteful or toxic.

As a members from the family Discodorididae they are able to retract its gills into a gill pocket. Many species are able to break off part of their mantle to distract predators. They generally have a narrow foot compared to the wide mantle skirt.