My Little Underwater Critters - Sea Slugs and Flatworms (Part 1)

I am going to jot about the mostly admired underwater creature, known as sea slugs. Well, in layman term, these invertebrates are known as nudibranchs. Just to make things clear that nudibranch (or nudibranchia) is the scientific term used to represent the order of true sea slug which is slightly different from other sea slugs in terms of morphology, anatomy, physiology and habitat . The other orders of sea slugs are sea hares, headshield slugs, sidegill slugs and sap-sucking slugs. Most non-scientific underwater photographer would mistakenly label all sea slugs as nudibranch. 

For those who are keen to know the scientific classification, or taxonomy of sea slugs, below is the full taxonomy of sea slugs up to order level;

                                            Kingdom : Animalia

                                            Phylum    : Mollusca

                                            Class       : Gastropoda

                                            Subclass  : Opisthobranchia
                                            Order      : Nudibranchia (True sea slug)
                                                             Cephalaspidea (Headshield slug)

                                                             Anaspidea (Sea hare)
                                                             Notaspidea (Sidegill slug)
                                                             Sacoglossa (Sap-sucking slug)

                                                          *source:  Behrens (2007) and Debelius (2001)

All photos posted in this blog are entirely from my own collections and my buddy's, taken from the diving trips in Malaysia, Indonesia and Philippines with my dive-buddies. That was 2-3 years back and now I do not dive that frequent as I have been focusing on traveling. I miss these cute, colourful and charming little creatures that I decided to post  their photos and to reminisce the moments of encounter with them. The arrangement of the sea slugs photos is in alphabetical order and i am trying my best to include the taxonomy in the caption.

As what my dedicated dive-buddy and I have been photographing to date, the most frequently sighted sea slugs are from the order nudibranchia and most of them belongs to the family Chromodoridiidae. This order is then divided into 4 suborders, with which the suborder Doridacea has the most families in it, altogether 14 families. 

Family: Chromodorididae

Genus: Ardeadoris

Species name: A. egretta

Location: Sipadan, Sabah, Malaysia

Genus : Ceratosoma

Species name: C. tenue

Location : Lembeh Straits, North Sulawesi, Indonesia

Photo credit: Kamaruddin Abd Manan

Genus : Chromodoris

Species name: C. annulata

Location : Coral Garden, Pulau Payar, Malaysia

Genus : Chromodoris

Species name: C. coi

Location : Lembeh Straits, North Sulawesi, Inonesia

* this is one of the most frequently sighted species and normally found on walls or boulders. 

Genus: Chromodoris

Species name: C. coi

Location: Pulau Aur, Johor, Malaysia

* Mating C. coi found on a wall at Reyner's Rock

Family: Chromodoridiidae 

Genus : Chromodoris

Species name: C. colemani

Location : Lembeh Straits, North Sulawesi, Indonesia

Photo credit: Kamaruddin Abd Manan

Genus: Chromodoris

Species name: C. dianae

Location: Mabul, Sabah, Malaysia

Genus: Chromodoris

Species name: C. fidelis

Location: Lembeh Straits, North Sulawesi, Indonesia

Genus : Chromodoris

Species name: C. hintuanensis

Location: Lembeh Straits, North Sulawesi, Indonesia

Family: Chromodoridiidae

Genus: Chromodoris

Species name: C. lochi

Location: Lembeh Straits, North Sulawesi, Indonesia

* this nudibranch should appear white here but improper white balance setting made it appeared bluish

Genus: Chromodoris

Species name: C. magnifica

Location: Cebu, Philippines

Genus: Chromodoris

Species name: C. strigata

Location: Lembeh Straits, North Sulawesi, Indonesia

Genus: Chromodoris

Species name: C. willani

Location: Sibuan island, Sabah, Malaysia

Family: Arminidae

Genus: Dermatobranchus

Species name: D.  cf. albus

* This is a juvenile Arminid which is less than 2 cm in length. Macro lens was used.

Family: Discodorididae

Genus: Discodoris

Species name: D. boholiensis

Location: Batu Ibai Penunjuk, Terengganu, Malaysia

Photo credit: Kamaruddin Abd Manan

Family: Flabellinidae

Genus: Flabellina

Species name: F. exoptata

Location: Lembeh Straits, North Sulawesi, Indonesia

*frequently sighted and one dive spot which has abundant of this species is in Batu Ibai Penunjuk reef

Genus: Glossodoris

Species name: G. atromarginata

Location: Lemberh Straits, North Sulawesi, Indonesia

Family: Halgerdidae

Genus: Halgera

Species name: H. batangas

Location: Lembeh Straits, N. Sulawesi, Indonesia

Family: Hexabranchidae

Genus: Hexabranchus

Species name: H. sanguenus

*Hexabranchus stands for 6 gills and this species can row up to 40 cm length. 

It's common name is Spanish Dancer

Before I keep on posting more photos here, I would like to share the variations of nudibranch of the species H. bullockii. Well, as the photos below, there are at least 4-5 variations of this species which is reallly interesting. It is difficult to determine if the variation depends on geographical factor, or it occurs randomly, since there is no specific observation done on this. Based on my experience diving in Malaysia and Indonesia waters, the purple H. bullockii can only be found in Celebes sea (Sibuan island, Mabul etc) but I have neer seen anything like that in Indonesia. But the bright pink H. bullockii nudibranchs have been sighted everywhere else, thought the shades of the pink varies. And as for the picture just below this paragraph, this was my first experience sighting this variation of H. bullockii. 

Family: Chromodoridiidae

Genus: Hypselodoris

Species name: H. bullockii

Location: Mawali Wreck, Lembeh Straits

Family: Chromodoridiidae

Genus: Hypselodoris

Species name: H. bullockii

Location: Lembeh Straits, North Sulawesi, Indonesia

The yellow coil is the egg mass of H. bullockii after mating. Note that nudibranchs are hermaphrodites.

Family: Chromodoridiidae

Genus: Hypselodoris

Species name: Hypselodoris bullockii

Location: Mabul, Sabah, Malaysia

* another variation of H. bullockii. This variation is found only in Celebes sea so far.

One of my favorite nudibranch because it is purple. Hehe...

Genus: Hypselodoris

Species name: H. bullockii

Location: Lembeh Straits, North Sulawesi, Indonesia

* Another variation of this species.

Genus: Hypselodoris

Species name: H. emma

Location: Lembeh Straits, N. Sulawesi, Indonesia

Genus: Hypselodoris

Species name: H. infucata

Location: Lembeh Straits, N. Sulawesi, Indonesia

Genus: Hypselodoris

Species name: H. maculosa

Location: Lembeh Straits, N. Sulawesi, Indonesia

Genus: Hypselodoris

Species name: H. whitei

Location: Lembeh Straits, N. Sulawesi, Indonesia

Family: Kentrodorididae

Genus: Jorunna

Species name: J. funebris

Location: Pulau Perhentian, Terengganu, Malaysia

This species is abundant in Malaysian underwater.

Local divers call it, Kungfu Panda and other names include

'funeral Jorunna' which I have no idea why it is called 'funeral'

Little Kungfu Panda about to feed on tunicates

Genus: Mexichromis

Species name: M. multituberculata

Location: Lembeh Straits, N. Sulawesi, Indonesia

A group of M. multituberculata which is a rare sighting anywhere else but in Lembeh

Nembrotha chamberlaini

Nembrotha cristata

Genus: Noumea

Species name: N. crocea

Location: Lembeh Straits, N. Sulawesi, Indonesia

Family: Phyllididae

Genus: Phylidiella

Species name: P. rudmani

Location: Kota Kinabalu, Sabah, Malaysia

Family: Phyllidiidae

Genus: Phyllidiopsis

Species name: P. phiphiensis

Location: Pulau Payar, Malaysia

Order: Notaspidea (Sidegill Slug)

Family: Pleurobranchidae

Genus: Pleurobranchus

Species name: P. forskalii

Location: L.I.P.I, Lembeh Straits, N. Sulawesi, Indonesia

* This slug was found during night dive, slightly bigger than a saucer

Another variation of P. forskalii

Species name: Prostheceraeus sp
Location: Lembeh Straits, N. Sulawesi, Indonesia

Species name: Pseudoceros bifurcus

Location: Menjangan Island, Bali, Indonesia

A flatworm, Pseudoceros sp., mimicking a nudibranch Glossodoris atromarginata. 

Famile: Phyllidiidae

Genus: Reticulidia

Species name: R. fungia

Location: Tunku Abdul Rahman Marine Park, Sabah, Malaysia

Genus: Risbecia

Species name: R. pulchella

Location: Pulau Payar, Malaysia

* A pair of R. pulchella is tailgating, or simply tailing and it is believed  

R. pulchella feeds on sponges

Genus: Risbecia

Species name: R tryoni

Location: Lembeh Straits: N. Sulawesi, Indonesia

Family: Polyceridae

Genus: Tambja

Species name: Tambja gabrielae

Location: Lembeh Straits, N. Sulawesi, Indonesia

One of the largest sea slugs in its order

Family: Polyceridae

Genus: Tambja

Species name: T. morosa

Location: Lemeh Straits, N. Sulawesi, Indonesia

The colour of T. morosa may be dull, but it is lovely to watch its graceful movement

(To be continued to part 2 after I have acquired all pictures in my laptop)