Dive Gozo | Mollusca

Mollusca:

Mollusca is the second largest phylum (level of classification) of invertebrate animals. The members are known as molluscs or mollusks. Around 85,000 extant (still existing) species of molluscs are recognized. The number of fossil species is estimated between 60,000 and 100,000 additional species. Source Wikipedia. The classes within the phylum are Gastropods, Opistobranchs, Polyplacophora, Bivalvia, Cephalopods and Scaphopoda.

Opistobranchs

Nudibranchs & Sea Slugs

Nudibranchs are a group of soft-bodied, marine gastropod molluscs which shed their shells after their larval stage. They are noted for their often extraordinary colours and striking forms. The name nudibranch literally means “naked gills”, and they breath either through their skin or secondary gills on their back. Whilst the different types can vary in physical shape they all have similar characteristics in that they have a set of tentacles called rhinophores at the head and gills (creata) at the rear. Some species can withdraw their rhinophores and gills into their body, so these may not always be seen. Nudibranchs are often casually called sea slugs and vice versa, as they are all the family of opisthobranchs.

A nudibranch is basically a sea slug, but there are some species of sea slugs that are not nudibranchs. They fall into two main groups, which are dorid nudibranchs and aeolid nudibranchs. The main difference between these two groups is their appearance and which body parts they use to breathe. The aeolid nudibranchs do not have specialized naked gills like the dorids. Instead, they usually have multiple paired rows of dorsal processes called cerata.

Peltodoris atromaculata, Formerly know as Discodoris

White body with large brown rounded blotches and spots. Similiar markings on the rhinophores and gills. Length 100mm

Discodoris Confusa Ballesteros

Photo credit Vera Wittenberg

Whitish with dark grey to brown blotches, rhinophores and gills pale yellow to brown. Length 60mm

Sea Lemon, Dendrodoris Limbata

Juvenile Black Doris, Dendrodoris nigra

This one was very little only 8mm long

Phyllidia flava formerly Doris Chrysoderma

Felimare picta, previously Hypselodoris elegans

A very variable species that has been described over different names. Atlantic Ocean species of Hypselodoris were all transferred to Felimare following a DNA phylogeny.
Several species were formerly considered to be subspecies of Felimare picta but several have now been elevated to species rank.

Felimare (Hypselodoris) picta azorica
Felimare (Hypselodoris) picta lajensis is a species, Felimare lajensis
Felimare (Hypselodoris) picta picta
Felimare (Hypselodoris) picta tema is a species Felimare tema
Felimare (Hypselodoris) picta webbi
Scource - Wikipedia

Felimare picta, previously Hypselodoris elegans

Dark blue or on adults can become very light almost a light green/yellow body with lots of yellow dots and lines on dorsum, mantle margin white and foot margin yellow. Rhinophores and gills same colour as body, but with yellow edging.

Juvenile Felimare picta

Pale blue body with three yellow lines on dorsum, with often other broken lines on adults, mantle margin white and foot margin yellow. Rhinophores and gills same colour as body, but with yellow edging.

Felimare Tricolour

Variable dark blue body with white or yellow midline between rhinophores and gills, mantle margin yellow and a series of pale blue dots between midline and mantle edge, lower yellow line below mantle edge, gills blue with yellow, rhinophores and oral tentacles as body colour.

Felimare Tricolour pair mating

Variable dark blue body with white or yellow midline between rhinophores and gills, mantle margin yellow and a series of pale blue dots between midline and mantle edge, lower yellow line below mantle edge, gills blue with yellow, rhinophores and oral tentacles as body colour.

Felimare Fontandraui

Variable dark blue body with white or yellow to orange midline which ends in a T between rhinophores and gills, this line branches in adults, mantle margin yellow to orange, lower yellow line below mantle edge, gills blue with yellow, rhinophores and oral tentacles as body colour.

Felimare Fontandraui

Variable dark blue body with white or yellow to orange midline which ends in a T between rhinophores and gills, this line branches in adults, mantle margin yellow to orange, lower yellow line below mantle edge, gills blue with yellow, rhinophores and oral tentacles as body colour.

Felimare Fontandraui

Variable dark blue body with white or yellow to orange midline which ends in a T between rhinophores and gills, this line branches in adults, mantle margin yellow to orange, lower yellow line below mantle edge, gills blue with yellow, rhinophores and oral tentacles as body colour.

Felimare Fontandraui

Variable dark blue body with white or yellow to orange midline which ends in a T between rhinophores and gills, this line branches in adults, mantle margin yellow to orange, lower yellow line below mantle edge, gills blue with yellow, rhinophores and oral tentacles as body colour.

Felimare Fontandraui

Variable dark blue body with white or yellow to orange midline which ends in a T between rhinophores and gills, this line branches in adults, mantle margin yellow to orange, lower yellow line below mantle edge, gills blue with yellow, rhinophores and oral tentacles as body colour.

Felimare Fontandraui

Variable dark blue body with white or yellow to orange midline which ends in a T between rhinophores and gills, this line branches in adults, mantle margin yellow to orange, lower yellow line below mantle edge, gills blue with yellow, rhinophores and oral tentacles as body colour.

Felimare Fontandraui

Variable dark blue body with white or yellow to orange midline which ends in a T between rhinophores and gills, this line branches in adults, mantle margin yellow to orange, lower yellow line below mantle edge, gills blue with yellow, rhinophores and oral tentacles as body colour.

Felimare krohni

Pink to pale blue body with three white to yellow lines on dorsum often broken, mantle margin yellow and foot margin white. Rhinophores and gills dark purple to reddish colour.

Felimare krohni

Pink to pale blue body with three white to yellow lines on dorsum often broken, mantle margin yellow and foot margin white. Rhinophores and gills dark purple to reddish colour.

Felimida luteorosea

Deep pink to dark reddish blue body with broad yellow mantle, a mix of small to large yellow spots on dorsum, rhinophores and gills as body colour.

Felimida purpurea purpurea

Body mottled pink to pale blue, mantle margin yellow with white fringe and the same on the end of the foot margin. Rhinophores and gills dark purple to reddish colour.
Length, these can grow up to approximately 4 cm long.
Photo credit Eva Bast

Felimida binza

Blue body, yellow midline on dorsum from gills to rhinophores, irregular yellow lines either side of midline to mantle, mantle margin broad white with yellow edging. Rhinophores and gills blue.

Felimida britoi Ortea

Pink to pale bluish body, , white and yellow midline on dorsum from gills to rhinophores, irregular yellow lines either side of midline to mantle, mantle margin broad white with yellow edging. Rhinophores and gills dark purple to bluish colour.

Felimida elegantula

Flabellina affinis

Pink to purple body, creata orange to red with purple band at top and white tips. Rhinophores are ringed, these and oral tentacles as body colour with white tips.

Berthellina edwardsii, common name Peach Sea Slug

Berthellina delicata common name Gum drop

Berthella Ocellata

It has an oval shape when extended and moving around, and circular when stationary. The head bears a pair of small black eyes and the mouth is underneath, with the buccal veil protruding on either side. The rhinophores are just in front of the eyes, and are tubular, with a split on the under surface; they project from the front edge of the mantle. When moving, the foot trails behind the slug; the underside of the foot is whitish or pale brown. There are two distinct colour forms of this sea slug, either brown, or whitish; in both cases the body is covered with white or pink, translucent, slightly-domed tubercles, each surrounded by a white rim. Wikipedia
General size is around 7 cm long. Vary rare that these grow so large, but they can reach up to 15cm long.

Berthella Ocellata

It has an oval shape when extended and moving around, and circular when stationary. The head bears a pair of small black eyes and the mouth is underneath, with the buccal veil protruding on either side. The rhinophores are just in front of the eyes, and are tubular, with a split on the under surface; they project from the front edge of the mantle. When moving, the foot trails behind the slug; the underside of the foot is whitish or pale brown. There are two distinct colour forms of this sea slug, either brown, or whitish; in both cases the body is covered with white or pink, translucent, slightly-domed tubercles, each surrounded by a white rim. Wikipedia
General size is around 7 cm long. Vary rare that these grow so large, but they can reach up to 15cm long.

Pleurobranchus testudinarius-6270035.jpg

Berthella Ocellata

It has an oval shape when extended and moving around, and circular when stationary. The head bears a pair of small black eyes and the mouth is underneath, with the buccal veil protruding on either side. The rhinophores are just in front of the eyes, and are tubular, with a split on the under surface; they project from the front edge of the mantle. When moving, the foot trails behind the slug; the underside of the foot is whitish or pale brown. There are two distinct colour forms of this sea slug, either brown, or whitish; in both cases the body is covered with white or pink, translucent, slightly-domed tubercles, each surrounded by a white rim. Wikipedia
Vary rare that these grow so large, but they can reach up to 15cm long.

Berthella Ocellata

It has an oval shape when extended and moving around, and circular when stationary. The head bears a pair of small black eyes and the mouth is underneath, with the buccal veil protruding on either side. The rhinophores are just in front of the eyes, and are tubular, with a split on the under surface; they project from the front edge of the mantle. When moving, the foot trails behind the slug; the underside of the foot is whitish or pale brown. There are two distinct colour forms of this sea slug, either brown, or whitish; in both cases the body is covered with white or pink, translucent, slightly-domed tubercles, each surrounded by a white rim. Wikipedia
Vary rare that these grow so large, but they can reach up to 15cm long.

Warty umbrella slug, Umbraculum umbraculum

Umbraculum umbraculum is a large mollusc growing to a length of up to 20 cm, with a relatively small external shell on the dorsal surface. This shell is a flattish cone and is usually encrusted with epiphytic organisms, both plant and animal. The mantle is roughly circular in outline, and is covered with pustules; the ground colour of the mantle varies, usually being orange or brownish, and the pustules are usually white. The mollusc does not elongate when crawling and the location of the head is revealed when it thrusts out its rolled rhinophores from beneath the shell. At the base of the rhinophores are a pair of eyes, and beneath is a cleft which contains the mouth. The radula is broad and is armed with many small teeth. The sole of the foot is smooth and flat. Wikipedia

Warty umbrella slug, Umbraculum umbraculum

Umbraculum umbraculum is a large mollusc growing to a length of up to 20 cm, with a relatively small external shell on the dorsal surface. This shell is a flattish cone and is usually encrusted with epiphytic organisms, both plant and animal. The mantle is roughly circular in outline, and is covered with pustules; the ground colour of the mantle varies, usually being orange or brownish, and the pustules are usually white. The mollusc does not elongate when crawling and the location of the head is revealed when it thrusts out its rolled rhinophores from beneath the shell. At the base of the rhinophores are a pair of eyes, and beneath is a cleft which contains the mouth. The radula is broad and is armed with many small teeth. The sole of the foot is smooth and flat. Wikipedia

Elysia timida

White body with red dots, generally has a green area on top due to the algae it eats. These tiny mollusc are in the super family sacoglossans. They have a unique way of flapping their paranoia as wings to move about. They can grow to a length of about 12 to 15mm.

Elysia timida

Elysia Viridis

It grows to a maximum of about 45mm in length. Its body colour can be green to bright red, this is dependent on the colour of the algae it is feeding on. There are usually scattered iridescent red, blue and green spots, and there can be white patches on the parapodial edges and black markings in the head and elsewhere.
It eats the filamentous algae Cladophora and Chaetomorpha as well as coenocytic algae Codium and Bryopsis .

Elysia Viridis

Okenia picoensis

Body is about 5mm in length, high and elongated.

Okenia picoensis

Body is about 5mm in length, high and elongated.

Okenia picoensis

Rhinophores are not always noticeable.

Okenia picoensis with eggs

Aglaja tricolorata

Although called a tricolour, it in fact only has the brown and white spotting. It is a "Headshield" sea slug and buries itself into the sand. It can be found on sandy bottoms quite shallow and is up to 40mm long. It has one long tail (a thin posterior flagellum), which can be over twice it's body length in size.

Aglaja tricolorata

Haminoea cyanomarginata, common name Bubble Shell Sea Slug

Thuridilla hopei

Tylodina perversa, common name False Limpet

Dendrodoris grandiflora

Pleurobranchus testudinarius

These can show quite a variation in background colour, from pale yellow to dark brown and even reddish purple. They apparently feed on ascidians and can grow up to 20 cm long

Gastropods

Sea Hares

The group Anaspidea, commonly known as sea hares (Aplysia species and related genera), are medium-sized to very large opisthobranch gastropod molluscs with a soft internal shell made of protein. The common name "sea hare" is a direct translation from Latin: lepus marinus, as the animal's existence was known in Roman times. The name derives from their rounded shape and from the two long rhinophores that project upwards from their heads and that somewhat resemble the ears of a hare.

Aplysia punctata and Aplysia parvula are the sole members of the subgenus Pruvotaplysia and so have many features in common. Externally, the main difference is said to be the black border in Aplysia parvula which is absent in Aplysia punctata.

Aplysia fasciata

Aplysia fasciata

Aplysia fasciata

Aplysia fasciata

Dark Spotted (Aplysia dactylomela)

Spotted (Aplysia dactylomela)

Spotted (Aplysia dactylomela)

Sea Hare eggs, Opisthobranchia

Aplysia spec Piran; Raggy

Aplysia spec Piran; Raggy

Aplysia punctata

Aplysia punctata

Aplysia parvula Sea Hare juvenile

Aplysia parvula Sea Hare juvenile

Other Gastropods

The gastropods, commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda. This class comprises snails and slugs from saltwater, from freshwater, and from the land.

Giant Tun (Tonna galea)

Giant Tun (Tonna galea)

Giant Tun (Tonna galea)

Giant Charonia tritonis (Trumpet triton)

Hairy Triton snail's eggs

Junior Charonia tritonis (Trumpet triton)

Bolma rugosa, Rough Star shell

Bolma rugosa juvenile

The juvenile shells have some fairly defined spines that, once adults, become simple protuberances, but often some spinosities persist in adult specimens too.

Whelk

Tarantinaea liginaria

Tarantinaea liginaria

Tarantinaea liginaria

Tarantinaea liginaria

Tarantinaea lignaria, snail eggs

Each egg pod (around 1cm dia) has a large number of eggs. Once hatched they escape throguh the hole at the top

Unidentied at present

Unidentied at present

Fusinus syracusanus

Osilinus Turbinatus

Osilinus Turbinatus

Osilinus Turbinatus

Osilinus Turbinatus

Clanculus jussieui

Clanculus jussieui

Tritia incrassata

Cerithium alucastrum

Polyplacophora

Chitons

Chitons are marine molluscs of varying size in the class Polyplacophora, formerly known as Amphineura. About 940 extant and 430 fossil species are recognized. They are also sometimes known as sea cradles or "coat-of-mail shells", or more formally as loricates, polyplacophorans, and occasionally as polyplacophores. Wikipedia

Rhyssoplax olivacea

Rhyssoplax olivacea

Rhyssoplax olivacea

Rhyssoplax olivacea

Rhyssoplax olivacea

Rhyssoplax olivacea

Rhyssoplax olivacea

Rhyssoplax olivacea

Rhyssoplax olivacea

Rhyssoplax olivacea

Rhyssoplax olivacea

Rhyssoplax olivacea

Rhyssoplax olivacea

Rhyssoplax olivacea

Rhyssoplax olivacea

Ischnochiton rissoi

Ischnochiton rissoi

Ischnochiton rissoi

Ischnochiton rissoi

Mottled Red (Tonicella marmorea)

Acanthochitona fascicularis

Lepidopleurus cajetanus

Lepidopleurus cajetanus

Lepidopleurus cajetanus

Lepidopleurus cajetanus

Cephalopods

Cephalopod is a class of molluscs, such as squid, cuttlefish and octopus, these are amongst the most neurologically advanced of all invertebrates. Cephalopoda means "head foot" and this group has the most complex brain of any invertebrate. Cephalopods are characterized by a completely merged head and foot, with a ring of arms and/or tentacles surrounding the head. The arms, tentacles, and funnel are all derivatives of the foot. Cephalopods move by expelling water from a tubular siphon under the head and have a group of muscular usually sucker-bearing arms around the front of the head, highly developed eyes, and usually a sac containing ink. Octopus and Squid use their ink as a defence mechanism to escape from prey. When feeling threatened, they can release large amounts of ink into the water using their siphon. This ink creates a dark cloud that can obscure the predators view so the cephalopod can jet away quickly, the ink is composed of secretions from two glands.