Juvenile of Polydactylus sp.(Family:Polynemidae)

This is a Juvenile of Polydactylus sp. It's a fish of Family Polynemidae. Polynemidae species is rare fish at Scuba Diving.  It inhabits the sandy bottom, sand, mud bottom of the bay. Sometimes entering the brackish water. and It's often observed around the beach. But, probably, they are doing "abortive migration" at Japanese sea. Because, Adult is not a lot in Japan.

Juvenile of Polydactylus  TL:50mm

Juvenile of Polydactylus   TL:50mm

Meristic Characters - D Ⅷ-Ⅰ,13; A Ⅲ, 12; P¹ 13+6; P² Ⅰ, 5; (This picture)

I could not getting the specimen of this species. In Japan so far, Polynemidae is known only 4 species from 2 genera of Eleutheronema and Polydactylus. I did think that it's Polydactylus sexfilis of these four from”Meristic Characters”, but there was a difference in the number of pectoral fine. Since the measurement of the pectoral fin is such from the image, it might not be accurate. It is very similar to the Polydactylus sexfilis, but perhaps It's a possibility other than known distribution and species. In recent years, the Polynemidae are known 8 genera 43 species in the world. Of these, have been known 21 species at the Polydactylus.

Polydactylus sexfilis (Valenciennes, 1831) - (Japanese name: Nanyo-agonashi)
D Ⅷ-Ⅰ,12-13; A Ⅲ, 11-12; P¹ 15-16+6; P² Ⅰ, 5;

Related species; (in Japan)

Eleutheronema tetradactylum (Shaw, 1804)  - (Japanese name: Minami-konoshiro)
D Ⅷ-Ⅰ,13-15; A Ⅲ, 14-16; P¹ 17-19+4; P² Ⅰ, 5;

Polydactylus plebeius (Broussonet, 1782) - (Japanese name: Tubame-konoshiro)
D Ⅷ-Ⅰ,12-13; A Ⅲ, 11-12; P¹ 15-18+5; P² Ⅰ, 5;

Polydactylus sextarius (Bloch & Schneider, 1801) - (Japanese name: Kataguro-konoshiro)
D Ⅷ-Ⅰ,12-13; A Ⅲ, 11-13; P¹ 13-15+6; P² Ⅰ, 5;

Pectoral filaments is very long and It reaches the anal fins.

Pectoral filaments 6

Pectoral soft rays does not branch

REFERENCES:
Motomura, H. 2004. Threadfins of the world. An annotated and illustrated catalogue of polynemid species known to date. Family Polynemidae. FAO Species Catalogue for Fishery Purposes. No. 3. Rome, FAO. 117 p., 151 figs, 6 pls.

Nakabo, T. (ed.), 2013. Fishes of Japan with pictorial keys to the species, third edition. Tokai University Press, Kanagawa, Pp, 2428. (in Japanese).

Fishbase.org
Family Polynemidae - Threadfins
Polydactylus sexfilis,  Sixfinger threadfin  : fisheries, aquaculture, gamefish, aquarium

Larva of Apolemichthys trimaculatus (Cuvier, 1831)

Taken at Kume-island Black Water Dive^® on from 28 to 31th july 2016. The larvae had many appeared at that week, but next week was very less. Depth of appearance of larvae was mainly from 8m to until surface.

Identification of Larvae of Pomacanthidae is very difficult because many species of the Meristic Characters are overlapping. Color of larvae are very similar both across species and genera. Of this time Identification was base on the color of advanced larvae.

Apolemichthys trimaculatus (Cuvier, 1831)

Larval stage, TL: about20mm

Most of the body is silver, dorsal is reddish brown.

Nape is slightly blacken.

Color of caudal peduncle is orange

Advanced larva

advanced larva, TL: about 22mm

Body yellowish, from nape to eye has dark pigment line and white framed eyespot on dorsal fin.

click to enlarge

Larva of Bothus myriaster Temminck & Schlegel, 1846

Taken at Kume-island Black Water Dive^® on 29th july 2016. This larva is not few. If anything, it appears many on the surface thure the year.

Japanese common name; Hoshi-Daruma Garei
English name; Oval Flounder
Scientific name; Bothus myriaster Temminck & Schlegel,1846

Meristic Characters - D 87; A 67; P¹ 9; V 38; (This picture)

• B. myriaster - D 85-97; A 61-73; P¹ 8-10(Eye side); V 37-39.

Larva of Bothus myriaster Temminck & Schlegel 1846　TL:about 50mm

P¹ 9 (Eye side)

Related species; (in Japan)

• Bothus mancus (Broussonet, 1782) - D 96-102; A 74-81; P¹ 11-13(Eye side); V 39-40.
• Bothus pantherinus (Rüppell, 1831) - D 88-100; A 64-72; P¹ 10-11(Eye side); V 37-38.

REFERENCES:
Nakabo, T. (ed.), 2013. Fishes of Japan with pictorial keys to the species, third edition. Tokai University Press, Kanagawa, Pp, 2428. (in Japanese).

Okiyama M. (ed), 2014 An Atlas of Early Stage Fishes in Japan Second Edition Tokai University Press, Japan. :Pp,1912. (in Japanese).

2016 Kumejima DIVE ESTIVANT Black Water Dive® will start soon.

2016　久米島　DIVE ESTIVANTでの Black Water Dive®はまもなく開始されます。
期間　7/28-7/31, 8/4-8/7

昨年の様子はhttp://www.blackwaterdive.net/2015/09/2015-bwd-vol4.html

Larva of Cirripectes quagga (Perciformes, Blennioidei, Blenniidae)

This larva is Cirripectes quagga (Fowler & Ball, 1924) . Japanese common name is "Marcus-Mino-kaeruuo". It has been distributed in South Japan too, but for some reason of ecology photo report seems not yet. It was shooting at Okinawa mainland in late May. This ecology photo might first be at Japan.

TL: about 36mm

Meristic Characters - D Ⅶ, 15; A Ⅱ, 16;  P¹ 15; P² Ⅰ,4; C ⅱ, 9, ⅱ; V 10+21.
(*Nakabo, T. (ed.), 2013)

soft rays of the caudal fin is branch off.

Fluorescent green dye has been distributed in the pectoral fins.

REFERENCES:

Nakabo, T. (ed.), 2013. Fishes of Japan with pictorial keys to the species, third edition. Tokai University Press, Kanagawa, Pp, 2428. (in Japanese).

Okiyama M. (ed), 2014 An Atlas of Early Stage Fishes in Japan Second Edition Tokai University Press, Japan. :Pp,1912. (in Japanese).

Tremoctopus gracilis (Eydoux & Souleyet, 1852) has tentacles of jellyfish to arms.

This time, I could shooting valuable male ecology of Tremoctopus gracilis (Eydoux & Souleyet, 1852) at Palau. That is probably of a third case in the world.

Tremoctopus gracilis is a very unique an octopus of open ocean-swimming with web on the arm. The male is very small compared to the female, So far, It's have been most captured in such investigation by the plankton net.

The first discovery is by David Paul of Melbourne University. It was the world's first ecological photographed at Great Barrier Reef, in Australia. after that, first report is by Dr Norman in 2002.
At that time, it has been reported to have the tentacles of cnidarians such as jellyfish. Then, that this species is holding tentacles at selectively Portuguese Man O' War (Physalia physalis) has also been re-reported at Tree of Life Web Project. So far, how to use of this jellyfish tentacles, it has been considered for the defense or attack.

Tremoctopus gracilis (Eydoux & Souleyet, 1852)　,male, ML:15mm

seems to be tentacles of Physalia physalis on the sucker arm.

Related report

Larva of Blanket Octopus
http://www.blackwaterdive.net/2016/01/larva-of-blanket-octopustremoctopus.html

REFERENCES:

Sweeney, M.J., Roper, C.F.E., Mangold, K.M., Clarke, M.R., and Boletzky, S. v. 1992. 'Larval' and juvenile cephalopods: a manual for their identification. Smithsonian Contributions to Zoology - No. 513. 282pp.

Norman, M.D. 2000. Cephalopods A World Guide. Frankfurt, Germany, IKAN Publishing. 320 pp.

Jereb,P., Roper,C.F.E.,Norman,M.D.,Julian,K.F., 2014. Cephalopods of the World. An annotated and illustrated catalogue of Cephalopod species known to date Volume 3 Octopods and Vampire Squids. FAO Species Catalogue for Fishery Purposes No.4, Vol.3. 382pp.

Tremoctopus - Tree of Life Web Project

Paralarva of Thysanoteuthis rhombus Troschel, 1857

This is paralarva of Thysanoteuthis rhombus Troschel, 1857. It was taken in the Ogasawara Islands.

It has transparency body and do the very unique pose that along the arm on top of the mantle.

According to (Okutani, 2015) and (Sweeney et al, 1992) are this squid distributed in the until vicinity of the south and North latitude 40 degrees of the whole world.

The adult is in the middle range of 450-650m.
Mantle length of the adult is about generally 300-850mm.

Side view is paralarva of Thysanoteuthis rhombus Troschel, 1857  (ML;about 7mm)

Front view is paralarva of Thysanoteuthis rhombus Troschel, 1857  (ML;about 7mm)

REFERENCES:

Voss NA, Stephen SJ, Dong Zh (1992). Family Cranchiidae, Prosch, 1849. In: Sweeney MJ, Roper CFE, Mangold KM, Clarke MR, von Boletzky S (ed) Larval and juvenile cephalopods: A manual for their identification. Smithson Contrib Zool 513, pp 187-210.

Okutani, T (2015). New editing World squids picture book Web Edition - National squid processing industry cooperatives(In Japanese)　pp 194.

Tree of Life Web Project - Thysanoteuthis rhombus


* Previously introduced as larva of Octopoteuthis sicula, it turned out to be Thysanoteuthis rhombus so I will correct it and resend it. (2016/11/16)