Octopus incella, Kaneko, Natsumi & Kubodera, Tsunemi, 2007

Kaneko, Natsumi & Kubodera, Tsunemi, 2007, A new intertidal octopus species, Octopus incella (Cephalopoda: Octopodidae), from Okinawa, southern Japan, Zootaxa 1440 (1), pp. 39-49 : 40-47

Octopus incella n. sp.

Figures 1–4 , Tables 1–2

Material examined. Holotype: NSMT –Mo. 75543, male 29.7 mm ML, 7 November 2003; Hamamoto (26°40' N, 127°53' E), 0.1 m depth, Okinawa I.: collected by N. Kaneko.

Paratype #1: NSMT –Mo. 75544, female, 28.2 mm ML, 7 November 2003; Hamamoto (26°40' N, 127°53' E), 0.1 m depth, Okinawa I.: collected by N. Kaneko

Paratype #2: NSMT–Mo. 75545, male, 31 mm ML, 11 January 2004; Hamamoto (26°40' N, 127°53' E), 0.1 m, Okinawa I.: collected by N. Kaneko

Paratype #3: NSMT–Mo. 75546, female, 30.2 mm ML, 11 January 2004; Hamamoto (26°40' N, 127°53' E), 0.1 m, Okinawa I.: collected by N. Kaneko

Diagnosis. Body small (28.2–31.0 mm ML) with arms of medium length (3.4–4.6 ML). Arms generally nearly equal in length, with arm formula of 2>/=3>/=4> 1. Webs between arms shallow in depth (WDI: 7.8– 19.0%) with web formula C = D = B = A> E. Both males and females with large suckers on all arms at 8th to 10th level from base (ASIn: 17.0% on 29.7 mm ML male, 18.5% on 28.2 mm ML female) without any abruptly enlarged suckers. Third right arm of male hectocotylized with 89 suckers and shorter than opposite arm (OAI: 85.7%). Ligula small, and calamus medium in size (LLI: 2.8%; CaLI: 33.3%); 5–6 gill lamellae per demibranch. Funnel organ W shaped. Terminal organ with diverticulum V shaped (TOLI: 14.2, 15.2%). Spermatophores short (SpLI: 23.7, 37.4%). No white spots on dorsal mantle, or any obvious marks on surface of whole body. Skin rough and small papillae scattered on dorsal surface. Primary papillae absent on dorsal surface of mantle and above eyes. Live animals pinkish white, dark brown to gray after fixation.

Description. Measurements and indices of holotype and paratypes are summarized in Tables 1 and 2 . All were fully matured, except for one female (paratype #1) which was considered to be submature because it had small, underdeveloped eggs in the ovary.

Dorsal view of the holotype shown in Fig. 1 A.

Small sized species (TL: 158–181 mm; TW: 19.4–33.9 g; ML: 28.2–31.0 mm) with round-shaped mantle (MWI: 58.7–77.0%). Head slightly narrower than mantle (HWI: 52.6–67.7%) with pronounced large eyes. Funnel moderate in length (FLI: 43.0–52.5%; FFuI: 29.5–38.3%). Funnel organ W shaped ( Fig. 1 B) and lateral limbs shorter than medial limbs (length of lateral limb: 3.3–3.8 mm; length of medial limb: 6.4–9.4 mm).

Arms moderate to long (3.4–4.6 ML) and generally equal in length. Arm formula 2>/=3>/=4>1; variable, dorsal arms usually slightly shorter than others. Arm width moderate (AWI: 12.3–16.2%). No arm autotomy observed.

Webs thick and moderately shallow (WDI: 7.8–19.0%) with web formula C = D = B = A> E. Webs generally equal in depth, but usually sector E shallowest.

Third right arm in males hectocotylized ( Fig. 1 C), shorter than the opposite arm (OAI: 85.7%). Hectocotylized arm with 89 suckers. Ligula small, narrow, and conical in shape. Ligula length 3.0 mm (LLI: 2.8%) and calamus length 1.0 mm (CaLI: 33.3%) in holotype. Hectocotylized arm of paratype #2 damaged, but with tiny ligula and calamus regenerating.

Arms with two rows of suckers ( Fig. 1 D). Sucker count on normal arms between 93 and 133. Largest suckers at 8th to 10th level from base (ASIe: 17.0% in 29.7 mm ML male, 18.5% in 28.2 mm ML female). Large suckers occur on almost all arms of both sexes, without any abruptly enlarged suckers.

Gills short (GLI: 21.5–31.1%), with 5–6 lamellae per demibranch.

Digestive organs shown in Fig. 2 A. Anterior salivary glands large, about half diameter of buccal mass. Posterior salivary glands well developed and huge, roughly twice the buccal mass. Oesophagus thin and straight. Crop diverticulum present, slightly thicker than oesophagus, straight in shape. Caecum coiled in approximately one loose whorl. Stomach bipartite. Caecum and stomach relatively small, about one-third of posterior salivary gland. Intestine long and thin, anal flaps present but tiny. Digestive gland ovoid in shape. Ink sac well developed and embedded in ventral surface of digestive gland. Ink released by live animals dark brown in color.

Upper beak ( Fig. 2 B) with sharply hooked rostrum and rounded jaw-edge. Hood broad, about one-third of upper beak. Crest slightly rounded and lateral wall broad. Lower beak ( Fig. 2 C) with short, pointed rostrum and rounded jaw-edge. Hood and wings narrow and crest slightly rounded. Lateral walls narrow, concave at posterior margin.

Radula with seven transverse rows of teeth and two marginal plates ( Fig. 2 D). Rachidian tooth with 1–2 lateral cusps on each side (typically 2). First lateral teeth very small with a low cusp. Second lateral teeth taller than first, triangular with cusp. Marginal teeth long, curved, and cuspidate, and taller than the second lateral teeth. Marginal plates small, flat, and smooth.

Male reproductive tract illustrated in Fig. 3 A. Terminal organ with diverticulum V shaped and short (TOLI: 14.2, 15.2%). Vas deferens duct thick and roughly coiled. Spermatophoric gland short and thick, accessory gland thick and robust. Appendix present, and spermatophore storage sac relatively large, more than twice length of terminal organ.

Spermatophores ( Fig. 3 B) narrow, and short to medium in length (SpLI: 23.7, 37.4%; SpWI: 0.8, 1.0%). Paratype #2 with 148 spermatophores in storage sac. Ejaculatory apparatus 21–23 coils, spermatophore reservoirs about half length of total spermatophore (SpRI: 45.6, 48.9%). Cap thread long.

Female reproductive organ illustrated in Fig. 3 C. Ovary ovoid with proximal oviducts short, and distal oviduct about three times longer than proximal. Oviducal glands round and pale in color, without radiating chambers. Spawned eggs ( Fig. 3 D) numerous (>1000 estimate) and small (EgL: 4.7 mm; EgW: 1.6 mm, EgLI: 15.5%, EgWI: 5.4%); attached to wall of occupied hole.

C Body color of live animals usually pinkish white; alarmed body pattern not observed. Color of preserved specimen dark brown to gray. No white spots on dorsal mantle, and no obvious marks on surface of whole body. Dorsal surface rough, but not highly sculptured. Small warts scattered on dorsal surface. No primary papillae on dorsal mantle or above eyes.

Etymology. In Latin, the species name in - and - cella means in a room, because this octopus has a small hole as its own room.

Life history. Octopus incella usually hide in small holes in boulders or dead corals, the diameter of which is less than 5 cm, and one individual occupies one hole. The occupied boulders and dead corals are scattered along the high tide line and are completely dried-up at low tide. Thus, this octopus is considered to have a high tolerance for dry conditions. The females lay eggs attached to the wall of the hole and take care of them.

The sightings of this animal have been limited, and details of its life history, foraging, and reproduction are not known.

Distribution. Octopus incella is known only from Okinawa Island at present ( Fig. 4 ). This octopus produces small eggs, and hatchlings are planktonic (Kaneko, pers. obs.). This indicates that the species potentially has a wide dispersion during its early life stages ( Boletzky, 1977). However, their specific habitat may restrict their distributional area.

Remark. Octopus incella is considered to be closely related to Octopus oliveri ( Berry 1914) in that both species possess the following characteristics: surface of skin with warts, without primary papillae or white dorsal spots; presence of large suckers in both sexes (ASIn: 14–22% in male, 10–18% in female O. oliveri ) but without abruptly enlarged suckers; V shaped terminal organ and diverticulum ( Sasaki 1929; O’Shea 1999). Octopus oliveri was described from Kermadec Islands in New Zealand by Berry (1914), with additional records from Ogasawara Islands in Japan ( Sasaki 1929) and Hawaii Islands (Bird, pers. com.). These two species are distinguished by the following characteristics: maturity size (69.0 mm ML in O. oliveri versus 31.0 mm ML in O. incella ) and number of gill lamellae (7–8 in O. oliveri versus 5–6 in O. incella ), but they have a similar habitats—living in holes or interstices of rocks and corals in shallow, intertidal zones.

Occurrences of these two species seem to be restricted to isolated oceanic islands in the tropical rim of the Pacific ( Figure 4 ). In particular, O. oliveri has a tendency to inhabit volcanic islands.

Figures

FIGURE 1. Octopus incella sp. nov. (Holotype, 29.7 mm ML male, NSMT – Mo. 75543). A. Dorsal view (scale bar: 15 mm), B. Funnel organ (scale bar: 2.5 mm), C. Hectocotylized arm tip (scale bar: 1.5 mm), D. Picture of oral view with pattern of arm suckers. Abbreviations: C—calamus; L—ligula.

FIGURE 2. Octopus incella n. sp. (Paratype # 2, 31 mm ML male, NSMT – Mo. 75545). A. Digestive organ (scale bar: 5 mm), B. Upper beak, C. Lower beak (scale bar: 2.5 mm), D. Radula (scale bar: 0.1 mm). Abbreviations: AF—anal flaps; ASG—anterior salivary gland; BM—buccal mass; C—caecum; CD—crop diverticulum; CR—crop; DG—digestive gland; I—intestine; IS—ink sac; L 1 — first lateral tooth; L 2 — second lateral tooth; M—marginal tooth; MP—marginal plate; O—oesophagus; PSG—posterior salivary gland; R—rachidian tooth; S—stomach.

FIGURE 3. Octopus incella n. sp. (A – B: Paratype # 2, 31 mm ML male, NSMT – Mo. 75545; C: Paratype # 1, 28.2 mm ML female, NSMT – Mo. 75544; D: Paratype, 30.2 mm ML female, NSMT – Mo. 75546). A. Male reproductive tract (scale bar: 5 mm), B. Spermatophore (scale bar: 2.5 mm), C. Female reproductive tract (scale bar: 2.5 mm), D. Laid eggs (scale bar: 2.0 mm). Abbreviations: AG—accessory gland; AP—appendix; CT—cap thread; D—diverticulum; DO—distal oviduct; EA—ejaculatory apparatus; O—ovary; OG—oviducal gland; SG—spermatophoric gland; SR—sperm reservoir; SS—spermatophore storage sac; T—testis; TO—terminal organ; VD—vas deferens.

FIGURE 4. Distribution of Octopus incella and O. oliveri. Symbols: open circle— O. incella, dark circle— O. oliveri.

Tables

TABLE 1. Measurements and counts of Octopus incella n. sp. A – E: web sectors from dorsal to ventral in order; Dmdamaged; L—left; NC—not counted; R—right; Sp—spermatophore; (n) number of spermatophores or eggs for calculating means

Status	Holotype	Paratype #2	Paratype #1	Paratype #3
NSMT-	Mo. 75543	Mo.75545	Mo.75544	Mo.75546
Sex	Male	Male	Female	Female
TL	171	172	181	158
TW (g)	33.9	19.4	29.5	23.5
MLd	29.7	31	28.2	30.2
MLv	20	20.2	19.3	18.8
MW	21.8	18.2	21.7	20.8
HW	17.9	16.3	19.1	18.1
FL	14.5	14.7	14.8	13
FFuL	9.9	10.8	10.8	8.9
WD-A	24	17.5	21	19
WD-B L/R	24/24	18.5/10.5	23/23	19/17
WD-C L/R	24/23	16.4/14.6	20/23	19/20
WD-D L/R	24/18	14.4/15	23/19	19/20
WD-E	18	12	17	15
WF	A=B=C=D>E	B>A>C>D>E	B=D>C>A>E	C=D>B=A>E
AL-1 L/R	117/112	Dm/127	126/121	91/Dm
AL-2 L/R	126/112	132/134	135/Dm	97/97
AL-3 L/R	126/108	133/Dm	130/131	108/Dm
AL-4 L/R	117/117	Dm/134	127/134	113/103
AF	2=3>1=4	2=4>3>1	2>4>3>1	4>3>2>1
AW	4.8	3.8	4.4	4
SC-1 L/R	104/93	Dm/113	119/115	112/D
SC-2 L/R	105/115	120/116	128/Dm	116/108
SC-3 L/R	122/89	131/Dm	133/128	125/Dm
SC-4 L/R	110/116	Dm/119	121/129	117/123
SDn	4.4	3.2	3.9	3.5
SDe	5.5	4.5	4.8	4.4
GC	5	6	5	5-6
GL	6.4	8.8	6.6	9.4
LL	3.0	Dm	-	-
CaL	1.0	Dm	-	-
TOL	4.5	4.4	-	-
Sp Count	NC	148
Sp whorls	21 (4)	23 (10)	-	-
SpL	7.05 (4)	11.6 (10)	-	-
SpW	0.1 (4)	0.1 (10)	-	-
SpRL	3.45 (4)	5.3 (10)	-	-
EgL	-	-	small	4.7 (10)
EgW	-	-	small	1.6 (10)

TABLE 2. Indices of Octopus incella n. sp. A – E: web sectors from dorsal to ventral in order; Dm—damaged; L—left; R—right

Status	Holotype	Paratype #2	Paratype #1	Paratype #3
NSMT-	Mo. 75543	Mo. 75545	Mo.75544	Mo.75546
Sex	Male	Male	Female	Female
MWI	77.0	68.9	73.4	58.7
HWI	67.7	59.9	60.3	52.6
MAI	20.9	26.7	23.6	23.1
AWI	15.6	13.2	16.2	12.3
ALI 1 R/L	429.1/446.8	Dm/301.3	377.1/393.9	409.7/Dm
ALI 2 R/L	Dm/478.7	321.2/321.2	377.1/424.2	432.3/425.8
ALI 3 R/L	464.5/461	Dm/357.6	363.6/424.2	Dm/429
ALI 4 R/L	475.2/450.3	341.1/374.2	393.9/393.9	432.3/Dm
WDI A	15.6	16.8	19.0	13.1
WDI B R/L	17.0/ 17.0	15/ 16.8	19/ 19	7.8/ 13.7
WDI C R/L	17/ 14.8	17.7/ 16.8	18.3/ 19	10.9/ 12.2
WDI D R/L	14.1/ 17	17.7/ 17.7	14.3/ 19	11.2/ 10.7
WDI E	12.6	13.3	14.3	9.0
ASIn	13.8	11.6	14.8	10.3
ASIe	17.0	14.6	18.5	14.5
FLI	52.5	43.0	48.8	47.4
FFuI	38.3	29.5	33.3	34.8
HcAI	363.6	Dm	-	-
OAI	85.7	Dm	-	-
GLI	21.5	28.4	23.4	31.1
LLI	2.80	Dm	-	-
CaLI	33.30	Dm	-	-
TOLI	15.2	14.2	-	-
SpLI	23.7	37.4	-	-
SpWI	1	0.8	-	-
SpRI	48.9	45.6	-	-
EgLI	-	-	-	15.5
EgWI	-	-	-	5.4