Callistoctopus xiaohongxu, Zheng & Xu & Li, 2022

Zheng, Xiaodong, Xu, Chenxi & Li, Jiahua, 2022, Morphological description and mitochondrial DNA-based phylogenetic placement of a new species of Callistoctopus Taki, 1964 (Cephalopoda, Octopodidae) from the southeast waters of China, ZooKeys 1121, pp. 1-15 : 1

Callistoctopus xiaohongxu sp. nov.

Figs 1 , 2 , 3 , 4

Type material.

Holotype: OUC-201808200301, mature ♂, 45.5 mm ML, Dongshan Seafood Market Pier, Zhangzhou, Fujian, China, 20 August 2018, coll. Paratypes: OUC-201812050301, mature ♂, 49.5 mm ML, Dongshan Seafood Market Pier, Zhangzhou, Fujian, China, 5 December 2018, coll. OUC-201812050302, mature ♂, 53.2 mm ML, Dongshan Seafood Market Pier, Zhangzhou, Fujian, China, 5 December 2018, coll. OUC-201812050303, mature ♂, 56.3 mm ML, Dongshan Seafood Market Pier, Zhangzhou, Fujian, China, 5 December 2018, coll. OUC-201806080302, immature ♀, 50.7 mm ML, Dongshan Seafood Market Pier, Zhangzhou, Fujian, China, 8 June 2018, coll. OUC-201812050305, mature ♀, 51.7 mm ML, Dongshan Seafood Market Pier, Zhangzhou, Fujian, China, 5 December 2018, coll. OUC-201812050306, mature ♀, 83.3 mm ML, Dongshan Seafood Market Pier, Zhangzhou, Fujian, China, 5 December 2018, coll.

Other material.

OUC-201812050304, mature ♂, 63.2 mm ML, Dongshan Seafood Market Pier, Zhangzhou, Fujian, China, 5 December 2018, coll. OUC-201806080301, immature ♀, 41.7 mm ML, Dongshan Seafood Market Pier , Zhangzhou, Fujian, China, 8 June, 2018, coll .

Diagnosis.

Small to moderate size (ML 41.7-83.3 mm). Colour of skin reddish-orange to reddish-brown, no papillae or patch. One or two lines of black chromatophores on the lateral margins of arms under the skin (Fig. 2A ). Head narrow (HWI 23.0-39.1). Arms of moderate length (ALI 154.9-336.3), thin (AWI 8.7-18.0). Web deep (WDI 15.7-22.9). Suckers small (SDI 5.0-6.9) and biserial. Enlarged suckers absent. Funnel organ \ /\ /-shaped, long (FLI 51.0-68.5). Gills with 8-9 lamellae per demibranch. Ligula moderate size (LLI 7.0-11.6) with groove.

Description.

Measurements and indices of nine specimens are presented in Table 2 . Small to moderate-size species (ML 41.7-83.3 mm), total length (TL) 195.7-382.1 mm, body weight up to 39.2 g. Skin smooth, one or two lines of black chromatophores on the lateral margins of arms under the skin (Fig. 2A ). Mantle slightly ovoid to elongate, muscular. Head width narrower than mantle width (HWI 23.0-39.1). Stylets absent. Funnel long (FLI 51.0-68.5), free funnel length around 24-46% funnel length (FFLI 23.9-46.0), funnel organ \∧/-shaped (Fig. 2B ). Outer limbs slightly shorter than medial limbs. Arms moderate length (ALI 154.9-336.3), slender (AWI 8.7-18.0), dorsal arms always longest (arm formula of most specimens belongs to 1> 2> 4> 3). Suckers in two rows (Fig. 2C ), small (SDI 5.0-6.9). In larger animals, 157-198 suckers on each normal arm, and the first or second arm has the most suckers. Enlarged suckers absent. Webs deep (WDI 15.7-22.9), typical web formula A> B> C> D> E. The third right arm of mature males hectocotylized, length approximately 60-80% of the opposite arm (Fig. 2D ). Ligula of moderate size, robust and cylindrical with deep groove. LLI ranges from 7.0-11.6 of arm length. Calamus of moderate size, around 25-30% of ligula length (CaLI 26.3-31.6). Hectocotylized arm with 70-83 suckers. Gills with 8-9 lamellae per demibranch.

Digestive tract (Fig. 3A ). Anterior salivary glands small, approximately one-third length of buccal mass. Posterior salivary glands triangular and smaller than buccal mass. Oesophagus long. Spiral caecum with one whorl. Intestine long. Digestive gland well developed, brown. Ink sac present, embedded in the digestive gland and attached to the intestine posteriorly. Ink sac opening into the anus. Anal flaps small.

Upper beak (Fig. 3B ) with short rostrum, narrow hood, and slightly curved crest. Ratios of upper beak measurements 0.28-0.32 for UHL/UCL, 0.12-0.18 for URW/UCL, and 0.23-0.38 for URL/UHL. Lower beak (Fig. 3C, D ) with a blunt rostrum, narrow hood, moderately broad wings and flared lateral walls separated in posterior, posterior notch deep. Radula (Fig. 3E, F ) with 7 teeth and 2 marginal plates per transverse row. Ratios of lower beak measurements 0.34-0.45 for LHL/LCL and 0.26-0.41 for LRW/LCL. Rhachidian tooth with 1-2 lateral cusps on each side; first lateral teeth small, sharp; second lateral teeth broad-based triangular, larger than first, sharp; marginal teeth long, curved, sharply pointed, longer than second lateral teeth; marginal plates flat.

Male reproductive tract (Fig. 4A ). In mature males, the terminal organ inverse 6-shaped. Spermatophore storage sac long. Accessory gland curved, longer than spermatophore storage sac. Spermatophore gland long. Vas deferens very short, narrow. Testis roundish, small. Spermatophores (Fig. 4B ) of moderate size, average length 60 mm, approximately 75% ML, narrow (average 1.5 mm in width); approximately 4-8 spermatophores in storage sac.

Female reproductive tract (Fig. 4C-E ). Ovary large, round in mature females. Two distal oviducts long. Two oviducal glands wider than distal oviducts. Mature females with approximately 65 large eggs (average 14.3 mm in length).

Integument (Fig. 5A ). Colour of live animal reddish-orange. Animal turning white when stressed or post mortem. In live animals, a linear structure appears on the tissue connecting two adjacent arms, forming a net-like structure (Fig. 5B ). Arm chromatophores under the skin distinct.

Etymology.

The name ' Callistoctopus xiaohongxu ', which refers to its small body size and reddish body colour, is the phonetic translation of the local Chinese name of this species in Zhangzhou, where specimens were collected.

Distribution.

According to fishermen in Zhangzhou, this species is distributed in the East China Sea and the South China Sea, mainly in Quanzhou, Fujian Province to Shanwei, Guangdong Province.

Molecular analyses.

Phylogenetic analyses were performed based on the fragments of the COI gene using Maximum likelihood (ML) and Bayesian inference (BI) methods. Fragments 593 bp in length were obtained from the mitochondrial COI gene of nine specimens. Both ML and BI trees showed a similar topology (Fig. 6 ) with a highly supported monophyletic clade (bootstrap value [BS] = 94%, posterior probability [PP] = 100%) containing all nine specimens identified as Callistoctopus xiaohongxu sp. nov. C. xiaohongxu sp. nov. belonged to the clade of ' O '. Octopus minor and other four species of Callistoctopus with [BS] = 82% and [PP] = 89%, respectively. Moreover, the COI gene analyses suggested that species of the genus Octopus used in this study were not clustered into one clade. Additionally, the genetic distance of C. xiaohongxu sp. nov. and the other 16 Octopodidae species ranged from 11.13 to 21.09% (Table 3 ).

Figures

Figure 1. Callistoctopus xiaohongxu sp. nov., holotype, male, 45.5 mm ML (OUC- 201808200301) A photograph of dorsal view B photograph of ventral view. Scale bars: 10 mm (A, B).

Figure 2. Callistoctopus xiaohongxu sp. nov. A proximal portion of arms 1 - 3 (left side), male, 49.5 mm ML (OUC- 201812050301) B funnel organ, male, 53.2 mm ML (OUC- 201812050302) C oral view of basal portion of arms, male, 63.2 mm ML (OUC- 201812050304) D distal portion of hectocotylus, male, 63.2 mm ML (OUC- 201812050304). Abbreviations: c, calamus; l, ligula. Scale bars: 10 mm (B, C, D).

Figure 3. Callistoctopus xiaohongxu sp. nov. A digestive system, female, 83.3 mm ML (OUC- 201812050306) B upper beak, lateral view, female, 50.7 mm ML (OUC- 201806080302) C lower beak, lateral view, female, 50.7 mm ML (OUC- 201806080302) D lower beak, ventral view, female, 50.7 mm ML (OUC- 201806080302) E, F scanning electron micrograph of radulae, male, 53.2 mm ML (OUC- 201812050302). Abbreviations: a, anus; asg, anterior salivary gland; bm, buccal mass; c, crest; ca, caecum; cr, crop; dg, digestive gland; h, hood; i, intestine; is, ink sac; lw, lateral wing; o, oesophagus; psg, posterior salivary gland; r, rostrum; st, stomach; w, wing. Scale bars: 10 mm (A-D); 200 μm (E, F).

Figure 4. Callistoctopus xiaohongxu sp. nov A reproductive system of male, 56.3 mm ML (OUC- 201812050303) B spermatophore, male, 56.3 mm ML (OUC- 201812050303) mm C reproductive system of female, 51.7 mm ML (OUC- 201812050305) D egg cluster, female, 51.7 mm ML (OUC- 201812050305) E single egg female, 51.7 mm ML (OUC- 201812050305). Abbreviations: ag, accessory gland; cb, cement body; do, distal oviduct; ea, ejaculatory apparatus; o, ovary; og, oviducal gland; sg, spermatophore gland; sr, sperm reservoir; ss, spermatophore storage sac; t, testis; tf, terminal filament; to, terminal organ; vd, vas deferens. Scale bars: 10 mm.

Figure 5. Callistoctopus xiaohongxu sp. nov. A live specimen B net-like structure on web.

Figure 6. Phylogenetic trees derived from Maximum likelihood (ML) and Bayesian inference (BI) methods based on the COI gene. Numbers at each node are bootstrap (left) for ML and posterior probability (right) for BI analyses, respectively.