Dextrasepiola taenia Lu & Okutani 2022, n.gen., n.sp.
Creators: name: Lu, Chung Cheng
name: Okutani, Takashi
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Cephalopoda
Sepiida
Sepiolidae
Dextrasepiola
Dextrasepiola taenia

description: Dextrasepiola taenia n.gen., n.sp.
Figures 1–5, 13; Table 2
Material examined: Holotype: MOV F80458: Redland Bay, Queensland, 27° 36' S, 153° 19' E, 1.2 m, CSIRO Moreton Bay Survey, J 43, Location 31, 10 Aug 1951, 1 male, mature, 8.2 mm mantle length (specimen #1).
Paratype 1: MOV F91359: Redland Bay, Queensland, 27° 36' S, 153° 19' E, 1.2 m, CSIRO Moreton Bay Survey, J 43, Location 31, 10 Aug 1951, 1 female, mature, 7.8 mm mantle length (specimen #2).
Paratype 2: MOV F74469: Peel Island, Queensland, 27° 30' S, 153° 21' E, 1.2 m, CSIRO Moreton Bay Survey, J 26, Location 41, 10 Aug 1951, 1 male, mature, 6.5 mm mantle length (specimen #3).
Paratype 3: MOV F91361: Peel Island, Queensland, 27° 30' S, 153° 21' E, 1.2 m, CSIRO Moreton Bay Survey, J 26, Location 41, 10 Aug 1951, 1 female, mature, 8.7 mm mantle length (specimen #4).
Other material: MOV F91360: Peel Island, Queensland, 27° 30' S, 153° 21' E, 1.2 m, CSIRO Moreton Bay Survey, J 26, Location 41, 10 Aug 1951, 2 specimens, poor condition, 1 female, juvenile, 5.4 mm mantle length, 1 specimen, sex indeterminate, 3.9 mm mantle length.
Diagnosis: Small sepioline with right arm I of mature male hectocotylised, copulatory apparatus in the form of a long tape-like process, no hook-like structure on the arm. Females with bursa copulatrix on right side of mantle cavity.
Description: Mantle (figs 1a–c) short dome-shaped, slightly longer than wide, fused with head dorsally for about 25% of width. Anterior ventral mantle margin shallowly concave with lateral projections at position of mantle-funnel connectives. Head wide, slightly narrower than mantle. Nuchal commissure narrow, not reaching beyond level of medial border of eyeball, approximately 25–40% of mantle width at level of nuchal commissure. Eyes large, elliptical, located dorso-laterally on head. Cornea membrane protecting eye attached to skin of head along dorsal margin. Olfactory papilla located behind posterior corner of eye orbit, ventral photosensitive vesicle not found. Funnel long and slender, reaching the level beyond anterior eye margin, free from head for 60–80% of funnel length. Funnel connects to head by an oblique muscle band extending from beneath anterior end of funnel locking cartilage to ventral side of head.
Funnel locking cartilage (fig. 1f) elongated oval with simple, slightly curved depression in the middle, mantle locking cartilage long, low ridge. Dorsal element of funnel organ (fig. 1g) Y-shaped pad with a small papilla at the apex. Behind each ramus is swelling that connects dorsal funnel organ with base of funnel retractor. Ventral elements of funnel organ (fig. 1g) a pronounced semi-spherical pad, becoming slightly narrower anteriorly, with a mamillar projection slightly posteriorly to centre. Funnel valve well developed on dorsal roof, tongue shaped, located well behind funnel aperture.
Fins (figs 1a–c) circular in outline, anterior border of fins projects forward prominently forming a deep cleft with mantle, anterior fin lobe reaching level halfway between fin insertion and mantle border or to mantle margin, posterior borders of fins convex, less pronounced. Length of fin base about 33% of mantle length.
Arms (figs 1a–c, 2a–c, 3) short, rounded aborally, flatten orally. All arms on both sexes with biserial suckers throughout. Because most suckers are lost, it was impossible to determine the sucker ring dentition and if the enlargement of suckers exists. In males, arm III is the longest and thickest, followed by arm II or arm IV. Right arm I of male (figs 1d–e, 3) with a flat, fleshy, tape-like long process, appeared to be modified sucker stalks of proximal third sucker of dorsal series and proximal fourth sucker of ventral series fused together throughout their length. Length of the process reaches to almost the level of arm tip, thickened along proximal portion ending in a blunt tip. No sucker on the tape-like process of holotype, but a remnant of a tiny sucker on the process of paratype 2 (fig. 3). Distal to the tape-like process, 19 suckers in two series to arm tip on holotype (23 suckers in paratype 2); no hook-like structures on the arm. Left arm I in males and both arms I in females with 28–30 suckers in two series, with no peculiar or unusual development or modification. Arm II with 27–35 suckers in both sexes with no noticeable special development in either sex. In males, arms III thickened proximally, slightly tapers distally to about half of arm length then abruptly tapers distally; swollen proximal part with no suckers except several remnants of suckers; distal part strongly curled towards mouth, with 17–19 suckers. In females, arm III similar to arm II with 21 suckers. Arm IV of both sexes with 26–31 suckers. In males, aboral keel and swimming membrane absent on arms I–III, well developed along whole length of arms IV. In females, aboral keel and swimming membrane present on distal half of arms I and II, and almost whole length of arms III and IV. Webs shallow between all arms except between arms III and IV (web D), which half encloses base of tentacles in both sexes, web E non-existent.
Tentacles weak, longer than arms. Club (fig. 4a) slightly expanded, minute carpal suckers in 4 series, minute manal suckers in 6 series, those on dorsal 2 series larger than the remaining suckers, numerous minute suckers in 8 series on dactylus. Sucker ring dentition of largest club sucker finely toothed around entire minute circle.
Gills with 15–20 lamellae per demibranch, plus a terminal lamella. A pair of dumbbell-shaped, yellowish photophores, opaque with both ends swollen on both sides of ink sac (figs 1g, 4b).
Upper beak (fig. 4d) rostrum slightly curved; jaw angle obtuse; wing long, shoulder (cutting edge) serrated; rostrum dark brown to black, hood, shoulder and dorsal part of lateral wall light brown, posterior part of hood, most of lateral wall unpigmented, transparent.
Note: Maturity 4, subadult – sexual characters well distinguished but gonads and accessory organs not completely developed; Maturity 5, adult – sexually mature with spermatophores in Needham’s sac in males; ovaries, nidamental and oviducal glands fully developed and ripe, eggs sometimes in oviducts, in females; DML, dorsal mantle length (mm) – measured from anterior-most point of mantle to posterior end of mantle; VMLI, ventral mantle length index – ventral mantle length, measured from anterior border of mantle at ventral midline, to apex of mantle, expressed as a percentage of DML; HLI, head length index – dorsal length of head measured from point of fusion of dorsal arms to anterior tip of dorsal mantle expressed as a percentage of DML; HWI, head width index – greatest width of head at level of eyes expressed as a percentage of DML; NCI, nuchal commissure width index – width of nuchal commissure expressed as a percentage of width of mantle at the position of nuchal commissure; MWI, mantle width index – mantle width at mantle opening expressed as a percentage of DML; FuLI, funnel length index – length of funnel from anterior funnel opening to posterior border of funnel measured along ventral midline expressed as a percentage of DML; FuWI, funnel width index – width of funnel at junction of funnel and head just anterior to funnel locking cartilages expressed as a percentage of DML; FFuI, free funnel index – length of funnel from the anterior opening to the point of dorsal attachment to head expressed as a percentage of funnel length; FLI, fin length index – greatest length of a single fin expressed as a percentage of DML; FBLI, fin base length index – length of fin attachment to mantle expressed as a percentage of DML; FWI, fin width index – greatest width of a single fin expressed as a percentage of DML; A 1 LI, arm I length index – length of arm I expressed as a percentage of DML; A 2 LI, arm II length index – length of arm II expressed as a percentage of DML; A LI, arm III length index – length of arm III expressed as a percentage of DML; A LI, arm IV length index – length of arm IV 3 4 expressed as a percentage of DML; A LI, right arm I length index – length of right arm I expressed as a percentage of DML (only in males); TtLI, tentacle length index R1 – total length of tentacular stalk and club expressed as a percentage of DML; ClLI, club length index – length of club, measured from proximal-most basal sucker to distal tip of club expressed as a percentage of DML; CIRC, club row count – number of longitudinal rows of suckers across width of club; GLI, gill length index – length of gill expressed as a percentage of DML; GWI, gill width index – greatest width of gill expressed as a percentage of DML; GiLC, gill lamellae count – number of lamellae on outer demibranch, excluding terminal lamella;A SC, sucker counts of arm I – total number of suckers or sucker stalks on arm I; A SC, sucker counts of 1 2 arm II – total number of suckers or sucker stalks on arm II; A SC, sucker counts of arm III – total number of suckers or sucker stalks on arm III; A SC, sucker counts of 3 4 arm IV – total number of suckers or sucker stalks on arm IV; A R1 SC, sucker counts of right arm I – total number of suckers or sucker stalks on right arm I (only in males); ClSI, club sucker index – diameter of largest club sucker expressed as a percentage of DML; A 1 SI, arm I sucker index – diameter of largest sucker on arm I expressed as a percentage of DML; A SI, arm II sucker index – diameter of largest sucker on arm II expressed as a percentage of DML; A SI, arm III sucker index – 2 3 diameter of largest sucker on arm III expressed as a percentage of DML; A 4 SI, arm IV sucker index – diameter of largest sucker on arm IV expressed as a percentage of DML; SpLI, spermatophore length index – length of spermatophore expressed as a percentage of DML; SpWI, spermatophore width index – greatest width of spermatophore expressed as a percentage of spermatophore length; SpRI, sperm reservoir index – length of sperm reservoir expressed as a percentage of spermatophore length; CBI, cement body index – length of cement body expressed as a percentage of spermatophore length; NidGI, nidamental gland index – length of nidamental gland expressed as a percentage of DML.
Lower beak (figs 4e, f) wide; rostrum with blunt tip; jaw edge rough, slightly serrated, jaw angle indistinct; blunt tooth on shoulder; no notch in hood; lateral wall without fold or ridge, roughly elongate rhomboidal with lower edge slightly concave, corner faintly produced; rostrum and hood light brown, posterior part of lateral wall and wings transparent. Radula (fig. 4c) seven series, each row with seven unicuspid teeth.
Gladius absent.
Spermatophores (figs 5a, b) small, five spermatophores from the holotype approximately 2–2.5 mm long (spermatophore length index 24–30), greatest width approximately 0.08–0.1 mm (spermatophore width index 3.4–4.8), sperm reservoir about 0.4–0.5mm (sperm reservoir index 19–22), structure complex, with spiral appearance in ejaculatory apparatus and the sperm mass, cement body 0.72–0.78 mm long (cement body index 30–36), connects to sperm reservoir by a narrow neck, oral end of cement body elongated funnel shaped.
Bursa copulatrix (figs 5c–f) open type, large, roughly ear-shaped, longer than wide; anteriorly extends medially towards midline, running antero-laterally just below right funnel locking cartilage, reaching posterior end of mantle cavity. Longitudinal opening of bursa close to mantle ventral midline, running along long axis of bursa. Mature females with large nidamental gland, (nidamental gland index 36.6–54.4).
Alcohol-preserved specimens brown in colour, dorsal mantle surface lighter than ventral surface. Dark chocolatebrown chromatophores scattered over brown-coloured background on both dorsal and ventral surfaces of head and mantle, and along aboral surface of all arms. Surfaces of fins devoid of chromatophores and pigmented spots. Skin smooth, lacking sculpture or papillae.
Etymology: Species epithet taenia from Latin taenia meaning tape-like. The name denotes the tape-like structure in the copulatory apparatus on the hectocotylised arm of the males.
Distribution: Only known from Moreton Bay, Queensland, Australia (fig. 13).
Remarks: This is the only known species in the genus. Due to the poor preservation of the specimens, nearly all suckers are lost or are without sucker rings. The description of sucker ring dentition and spermatophores must wait until better materials are available.
The poor state of preservation resulted in distorted morphology of the specimens studied. This most certainly contributes to the wide range of the morphometric indices listed in Table 2.
description: Published as part of Lu, Chung Cheng & Okutani, Takashi, 2022, Two new genera and species of sepioline squids (Cephalopoda: Sepiolidae) from Australia, pp. 1-23 in Memoirs of Museum Victoria 81 on pages 3-7, DOI: 10.24199/j.mmv.2022.81.01, http://zenodo.org/record/10666316