Ancistrocheirus sp.A

Arnold, Sam, Nos, David, Sáez-Liante, Raquel & Fernández-Álvarez, Fernando Á., 2025, Diversity in the squid family Ancistrocheiridae and description of a new family of the order Oegopsida (Cephalopoda), Zoological Journal of the Linnean Society 204 (3) : -

Ancistrocheirus sp.A

( Figs 5–6; Tables 8–9)

Examined material: NHM 20240083, 2 ♀♀, 165 and 180 mm DML, North Atlantic Ocean , 47ºN, 6º 20′ W .

Description

Specimens up to 180 mm DML ( Fig. 5A–D). The body is gelatinous with a short tail and purplish pink in colour. The mantle is relatively narrow with an MWI of 44.4%–50.9% of DML. The mantle has 24 photophores with the pattern 6 + 2 + 4 + 2 + 4 + 2 + 4 ( Fig. 5D). Large rhomboidal fins that extend along almost the whole mantle length 72.2%–86.1% of DML, relatively narrow fins compared to other species in this genus, with a FWI of 84.4%–93.9% of DML. The head is long and narrow with an HLI of 36.1%–39.4% of DML and with an HWI of 27.8%–30.3% of DML. Five large photophores surround each eye, of which two are ventral, two are dorsal, and one is lateral ( Fig. 5D). Two small photophores are located between the two ventral photophores close to each eye ( Fig. 5D).

Funnel length is 19.4%–21.8% of DML. The funnel component of the locking apparatus is 10.4%–12.0% of DML, the shallow mantle component is 10.1% of DML and extends towards the anterior end of the mantle.

The gladius is slightly pointed with a developed rachis ( Fig. 5E). The gladius length is 103.0%–133.3% DML. The gladius width is 14.4%–16.7% DML. The rachis in both individuals was broken at the end; however, as only the tips were missing, an estimate of 15.1%–18.0% DML was made. The rostrum was broken for both individuals and could not be measured.

Arms are short and relatively equal in length, range 61.7%– 80% of DML, with arms II and III slightly longer than I and IV. The average length of Arm I is 116.5 mm, arm II is 125 mm, arm III is 126.5 mm, and arm IV is 113 mm. Each arm has hooks in two indistinct alternating rows. The hooks in Arm IV are approximately one-fourth smaller than in the other arms. Approximately 50 hooks are present on each arm, with the first ~15 hooks being similar in size and then decreasing in size towards the tip of the arm. At the tip of the arms there are ~30 small suckers. Arm hook curvature is between 33º and 41º ( Fig. 5F, G).

Tentacles are short, ranging from 148 to 160 mm, representing 82.2%–97.0% of mantle length. The tentacle club is 23.9–26.7% DML. The club is formed by four or five carpal suckers and knobs, the manus has nine dorsal hooks and eight ventral hooks ( Fig. 6), the dactylus has 25–30 circular suckers. The hook D3 is largest in the dorsal series, while D1 and D9 are smaller than the other dorsal hooks; the remaining dorsal hooks are similar in size. There is a lot of variation in size for all hooks in the ventral series: V1 is the smallest hook in the ventral series, after which the size steadily increases ~ 2 mm per hook till hook V4. The hook V4 is usually slightly smaller than V5, which is the largest in the ventral series, being 16.2% of the club length. After hook V5, the size of the hooks gradually decreases again to hook V8, which is slightly larger than hook V1. The curvature of the hooks ( Table 9) decrease with size; D1 had the sharpest angle of 21.5º, while hook V5 had the largest angle of 46.8º.

The beak has a greater hood and a lighter pigmentation pattern than in other examined Ancistrocheirus of a similar size ( Fig. 5H–J). The LRL was about 5 mm.

The radula has seven transverse rows of teeth. The rachidian teeth are tricuspid with hooked lateral cusps and a rachidian average length of 0.33 mm in the ventral part of the structure and 0.57 mm in the dorsal one. The L1 row is bicuspid with a hooked lateral cup and an overall length of 67.5%–89.7% RL ventrally and 68.0%–80.1% RL dorsally, while the second lateral row is unicuspid with a length of 108.7%–148.1% RL ventrally and 125.5%–140.5% RL dorsally. The marginal rows are unicuspid with a length of 151.6%–233.4% RL ventrally, the dorsal marginal teeth could not be measured.

Locality: North-eastern Atlantic Ocean, 47ºN, 6º 20′ W.

Remarks: The specimens were fixed shortly after capture, as the arms and tentacles show signs of contraction. Thus, they might appear shorter than in others that were fixed long after their death. The early subadult Ancistrocheirus sp. 2 CEP331, whose complete mitogenome was sequenced under GenBank Accession number OQ942691 ( Fernández-Álvarez et al. 2023), has a photophore pattern and gladius morphology compatible with Ancistrocheirus sp. A . Regrettably, only the mantle of CEP331 was sampled, and the arm crown cannot be used to determine whether the three specimens are conspecific. Future studies using molecularly identified adult specimens suitable for morphological examination are needed to link Ancistrocheirus sp. A with a molecular species and then to provide an appropriate name for it.