Ancistrocheirus alessandrinii ( Vérany, 1847 )

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 alessandrinii ( Vérany, 1847)

( Figs 3–4; Tables 6–7)

Diagnosis: Ancistrocheirus with 22 photophores with the pattern 6 + 2 + 4 + 2 + 4 + 2 + 2 in ventral mantle; gladius leaf-shaped with a poorly developed rachis; arm hooks with angles between 61 and 77º.

Synonyms: Loligo alessandrinii Vérany, 1847 . Holotype: MHNNice2007.0.6005, Muséum d’Histoire Naturelle de Nice, France. Type locality: Messina , Sicily, Italy.

Enoploteuthis polyonyx Troschel, 1857 fide Pfeffer (1879). Type locality: Messina (?) fide ( Sweeney 2017). Type repository unresolved after Sweeney (2017).

Neotype: ICMC000316 , 1♀, 175 mm DML, 01/08/2015, Roses, 42.3951ºN 3.5125ºE, depth 600 m. GenBank COI accession number: OQ755038. GenBank 12S accession number: OQ750435.

Neotype locality: Roses, north-western Mediterranean Sea.

Additional material: ICMC00114 . 1♂, 52 mm DML, 27/09/2017, Palamós , 42.1080ºN, 3.5589ºE. GenBank COI accession number: OQ755031. GenBank 12S accession number: OQ750426 . ICMC000303 , 1♀, 181 mm DML, 24/04/2015, Tarragona , depth 435– 591 m. ICMC000403 . 1♀, 200 mm DML, 06/07/2023. Arenys de Mar. 41.3679ºN, 2.7869ºE, depth 532 m. ICMC000404 . 1♀, 160 mm DML, 06/07/2023, Arenys de Mar. 41.3679ºN, 2.7869ºE, depth 532 m. ICMC000405 . 1♀, 170 mm DML, 04/10/2021, Tarragona , 40.8333ºN, 1.3166ºE, depth 507 m. ICMC000406 . 1♀, 175 mm DML, 31/08/2021, Tarragona , 40.83333ºN, 1.4166ºE, depth 546 m. ICMC000407 . 1♀, 210 mm DML, 31/08/2021, Tarragona , 40.83333ºN, 1.4166ºE, depth 546 m.

Description

Specimens ( Fig. 3A–D) up to 210 mm DML, probably there is sexual dimorphism in size, with the only known mature male being 52 mm DML. Females have gelatinous bodies with a short tail and are purple in colour. The mantle is relatively narrow with an MWI of 35.3%–57.9% of DML. The mantle has 22 photophores with the pattern: 6 + 2 + 4 + 2 + 4 + 2 + 2 ( Fig. 3D). The length of the large rhomboidal fins is 75.2%–82.4% of DML and the FWI is 90.0%–115.8% of DML. The head is large with an HLI of 39.0%–50.0% of DML and a HWI of 26.5%–41.9% of DML. Five large photophores surround each eye, two of them in the ventral surface of the head, two in the dorsal and one in the lateral ( Fig. 3B, D). Two smaller photophores are located between the two ventral photophores close to each eye ( Fig. 3D).

The funnel length is 10.3%–22.7% of DML. The funnel component of the locking apparatus is 10.0%–12.0% of DML, the mantle component is 5.6%–10.3% of DML. The mantle component is shallow, extending towards the anterior end of the mantle.

The gladius is leaf-shaped with a minute rostrum and a poorly developed rachis ( Fig. 3E). Due to the lack of development in the rachis, it is difficult to identify where the rachis begins, an estimate of 11.4%–15.6% of DML was made. Gladius length ranges between 100.0% and 123.1% of DML, variation is probably due to different degrees of mantle contraction due to fixation. The gladius width ranged between 16.7% and 24.1% of DML. The dorsal keel depth ranges between 0.6% and 2.0% DML. The rostrum ranges between 0.8% and 2.0% of DML.

The arms are long and approximately equal in length, ranging between 46.5% and 92.1% of DML. Each arm has hooks in two indistinct alternating rows. The hooks in Arm IV are approximately 25% smaller than in the other arms. Approximately 50 hooks on each arm, of which the largest in adults is 4–5 mm long, although there is almost no difference in size between the first ~15 anterior hooks. The hooks curve between 44º and 77º ( Fig. 3F, G). The tips of the arms have approximately 40 small circular suckers in two aligned rows, whose morphology suggests they are transitioning to hooks. The terminal sucker surfaces are covered with ~25 small teeth of 10 µm length.

The tentacles are long, with a total length of 330–544 mm and a TeLI of 194.1%–259.0% of DML and a CLI of 26.0%–31.3% of DML. The club is formed by four or five carpal suckers and knobs, the manus has nine dorsal hooks and eight ventral hooks ( Fig. 4; Table 7), the dactylus has 20–26 suckers. Hook D2 is the largest in the dorsal series. Hooks D1 and D2 are equal in size to their ventral counterparts. Hook V4 and V5 are the largest in the ventral series and in the whole tentacle, being 16.1% of the club length. The distal dorsal hook D9 is small and flat; therefore, it could be confused with a sucker of the dactylus. The curvature of the hooks decreased with size, V8 had the sharpest angle of 37º while hook D5 had the largest angle of 58.6º.

The LRL ranges between 5 and 7 mm, averaging at 2.1% DML. The lower beak length is 242.4%–362.3% of LRL, and the depth is 253%–320% of LRL. The rostrum and shoulders are pigmented, whereas the hood and lateral wings have moderate to no pigment ( Fig. 3H, I). The hood ranges between 60.6% and 100% of LRL. The upper beak is more pigmented than the lower beak ( Fig. 3J).

The radula ( Fig. 3K) has seven transverse rows of teeth. The R teeth are tricuspid with hooked lateral cusps and an average rachidian length (RL) of 0.47 mm ventrally and 0.56 mm dorsally. The L1 row is bicuspid with a hooked lateral cup and an overall length of 57.4%–126.8% of RL ventrally and 76.2%– 111.6% of RL dorsally, while the L2 row is unicuspid with a length of 68.1%–192.2% of RL ventrally and 80.4%–160.4% of RL dorsally. The M rows are unicuspid with a length of 85.4%– 297.1% of RL ventrally and 124.8%–288.6% of RL dorsally.

The male individual ICMC000114 (52 mm DML) is gelatinous and has a light pink colour. The mantle is relatively narrow with an MWI of 38.8% of DML. The ventral mantle skin was broken in the posterior end, the photophore pattern in the anterior mantle starts with 6 + 2 + 4, which is also found in the females. The large rhomboidal fins have a 77.1% FLI. The fins are broad but broken. The head is large with an HLI of 52.2% of DML and an HWI of 77.1% of DML. Same head photophore pattern as in females.

The funnel length is large: 31.7% of DML. The funnel component of the locking apparatus is 19.7% of DML. Arms I and II are the shortest, 79.4% of DML and 64.9% of DML, respectively. Each arm has hooks in two indistinct alternating rows. Approximately 50 hooks on each arm, of which the largest are ~ 2 mm, although there is almost no difference in size between the first ~15 anterior hooks. The gladius was found to be 50% longer than the mantle, which is probably due to the contraction of the animal when fixed. The gladius has the same leaf shape as found in mature females. The GWI was 24.3% of DML, and the dorsal keel depth was 2.3% of DML. The spermatophoric reaction was triggered and, therefore, the spermatophore ( Fig. 3L) internal structure was not possible to be studied. The specimen had three large spermatophores with an average total spermatophoric length of 27.8 mm, which equals 53.5% ± 1.8% of DML.

Distribution: Mediterranean Sea and Eastern and Western North Atlantic.

Name of the species in phylogenetic studies: ‘Undescribed Ancistrocheiridaespecies’,‘newspeciesofAncistrocheiridae’, and Ancistrocheirus alessandrinii ( Roura et al., 2019) ; Ancistrocheirus sp. ( Fernández-Álvarez et al. 2022); Ancistrocheirus sp. 1 ( Fernández-Álvarez et al. 2023; this work).

Remarks

The GenBank sequence OR304287 comes from a specimen sampled in Indian waters, and it is named here as Ancistrocheirus cf. lesueurii (= Ancistrocheirus sp. 4 , Remarks’ section of Ancistrocheirus lesueurii ). The molecularly detected Ancistrocheirus sp. 3 and Ancistrocheirus sp. 6 (private sequences available at BOLDSYSTEMS and not added here in the analyses; Supporting Information, Fig. S1) were collected in Pacific waters. As none of these three species is formally linked to A. lesueurii , it is not possible to exclude based only on molecular characters, if the A. alessandrinii individuals examined here actually belong to A. lesueurii . However, the characteristic morphology of the gladius of A. alessandrinii ( Fig. 3E) diverged from that depicted by Férussac and d’Orbigny (1834 –48: pl. 11, fig. 2) in the original description of A. lesueurii , as the latter has a very distinctive and well-developed rachis. Thus, there is an objective morphological character supporting the taxonomic treatment suggested in this work. Besides, no individual sequenced in Indopacific waters clusters with individuals of A. alessandrinii as redescribed in this work.

The tentacle club ( Fig. 4) has 17 hooks with nine dorsal hooks only found in three out of seven female adults. In most other specimens a scar could be found where a ninth hook was expected. That might explain why it has previously been described that Ancistrocheiridae have 15 or 16 hooks ( Jereb and Roper 2010). However, some oegopsid squid can have variable numbers of manus hooks [e.g. Onykia knipovitchi ( Filippova, 1972) ( Jereb and Roper, 2010) ]. Additionally, it was found for ICMC000405 and ICMC000406 that in the radular teeth, L1 hooks were tricuspid in some teeth and bicuspid in others, indicating some intraspecific variation in this other character.

The spermatophores ( Fig. 3L) are large, with an SpL representing 52.3%–55.7% of DML, and the SpC was three in the studied specimen. Previous measurements by Hoving and Lipinski (2014) of fixed specimens originating from South Africa found relatively smaller spermatophores with SpL 22%–46% DML and a SpC of up to 77. Moreover, some males described by Hoving and Lipinsky (2014) showed developed nidamental glands. South African male Ancistrocheirus were also sensibly larger, up to 265 mm DML for non-intersex males and 320 mm DML for males with nidamental glands ( Hoving et al. 2006), while the male specimen of A. alessandrinii was 52 mm DML. The spermatophore morphology of South African Ancistrocheirus is quite different from what was observed in A. alessandrinii , and such morphological differences in reproductive organs indicate speciation (De Queiroz 2007).

This species corresponds with Ancistrocheirus sp. 1 from the molecular analyses from this work. So far, this species has been found between Cape Verde to the north-western and eastern Atlantic and the Mediterranean ( Fig. 8), a pattern commonly found in many oegopsid squids, probably caused by the barriers created by the ocean currents ( Fernández-Álvarez et al. 2023). Roura et al. (2019) unclearly referred to some sequenced specimens from Morocco either as ‘undescribed Ancistrocheiridae species’, ‘new species of Ancistrocheiridae’, or A. alessandrinii , and argued that their sequencing might refer to the last taxonomic name, as North Atlantic waters are close to the Mediterranean Sea, where A. alessandrinii was described. Since the type locality of Ancistrocheirus alessandrinii is in the Mediterranean, this name should be applied to Ancistrocheirus sp. 1 . All the previous reports of A. lesueurii from Mediterranean waters (e.g. Bello et al. 1994, Zaragoza et al. 2015), including those from the Adriatic (Bello 1991) and Ionian Sea ( d’Onghia et al. 1997), are considered here as A. alessandrinii .

The holotype MHNNice2007.0.6005 of Ancistrocheirus alessandrinii is located at Muséum d’Histoire Naturelle de Nice. It was originally described by Vérany (1847) under the name Loligo alessandrinii . This individual was a paralarva; given that the morphology of paralarvae in the family Ancistrocheiridae is currently not well known at the global scale, this description currently does not provide much information towards assigning it to a species. This specimen has deteriorated to dust and has no characters left to study at all. There is no way to recover either molecular or morphological information from the destroyed holotype. Thus, it is considered that the provisions needed to designate a neotype under Articles 75.1 and 75.3.4 of the International Code of Zoological Nomenclature (ICZN and International Commission on Zoological Nomenclature 1999) are met. According to the ICZN Article 76.3, the type locality of the species becomes the locality of the neotype, in this case Roses in the north-western Mediterranean Sea. As both type localities are from the Mediterranean Sea, the ICZN Article 75.3.6 is also satisfied. The proposed neotype ICMC000316 is conserved in excellent condition, and mitochondrial genes COI and 12S are sequenced and available at GenBank under the accession numbers OQ755038 and OQ750435, respectively. The selection as the neotype of this specimen, which links morphological and molecular data, ensures future taxonomic stability of the name A. alessandrinii .

In the juvenile A. alessandrinii specimen sequenced under the GenBank Accession number MW255567 [complete mitogenome, Fernández-Álvarez et al. (2022)], the gladius had a defined rachis, which is inconsistent with the remaining sequenced specimens, including the relatively small male ICMC000114 (52 mm DML), which might indicate that the loss of a distinct rachis might be an ontogenetic process, and the distinct gladius shape associated with A. alessandrinii develops after the juvenile stage. Thus, this character might not be suitable for early ontogenetic stages. However, the juvenile with the developed rachis came from the Atlantic, not from the Mediterranean. According to the mGMYC analysis, Atlantic and Mediterranean A. alessandrinii might be two distinct species, and a mild genetic isolation was found among Mediterranean and Atlantic A. alessandrinii specimens, which is unlikely to represent a speciation event. However, it is noteworthy that extremely low distances have been found among described cephalopod species for some mitochondrial markers (e.g. Fernández-Álvarez et al. 2021, Sanchez et al. 2021). Currently, there are no adults molecularly confirmed to be Ancistrocheirus alessandrinii from the Atlantic to ensure if this feature is ontogenetic or an exclusive feature of Mediterranean specimens.

Incertae sedis