Chtenopteryx sicula ( Vérany, 1851 )

Escánez, Alejandro, Roura, Álvaro, Riera, Rodrigo, González, Ángel Francisco & Guerra, Ángel, 2018, New Data on the Systematics of Comb-fin Squids Chtenopteryx spp. (Cephalopoda: Chtenopterygidae) from the Canary Islands, Zoological Studies 57 (40), pp. 1-11 : 5-7

Chtenopteryx sicula ( Vérany, 1851)

( Figs. 2B, 2D , 4 )

Synonyms: Calliteuthis neuroptera Jatta, 1896 ; Chtenopteryx fimbriatus Appellöf, 1890 ; Ctenopteryx cyprinoides Joubin, 1894 .

Material examined: Fifty-one specimens of C. sicula were captured around El Hierro, La Palma and Tenerife ( Spain, NE Atlantic Ocean) (see Table 1 and 3 for details).

Description: The diagnostic characters of the specimens caught in the Canary Islands agree with those described by Guerra (1992). A dorsal light organ is present in the posterior part of the mantle in mature males ( Fig. 3B ). The studied specimens have a clear visceral photophore on the ink sac dorsal to the intestine in immature and mature males and females ( Fig. 2D ). Buccal membrane with two series of suckers. Suckers on arms I-II and III have the suckers in two transversal series along the arms and four series distally ( Fig. 4A, B ), while sucker on arms IV are positioned in two zigzag transversal series ( Fig. 3C ), whilst the tentacular clubs present 8-14 series of suckers.

Genetic analysis

Of the 582 bp aligned for COI sequences, 95 were variable and 78 were parsimony-informative sites. Mean nucleotide composition was 29.8% (A), 35.6% (T), 19.8% (C) and 14.8% (G). The twelve partial COI sequences of Chtenopteryx species analysed in this study clustered in four distinct groups in the MaxL phylogenetic tree ( Fig. 5 ). A well supported group with bootstrap values of 99 (BP = 99) was identified as C. sicula (Atlantic Ocean). A second group was identified as C. sicula (Pacific Ocean) (BP = 100). A third clade was identified as C. canariensis group (BP = 99), and finally a clade formed by a unique sequence was identified as Chtenopteryx sp. (West Pacific) ( Fig. 5 ).

The partial COI sequence obtained for C. canariensis was clustered with two COI sequences classified as C. sicula (EU735369: caught in the Bear Seamount, NW Atlantic) and Chtenopteryx sp. (EU735388: collected north of the Azores archipelago, eastern Atlantic). The specimens belonging to this clade shared the same haplotype and therefore intragroup genetic divergence was TN = 0. The three C. sicula partial COI sequences obtained in this study grouped together with a C. sicula (GU145076) collected in the SW Atlantic Ocean. The intragroup genetic distance for this clade was TN = 0.004 ± 0.002. Finally, the clade formed by the GenBank sequences HQ386019; HQ386018; AY557526; AY293705, classified as C. sicula and collected from the Pacific Ocean, showed an intragroup genetic distance of TN = 0.001 ± 0.001.

The pairwise intergroup genetic distances between the four clusters formed in the MaxL phylogenetic tree ranged from 9.8% to 12.4% ( Table 4). The more divergent clades corresponded to those including C. sicula and C. canariensis , while the lowest divergence was obtained between C. sicula from the Pacific Ocean and C. canariensis .

Figures

Fig. 2. (A) Chtenopteryx canariensis, 43 mm ML female specimen captured in Canary Islands, ventral view. (B) Chtenopteryx sicula, 34 mm ML mature female captured in Canary Islands. (C) Ink sack of C. canariensis without visceral photophore. (D) Visceral photophore on ink sack of C. sicula.

Fig. 4. (A) Detail of the two suckers series on proximal part of arm I in C. sicula. (B) Detail of the four suckers series on distal par of arm III, in C. sicula. (C) Arm IV of C. sicula, with two zig-zag transversal series of suckers. Black arrows point to suckers.

Fig. 3. Ventral eyeball photogenic tissue in C. canariensis. (B) Dorsal light organ on mantle of mature male of C. sicula.

Fig. 5. Maximum-likelihood phylogenetic tree of the genus Chtenopteryx based on COI sequences. Bootstrap values are shown in the nodes. Accession numbers correspond to table 2. *: samples collected in the Canary Islands.