Sepietta Naef, 1912

Bello, Giambattista, 2020, Evolution of the hectocotylus in Sepiolinae (Cephalopoda: Sepiolidae) and description of four new genera, European Journal of Taxonomy 655 (655), pp. 1-53 : 42-43

Sepietta Naef, 1912

Fig. 18

Sepietta Naef, 1912: 248 .

Type species

Sepiola oweniana d’Orbigny in Férussac & d’Orbigny, 1841 , by monotypy.

Diagnosis

Sepiolinae with fins rounded or bluntly angled laterally; their length about half mantle length. Suckers biseriate on all arms. Tentacle club suckers in 12 or more longitudinal rows. Mantle-head occipital band narrow (not reaching over the ocular globes). Ventral mantle margin slightly sinuate, without any deep funnel indentation. Gladius present, reduced. Visceral photophores absent. Hectocotylus (male left arm I) tripartite: basal part with three or four suckers, two ventral and one or two dorsal; copulatory apparatus with transverse formation of two ventral and two dorsal modified suckerless pedicels of various degrees of development, all four of them fused at their bases, ventral-most one longest and hook-shaped; distal part with some proximal suckers of dorsal row enlarged, wide space between the two sucker rows ( Naef 1923). Female bursa copulatrix roughly ear-shaped, devoid of cover.

Included species

Sepietta oweniana (d’Orbigny in Férussac & d’Orbigny, 1841) , S. neglecta Naef, 1916 and S. obscura Naef, 1916 .

Remarks

This is a well-established genus distributed in the NE Atlantic Ocean and the Mediterranean. Its most evident character is the lack of any visceral light organ, which is a derived condition, i.e., light organs secondarily lost. Sepietta oweniana and S. neglecta are sister species (Bello 2019a) and are distinguished from S. obscura , in addition to hectocotylian characters, by their fin shape (that is bluntlyangled in the former ones and rounded in the latter), as well as by the number of longitudinal sucker rows on tentacle clubs (fewer in the latter) and the occurrence of only three suckers in the basal part of the S. obscura hectocotylus. Sepietta obscura , contrary to the other two species, dwells in shallow depths and has a narrower distribution, in the Atlantic Lusitanian waters and the Mediterranean Sea (Bello 2019a).

Figures

Fig. 18. Hectocotylus of Sepietta oweniana (d’Orbigny, 1841). The arrows starting from the letters V and D indicate the two ventral and two dorsal modified pedicels, respectively, which form the transversal crest of the copulatory apparatus.