Onychoteuthidae Gray, 1847

The family Onychoteuthidae was recently revised by Bolstad (2010), who recognized the following seven genera (with about 25 species).

Introduction

Onychoteuthids are small (ca. 7 cm ML) to large (ca. 2 m ML), muscular squids that have two series of smooth-ringed suckers on the arms and two series of hooks on the tentacular clubs (and, rarely, marginal suckers as well). Some species are common open ocean squids (e.g., Onychoteuthis spp.); others live near the ocean floor along continental or island slopes (bathyal region) (e.g., Onykia spp.).

Brief diagnosis:

• with buccal connectives attaching to ventral borders of arms IV.
• with simple, straight funnel-locking apparatus.
  
• with hooks on the tentacular clubs and two series of suckers on the arms.
• with rostrum on conus of gladius.

Characteristics

1. Arms
   1. Arm suckers biserial with smooth rings.
      
   2. Hectocotylization absent.
      
      
2. Tentacles
   1. Tentacular club with two medial series of hooks; ventromedial series with larger hooks.
   2. Marginal club suckers absent by subadult stages of most genera.
   3. Club suckers generally limited to carpal locking-apparatus and terminal pad in subadults, although a dactylus is present in Notonykia and possibly Kondakovia.
   4. Carpal locking apparatus with circular to oval shape that is usually defined by a ridge or elevation.
   

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   Figure. Oral view of the tentacle club of Onychoteuthis borealijaponica, 81 mm ML, off California. Drawing from Young (1972).

3. Buccal crown
   1. Buccal connectives attach to ventral sides of Arms IV.
      
      
4. Head
   1. Head with three primary (ventro-lateral) occipital folds in all genera; 3-8 secondary occipital folds also present in some genera (Onychoteuthis, Ancistroteuthis, Notonykia).
   2. Beaks
      1. Lower beak with a step following jaw angle.
         

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         Figure. Anterior-oblique views of the lower beak. Arrows point to the step of both beaks. Left - Notonykia africanae, 100 mm ML, paratype. Modified from Nesis, et al., 1998. Right - Walvisteuthis virilis, mature male, NMNH specimen. The step ("angle ridge") lies just beyond the jaw angle where the rostral edge continues medially onto the lateral wall. That is, where the rostral edge merges into the lateral wall, the two are not flush along the medial beak surface. A well defined step is a characteristic feature of the lower beak of all members of the Onychoteuthidae. Such a step is seen outside the family only in Pholidoteuthis boschmai and to a lesser extent in some Enoploteuthis (Clarke, personal communication). Photograph by R. Young.

5. Funnel
   1. Funnel locking-apparatus with straight groove.
      
      
6. Photophores
   1. Photophores present only in Onychoteuthis and possibly Ancistroteuthis.
      
      
7. Gladius
   1. Gladius with primary conus.
   2. Gladius with rostrum, usually prominent.

Comments

The following table compares the major features that separate the genera (modified from Bolstad 2010).

¹ - Absent from mantle cavity; may be present on ventral surface of eye (nature of tissue undetermined)

* - indicates unique character within family

The following drawings illustrate the characters used in the table above.

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Top row:

• Occipital folds - Side view of the head of Onychoteuthis sp. Drawing modified from Pfeffer (1912).
• Visceral photophores - Ventral view, Onychoteuthis sp., off Florida. Drawing from Young (1972).
• Rostrum of gladius - Ventral and side views, Onykia ingens. Drawing modified from Pfeffer (1912).

Bottom row:

• Warts - Skin of Onykia ingens. Drawing modified from Pfeffer (1912).
• Marginal suckers - Oral view of tentacle club of Kondakovia longimana. drawing from Filippova (1972).
• Fin shapes: Left - Onykia robsoni, sagittate fins. Drawing modified from Kubodera et al. (1998). Middle - Callimachus rancureli, Oval fins. Drawing modified from Kubodera et al. (1998). Right - Kondakovia longimana, rhomboidal fins. Drawing modified from Filappova (1972).

Nomenclature

A list of all nominal genera and species in the Onychoteuthdae can be found here. The list includes the current status and type species of all genera, and the the current status, type repository and type locality of all species and all pertinent references.

Discussion of Phylogenetic Relationships

(Modified from Bolstad [2010]): Several studies have addressed genetic relationships within the Onychoteuthidae.  Bonnaud et al. (1998) analysed 16S rRNA sequences from eight onychoteuthid species (from four genera).  Notably, Callimachus youngorum (their ‘Onykia sp.’) appeared most closely related to the ‘Moroteuthis’ group—more closely related, in fact, than was F. knipovitchi, which until recently was also considered an Onykia species. Wakabayashi et al. (2007) conducted a similar study (using CO1) on nine onychoteuthid species from three genera.  In their results, three Onykia species grouped closely together, with O. (M.) ingens slightly more distant; the Onycho­teuthis species also grouped together; and F. knipovitchi did not fall out with the Onykia species, but rather the Onychoteuthis group.

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Figure. Summary of previous genetic studies on the Onychoteuthidae. A: ‘Tree obtained after neighbor-joining analysis of 16S sequences,’ modified from Bonnaud et al. (1998), fig. 6. B: ‘NJ tree of standard species and paralarvae’ (based on CO1 sequences), modified from Wakabayashi et al. (2007), fig. 2. Species names have been updated; where applicable, original species ID appears in smaller font following updated name. © (2010), Wakabayashi et al. (2007), Bonnaud et al. (1998).

Nesis (2000) assessed relationships within the family based on morphology and zoogeography, discussing primitive/advanced character states and likely phylogeny. He considered dense, muscular tissues, smooth skin on the mantle, and the absence of photophores and secondary occipital folds all to be primitive states, with ammoniacal tissues, sculptured skin, secondary occipital folds, and photophores representing more advanced states. Nesis also discussed the presence of both ‘primitive’ and ‘advanced’ genera in every zoogeographical zone (although he considered Onykia primitive and ‘Moroteuthis’ advanced, separating them based on the presence or absence of ammonium chloride (a bouyancy device) and concluded that the family evolved in the tropics.

Distribution

The family is absent from the Arctic Ocean but, otherwise, is found throughout the world's oceans (Nesis 1982/87).

Other Names for Onychoteuthidae Gray, 1847

• Hooked squids

References

Arkhipkin, A. I. and Ch. M. Nigmatullin. 1997. Ecology of the oceanic squid Onychoteuthis banksi and the relationship between the genera Onychoteuthis and Chaunoteuthis (Cephalopoda: Onychoteuthidae. J. Mar. Biol. Ass. U. K. 77:839-869.

Bolstad, K.S.R. 2010. Systematics of the Onychoteuthidae Gray, 1847 (Cephalopoda: Oegopsida). Zootaxa, 9626: 186 pp.

Bonnaud, L., P. G. Rodhouse and R. Boucher-Rodoni. 1998. A phylogenetic study of the squid family Onychoteuthidae (Cephalopoda: Oegopsida). Proc. R. Soc. Lond. B 265:1761-1770.

Kubodera, T., U. Piakowski, T. Okutani and M. R. Clarke. 1998. Taxonomy and zoogeography of the family Onychoteuthidae. Smithson. Contr. to Zool., No. 586 (vol. II):277-291.

Nesis, K. N. 1982/87. Abridged key to the cephalopod mollusks of the world's ocean. 385,ii pp. Light and Food Industry Publishing House, Moscow. (In Russian.). Translated into English by B. S. Levitov, ed. by L. A. Burgess (1987), Cephalopods of the world. T. F. H. Publications, Neptune City, NJ, 351pp.

Nesis, K.N. 2000. Squids of the family Onychoteuthidae: phylogeny, biogeography, and way of life. Zoologichesky Zhurnal, 79(3):272-281.

Nesis, K. N. and I. V. Nikitina. 1986. A new family of deepsea squids (Cephalopoda, Oegopsida) from the Southeastern Atlantic. Zool. Zhurn. 65: 47-54.

Nesis, K. N. and I. V. Nikitina 1992. New records of oceanic squids Walvisteuthis virilis Nesis et Nikitina, 1986 and Nototeuthis dimegacotyle Nesis et Nikitina, 1986 (Cephalopoda, Oegopsida) from the South Atlantic and the South Pacific. Ruthenica 2: 55-58.

Nesis, K. N., M. A. C. Roeleveld and I. V. Nikitina. 1998. A new genus and species of onychoteuthid squid from the Southern Ocean. Ruthenica 8:153-168.

Tsuchiya, K. and T. Okutani. 1991. Growth stages of Moroteuthis robusta (Verrill, 1881). Bull. Mar. Sci. 49:137-147.

Wakabayashi, T., Kubodera, T., Sakai, M., Ichii, T. & Chow, S. 2007. Molecular evidence for synonymy in the genera Moroteuthis and Onykia and identification of their paralarvae from northern Hawaiian waters. Journal of the Marine Biological Association of the United Kingdom, 87: 959–965.

Young, R. E. 1972. The systematics and areal distribution of pelagic cephalopods from the seas off Southern California. Smithson. Contr. Zool., 97: 1-159.