Bathyteuthidae

Bathyteuthis was erected as a new genus by Hoyle (1885a) for a new species of deep sea squid (B. abyssicola) captured from 2900 m during the CHALLENGER Expedition. It was caught in the Southern Ocean, Indian Ocean segment, between the subantarctic islands of Crozets Island and Prince Edward Island. In the same year Verrill (1885) described a new genus and species, Benthoteuthis megalops, captured the previous year by the ALBATROSS in 1960 m off Martha’s Vineyard, New England.

Neither author designated a family for these new genera. Hoyle (1885b) immediately recognized that Benthoteuthis was a synonym of Bathyteuthis (which had publication priority by 2 months), and he mentioned in 1886 the possibility that the two species might be conspecific. But it was not until 1900 that Pfeffer actually synonymized B. megalops with B. abyssicola when he erected the Family Bathyteuthidae.

The family also contained another unusual genus, Chtenopteryx, which eventually was separated as a subfamily by Grimpe in 1922 and elevated to family Chtenopterygidae by Allen (1945). Two additional species were described in 1968 by Roper: Bathyteuthis bacidifera and Bathyteuthis berryi, and the family was monographed by Roper (1969).

A member of the bathyteuthid families ...

• With buccal connectives attaching to dorsal border of Arms IV.
• With small, separate, paddle-like fins.

This family contains a single genus, Bathyteuthis, with six species described: 

• Bathyteuthis abyssicola
• Bathyteuthis bacidifera
• Bathyteuthis berryi
• Bathyteuthis devoleii
• Bathyteuthis inopinata
• Bathyteuthis numerosa

They are found throughout the world's oceans.

1. Arms
   
   1. Arms short, joined by a low, fleshy web.
   2. Arms I-III with 2 longitudinal series of suckers proximally, increasing to 4 series of irregularly placed suckers distally in adults.
      

      

      Figure: Oral view of brachial crown of B. abyssicola, Hawaiian waters. Suckers on the dorsal six arms are in two series at the base of each arm but merge into four series distally. Note the web between the arms. Photograph by R. Young.

   3. Buccal connectives attach to dorsal border of arms IV.
2. Tentacles
   
   1. Tentacular club short, unexpanded, with 8-10 longitudinal series of numerous, minute suckers.
3. Head
   
   1. Eyes semitubular, anteriorly directed.
      
      
      Figure. Dorsal view of a 20 mm ML B. abyssicola showing forward-looking eyes and photophores (arrow) at the bases of the arms. Photograph by R. Young, R/V G. O. Sars, Mar-Eco cruise, North Atlantic.
      
      
4. Funnel
   
   1. mantle-funnel locking apparatus with a simple, straight ridge and groove.
       
      Figure. Ventralview of Funnel locking-aparatus of B. abyssicola from Hawaiian waters. Photograph by R. Young.
5. Fins
   
   1. Fins small, separate, round with anterior and posterior lobes.
6. Photophores
   
   1. Arms I-III with single, simple photophore embedded in subcutaneous aboral tissue at each arm base (see Figure above).

 Unusual features:  Bathyteuthis spp. have large, orange-colored photosensitive vesicles just posterior to the forward-looking eye. The photosensitive vesicles are extra-ocular photoreceptors that apparently monitor bioluminescent light arising outside of the visual field, including the mantle cavity. In the latter case, small, luminescent organisms inadvertently drawn into the mantle cavity with the respiratory current could reveal the presence of the squid to potential predators in the dark waters of the deep-sea. The photosensitive vesicles of Bathyteuthis are among the largest known in any cephalopod.

Species of Bathyteuthis have a peculiar pore just anterior to the funnel that lies between the embedded funnel adductor muscles. This pore leads into a short canal that bifurcates then each branch ends blindly. The function of this structure is unknown.

Presumably all species in the genus brood their young by carrying embryos in an egg sheet held by the arms (Bush, et al., 2012).

The paralarva is easily recognized by the tentacle and arm IV bases that extend well posterior to the bases of arms I-III (see fig. B below). The position of the digestive gland is well posterior to the cephalic cartilage but it is not visible through the mantle of the preserved paralarva.

Figure. Paralarvae of B. abyssicola, 4 mm ML.
Left - A: Ventral view.B : Ventral view of the head and brachial crown with the funnel removed to show how far posteriorly the bases of the tentacles and arms IV lie. The bases of arms I-III lie anterior to the eyes. C: Dorsal view. Drawings of paralarva from Hawaiian waters by R. Young. Bar = 1 mm.
Oral view of the branchial crown and tentacular club. Drawings of paralarva from western North Atlantic (from Roper and Sweeney, 1992).