Cranchia scabra

Tentacles

• Suckers in a transverse row on club manus of equal size.
• Diagonally set pairs of suckers and pads on distal 2/3 of tentacular stalk

Arms

• Arm III with slight aboral keel.
• Arms with 40-70 spherical suckers
• Sucker teeth are generally angular but can be more rounded in basal pairs of suckers.
• Mature females with darkened, brachial organs on all arms, those on arm III enlarged. 

Figure Ventral view of a maturing (?) but damaged female C. scabra, Gulf of Mexico, 150 mm ML, showing the red-pigmented photophores at the tips of the arms. Photograph by M. Vecchione.

Head

• Eyes sessile in paralarvae (this is uncommon in Cranchiidae and can help with paralarval identification).

Photophores

• Fourteen oval photophores on each eye (ventral-proximal series of 8 photophores, ventral-distal series of 4 photophores near lens and dorsal series of two photophores near lens).

Figure Ventral view of most ocular photophores of C. scabra. The dorsal series of photophores is not visible. Photograph by M. Vecchione.

Mantle

• Mantle is rotund and covered with cartilaginous tubercles bearing 3-5 sharp cusps.

Figure. Lateral view of part of the mantle and head of a 30 mm ML C. scabra showing tubercles. Photograph by R. Young.

Fins

• Each fin is circular to oval in shape with free posterior lobes.  Tubercles are present on dorsal surface of the fins, radiating outward from the gladial midline.

Cranchia scabra is the only known member of the genus Cranchia. 

Cranchia is found circumglobally at both tropical and sub-tropical latitudes (43°N to 43°S).  The species is believed to exhibit ontogenetic descent (living in epipelagic waters in infancy and descending deeper into the water column upon maturation).  The deepest recorded C. scabra was discovered at 2000 meters depth (Jereb & Roper, 2010).

Cranchia is one of the few cranchiid genera to undergo relatively minimal morphological development throughout ontogeny.  As mentioned previously, paralarvae are most often recorded between 500-0m depth while adults are frequently found at lower depths.  Like other cranchiids, the eyes will expand in size during maturation, but unlike many other Cranchiidae are not stalked in younger life stages.  Tubercles become more complex throughout development and cover greater areas of the outer mantle and fins as the animal develops.

Upon reaching maturation, secondary sexual characteristics develop.  In females, brachial end organs form on all arms, with those on arms III being longer than the others (Evans, 2018).  Mature males develop a hectocotylus on right Arm IV, with minor modifications on Arm III (Voss, 1980).   

Figure Paralarval C. scabra. Left - Ventral and dorsal views, 4.7 mm ML, Hawaiian waters. Chromatophores were faint and pattern may not be complete; at slightly larger sizes the chromatophores cover the entire mantle. Drawings by R. Young.  Right - Ventral view, 8 mm ML, showing tubercules, not chromatophores. Drawing from Voss, 1980, p. 377, printed with the permission of the Bulletin of Marine Science. Scale bar is 1 mm.

Voss (1983) found strong phylogenetic support for character distinctions between the sub-families Cranchiinae and Taoniinae and indicated that Cranchia and Liocranchia likely had the most primitive physical characters.  Evans (2018) found Leachia to be the most basal of the Cranchiinae, but molecular data for the Cranchiinae was limited in his research.  More genetic assessments are needed to better understand phylogenetic relationships between the Cranchiinae. 

Cranchia scabra is thought to be a circumglobal species.  No known ecological or morphological differences are known between geographically separate groups. 

Cranchia scabra Leach, 1817: 140; Leach, 1818: 13, Pl. 18; Owen 1836: 103–108, Pl. XXI fig. 1–5; Férussac & d’Orbigny, 1834: 222–224, Pl. I fig. 1; d’Orbigny, 1845: 239–240, Pl. 8; Steenstrup, 1861: 28–31; Chun, 1910: 257–262, Pl. XLVIII fig. 1–2, Pl. XLIX, L, LX fig. 1–6; Pfeffer, 1912: 678–689; Robson, 1924: 10; Young, 1972: 78–80; Imber, 1978: 448–449, fig. 1a; Voss, Stephen, & Dong, 1992: 188–189, fig. 217; Reid, 2016: 82–83.

Loligo cranchii d’Blainville, 1823: 123.

Octopus (Philonexis) eylais d’Orbigny, 1834: 20, Pl. I fig. 8–14.

Cranchia hispida Pfeffer, 1884: 27, fig. 37.

Cranchia tenuitententaculata Pfeffer, 1884: 26–27, fig. 36.

Cranchia scabra hispida Pfeffer, 1912: 690–691, Pl. 48 fig. 27.

Cranchia scabra tenuitentaculata Pfeffer, 1912: 689–690, Pl. 48 fig. 28.

The larval glass squid (genus Cranchia) - Black Water dive in Kume Island, Okinawa Japan