Some species of Megalocranchia are very large and can reach 1800 mm ML, (Tsuchiya and Okutani, 1993). The vertical distribution is best known in M. fisheri. The paralarval stage, which reaches 40-50 mm ML, is spent in near-surface waters. Larger individuals occupy mesopelagic depths during the day and migrate into near-surface waters at night (Young, 1978).

Brief diagnosis:

A taoniin ...

• with photophores on the digestive gland.

1. Tentacles
   1. Tentacular clubs with suckers only.
   2. Tentacular stalk with two series of suckers and pads in mid-third, then four series to carpal group.
      
      
2. Head
   
   1. Beaks: Descriptions can be found here: Lower beaks; upper beaks.
      
      
3. Funnel
   1. Funnel valve present.
   2. Funnel organ: Dorsal pad with two triangular flaps, no papillae.
      
      
4. Mantle
   1. Tubercules absent at funnel-mantle fusion.
   2. Paralarvae (to ca. 50 mm ML) with thick gelatinous dermis on mantle.*
      
      
5. Fin
   1. Anterior 10-15% of fin inserts on mantle (in subadults).**
      
      
6. Photophores
   1. Photophores present on digestive gland.*
   2. Photophores present on tips of arms I-III or only II or only III of adult females.
      

      Figure. Visceral photophores from a subadult, M. fisheri, off Hawaii. The visceral photophores contain four reflecting cups (green). The intestine, partially covered with red pigment, is seen here passing between photophores of either side. The barely-discernable digestive gland is the fuzzy central dark region. Photograph by R. E. Young.

*Within family, unique to this genus.
**Within family, unique degree of mantle attachment. Most genera lack a mantle attachment but two have more than 30% of fin attached to the mantle(Egea, Teuthowenia) rather than to the gladius.

Comments

Characteristics are from Voss (1980).

This genus occurs circumglobally in tropical and subtropical waters (Voss, 1992).

Depth range based on 161 specimens in 6 taxa.
Water temperature and chemistry ranges based on 150 samples.

Environmental ranges
  Depth range (m): 9 - 3272
  Temperature range (°C): 2.336 - 28.444
  Nitrate (umol/L): 0.122 - 39.804
  Salinity (PPS): 34.009 - 36.622
  Oxygen (ml/l): 1.354 - 6.225
  Phosphate (umol/l): 0.028 - 2.788
  Silicate (umol/l): 0.799 - 105.381

Graphical representation

Depth range (m): 9 - 3272

Temperature range (°C): 2.336 - 28.444

Nitrate (umol/L): 0.122 - 39.804

Salinity (PPS): 34.009 - 36.622

Oxygen (ml/l): 1.354 - 6.225

Phosphate (umol/l): 0.028 - 2.788

Silicate (umol/l): 0.799 - 105.381
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

Paralarvae of M. fisheri from Hawaiian waters have been identified. The large posterodorsal mantle chromatophore seen in both stages is distinctive among cranchiid paralarvae from these waters. What appears to be an unusually long club may actually be a combination of the club with a large number of carpal suckers on the distal stalk.

Barcode of Life Data Systems (BOLD) Stats
                                        

Specimen Records:	1	Public Records:	1
Specimens with Sequences:	1	Public Species:	1
Specimens with Barcodes:	1	Public BINs:	1
Species:	1
Species With Barcodes:	1

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