Vitreledonella richardi Joubin, 1918

Introduction

Little information exists on the biology or ecology of this pelagic octopod. It has a cosmopolitan distribution in tropical and subtropical waters where it lives at meso- to bathypelagic depths. The body is gelatinous, transparent and almost colourless. The peculiar long, narrow shape and position of the digestive gland is seen in the title photograph. The stomach and caecum, unlike most other octopods, is reportedly located anterior to the digestive gland. The photo, however, indicates that it actually lies on the dorsal surface of the transversely oriented digestive gland. The title photograph also shows the hectocotylized third left arm. On the other arms the suckers are enlarged outside the web (see title photograph).

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Figure. Side view of the tip of hectocotylus of V. richardi, Hawaiian waters. The hectocotylus has an unusual oval vesicle with a slender papilla at its tip. Photograph by R. Young

One of the most distinctive features of V. richardi is the nearly rectangular shape of each eye as is seen from the side. The elgonate shape of the eye is inhanced by a ventral appendage (rostrum) that helps to camouflage the eye.

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Figure. Lateral side of the head of V. richardi showing the unusual shape of the eye.  Photograph by R. Young

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Figure. Dorsal view of the head of V. richardi showing the long optic stalks. Photograph by R. Young

Brief diagnosis:

An incirrate octopod ...

• with heteroglossan radula.
• with left arm IV hectocotylized but not detachable.
  

Characteristics

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Figure. The radula of V. richardi. Modified from Thore (1949).

1. Arms
   1. Suckers in single series, widely separated from one another.
   2. Left arm III hectocotylized; spherical vesicle present near tip.
      
      
2. Eye
   1. Shape nearly rectangular, rostrum present.
      
      
3. Mantle
   1. Mantle opening broad.
      
      
4. Viscera
   1. Radula with multicuspid rhachidian (with a-seriation) and unicuspid first and second lateral teeth (= heteroglossan radula) (drawing on right).
   2. Digestive gland long and slender.
   3. Stomach dorsal to digestive gland.

Nomenclature

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

Life History

Mating in pelagic octopods poses some problems. Male argonautoids have solved this simply by detaching a hectocotylized arm and giving it to the female. One submersible observation on Vitreledonella suggests that they mate a bit differently:

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Figure. These pictures are from a video sequence taken from a submersible at about 900 m depth off Hawaii. A Vitreledonella drifted into view but clearly has too many arms. A closer look indicates that one octopus is within the web of another; presumably they are mating. Unfortunately, the hectocotylus cannot be identified. Photographs from Young, et al., 1999.

The females apparently brood their eggs within the mantle cavity until hatching (Joubin, 1937).

Behavior

V. richardi maintains the digestive gland in a vertical orientation as it swims. The slender shape of this opaque organ and its vertical orientation will result in the otherwise transparent octopod casting a minimal shadow. Concealment is important when the octopod is at the upper end of its habitat where the downwelling light is dim but strongly directional. An AVI format video clip of this animal showing the vertical orientation of the digestive gland is available at Cephalopods in Action.

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Distribution

The best vertical distribution data is from the eastern North Atlantic. Until about 40 mm ML, most captures have been in the upper 300 m. The larger octopods have a very broad vertical distribution with most captures occuring in the upper mesopelagic zone but with some at lower mesopelagic depths during both the day and night. At night two captures were made in the lower regions of the epipelagic zone (Clarke and Lu, 1975 and Lu and Clarke, 1975).

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Figure. Vertical distribution of V. richardi. All captures were made with opening/closing trawls. Bars represent a capture and the bar length indicates the depth range of the trawl while open. Yellow bars indicate a daytime capture and blue bars a nighttime capture. Graph modified and redrawn from Clarke and Lu, 1975 and Lu and Clarke, 1975.

The geographical distribution of V. richardi is throughout the tropical and subtropical regions of the world's oceans (Nesis, 1982).

References

Clarke, M. R. and C. C. Lu. 1975. Vertical Distribution of cephalopods at 18 N 25 W in the North Atlantic. Journal of the Marine Biological Association of the United Kingdom, 55 (1): 165-182.

Joubin, L. 1918. Etudes preliminaires sur les cephalopodes recueillis au cours des croisieres de S.A.S. le Prince de Monaco, 6e Note: Vitreledonella richardi Joubin. Bull. Inst. Oceanogr. Monaco 340: 1-40.

Joubin, L. 1937. Les octopodes de la croisiere du "Dana" 1921-22. Dana Report, 11: 1-49.

Lu, C. C. and M. R. Clarke, 1975. Vertical Distribution of cephalopods at 11 N 20 W in the North Atlantic. Journal of the Marine Biological Association of the United Kingdom, 55 (2): 369-389.

Nesis, K. N. 1982. 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.

Roper, C. F. E., R. E. Young and G. L. Voss (1969). An illustrated key to the families of the order Teuthoidea. Smiths. contr. zool., 13:1-32.

Thore, S. 1949. Investigations on the "Dana" Octopoda. Dana-Report No. 33, 85pp.

Young, R. E., M. Vecchione and D. Donovan. 1999. The evolution of coleoid cephalopods and their present biodiversity and ecology. South African Jour. Mar. Sci. .