Overview

Brief Summary

Introduction

These common inshore squids of the Indo-West Pacific are targets of important large-scale and artesanal fisheries. Uroteuthis spp. are the only squids in the Loliginidae that possess photophores.

Brief diagnosis:

A loliginid ...

  • with a pair of photophores on the ink sac.

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Comprehensive Description

Nomenclature

From Vecchione et al., 1998:

The pair of photophores on the ventral surface of the ink sac in all of these species is perhaps the strongest indication of a close relationship among species to be found in this family. This relationship is further supported by similarities in the hectocotylus and arm-sucker dentition. These characters led Natsukari (1984) to establish the genus Photololigo for the Indo-West Pacific species with photophores, formerly assigned to either Loligo or Doryteuthis. However, Uroteuthis bartschi also has similar photophores, a similar hectocotylus and arm suckers, and an Indo-West Pacific distribution. The elongation of the posterior mantle, which was given generic status in the description of Uroteuthis, is the extreme example in a cline of mantle elongation, similar to that found in the eastern Atlantic where Alloteuthis is the extreme example. This elongation is so extreme in Uroteuthis as to cause a discontinuity in the cline. It thus warrants separate taxonomic status, but the sole recognized species in this taxon possesses all of the generic characters of Photololigo. Thus, it should be included in the genus that Natsukari described. Unfortunately, priority therefore goes to Uroteuthis as the name of the genus, rather than the more descriptive Photololigo. Aside from the photophores, Uroteuthis s.s. and Alloteuthis can be separated based upon position of the fins, lateral versus terminal respectively, and tentacular ring dentition. Therefore, elongation of the mantle end in these two taxa appears to be analogous, not homologous.

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Characteristics

  1. Arms
    1. Proximal margin of sucker rings with semicrescent plate; distal margin with square teeth.
    2. Hectocotylus:
      1. Two rows of papillae present; ventral crest absent.

  2. Tentacles
    1. Tentacular clubs expanded, suckers in four series.

  3. Mantle
    1. Mantle generally elongate and pointed posteriorly.

  4. Fins
    1. Fins in adults generally rhomboidal and longer than broad, tapering posteriorly.
    2. Fins may or may not reach posterior tip of mantle.

  5. Photophores
    1. Pair of organs on ventral surface of ink sac; intestine separates members of the pair.


    Figure. Ventral view of the visceral photophores (arrow) of (probably) Uroteuthis edulis, Japanese fish market. Photograph by Sabrina Pankey.

  6. Viscera
    1. Eggs small.
    2. Spermatophore cement body short.

Comments

Uroteuthis (Uroteuthis) is distinguished from the other two subgenera by a greatly elongate "tail" with "lateral" fins which to not extend to the tip of the tail. In Uroteuthis (Photololigo) and Uroteuthis (Aestuariolus) the elongation of the posterior mantle is variable but not tail-like and when the mantle is elongate, the fins extend along the sides to the posterior tip.

Figure. Dorsolateral view of U. (U.) bartchi, holotype, 199 mm ML, male, preserved, Philippine waters at 06°05'N, 121°00'E, showing elongate tail and lateral fins. The bend in the tail is an artifiact of preservation. Photograph by R. Young.

Uroteuthis (Photololigo) differs from Uroteuthis (Aestuariolus) in that the modified portion of hectocotylus is less than entire arm; that is, the proximal portion is not modified. In Uroteuthis (Aestuariolus) the entire arm is modified. The structure of the photophores also differs somewhat between the two subgenera.


Figure. Top - Oral view of the hectocotylus of Uroteuthis (Photololigo) edulis, 73 mm ML, male, preserved, East China Sea at 21°42'N, 114°50'E, preserved. Note the normal suckers in the proximal region of the arm. Bottom - Oral view of the hectocotylus of Uroteuthis (Aestuariolus) nocticula , 53 mm ML, male, preserved, Bass Strait, Australia at 37°51'S, 144°56'E. Note that only modified suckers are in the proximal region of the arms. Photographs by R. Young.

Figure. Dorsal view of Uroteuthis (Aestuariolus) noctiluca, paratype, preserved. Photograph by R. Young.

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Distribution

The Indo-West Pacific distribution of all of these species supports the contention that they comprise a natural, closely related species group.

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Ecology

Habitat

Depth range based on 4 specimens in 8 taxa.
Water temperature and chemistry ranges based on 2 samples.

Environmental ranges
  Depth range (m): 62 - 165
  Temperature range (°C): 21.787 - 23.253
  Nitrate (umol/L): 1.362 - 3.670
  Salinity (PPS): 34.324 - 34.425
  Oxygen (ml/l): 4.538 - 4.843
  Phosphate (umol/l): 0.338 - 0.366
  Silicate (umol/l): 6.809 - 8.177

Graphical representation

Depth range (m): 62 - 165

Temperature range (°C): 21.787 - 23.253

Nitrate (umol/L): 1.362 - 3.670

Salinity (PPS): 34.324 - 34.425

Oxygen (ml/l): 4.538 - 4.843

Phosphate (umol/l): 0.338 - 0.366

Silicate (umol/l): 6.809 - 8.177
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

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Evolution and Systematics

Evolution

Discussion of Phylogenetic Relationships

View Uroteuthis Tree

Type species.--Uroteuthis bartschi Rehder, 1945, by original designation.

In a revision of Loliolus, Lu et al. (1985) described a new species: L. noctiluca. They included this species in Loliolus because its hectocotylization was a modification of the entire length of the arm, the original diagnostic character of the genus Loliolus. However, the hectocotylus of L. noctiluca is otherwise very different from those of the other species of Loliolus in that it lacks a ventral crest and both the dorsal and ventral rows of suckers are modified into papillae. The hectocotylus of L. noctiluca is thus similar to those of the Uroteuthis and Photololigo species except that more of the arm is modified, making it the extreme in a cline of the percentage of arm length that is modified by hectocotylization. Furthermore, L. noctiluca was so named because of structures on the ink sac believed to be photophores. These characters, together with similarity in arm-sucker dentition, indicate that this species should be included in the subgenus Photololigo of the genus Uroteuthis.

Yeatman (1993) has presented evidence that some species of Uroteuthis (Photololigo) are actually species complexes.

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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage

Barcode of Life Data Systems (BOLD) Stats
                                        
Specimen Records:133Public Records:104
Specimens with Sequences:132Public Species:5
Specimens with Barcodes:132Public BINs:12
Species:5         
Species With Barcodes:5         
          
Creative Commons Attribution 3.0 (CC BY 3.0)

© Barcode of Life Data Systems

Source: Barcode of Life Data Systems (BOLD)

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Barcode data

Creative Commons Attribution 3.0 (CC BY 3.0)

© Barcode of Life Data Systems

Source: Barcode of Life Data Systems (BOLD)

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Locations of barcode samples

Collection Sites: world map showing specimen collection locations for Uroteuthis

Creative Commons Attribution 3.0 (CC BY 3.0)

© Barcode of Life Data Systems

Source: Barcode of Life Data Systems (BOLD)

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