Magnoteuthis microlucensRichard E. Young, Michael Vecchione, and Annie Lindgren
Magnoteuthis microlucens, previously listed here as Mastigoteuthis sp. A, is the most common species of the genus around the main Hawaiian Islands. It has numerous tiny photophores that lie beneath the outer layer of integumental chromatophores. The photophores are so small that they cannot be recognized as photophores without the aid of a microscope.
A Magnoteuthis with ...
- minute integumental photophores.
- a tropical Pacific habitat.
- Arms II moderate in length, 46% of ML, 69% of arms II length.
- Large arm suckers generally with closely-set, rounded teeth on the distal margin, occasionallly fused; sometimes smaller, more proximal teeth with narrower, more distinctly separated teeth. Click on an image to view larger version & data in a new window
Figure. Oral view of an arm sucker (sucker 26, arm III) of Mg. microlucens, paratype. Photograph by R. Young.
- Funnel component of the funnel/mantle locking-apparatus flask-shaped with narrow stem.
- Mantle component without a nostril. Click on an image to view larger version & data in a new window
Figure. Funnel-mantle locking-apparatus of Mg. microlucens, holotype, Equatorial Pacific. Left - Frontal view of funnel component. Middle - Frontal view of mantle component. Right - Side view of mantle component. Blue stain = methylene blue. Photographs by R. Young.
- Minute ("lens" diameter less than 0.1 mm) integumental photophores present but unrecognizable to naked eye due to small size and structure.
- Integumental photophores present on aboral surfaces of all arms, on dorsal and ventral surfaces of Head, mantle and fins, on ventral surface of funnel.
- Integumental photophores lie beneath the surface layer of chromatophores.
- Eyelid photophores absent. Click on an image to view larger version & data in a new window
Figure. Ventral view of the head of Mg. microlucens, holotype, Equatorial Pacific. Outer chromatophores were lost during capture leaving the scattered photophores visible. Enlargement at right allows photophores to be recognized by the presence of small, oval lenses. Photographs by R. Young.
Figure. Photophores of Mg. microlucens. Left - Anteriolateral view of the head near the eye opening looking at the lenses of the photophores. Right - High magnification of two photophores (one indicated by the arrow) and a few, lighter-red chromatophores that are more superficially located from a damaged region of the side of the head, 160 mm ML, Hawaiian waters.
We identify structures here as photophores on the basis of a dark, pigmented "cup" and a spherical, whitish "lens" and their distribution as a separate layer beneath most chromatophores. No bioluminescence has been observed or attempted to be observed. Mg. microlucens is unique among members of Magnoteuthis in having photophores. If the surface chromatophore layer is intact, the deeper lying photophores can be difficult to recognize even under a microscope. Mastigoteuthis sp. A also differs from Mg. magna in the more elongate shape of the posterior bulb of the funnel locking-apparatus, dentition of the arm suckers and details of the beaks.
Mg. microlucens is most closely related to Mg. magna based on morphological evidence (see the Magnoteuthis page). Molecular data indicate substantial divergence across the three genes examined (see Table below) and confirms that Mg. microlucens is a separate species from Mg. magna. Hebert et al (2003) hypothesized a 2% rate of divergence in the COI locus as a general guideline for identifying distinct species, here the rate of divergence between Mg. microlucens and the morphologically similar Mg. magna was almost 10%. The more morphologically distinct Mastigopsis hjorti had a COI sequence divergence rate 12% with Mg. microlucens, only slightly greater than that of Mg. magna which further emphasizes the surprising result of 10% difference seen with Mg. magna (Young, Lindgren and Vecchione, 2008) (see also the Discussion of Phylogenetic Relationships on the Mastigoteuthidae page).
|Locus||Base pairs||Mg. magna||Mastigopsis. hjorti|
|Mg. microlucens||COI rRNA||658||9.89% ||11.7%|
|Mg. microlucens||16S rRNA||528||3.40% ||6.02%|
|Mg. microlucens||12S rRNA||404||5.13% ||7%|
Figure. Ventral and dorsal views of Mg. microlucens paralarvae, Hawaiian waters. Left - 4.6 mm ML. Right - 7.2 mm ML. Scale bar = 1 mm. Drawings from Young (1991) labeled as Mastigoteuthis inermis.
At 5 mm ML Mg. microlucens paralarvae are separated from similar-sized paralarvae of Echinoteuthis. famelica, the only other common mastigoteuthid in Hawaiian waters, by the broader body shape, larger eyes, more posterior digestive gland and tentacular suckers and chromatophores restricted to the distal end of the tentacle. At 7 mm ML the presence of short fins (1/5 of ML vs 1/3 of ML) distinct anterior and posterior fin lobes (vs somewhat lanceolate fins) and tentacle suckers restricted to the club (vs along full tentacle) also distinguishes Mg. microlucens. At larger sizes, the slender shape, elongate fins and, by at least 17 mm ML, skin tubercules easily distinguish Echinoteuthis famelica. The differences between the two species diminish at sizes below 4.5 mm ML. The position of the digestive gland is useful to at least 3.5 mm ML. The smallest Mg. microlucens paralarva captured had a mantle length of 2.5 mm ML.
We have seen one mature male, 215 mm ML but no mature females.
Type locality: Equatorial Pacific south of Hawaii.
We have captured Mg. microlucens in the region of the Hawaiian Archipelago to about ca. 26°N and south to the equator. This is the most common mastigoteuthid encountered in the region of the high (main) Hawaiian Islands.
The vertical distribution of Mg. microlucens in Hawaiian waters was examined by Young (1978). During the day most captures came from depths of 675-870 m; nighttime captures came from 255 to 725 m with most squid taken between 250 and 450 m.
Figure. Vertical distribution chart of Mg. microlucens. Captures were made with both open and opening/closing trawls. Bar - fishing depth-range of opening/closing trawl. Circle - Modal fishing depth for either trawl. Blue-filled circle - Night capture. Yellow-filled circle - Day capture. Note the breaks in the x-axis. Chart modified from Young (1978, labeled as Mastigoteuthis inermis).
Hebert, P.D., S. Ratnasingham, and J.R. de Waard. 2003. Barcoding animal life: cytochrome c oxidase subunit I divergences among closely related species. Proc. R. Soc. Lond. B., 270: S96-S99
Young, R. E. 1978. Vertical distribution and photosensitive vesicles of pelagic cephalopods from Hawaiian waters. Fish. Bull., 76: 583-615.
Young, R. E. (1991). Chiroteuthid and related paralarvae from Hawaiian waters. Bull. Mar. Sci., 49: 162-185.
Young, R. E., A. Lindgren and M. Vecchione. 2008. Mastigoteuthis microlucens, a new species of the squid family Mastigoteuthidae (Mollusca: Cephalopoda). Proc. Biol. Soc. Wash. 121(2): 276-282.
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- First online 19 November 2007
- Content changed 06 December 2014
Citing this page:
Young, Richard E., Michael Vecchione, and Annie Lindgren. 2014. Magnoteuthis microlucens http://tolweb.org/Magnoteuthis_microlucens/65304/2014.12.06 in The Tree of Life Web Project, http://tolweb.org/. Version 06 December 2014 (under construction).