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Description

Graneledone macrotyla, new species
Figures 3a–g

 

 

Material studied: Holotype, a female, mantle length 34.5 mm, EL­TANIN Sta. 1592, 54°43'S, 55°30'W in 1647-2044 m with 10-foot Blake trawl, March 14, 1966. USNM 729678.

 

Description: Only a single specimen of this species was found in the collections. It is, however, so different from any known species of Graneledone that I do not hesitate to describe it as new.

 

The mantle wall is thick and muscular with some semigelatinous ma­terial forming an outer layer. The mantle is large, round, but somewhat dorsoventrally flattened, and is very wide. There is no noticeable con­striction between the mantle and the head ( Fig. 3a, b ).

 

The mantle aperture is small and the funnel-mantle locking apparatus is weakly developed. The funnel is stout and tubular but it is united to the ventral surface of the head for most of its length. The funnel is VV-shaped and stout with broad lateral limbs slightly stouter than the median limbs (Fig. 3c).

 

The head is broad with medium sized eyes which do not project. There is a slight constriction between the head and the bases of the arms.

 

The brachial crown is well developed. The arms are moderately long, stout, and taper gradually to slender points. The arm formula is 2.3.1.4. The suckers are small and crowded together but arranged regularly in a single row.

 

The web is moderately deep. The web formula is C.D.B=A.E. The web extends as a broad membrane up the ventral side of each arm nearly to the tip.

 

The mantle had been opened in search of mesozoan parasites and some of the internal organs were damaged. The gills are small, about equally developed in each demibranch, with 7 lamellae, including the terminal ones, on the outer demibranch.

 

The digestive tract was dissected ( Fig. 3d). The beaks offer no par­ticular differences but are well developed (Fig. 3e). The radula con­sists of a rachidian with asymmetrically arranged cusps as shown in the figure (Fig. 3f). The admedian is small and somewhat bicuspid with the outer cusp more pronounced. The second lateral has a broad inner cusp with a short base. The third lateral is short, stout, and broad. The marginal plates are roughly triangular and rugose, the ridges or plications extending longitudinally of the plate.

 

 

TABLE 5. Measurements (in mm) and indices of the female holotype of Graneledone microtyla, new species.

                                                                                                                               
 

Mantle length

 
 

34.5

 
 

 
 

 
 

Mantle width

 
 

38.0

 
 

MWI

 
 

110.0

 
 

Head width

 
 

36.0

 
 

HWI

 
 

104.0

 
 

Arm length

 
 

I

 
 

81.0

 
 

ALI

 
 

70.0

 
 

 
 

II

 
 

87.0

 
 

MAI

 
 

39.7

 
 

 
 

III

 
 

83.0

 
 

 
 

 
 

 
 

IV

 
 

80.0

 
 

 
 

 
 

Sucker diameter

 
 

2.5

 
 

S1n

 
 

7.2

 
 

Arm width

 
 

7.5

 
 

AWI

 
 

21.7

 
 

Length of gills

 
 

8.0

 
 

 
 

 
 

Gills

 
 

7

 
 

 
 

 
 

Total length

 
 

124.0

 
 

 
 

 
 

Web depth

 
 

A

 
 

24.0

 
 

WDI

 
 

32.2

 
 

 
 

B

 
 

24.0

 
 

 
 

 
 

 
 

C

 
 

28.0

 
 

 
 

 
 

 
 

D

 
 

25.5

 
 

 
 

 
 

 
 

E

 
 

20.0

 
 

 
 

 
 

Arm formula

 
 

2.3.1.4

 
 

 
 

 
 

Web formula

 
 

CDB=AE

 
 

 
 

 
 

 

The anterior salivary glands are small; the posterior salivary glands are triangular and small. The esophagus is stout and along much of its length is slightly dilated forming an indistinct crop of the type shown by Robson (1932, Fig. 30b) for Bathypolypus and which in fact is not a crop. This dilated portion of the esophagus leads into a strongly dif­ferentiated two-parted stomach and a distinct large, spiral caecum. The intestine is large, slightly dilated, and bent almost double upon itself. The anal pore is round, without the usual anterior and posterior folds or lateral flaps. There is no trace of an ink sac.

 

The crop and stomach were opened but contained little food remains. None was identifiable.

 

The genitalia unfortunately were removed at the time of capture while searching for mesozoans.

 

The sculpture is distinctive (Fig. 3a, b, g). There is a low, thin, pe­ripheral keel or raised line around the mantle. Above the keel the sur­face is covered with well separated, distinct rugosities consisting of simple, sharp, cartilaginous tubercles, slightly larger groups of simple tubercles, and large areas 3-7 mm in diameter consisting of a pale raised area with small, simple tubercles surrounding an erect, central, sharp spine. There is a row of tuberculous papillae around each eye and a gigantic tuberculate cirrus about 10 mm in diameter above each eye. A color photograph of the living animal taken aboard the ship shows the two cirri erected to a height of about 15 mm. The tuberculations extend onto the web and bases of the arms nearly to the level of the web mar­gin. There are no tubercles on arms III and IV nor on the ventral sur­face of the head and mantle.

 

The color is a brownish red with deeper purple in the area of the brachial crown. The raised pale areas are creamy brown.

 

Holotype: U.S. National Museum of Natural History 729678.

 

Type-locality: Near the Falkland Islands, Eltanin Sta. 1592, 54°43'S, 55°30'W in 1647-2044 m.

 

Discussion: G. macrotyla resembles no other member of the genus in its superficial appearance. The few tubercles varying in size from minute to extraordinarily large ones, with a single enormous tubercle over each eye, immediately separates this species from all others in the genus. The radula is even more octopodan in general shape than that of G. challengeri which it most closely resembles in this feature.

 

The name macrotyla is derived from the Greek meaning large knobs and refers to the large tuberculations characteristic of the species.”

 

(Voss, 1976: 454-457)

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Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© National Museum of Natural History, Smithsonian Institution

Source: Antarctic Invertebrates Website (NMNH)

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