Boreonymphon ossiansarsi Knaben in Just, 1972,

Phylum:Arthropoda Siebold, 1848
Class:Pycnogonida Latreille, 1810
Order:Pantopoda Gerstaecker, 1863
Family:Nymphonidae Wilson, 1878
Genus:Boreonymphon Sars, 1888

Hltpe (selected by Knaben) : male of 17 mm with young of 3 to 6 mm. Michael Sars St. 13, 1900, 66°42'N, 16°40'W, 590 m, 0.11°C. Zoological Museum, University of Bergen (Cat. No. 26 630).

Body: slender, width of body equalling length of first two body segments together; lateral processes not touching each other. Ocular segment as long as the last three segments together. All bristles on the body very short; bristles present along dorsal hind edges and dorso-medially on all segments and along the front edge of ocular segment. Segment 4 with a weak node bearing a few bristles in front of the abdomen. Lateral processes with small bristles on the dorsal surface, especially in distal third.
Abdomen : straight, with parallel sides in dorsal view. In lateral view ventral side straight, dorsal side bulging in distal third before tapering towards apex.

Eye tubercle: very low.

Proboscis: generally strongly conical, but bulging in the middle. As long as ocular segment. Naked. Width at base 11/2 times the width of scapus base.
Ghelifores: scapi parallel; club-shaped in dorsal view, with a broad base followed immediately by a strong constriction. Distal 4/5 widening evenly towards the apex. Space between scapi at constriction level as broad as scapus base. Scapi evenly but not densely covered with small bristles. Chelae strong and coarse. Movable finger as long as palm, abruptly and strongly curving in the middle. Fixed finger of same strength as movable, but far less curved. Tip of movable finger hits fixed finger proximal to the tip of the latter. Movable finger bears a long cluster of small bristles ventrally on proximal half. Palm much inflated, unevenly covered with small bristles.

Palps: when stretched out the third joint of the palp does not quite reach apex of proboscis. Ratio between joints 2 and 3 is 3:2. Joints 4 and 5 of equal length, and together as long as joint 3. Joints 2-4 unevenly covered with small bristles. Fifth joint more evenly covered, but proximal third naked.

vigers: ratio between joints 4 and 5 is 3:5. Joint 4 strongly club-shaped and with scattered bristles. Joint 5 curved, very slender, and densely covered with bent, generally backward-pointing bristles. Joint 61/3 the length of 5, with scattered bristles as in joint 4.

Legs: all legs have femur and 1st tibia of equal length and 2nd tibia about 1/6 longer. Femur distally widening. Ratio between femur and the three coxae together is 5:3. Second tibia three times as long as tarsus and propodus together (slightly less in first leg). Ratio between tarsus and propodus is 5:6 (Fig. 7A). Claws 1/4-1/2 the length of propodus. Auxiliary claws present but minute. Legs covered by small bristles, the density of which increases distally. Tarsus and propodus have naked sides, but the naked band is very narrow in the tarsus, especially of the first leg.

Variations

Shape: the eye tubercle may be almost indistinguishable.

Others: in some specimens the auxiliary claws are absent in one or more legs.

Females: generally as males, but joint 5 of the oviger is subequal to or slightly longer than joint 4 and armed with short, straight bristles only.

Literature

  • Just J. (1972). Revision of the genus Boreonymphon G.O. Sars (Pycnogonida) with a description of two new species, B. Ossiansarsi Knaben and B. compactum Just. Sarsia, 49, 1-28.

Author: Zakharov Denis V. / 22.02.2017
Last edit: Zakharov Denis V. / 14.03.2017

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