Primno Guérin­Méneville, 1836

Zeidler, Wolfgang, 2004, A review of the families and genera of the hyperiidean amphipod superfamily Phronimoidea Bowman & Gruner, 1973 (Crustacea: Amphipoda: Hyperiidea), Zootaxa 567, pp. 1-66 : 20-22

Genus Primno Guérin­Méneville, 1836

Primno Guérin­Méneville, 1836b: 2 .

Euprimno Bovallius, 1889: 397 .

Type species

Primno macropa Guérin­Méneville, 1836 by monotypy. The holotype is in the ANSP ( CA 2685 ), in the Guérin­Méneville collection (No. 435): once alcohol preserved, now dry (see Zeidler 1997).

Diagnosis

Body length up to 21 mm, but usually about 10 mm. Head, quadrate with small rostrum. Pereonites 1 & 2 separate. Pereopods 3, 4 & 6 simple, with some teeth on margin of carpus and sometimes also merus. Pereopod 5 prehensile, entire anterior margin of carpus dentate, with several long teeth separated by groups of short teeth; propodus shorter than carpus; dactylus appears to be extension of propodus with limited articulation. Pereopod 7 with all articles present, but basis longer than remaining articles combined; dactylus digitiform, with ring of spinules at apex in female. Gills without folds.

Six species.

Remarks

Bowman (1978) revised this genus and recognised four species previously lumped as P. macropa . Additional species have been described subsequently by Bowman (1985) and Sheader (1986).

Species of Primno are often found in abundance in near­surface waters (e.g. Stephensen 1924, Yoo 1971, Thurston 1976, Tranter 1977, Young & Anderson 1987, Vinogradov 1991).

Their association with gelatinous hosts remains to be established, and may be limited to juvenile stages. The adults are active swimmers, and larval development is more direct than in other hyperiideans, resulting in the release of active juveniles from the marsupium of females. Bowman (1978) suggests that the modified dactylus of pereopod 7 of females may be used to transfer juveniles from the marsupium to a gelatinous host, as has been observed in Vibilia ( Laval 1963) . The only record of an association with gelatinous plankton is that of Daniel (1973), who found “ Euprimno macropus ” within the posterior nectophores of the siphonophores Abylopsis tetragona and Sulculeolaria chuni . This record however, may not represent a true association as the position of the hyperiidean does not rule out the possibility of a passive introduction during sampling ( Laval 1980).

Bowman (1978) provides a summary of biological information on Primno and Yoo (1972), Ikeda (1995) and Sheader and Batten (1995) provide additional information.

Key to the species of the genus Primno

1. Pereopod 5; longer teeth on anterior margin of carpus nearly as long as width of carpus ....................................................................................................................................... 2

­ Pereopod 5; length of longer teeth on anterior margin of carpus about 0.3–0.5 x width of carpus ........................................................................................................................ 5

2. Pereopod 5; row of teeth on anterior margin of carpus with short tooth proximally .... 3

­ Pereopod 5; row of teeth on anterior margin of carpus with one of the longer teeth proximally .................................................................................................................... 4

3. Distribution restricted to southern hemisphere; subantarctic province. Rostrum conforming to contour of head, about 0.4x width of head .................................................... ............................................................................... P. macropa Guérin­Méneville, 1836

­ Distribution restricted to North Pacific; subarctic province. Rostrum truncate, limited to space between first antennae P. abyssalis (Bowman, 1968)

4. Pereopod 7; basis length about 1.2 x length of remaining articles combined................. .............................................................................................. P. johnsoni Bowman, 1978

­ Pereopod 7; basis length more than 1.5x length of remaining articles combined .......... .............................................................................................. P. latreillei Stebbing, 1888

5. Pereopod 5; length of longer teeth on anterior margin on carpus about 0.3x width of carpus. Pleon subequal in length to pereon ........................ P. brevidens Bowman, 1978

­ Pereopod 5; length of longer teeth on anterior margin of carpus about 0.5x width of carpus. Pleon length about 1.4x length of pereon .................... P. evansi Sheader, 1986