Tryphana Boeck 1871

Genus Tryphana Boeck, 1871

(Figs 28–30)

Tryphana Boeck, 1871: 9.— Gerstaecker 1886: 483.— Bovallius 1887b: 572 –573.— Stebbing 1888: 1538.— Sars 1890: 16.— Schellenberg 1927: 648 (key), 653–654.— Pirlot 1929: 135.— Hurley 1955: 180 (incl. key).— Bowman & Gruner 1973: 46 (key), 48.— Vinogradov et al. 1982: 393.— Shih & Chen 1995: 170 (key), 187.— Vinogradov 1999: 1204.

Type species. Tryphana malmi Boeck, 1871 by monotypy. Type material could not be found at the NRS, ZMUC or in any major Norwegian Museum (Vader pers. comm.) and is considered lost. Although the description of Boeck (1871) is limited, he later (Boeck 1872) provides some illustrations which readily characterise this genus. The type locality is the north-east Atlantic, Hardangerfjord, coast of Norway.

Diagnosis. Body shape robust or globular. Head round, with slight beak. Eyes occupying most of head surface; grouped in one field on each side of head. Antennae 1 of males with 2-articulate peduncle; flagellum with enlarged, globular callynophore, with aesthetascs arranged in one-field brush medially; with two articles terminally; subterminal article very elongate, inserted on antero-dorsal corner of callynophore; terminal article, small, inserted mid-way anteriorly on sub-terminal article. Antennae 1 of females with 2-articulate peduncle; callynophore, with one smaller article inserted terminally. Antennae 2 of males 5-articulate; strongly zig-zagged, with most articles folded back on each other; positioned obliquely and dorsally into head; basal article distinctly inflated, about half or less the length of following article; articles 2 & 3 sub-equal in length; article 4 more slender and slightly longer than previous one; terminal article very slender, whip-like, slightly longer than any other. Antennae 2 of females 2- articulate. Mandibular palp present in both sexes; 2-articulate in females; 3-articulate in males. Mandibular incisor relatively broad, with several teeth, with relatively large distal lobe medially (? only on left); in male orientated more or less parallel to palp. Maxillae 1 consisting of elongate, quadrate plates. Maxillae 2 consisting of elongate plates, rounded terminally, with rounded medial bulge. Maxilliped with inner lobes incompletely fused, separated for terminal half; medial margin of outer lobes with fringe of setae or membranous fringe. Gnathopoda simple. Gnathopod 1 with very broad basis, with bulging anterior margin; propodus with postero-distal corner produced into tooth-like process. Gnathopod 2 with relatively broad, quadrate basis; dactylus abnormal, relatively elongate, with rounded antero-distal knob, armed with numerous setae. Pereopods 3–6 with robust articles; dactylus closing against produced distal margin of propodus, forming poorly developed sub-chela. Pereopods 3 & 4 sub-equal in length to pereopods 5 & 6. Pereopod 5; basis broader distally, almost twice as wide as merus, non-locking but may overlap with P6; articles 3–7 inserted terminally to basis. Pereopod 6; basis marginally broader proximally, slightly more than twice as wide as merus, does not overlap, or lock, with opposing pereopod; articles 3–7 inserted terminally to basis. Pereopod 7 reduced in size with large basis; all articles present; dactylus normal. Uropoda all with articulated exopoda and endopoda, all lanceolate, usually with serrated margins.

Species. Tryphana malmi Boeck, 1871.

Sexual dimorphism. The sexes are very similar in gross morphology, differing mainly in the morphology of the mandibles and antennae. Males tend to have a slightly pointed head, which is also slightly narrowed anteriorly. Remarks. This is a very distinctive genus, as noted above, and is currently considered to be monotypic.

Very little is known regarding its biology. Laval (1980) recorded it from the siphonophore Ceratocymba sagittata and Gasca et al. (2006) from the medusae Mitrocoma cellularia and Solmissus incisa. Gasca et al. (2014) also record it from Solmissus incisa and in addition, on the hydomedusa Eutonina indicans and the siphonophores Resomia ornicephala and Physophora hydrostatica.

Tryphana malmi is an uncommon but widely distributed species, known mainly from records from temperate regions (Dick 1970). It seems to be epipelagic in habit (Thurston 1976).