Lanceola galatheae, Zeidler, 2009

Zeidler, Wolfgang, 2009, A review of the hyperiidean amphipod superfamily Lanceoloidea Bowman & Gruner, 1973 (Crustacea: Amphipoda: Hyperiidea), Zootaxa 2000, pp. 1-117 : 54-59

Lanceola galatheae sp. nov.

( Figs 19 & 20)

Material examined. Holotype. Male, 17.6 mm ( ZMUC CRU-9928); North Indian Ocean, north-west of Cocos-Keeling Islands [09°02’N 93°07’E]; Galathea Stn. 318, 2800 mw, 5 May 1951.

Description of holotype. Male, 17.6 mm. Pereon relatively slender; length 1.6x pleon; pereonites 5–7 with slight lateral ridge just above coxae. Pleon much deeper than pereon with distinct mid-lateral ridge;

pleonite 1 with slight dorsal denticle. Head with short broad, rounded rostrum. Eyes relatively large, composed of paired crystalline cones. Antennae 1 (right missing) as long as head and first 1.5 pereonites combined; callynophore lanceolate with numerous well-developed aesthetascts; terminal article obliquely rounded, slightly longer than preceding two articles combined. Antennae 2 length twice A1, as long as head and first 3.5 pereonites combined; fourth peduncular article with short rounded lobe overlapping following article medially. Gnathopod 1 relatively slender; basis about as long as ischium-propodus combined; carpus with broad distal margin, anterodistal and posterodistal corner projected away from propodus, proximal margin of propodus occupies 0.6x width of distal margin of carpus; dactylus length about half propodus. Gnathopod 2 relatively slender; basis slightly longer than ischium-propodus combined; dactylus length almost 0.4x propodus. Pereopod 3 similar to, but marginally shorter than, P4; basis length 1.7x merus; carpus marginally shorter than merus; propodus slightly shorter than carpus (equal in length in P4); dactylus length almost 0.3x propodus. Pereopods 5–7 with retractile and hooded dactyls; spoon-shaped formation of propodus “forked” with relatively deep groove, for relatively straight dactylus, ending in sharp process either side of groove. Pereopod 5; length 1.2x P4; basis length 1.6x merus; carpus subequal in length to merus; propodus length 1.2x carpus; dactylus relatively straight, length slightly more than 0.2x propodus. Pereopod 6 almost as long as pereon and pleon combined, about 1.3x length P5; basis slightly longer than merus; merus with distinctive bulge midway along anterior margin; carpus slightly longer than merus but slightly shorter than basis; propodus length 1.5x carpus; dactylus relatively straight, length slightly more than 0.1x propodus. Pereopod 7; length 0.6x P6; basis length twice merus; carpus subequal in length to merus; propodus length 1.4x carpus; dactylus fully hooded, slightly curved, length about 0.3x propodus. Peduncles and rami of uropoda not especially broad. Peduncle of U1 just reaches limit of peduncle of U3. Telson pointed, slightly exceeding limit of peduncle of U3.

Colour of living specimen not known.

Etymology. This species is named for the Danish research vessel Galathea which caught the specimen during its global circumnavigation in 1950–52.

Remarks. Although only known from the unique type, the characters distinguishing this species are well defined and, in combination, unlike any other congener. The structure of the eyes, composed of crystalline cones, places this species with L. sayana , L. felina and L. intermedia . It is readily distinguished from L. felina by the longer telson and from L. sayana by the lack of a hook-shaped rostrum and in not having the terminal articles of the first antennae fused. From L. intermedia , it is distinguished by a combination of characters; the overall habitus; the short, more delicate rostrum; the more slender and relative lengths of pereopods 5–7; the different structure of the dactyls and spoon-shaped process of pereopods 5–7; the anterior bulge of the merus of pereopod 6; the pointed telson and the significantly shorter process of the fourth peduncular article of the second antennae.

A distinctive character of this species is the structure of the dactylus and associated spoon-shaped formation of pereopods 5–7. In most species of Lanceola the spoon-shaped processes, if present are rounded, with a slit for the fully retractile dactylus, which is usually strongly curved. In L. galatheae this process is less bulbous, ending in two sharp points with a groove in-between to accommodate a relatively longer and straighter dactylus. Amongst the Lanceola , this character is only approximated by L. longidactyla but is less prominent than in L. galatheae .

Other distinctive characters of L. galatheae are the distally wide margin of the carpus of the first gnathopoda, with sharp corners and the slight anterior bulge of the merus of pereopod 6. The former character is similar to that found in L. serrata but is not as wide relative to the proximal margin of the propodus. Also, in most species of Lanceola , and even in L. serrata to a lesser extent, the anterodistal and posterodistal corners of the carpus of the first gnathopoda are rounded. The latter character has not been seen in any other species of Lanceola and may be a deformity of the present specimen.

The type has well-developed, delicate gills; the callynophore of the first antennae is furnished with a dense brush of aesthetascts and the genital papillae are well developed, all indicating that this is most likely a sexually mature specimen.

Distribution. Only known from the unique type from the north-western part of the Indian Ocean as detailed above. The eye structure indicates that it probably inhabits surface waters.