Vibilia thurstoni, Zeidler, 2003

Zeidler, Wolfgang, 2003, A review of the hyperiidean amphipod superfamily Vibilioidea Bowman and Gruner, 1973 (Crustacea: Amphipoda: Hyperiidea), Zootaxa 280 (1), pp. 1-104 : 65-69

Vibilia thurstoni sp. nov. ( Figs 30 & 31 )

Material examined

Holotype: female, 5.1 mm ( SAM A42379 ). South Indian Ocean , off South Africa, SSE of Kosi Bay [27º23.0’S, 33º02.9’E]; collected by Meiring Naude (stn. SM 70D), bongo 200 m, 20 May 1976. Sea surface temperature 25ºC.

Paratype: ovigerous female, 4.8 mm ( SAM A42380 ). South Indian Ocean , off South Africa, S of Kosi Bay [27º37.7’S, 32º47.8’E]; collected by Meiring Naude (stn. SM 76D), bongo 200 m, 21 May 1976. Sea surface temperature 25ºC .

Diagnosis

Body length about 5 mm. Antenna 1 as long as head and first pereonite; flagellum with parallel margins, obliquely truncate ventrally for distal half. Gnathopod 2; carpal process about 0.6x length propodus. Pereopods 3 & 4; dactylus length about 0.6x propodus. Pereopods 5 & 6; dactylus length about half propodus. Pereopod 7; basis maximum width about two­thirds length, as long as ischium to mid­propodus combined, with small rounded posterodistal lobe partly overlapping ischium and proximal half of merus. Lateral corners of last urosomite not produced. Uropod 3; peduncle about one­third longer than rami; endopod marginally longer than exopod; sexual dimorphism of endopod unknown. Telson triangular, as wide as long, length almost 0.7x peduncle of U3.

Description of holotype

Female 5.1 mm. Antenna 1 as long as head and first pereonite; flagellum with parallel margins, obliquely truncate ventrally for distal half, width slightly more than 0.5x length. Antenna 2 length about 0.8x A1; 6­articulate. Head as long as deep, about as long as first 2.5 pereonites. Eyes oval. Gnathopod 1; basis almost as long as ishium to propodus combined; basis, merus and carpus with one strong seta on posterodistal corner, ischium with two strong setae; carpus slightly shorter than propodus; propodus with posterior margin toothed for distal two­thirds; dactylus slightly shorter than half of propodus. Gnathopod 2; basis slightly shorter than remaining articles combined; merus with four strong setae on distal margin; carpal process about 0.6x length propodus; propodus slightly shorter than anterior margin of carpus, with posterior margin toothed for most of its length; dactylus length 0.4x propodus. Pereopods 3 & 4; basis about as long as merus and carpus combined; carpus subequal in length to propodus; merus length about 0.75x propodus; dactylus length about 0.6x propodus for P3, slightly longer for P4. Pereopod 3 slightly shorter than P4. Pereopod 5; basis as long as merus and half of carpus combined; carpus slightly shorter than merus; propodus as long as basis, with toothed anterior margin; dactylus length 0.4x propodus. Pereopod 6 like P5 but marginally longer, with basis only slightly shorter than merus and carpus combined; carpus with three strong setae on anterior margin and toothed for distal half; propodus length only three­quarters basis and dactylus length 0.5x propodus. Pereopod 7 length about 0.6x P6; basis maximum width almost 0.7x length, as long as ischium to mid­propodus combined, with small rounded posterodistal lobe partly overlapping ischium and proximal half of merus; merus with one strong seta near anterodistal and posterodistal corner; propodus length 1.3x carpus; dactylus length two­thirds propodus, with rounded distal margin. Uropod 1; peduncle with outer margin toothed for distal half; rami subequal in length, about 0.7x peduncle; exopod deeply toothed on both margins; endopod deeply toothed on outer margin and for distal half of inner margin. Uropod 2; peduncle slightly longer than rami; exopod marginally shorter than endopod, inner margin deeply toothed, outer margin toothed for distal half; endopod deeply toothed on inner margin and only distally on outer margin. Uropod 3; rami with small teeth on both margins; endopod marginally longer than exopod, about three­quarters as long as peduncle. Telson triangular, about as wide as long, length almost 0.7x peduncle of U3 but only reaching it midway.

Variation The paratype is like the holotype. The male of this species is unknown.

Etymology

This new species is named for Dr M.H. Thurston, formerly of the Southampton Oceanography Centre, in recognition of his contribution to the knowledge of hyperiideans and for his generosity in assisting me with my studies .

Remarks

This new species is most similar to V. viatrix but also resembles V. antarctica . It resembles both species in the shape of A1, P7 and the telson but is more like V. viatrix in having long dactyls on P3–6 and in having U1 & 2 with deeply toothed rami. Vibilia thurstoni differs from both V. antarctica and V. viatrix as follows; G1 & 2 are not as heavily armed with strong setae; the carpal process of G2 is much shorter, only 0.6x length of propodus; the dactyls of P5 & 6 are relatively longer; the anterior margin of the carpus of P6 is not as heavily armed with robust setae; the basis of P7 is not as broad and the carpus is slightly longer than the merus, and the peduncle of U3 is relatively wider. In addition, V. thurstoni differs from V. viatrix in that the posterodistal corner of the propodus of G2 is not produced and the articles of P3 & 4 are relatively more slender and the dactlys relatively shorter, and from V. antarctica in that the dactyls of P3 & 4 are considerably longer and the rami of U1 & 2 are more deeply toothed.

It is likely that this species has been confused with V. viatrix in the past but is readily distinguished by the form of G1 & 2 and the relative lengths of the dactyls of P3–6 as detailed above. Vibilia thurstoni also seems to be a smaller species than V. viatrix or V. antarctica because the paratype is ovigerous at 4.8 mm.

Distribution

Only known from two localities, from the South Indian Ocean, off South Africa, SSE and S of Kosi Bay.

Figures

FIGURE 30. Vibilia thurstoni sp. nov., SW Indian Ocean, SAM A42379. Holotype female, 5.1 mm. A, lateral view. Scale bars = 0.5 mm (A), 0.2 mm (remainder).

FIGURE 31. Vibilia thurstoni sp. nov., SW Indian Ocean, SAM A42379. Holotype female, 5.1 mm. Scale bar = 0.2 mm.