Vibilia laticaudata, 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 : 69-73

Vibilia laticaudata sp. nov. ( Figs 32 & 33 )

Material examined

Holotype: female 4.8 mm ( SAM A42377). South Indian Ocean , off South Africa, SSE of Kosi Bay [27º16.0’S, 32º59.6’E]; collected by Meiring Naude (stn. SM 11), bongo 150 m, 24 May 1975. Sea surface temperature 23.9ºC.

Paratype: female 5.0 mm ( SAM A42378). Collected with holotype .

Diagnosis

Body length about 5 mm. Antenna 1 as long as head and first pereonite; flagellum oval, distal margin rounded. Gnathopod 2; carpal process about as long as propodus. Pereopods 3 & 4; dactylus length about 0.3x propodus. Pereopods 5 & 6; dactylus length about 0.2x propodus. Pereopod 7; basis maximum width almost 0.7x length, slightly longer than ischium to carpus combined, with relatively small, rounded posterodistal lobe not overlapping ischium; carpus and propodus with small anterodistal process. Lateral corners of last urosomite produced, partly overlapping peduncle of U3. Uropod 3; peduncle subequal in length to rami; endopod marginally longer than exopod; sexual dimorphism of endopod unknown. Telson oval, twice as wide as long, length about 0.7x peduncle of U3.

Description of holotype

Female 4.8 mm. Antenna 1 marginally longer than head and first pereonite; flagellum oval, width about 0.6x length, with rounded anterior margin and two small, elongate terminal articles. Antenna 2 length about 0.7x A1; 5­articulate. Head two­thirds as long as deep, about as long as first two pereonites. Eyes oval. Gnathopod 1; basis as long as ischium to propodus combined; basis, merus and carpus each with one strong seta on posterodistal corner; carpus and propodus subequal in length; propodus with posterior margin toothed for distal two­thirds; dactylus slightly longer than half of propodus. Gnathopod 2; basis as long as remaining articles combined; merus with only two strong setae on distal margin; carpal process as long as propodus; propodus slightly shorter than anterior margin of carpus, with posterior margin toothed for distal half; dactylus half­length propodus. Pereopods 3 & 4; basis about as long as merus and carpus combined; carpus marginally longer than merus; propodus marginally longer than carpus; dactylus length about 0.3x propodus. Pereopod 3 slightly shorter than P4. Pereopods 5 & 6; basis slightly shorter than merus and carpus combined; carpus slightly longer than merus; propodus about onethird longer than carpus, without small teeth on anterior margin; dactylus length 0.2x propodus. Pereopod 5 slightly shorter than P6. Pereopod 7 half­length P6; basis maximum width almost 0.7x length, slightly longer than ischium to carpus combined, with relatively small, rounded posterodistal lobe, not overlapping ischium; carpus and propodus with anterodistal corner produced into small process; propodus slightly longer than carpus; dactylus marginally longer than propodus with rounded distal margin. Last urosomite with lateral corners produced, partly overlapping peduncle of U3. Uropod 1; rami with margins toothed for distal one­third; exopod slightly longer than endopod, length about 0.8x peduncle. Uropod 2; rami with few teeth distally on both margins; exopod marginally longer than endopod, only slightly shorter than peduncle. Uropod 3; exopod with small teeth on inner margin for distal half, outer margin not toothed; endopod with smooth margins; endopod marginally longer than exopod, subequal in length to peduncle. Telson oval, twice as wide as long; length about 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

The species name is derived from the Latin “lati” and “cauda” meaning broad or widetailed.

Remarks

The most unusual feature of this new species is the extremely wide telson, a character not found in any other congener. Vibilia laticaudata belongs to the group of species in which the lateral corners of the last urosomite are produced, partly overlapping the peduncle of uropod 3; viz. V. armata , V. chuni , V. cultripes , V. longipes and V. pyripes . Apart from the telson, it is distinguished from all of the above as follows. From V. armata and V. chuni by the shape antenna 1 and the shorter peduncle of uropod 3 relative to the exopodite, and additionally from V. chuni by the longer carpal process of gnathopod 2 and the form of pereopod 7. From V. pyripes by the general habitus, the longer carpal process of gnathopod 2, the form of pereopod 7 and in not having the peduncle of uropod 3 constricted at the base. From V. cultripes by the more evenly rounded flagellum of antenna 1, the longer carpal process of gnathopod 2, the lack of strong setae on the anterior margin of the carpus of pereopod 6 and the anterodistal process of the carpus and propodus of pereopod 7 is not as pronounced and the dactylus is not knife­shaped. From V. longicarpus by the more evenly rounded flagellum of antenna 1, the relatively shorter dactylus of pereopods 3­6, the rami of uropods 1­3 are not as deeply toothed and the anterodistal process of the carpus and propodus of pereopod 7 is relatively more pronounced.

Vibilia laticaudata resembles V. pyripes in the shape of the flagellum of antenna 1; V. cultripes in the length of the dactylus of pereopods 3­6 and the ornamentation of uropods 1 & 2 and V. longicarpus in the carpal length of gnathopod 2 and the general form of pereopod 7. Despite the extraordinary width of the telson, it is as long as for V. cultripes , slightly less than for V. pyripes and slightly longer than for V. longicarpus , relative to the peduncle of uropod 3.

The presence of elongate terminal articles on antenna 1 and the slightly thickened articles of antenna 2, and pereopod 7, indicate that the holotype and paratype may not be fully mature. However, the species is readily distinguished from all of its congeners by the telson and other characters as detailed above.

Distribution

Only known from the type locality, the South Indian Ocean , off South Africa, SSE of Kosi Bay.

Figures

FIGURE 32. Vibilia laticaudata sp.nov., SW Indian Ocean, SAM A42377. Holotype female, 4.8 mm. Scale bars = 0.5 mm (A), 0.2 mm (A1 & 2, Us), 0.1 mm (Mxp).

FIGURE 33. Vibilia laticaudata sp. nov., SW Indian Ocean, SAM A42377. Holotype female, 4.8 mm. Scale bar = 0.2 mm.