Vibilia elongata, SHIH & HENDRYCKS, 2003

SHIH, CHANG-TAI & HENDRYCKS, ED A., 2003, A new species and new records of the genus Vibilia Milne Edwards, 1830 (Amphipoda: Hyperiidea: Vibiliidae) occurring in the eastern Pacific Ocean, Journal of Natural History 37 (3), pp. 253-296 : 288-293

Vibilia elongata sp. nov.

( figures 16 , 17 )

Materials examined. See table 3.

Types. Holotype, female, 2.9 mm, body and slide mount of appendages, IPHC station 930–293C, 12 April 1930, 53°52∞N, 158°29∞W, 900– 700 m, USNM 310354 . Paratypes: 2 females, 2.6 mm, 2.7 mm, IPHC station 930-122B, 13 February 1929, 59°26∞N, 143°41∞W, 525– 400 m, USNM 310355 ; female, 2.7 mm, IPHC station 930-124B, 14 February 1929, 59°20∞N, 142°09∞W, 600– 400 m, USNM 310356 ; female, 2.9 mm, IPHC station 930-293B, 12 April 1930, 53°52∞N, 158°29∞W, 600– 400 m, USNM 310357 ; female, 2.9 mm, body and slide mount of appendages, IPHC station 930-297C, 13 April 1930, 52°00∞N, 155°23∞W, 900– 700 m, USNM 310358 ; female, 2.4 mm, body and slide mount of appendages, IPHC station 930-289B, 11 April 1930, 55°10∞N, 156°03∞W, 600– 400 m, CMNC 2001–0017 ; female, 2.8 mm, IPHC station 930-290B, 11 April 1930, 54°54∞N, 157°01∞W, 600– 400 m, CMNC 2001–0018 ; female, 2.8 mm, IPHC station 930-294B, 12 April 1930, 53°25∞N, 157°42∞W, 600– 400 m, CMNC 2001–0019 .

Description of female (holotype, 2.9 mm). Head length three-quarters height, equal to combined length of pereonites 1–2 plus one-half of pereonite 3; nearly rectangular when viewed laterally. Rostrum straight, slender, nearly one-third as long as remainder of head. Eyes small, oval with few ocelli, arranged in three rows. Antenna 1 very long, equal to combined length of head, pereonites 1–3, plus two- thirds of pereonite 4; flagellum length 3.7 times peduncle and five times height. Antenna 2 minute, three-articulate, slightly shorter than peduncle of antenna 1. Mandible with left lacinia mobilis nearly as wide as incisor, bearing eight teeth on distal margin; right lacinia mobilis bent obliquely, about two-thirds as wide as incisor, with fine denticles on distal margin, incisor with eight teeth on distal margin; accessory spine row with about four short spinules; palp long, about twice length of mandible body, third segment narrowing distally to a sharp point, longer than second and first combined, with a single row of fine setae; molar small, columnar, triturative. Upper lip bilobed, slightly asymmetric. Lower lip outer lobes rounded and tilted. Maxilla 1, outer plate with six spine teeth distally; palp strongly exceeding outer plate, distally tapering with a single seta and many setules on distal half. Maxilla 2 lobes fused, with distal end round and setose. Maxilliped fused inner lobes short, about 0.25 as long as outer lobes; outer lobe 2.5 times as long as wide, inner margin straight, very finely serrated with about four teeth, outer margin rounded, smooth with three fine setae.

Pereon 1.5 times as long as pleon, height increasing posteriorly, pereonite 7 about 1.4 times as high as pereonite 1. Coxae increasing in length from pereonite 1 to 6 and significantly decreased in 7; ventral margin of coxae 5 and 6 with a notch in mid-length, very deep in coxa 6. Pereopod 1, anterior margin of basis convex in the middle, propus slender, length 2.4 times width, simple, anterior margin lacking setae, posterior margin almost smooth and distal margin as wide as dactyl. Pereopod 2 chelate, carpal process reaching to distal margin of propus, with about four or five weak teeth on anterior margin; propus slender, length 2.2 times width, posterior margin with two fine teeth and three setules distally. Pereopods 3 and 4, dactyls longer than one-half of propus. Pereopod 4, coxa with a slight posterodistal lobe and posterior margin with a shallow emargination. Pereopod 5 about 1.4 times as long as pereopod 3, basis 1.2 times as long as ischium and merus combined, propus 0.8 times as long as merus and carpus combined and 0.8 times as long as basis. Pereopod 6 carpus, anterior margin lacking spines. Pereopod 7 with complete seg- mentation, basis 0.6 times as long as ischium to dactyl combined, anterior margin slightly concave, posterior margin rounded, posterodistal lobe short, not exceeding ischium; merus with a produced anterodistal corner; carpus and propus not produced at anterodistal corner; dactyl sharply pointed distally, lacking scales. Pereopods 2–5 with oostegites.

Pleon 2.5 times as long as urosome, pleonites 1–3 subequal in length. Posterodistal corner of pleonites 1 and 2 roundly angular; pleonite 3 with angular posterodistal corner, ventral margin concave distally.

Urosomites 2 and 3 fused, laterodistal corners not produced. Uropod 1 protopod 0.7 times as long as exopod, with three large teeth on both margins of endopod; exopod, inner margin with one tooth, outer margin with six large teeth. Uropod 3 protopod length 1.5 times exopod and 3.4 times width; inner margin of exopod and outer margin of endopod very finely serrated. Telson separate from double urosomite, broadly triangular, rounded distally, as broad as long.

Male is unknown.

Size. Female: 2.40–2.90 mm.

Distribution. Pacific Ocean: eastern North Pacific from 4°– 59°N.

Etymology. The species name is from the Latin elongatus (prolonged) referring to the elongate antenna 1, pereopods and uropods.

Remarks. Vibilia elongata is unique in its slender appendages. Morphologically it appears close to V. affinis and V. caeca in possessing elongate and slender antenna 1 and slender body. It can be easily differentiated from V. affinis by the following characters: eyes with few ocelli arranged in three rows (versus well-compact ocelli), pereopods 5 and 6 relatively longer than pereon (versus shorter than pereon), uropod 3 extending posteriorly beyond the distal end of uropod 2 (versus not reaching the distal end of uropod 2) and uropods 1 and 2 with exopods and endopods longer than respective protopod (versus shorter than respective protopod). There have been very few records of V. affinis since its first description by Bate (1862). Bovallius (1887a, 1887b), Behning (1913) and Vinogradov et al. (1982, 1996) simply repeated Bate’s record. Irie (1958, 1959), without any remarks on the morphology, included it in his list of hyperiid amphipods found in the North Pacific, in the Tsushima Current and seas adjacent to Japan. Bovallius (1887b), Behning (1913) and Vinogradov et al. (1982, 1996) provided a description based on Bate (1862); Vinogradov et al. (1982, 1996) and Bovallius (1887b) reproduced Bate’s original illustration in their publications. Bate’s original description and illustration are totally inadequate for species recognition. The true identity of Irie’s (1958) records is therefore questionable. We attempted to borrow Bate’s type of V. affinis , but were told that it was lost. In view of the differences stated above, we strongly believe that V. elongata is significantly different from V. affinis and that, without doubt, they cannot be regarded as the same species.

Although overlapping in their distribution, V. elongata can be easily separated from V. caeca by the following characters; eye present with three rows of ocelli (versus eye absent), pereopods 2 and 3 propus slender, posterior margin nearly smooth (versus subrectangular and stout, posterior margin with serrations), pereopod 7 merus with strongly produced anterodistal corner (versus without produced anterodistal corner), uropod 1 protopod shorter than outer ramus (versus longer than protopod), uropod 1 outer ramus with one tooth near distal end of inner margin (versus with six teeth on inner margin) and telson is broadly triangular (versus sharply triangular).

Like V. elongata , V. australis also has an elongate antenna 1 and eyes composed of three rows of ocelli. However, they are very different in the general appearance and particularly in the shape of the pereopod 1 basis, the spination of pereopods 1 and 2 propus, pereopod 2 carpus, pereopod 7, uropod 1 spination and telson shape (compare figures 3 and 4 with figures 16 and 17 ). Vibilia australis is widely distributed in all oceans.

Among species of Vibilia , V. elongata is one of the smallest, reaching a known maximum size of 2.9 mm. Only V. wolterecki is in this size range, with specimens in our study reaching 3.04 mm.

Key to the species of the genus Vibilia Milne Edwards, 1830

( V. peroni is not included in the key because the original publication hardly had any description of the species.) 1 Pereopod 7 with four segments, the distal segment vestigial. Eyes without ocelli...

................. V. alberti ( Chevreux, 1905) – Pereopod 7 with six segments (basis to dactyl). Eyes with ocelli or eyes absent.. 2

2 Laterodistal corners of last urosomite produced.......... 3 – Laterodistal corners of last urosomite not produced......... 8

3 Pereopod 2 simple, carpal process absent...... V. bovallii Bonnier, 1896 – Pereopod 2 chelate or subchelate, carpal process present........ 4

4 Pereopod 7 with carpus and propus produced at anterodistal corner......

................. V. cultripes Vosseler, 1901 – Pereopod 7 with carpus and propus not produced at anterodistal corner.... 5

5 Pereopod 7 with basis longer than ischium to dactyl combined.......

.............. V. chuni Behning and Westwood, 1912 – Pereopod 7 with basis shorter than ischium to dactyl combined...... 6

6 Antenna 1 flagellum length more than twice height. Pereopod 2 chelate, with carpal

process reaching distal margin of propus..... V. armata Bovallius, 1887 – Antenna 1 flagellum length less than twice height. Pereopod 2 chelate or subchelate. 7

7 Pereopod 2 chelate, with carpal process reaching distal margin of propus. Pereopod 5 with propus 0.9 times as long as basis. Uropod 3 protopod longer than wide................... V. longicarpus Behning, 1913

– Pereopod 2 subchelate, with carpal process not reaching mid-length of propus. Pereopod 5 with propus 1.1 times as long as basis. Uropod 3 protopod as long as wide................. V. pyripes Bovallius, 1887

8 Antenna 1 as long as head and pereonites 1–3 combined or longer..... 9 – Antenna 1 shorter than head and pereonites 1–3 combined....... 10

9 Eyes with compact ocelli. End of uropod 3 not exceeding end of uropod 2....................... V. affinis Bate, 1862

– Eyes with few ocelli arranged in three rows. End of uropod 3 exceeding end of uropod 2................... V. elongata sp. nov.

10 Pereopods 5 and 6 more than twice as long as pereopods 3 and 4; propus as long as

merus and carpus combined.......... V. edwardsi Bate, 1862 – Pereopods 5 and 6 less than twice as long as pereopods 3 and 4; propus shorter than merus and carpus combined................ 11

11 Eyes absent or with ocelli arranged in three rows.......... 12 – Eyes with numerous ocelli compactly arranged........... 14

12 Eyes absent. Pereopod 2 chelate, with carpal process reaching distal margin of propus................. V. caeca Bulycheva, 1955 – Eyes with ocelli arranged in three rows. Pereopod 2 chelate or subchelate... 13

13 Urosomites 2 and 3 completely or partially separate. Pereopod 5 propus nearly as

long as combined length of merus and carpus.... V. wolterecki Behning, 1939 – Urosomites 2 and 3 fused. Pereopod 5 propus about 0.6 times as long as combined length of merus and carpus......... V. australis Stebbing, 1888

14 Pereopod 2 with carpal process reaching distal margin of propus. Pereopod 7 with

basis as long as ischium to dactyl combined.... V. antarctica Stebbing, 1888 – Pereopod 2 with carpal process not reaching distal margin of propus. Pereopod 7 with basis shorter than ischium to dactyl combined......... 15

15 Pereopod 1 propus with six teeth on posterior margin.. V. dentata Chevreux, 1900 – Pereopod 1 propus finely serrated on posterior margin........ 16

16 Pereopod 1 subchelate; propus with posterior distal corner roundly produced.. 17 – Pereopod 1 simple; propus with distal margin not wider than dactyl..... 18

17 Antenna 1 as long as head and pereonite 1 combined. Pereopod 7 basis shorter than

two-thirds of ischium to dactyl combined..... V. robusta Bovallius, 1887 – Antenna 1 as long as head and pereonites 1 and 2 combined. Pereopod 7 basis longer than two-thirds of ischium to dactyl combined.... V. viatrix Bovallius, 1887

18 Antenna 1 shorter than or as long as head and pereonite 1 combined.... 19 – Antenna 1 longer than head and pereonite 1 combined........ 21

19 Urosomites 2 and 3 separate. Pereopods 5 and 6 with basis longer than propus.................... V. longipes Bovallius, 1887 – Urosomites 2 and 3 fused. Pereopods 5 and 6 with basis shorter than or as long as propus..................... 20

20 Pereopod 2 with carpal process extending to more than three-quarters length of

propus. Pereopod 7 with anterodistal corner of carpus and propus not produced................... V. gibbosa Bovallius, 1887 – Pereopod 2 with carpal process not reaching three-quarters length of propus. Pereopod

7 with anterodistal corner of carpus and propus produced..................... V. hirsuta Behning and Woltereck, 1912

21 Antenna 1 as long as head and pereonites 1 and 2 combined....... 22 – Antenna 1 shorter than head and pereonites 1 and 2 combined...... 23

22 Pereopod 5 with basis longer than ischium and merus combined. Uropod 1 with

protopod twice as long as exopod.... V. borealis Bate and Westwood, 1868 – Pereopod 5 with basis shorter than ischium and merus combined. Uropod 1 with protopod slightly longer than exopod.. V. stebbingi Behning and Woltereck, 1912

23 Urosomites 2 and 3 separate. Telson semicircular... V. jeangerardi Lucas, 1845 – Urosomites 2 and 3 fused. Telson triangular.... V. propinqua Stebbing, 1888

Figures

FIG. 16. Vibilia elongata sp. nov. Female, holotype, 2.9 mm, IPHC station 930-293C. Scale bars=0.1 mm unless otherwise indicated.

FIG. 17. Vibilia elongata sp. nov. Appendages of the holotype. Scale bars=0.1 mm.

FIG. 3. Vibilia australis Stebbing, 1888. Female, 4.2 mm, COFF station 539-8698. Male, 4.3 mm, COFF station 539-8698. Scale bar of female body=1.0 mm, otherwise bars= 0.1 mm unless otherwise indicated.

FIG. 4. Vibilia australis Stebbing, 1888. Appendages of female and male of figure 3. Appendages, if unspecified with sex, belong to the female. Scale bars=0.1 mm.