Protoaeginella verrucosa, Guerra-García, 2004

Guerra-García, José M., 2004, Deep-sea Caprellidea (Crustacea, Amphipoda) from Azores with the description of three new species, Zoosystema 26 (2), pp. 235-262 : 251-256

Protoaeginella verrucosa n. sp.

( Figs 12-15 )

TYPE MATERIAL. — Holotype: stn 64, (MNHN- Am 5254). Allotype: stn 64, (MNHN-Am 5255). Paratypes: stn 126, 1 (MNHN-Am 2947), and stn 64, 4, 9 (MNHN-Am 5256).

ETYMOLOGY. — The specific name is descriptive of the numerous small tubercles on the body.

DISTRIBUTION. — So far, only known from the Azores.

DESCRIPTION

Holotype, male (6.9 mm)

Lateral view ( Fig. 12A ). Body densely covered with numerous small tubercles. Eyes absent but there is an indistinct ocular spot. Pereonite 1 fused with head although the suture between them is very distinct. Pereonites 2 to 5 increasing in length. Pereonites 4 and 5 curved. Pereonite 7 the shortest.

Gills ( Fig. 12A ). Present on pereonites 3-4, elongate, length about four times width.

Mouthparts. Upper lip ( Fig. 13E ) symmetrically bilobate, without setullae apically. Mandibles ( Fig. 13B, C ) with three-articulate palp; distal article of palp with a row of five setae on left mandible ( Fig. 13C ) and three setae on the right mandible ( Fig. 13B ); mandibular molar present, strong; incisor five-toothed in both mandibles; left mandible with lacinia mobilis five-toothed followed by a row of three setae; right mandible with lacinia apparently four-toothed, although irregularly dentate, followed by two plumose setae; molar flake present in right mandible, elongate. Lower lip ( Fig. 13D ) inner and outer lobes well demarcated, without setulae; inner lobes rounded. Maxilla 1 ( Fig. 13F ) outer lobe carrying seven spiniform setae; distal article of the palp with four robust setae apically and one plumose seta medially. Maxilla 2 ( Fig. 13G ) inner lobe rectangular, carrying five setae distally; outer lobe rectangular, 1.2 times as long as inner lobe, with eight apical setae. Maxilliped ( Fig. 13A ) inner plate carrying two nodular setae (short and robust, like a tooth), and four plumose setae; outer plate oval, 1.8 times as long as inner plate, with two or three nodular setae, one distal apical simple seta and one simple lateral seta; palp four-articulate, second and third article setose.

Antennae. Antenna 1 ( Fig. 14A ) about one sixth of body length; distal article of the peduncle provided with a small accessory flagellum which carries two distal setae; flagellum seven-articulate. Antenna 2 ( Fig. 14B ) without swimming setae; proximal peduncular article with acute distal projection; flagellum two-articulate, setose.

Gnathopods. Gnathopod 1 ( Fig. 14C ) basis a little longer than ischium to carpus combined; propodus palm with a pair of grasping spines proximally; grasping margin of propodus palm with small setulae on the anterior half; dactylus serrate. Gnathopod 2 ( Fig. 14D ) inserted on the anterior half of pereonite 2 ( Fig. 12A ); basis 0.7 times as long as pereonite 2, with rows of tubercles; ischium rectangular; merus rounded; carpus short and triangular; propodus elongate, almost as long as basis; palm with proximal projection provided with a single spine, followed by another projection medially and scarcely serrate margin on distal half; dactylus with smooth margin, provided with a row of tiny setulae.

Pereopods. Pereopods 3, 4 and 5 absent; a tiny knob without setae instead of the pereopod 5 ( Fig. 12A ). Pereopods 6 and 7 missing in male holotype ( Fig. 12A ) described from a male paratype (MNHN-Am 5256). Pereopod 6 ( Fig. 15A ) attached to the posterior end of the pereonite 6, six-articulate, basis without carina, ischium short and rectangular; merus and carpus palm carrying row of fine setae; propodus palm with a row of robust acute setae. Pereopod 7 ( Fig. 15B ) similar to pereopod 6.

Penes ( Fig. 15C ). Penes large and wide, almost as long as wide, situated laterally.

Abdomen ( Fig. 15C ). Abdomen with indistinct dorsal suture line, apparently two-segmented. Two pairs of appendages. The first pair apparently two-articulate; distal article three times as long as the proximal article, with a seta medially and ending in minute spines. Second pair of appendages smaller, one-articulate, with one medial seta and ending in minute spines. Lateral lobes with a big seta and dorsal lobe with two plumose setae.

Allotype, female (4.8 mm)

Oostegites 3 and 4 setose ( Fig. 12B ). Genital papillae ( Fig. 12B ) with a seta medially. Basis of gnathopod 2 with few tubercles; palm of gnathopod 2 without the projection medially and not distally serrated ( Fig. 12E ). Abdomen ( Fig. 15D ) also with two pairs of appendages, as in the male. REMARKS

The body length measured for the males of P. verrucosa n. sp. was 6.50 ± 0.54 mm (mean ± standard deviation) (range 5.83-7.21 mm). For the females it was 4.58 ± 0.32 mm (4.00- 5.01 mm). In connection with the intraspecific variation, the morphological characters of antennae, mouthparts, gnathopods, pereopods and abdomen are constant in all the specimens examined, except for the setal formula of the mandibular palp (1-x-1) where “x” can be 1, 2 or 3. Furthermore, the number of robust setae distally in the palp of the maxilla 1 can be three or four.

The new species Protoaeginella verrucosa n. sp. superficially resembles P. muricata described by Laubitz & Mills (1972); the lateral view is extremely similar due to the presence of abundant small tubercles on the body. Nevertheless, both species can be easily distinguished by checking the abdomen which is very different in both species. The abdomen is five-segmented in P. muricata , bearing only a pair of minute appendages ( Laubitz & Mills 1972), whereas it is two-segmented in P. verrucosa n. sp., bearing two pairs of appendages. According to the presence of two pairs of appendages in the male and female abdomen, we could justify the erection of a new genus for P. verrucosa n. sp., since the remaining species of Protoaeginella have only one pair of appendages. However, although the abdomen of P. muricata and P. spinipoda are different enough to consider two different genera, Laubitz & Sorbe (1996) preferred to consider both species in the same genus based on the similarities in antennae, pereonites, pereopods and mouthparts. In the case of P. verrucosa n. sp. we have also considered it in the genus Protoaeginella mainly based on the presence of accessory flagellum in antenna 1 and absence of pereopods 3, 4 and 5.

As far as it is known, there are only two other caprellid genera which have the accessory flagellum on antenna 1, Parvipalpina Stephensen, 1944 and Protellina Stephensen, 1944 . In these two genera, pereopod 5 is present (although very reduced in Parvipalpina ) whereas it is absent in Protoaeginella ( Stephensen 1944) .

So far, the genus Protoaeginella is restricted to deep waters of the North Atlantic ( Laubitz & Mills 1972; Laubitz & Sorbe 1996; present study).

Figures

FIG. 12. — Protoaeginella verrucosa n. sp., lateral view; A, male showing a detail of base pereonite 5; B, female showing a detail of genital papillae. Scale bar: 1 mm.

FIG. 13. — Protoaeginella verrucosa n. sp., mouthparts; A, maxilliped; B, right mandible; C, left mandible; D, lower lip; E, upper lip; F, maxilla 1; G, maxilla 2. Scale bars: 0.05 mm.

FIG. 14. — Protoaeginella verrucosa n. sp.; A-D, male; A, antenna 1 showing a detail of the accessory flagellum; B, antenna 2; C, gnathopod 1; D, gnathopod 2; E, female gnathopod 2. Scale bars: 0.1 mm.

FIG. 15. — Protoaeginella verrucosa n. sp.; A, male pereopod 6; B, male pereopod 7; C, male abdomen; D, female abdomen. Scale bars: A, B, 0.3 mm; C, D, 0.05 mm.