Diastylis argentata Calman, 1912

Moretti, Ariadna N. & Roccatagliata, Daniel, 2007, On two allied species of the genus Diastylis from southern South America: D. granulata Zimmer, 1921 and D. argentata Calman, 1912 (Crustacea: Cumacea: Diastylidae), Journal of Natural History 41 (41 - 44), pp. 2621-2639 : 2635-2638

Diastylis argentata Calman, 1912

( Figures 8C, D , 9D, E )

Diastylis argentata Calman 1912, p 649 –651, Figures 70–75 (original description, type locality: off Chile coast; 46 ° 479300S, 75 ° 159000W; 61 fathoms (5 112 m )); Brandt et al. 1999, p 545, Table 1 (Beagle Channel, new record); Mühlenhardt-Siegel 1999, p 297 – 300, Tables 2–4 (reproduced the record already mentioned by Brandt et al. 1999); Băcescu 1992, p 278 (catalogue).

Ekdiatylis argentatus Stebbing 1912, p 155 ; Stebbing 1913, p 137 –138 (catalogue); Hale 1937, p 51 –52.

Diastylis argentatus Day 1980, p 266 (key).

Material examined

Chile: Magellan Straits : RV Victor Hensen, Sta. 874 D, Bahía Voces, 53 ° 439S, 70 ° 56.19W, 335 m, 25 October 1994, three ovigerous ♀♀, four preparatory ♀♀, one preparatory „, four juveniles ( ZMH K-41453a), one ovigerous ♀ (mounted on a stub for SEM, ZMH K- 41453b). Off Puerto Montt coast: Metrencue, Calbuco, 41 ° 449000S, 73 ° 069000W, 25 m,? July 2006, coll. P. González Salvo, one adult „ (MACN-In 37158) . Argentina: Beagle Channel : Bahía Lapataia, L-2, 54 ° 879S, 68 ° 479W, 120–140 m, 12 May 1999, coll. C. Romero, one juvenile (MACN-In 37157); Punta Segunda, 54 ° 869S, 68 ° 039W, 94–96 m, 17 May 1999, coll. C. Romero, one subadult ♀ (MACN-In 37159); Punta Segunda, 54 ° 849S, 68 ° 069W, 91–102 m, 6 September 1999, coll. C. Romero, one ovigerous ♀ (damaged) (MACN-In 37160) .

Brief redescription of adult male (MACN-In 37158)

Total length approximately 8.3 mm.

Carapace ( Figure 8C, D ). Surface whitish, brittle, and polished, with a few small denticles scattered on pseudorostral and frontal lobes. Width approximately 0.4 times its length. Inferior margin with a row of teeth. Sides of carapace with: (1) a pair of anterolateral horns (cornua), (2) an anterolateral row of teeth ending at the level of each horn some distance above them, and (3) an inferolateral row of teeth starting near each horn and ending at posterior margin of carapace, posterior teeth the largest. Eyelobe small, subtriangular, without lenses. Antennal notch shallow. Pseudorostrum approximately three times as long as ocular lobe.

Pereonites. Pereonite 2 with few small teeth on dorsal surface; pereonites 2–4 with marginal teeth; pereonites 3 and 4 with one dorsolateral row of teeth on each side; pereonite 5 with one dorsolateral tooth on each side and two or three large teeth on each posterolateral angle.

Pleonites. Pleonite 1 with one dorsolateral, one lateral, and one ventrolateral tooth on each side, and two contiguous unequal medial teeth ventrally. Pleonites 2–4 with two dorsolateral teeth distally. Pleonite 4 with serrations on ventral margins (most distal tooth the largest). Pleonite 5 with one middorsal row of teeth that increase in size towards distal end, and two dorsolateral teeth and one ventrolateral serration on each side (most distal tooth the largest).

Telson. Preanal part approximately 0.75 times as long as postanal part.

Brief description of an ovigerous female from Bahía Voces, Magellan Straits ( ZMH K- 41453b)

Total length 8.8 mm (this measure is rather unsatisfactory because the pleon is arched).

Carapace ( Figure 9D, E ). Carapace as male except for: width 0.72 times its length (0.78– 0.84 in other three ovigerous females examined), longitudinal row of anterolateral teeth clearly surpassing frontal lobe, having a row of minute teeth running backwards from posterior end of each frontal lobe fissure, and lacking inferolateral row of teeth.

Pereon and pleon. Teeth and serrations as in ovigerous female of D. granulata .

Telson. Preanal part approximately as long as postanal part.

Distribution

From off Puerto Montt coast to the west mouth of the eastern entrance of the Beagle Channel, 94–335 m depth ( Chile) .

Figures

Figure 8. (A, B) Diastylis granulata Zimmer, 1921, ovigerous female (MACN-In 37153): (A) habitus in lateral view; (B) carapace and pereon in dorsal view. (C, D) Diastylis argentata Calman, 1912, adult male (MACN-In 37158): (C) habitus in lateral view; (D) carapace and pereon in dorsal view, and a detail of the longitudinal row of teeth, which are apparently worn out. Scale bar: 1 mm (A–D).

Figure 9. SEM photographs. (A–C) Diastylis granulata Zimmer, 1921, subadult male (MACN-In 37155): (A) anterior part of the body in lateral view; (B) anterior part of the body in dorsal view and a detail of the arched row of teeth; (C) enlarged view of anterior part of the carapace. (D, E) Diastylis argentata Calman, 1912, ovigerous female (ZMH K-41453b): (D) anterior part of the body in lateral view; (E) anterior part of the body in dorsal view and a detail of the anterolateral row of teeth. Number 1 stands for the rows of teeth running backwards from the frontal lobe; number 2 stands for the ‘‘supplementary’’ rows of teeth. Scale bars: 0.5 mm (A, B, D, E); 0.2 mm (C).