Platytyphlops orbicularis ( Calman, 1905 )

Roccatagliata, D., 2023, The genus Platytyphlops (Cumacea: Crustacea): A new species from Argentina, taxonomic status of Platytyphlops orbicularis (Calman, 1905), and remarks on the genus, Zoologischer Anzeiger 302, pp. 284-292 : 289-290

Platytyphlops orbicularis ( Calman, 1905)

Figs. 7 , 8C–E

Platyaspis orbicularis Calman, 1905: 43 , Figs. 77–81.

Platytyphlops orbicularis — Stebbing, 1912: 144, 161 (in part); 1913: 158, 159 (in part, catalog). — Zimmer, 1980: 18 (in part). — Gerken, 2018: 139 (key), 145, 158, 181 (in part).

Platysympus orbicularis — Hansen, 1920: 52.

Paralamprops orbicularis — Reyss, 1978a: 12 [“Sta. 44, 1 specimen ”, Biscay Bay, RV Sarsia]. — Day, 1978: 148 (in part, key). — B˘acescu, 1988: 25 (in part, catalog). — Jones, 1990: 78, 80 (tables). — Gerken and Watling, 1999: 203, 204. — Watling and Gerken, 2005: 139 (table).

3.2. Material examined

THALASSA 70, Sta. W357, 43 ◦ 37 ′ N, 02 ◦ 19.2 ′ W, 770 m, 04 Oct 1970: 3 SA ♀♀, 2 A ƋƋ, 1 SA Ƌ ( MACN-In. 44073 ) . BIOGAS II, Sta. DS33, 47 ◦ 39.7 ′ N, 08 ◦ 05.5 ′ W, 2338 m, 20 Apr 1973: 1 juv. ( MACN-In. 44074 ) .

3.2.1. Description of the adult male (habitus and appendages description are based on specimens MACN-In. 44073a and MACN-In. 44073b)

Total length: 8.2 mm.

Carapace ( Figs. 7A and 8C, D ) dorso-ventrally flattened; approximately as long as wide, broadly rounded anteriorly. With a marginal carina; a double mid-dorsal carina runs from anterior margin of frontal lobe to anterior end of a wide median gutter; a pair of submedian carinae at each side of the wide median depression, which extends almost to posterior margin (these carinae become more evident when the specimen is inclined, see Fig. 8D ). Marginal carina without teeth. Pseudorostral lobe longer than ocular lobe, with a median notch (visible in dorsal view). Ocular lobe triangular, no lenses. Frontal lobe not interrupted dorsally, i.e., ocular lobe separated from frontal lobe by frontal suture.

Free thoracic segments ( Fig. 7A ) 0.7 as long as carapace.

Abdomen very long, without carinae, 1.33 times as long as cephalothorax.

Pleonites 1–5 increasing in length backwards. Pleonite 6 1.52 times longer than wide.

Telson ( Fig. 7D ). 1.54 times as long as pleonite 6.

First antenna ( Fig. 7B ). Peduncle, article 1 1.33 times as long as articles 2 and 3 together. Article 2 1.69 times article 3. All three articles with many setulate setae. Main flagellum shorter than peduncle, composed of 5 articles, article 1 thicker and with a large number of aesthetascs (2 of them fully drawn, remaining ones cut basally), article 4 with an aesthetasc distally; article 5 minute, with an aesthetasc halfway along article. Accessory flagellum 0.9 as long as main flagellum, composed of 4 articles, last one minute.

Fifth pereopod ( Fig. 7C ) minute, without setae (except for dactylus distal seta), slightly longer than half its pereonite, approximately 0.25 as long as basis of pereopod 4. All articles distinct.

Uropod ( Fig. 7D ). Peduncle 1.71 times as long as telson, inner margin with approximately 30 robust setae (only the seta socket usually remains). Rami broken.

Penial papillae ( Fig. 7C ), without setae or elaboration, extending from the genital pores.

3.2.2. Description of the subadult female (habitus based on specimen MACN-In. 44073c and MACN-In. 44073d)

Total length: 9.6 mm.

Carapace ( Fig. 7E ) as adult male, except for nearly circular in dorsal view, 1.08 times wider than long. Middorsal carina single, finely denticulated (with microscopic teeth only visible under high magnification).

Fifth pereopod ( Fig. 8E ), even shorter than in the male, without setae (except for dactylus distal seta), less than 0.5 as long as its pereonite, approximately 0.2 as long as basis of pereopod 4. All articles distinct.

The poor condition of the specimens prevents further description.

3.2.3. Distribution

North-East Atlantic, 423–2338 m (see Fig. 1 , Table 1 ).

Figures

Fig. 7. Platytyphlops orbicularis (Calman, 1905). Adult male (MACN-In. 44073a): A. Cephalothorax in dorsal view; B. First antenna; C. last thoracic segment and fifth pereopod (fourth pereopod broken), arrow points penial papilla. D. last two pleonites, telson and uropods. Subadult female (MACN-In. 44073c): E. carapace and first two free thoracic segments, in dorsal view. Scale bars: A, E, 3 mm; C, D, 1 mm; B, 0.5 mm.

Fig. 8. Stereoscopic microscope photographs. — Platytyphlops uteae n. sp. A. Adult male (Holotype MACN-In. 44066), cephalothorax in dorsal view. B. Subadult female (Paratype MACN-In. 44069b), last thoracic segment, first pleonite and fifth pereopods in lateral view. — Platytyphlops orbicularis (Calman, 1905). C. Adult male (MACN-In. 44073b), carapace and first two free thoracic segments in dorsal view. D. Same specimen inclined both antero-posteriorly and laterally (carapace and pereonites 1–5 visible). E. Subadult female (MACN-In. 44073d), last thoracic segment, first pleonite and fifth pereopod, in lateral view. Abbreviations: mc: double mid-dorsal carina, smc: submedian carinae, pr.5, fifth pereonite (= last thoracic segment), pl.1: first pleonite, P5: fifth pereopod. Scale bars: A-E, 1 mm.

Fig. 1. Distribution of Platytyphlops uteae n. sp. (triangles) and Platytyphlops orbicularis (Calman, 1905) (circles). New records in red, previous records in blue. Specimens collected by the surveys Chain 50 and Chain 58 are tentatively assigned to P. uteae n. sp. See Table 1 for additional information on the stations. (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)