Platytyphlops uteae, Roccatagliata, 2023

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 : 285-289

P. uteae n. sp.

( Figs. 1–6 , 8A, B ).

Paralamprops orbicularis — Calman, 1912: 631, 634, Figs. 29–39. — Day, 1978: 148 (in part, key). — B˘acescu, 1988: 25 (in part, catalog).

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).

? Paralamprops orbicularis — Reyss, 1978a: 12 [new records: Gay Head-Bermuda transect].

3.1. Material examined

ARGENTINA: WHOI Atl. II-60: Sta. 239, 36 ◦ 49 ′ S, 53 ◦ 15.4 ′ W, 1679 m, 11 Mar 1971: 1 A Ƌ (HOLOTYPE, MACN-In. 44066 ), 1 A Ƌ (anterior part only), 1 SA Ƌ (anterior part only), 4 mancae (PARATYPES, MACNIn. 44067 ). WHOI Atl. II-60: Sta. 237, 36 ◦ 32.6 ′ S, 53 ◦ 23 ′ W, 1011 m, 11 Mar 1971: 1 ovigerous ♀ (anterior part only), 1 SA ♀ (anterior part only), 2 A ƋƋ (complete), 2 A ƋƋ (anterior part only), 2 SA ƋƋ (anterior part only), 1 manca? (anterior part only) (PARATYPES MACN-In. 44068 ). Talud Continental III, RV Puerto Deseado , L55: 37 ◦ 52.154 ′ S, 53 ◦ 51.582 ′ W, 1712 m, 08 Sep 2013. 1 ovigerous ♀ (pleonite 6 and uropods missing), 1 SA ♀ (PARATYPES MACN-In. 44069 ). Talud Continental III, RV Puerto Deseado , L59, 37 ◦ 49.688 ′ S, 54 ◦ 05.236 ′ W, 1398 m, 10 Sep 2013: 1 SA ♀ (PARATYPES MACN-In. 44070 ). — EAST COAST OF USA: WHOI Knorr, 35, Sta. 346, 39 ◦ 54.1 ′ N, 70 ◦ 10.7 ′ W, 457 m, 03 Dec 1973: 1 ovigerous ♀, 1 SA ♀, 2 A ƋƋ (1 complete, 1 anterior part only), 3 juvs, 1 manca? (anterior part only) ( MACN-In. 44071 ). WHOI Chain 88, Sta. 207, 39 ◦ 51.3 ′ N, 70 ◦ 54.3 ′ W, 811 m, 21 Feb 1969. 1 ovigerous ♀, 2 SA ♀♀ (1 of them anterior part only), 1 SA Ƌ (infested with a cryptoniscus larva), 1 juv., 1 manca? (anterior part only) ( MACN-In. 44072 ) .

3.1.1. Description of the adult male (habitus based on the holotype MACNIn. 44066, appendages on the paratype MACN-In. 44068a)

Total length (Holotype): 16.8 mm.

Carapace ( Figs. 2A and B , 8A ) dorso-ventrally flattened; 1.07 times longer than wide. With two carinae only, viz., a marginal carina, and a double mid-dorsal carina anteriorly, surpassing frontal lobe by a short distance. Marginal carina without teeth. Pseudorostrum longer than ocular lobe, apically with a median notch when viewed from above. Ocular lobe triangular, without lenses or tumidities. Frontal lobe not interrupted dorsally, i.e., ocular lobe separated from frontal lobe by frontal suture.

Free thoracic segments ( Figs. 2A and B , 8A ) 0.80 as long as carapace.

Abdomen ( Fig. 2B ) very long, without carinae, 1.33 times as long as cephalothorax. Pleonites 1–5 increasing in length backwards. Pleonite 6 ( Fig. 5F ) 1.75 times longer than wide.

Telson ( Fig. 5F ) 1.37 times as long as pleonite 6, with 4 lateral robust setae (last pair subterminal) and 4 terminal robust setae. Variation: with 3 terminal robust setae in the holotype as well as in the remaining specimens examined. Thus, the presence of 4 terminal robust setae in the specimen drawn, seems to be an abnormal condition.

First antenna ( Fig. 2C ). Peduncle, article 1 1.27 times as long as articles 2 and 3 together. Article 2 1.55 times as long as article 3. All three articles with many setulate setae. Main flagellum shorter than peduncle, composed of 6 articles, article 1 thicker and with many aesthetascs (2 of them fully drawn, remaining ones cut basally), article 5 with an aesthetasc distally; article 6 minute, with an aesthetasc halfway along article. Accessory flagellum 0.8 as long as main flagellum, composed of 4 articles, distal one minute. Variation: Adult male (paratype MACN-In. 44067b). Right antenna, main flagellum with 7 articles (distal one minute). Left antenna broken.

Second antenna ( Fig. 2D ). Peduncle of 5 articles, article 1 with 1 setulate seta, article 2 with 2 setulate setae, article 3 without setae, article 4 and 5 with ranks of setae. Flagellum with short articles, reaching fourth pleonite. Second peduncle article with a rudimentary squama (exopod?) on distal end.

Mandible navicular, incisive process with 4 teeth. Left mandible ( Fig. 3A ) with a lacinia mobilis plus 16 setae between incisor and molar processes. Right mandible with 17 setae between incisor and molar processes.

First maxilla ( Fig. 3B ). Outer endite with 11 stout distal setae, inner endite with 4 stout distal setae, both endites with weak setae on outer distal margin. Palp with 2 unequal setae carrying teeth pointed upwards.

Second maxilla ( Fig. 3C ). Outer endite with 3 serrate setae and 3 serrulate setae distally. Inner endite with 3 serrate setae and 1 serrulate seta distally. Protopodite, inner margin with 4 (5 in the opposite maxilla) serrate setae and a row of 40 simple setae on inner margin having a wide proximal base that narrows abruptly, distal end with serrulate and simple setae (those behind endites omitted), outer margin with a broad transparent area (exopodite after Hansen, 1925). Note: the 40 setae on protopodite inner margin appears to be simple (not feather-like), however, the material is quite deteriorated after many years in ethanol 70%. Thus, this feature needs confirmation.

First maxilliped ( Fig. 3D ). Basis, inner margin with 9 setulo-serrate setae, endite with 2 coupling setae, setulate setae and comb-like setae distally. Ischium absent. Merus with a large setulate seta on ventral surface near inner margin (not drawn) and 1 large setulate seta on outer margin (absent in the appendage drawn; shown in broken lines based on the examination of the opposite appendage). Carpus with 9 comb-like setae on inner margin and many setulate setae on ventral surface (only those setulate setae interspersed between comb-like setae are drawn), outer margin with a large setulate seta. Propodus with 3 stout diverging setae (2 serrulate, 1 setulate) and many setulate setae on distal margin, outer margin with 3 setulate setae (1 distinctly larger than the other 2). Dactylus with 2 serrulate setae and 2 small simple setae. Epipodite with 8 branchial lobules.

Second maxilliped ( Fig. 4A ). Basis 1.35 times as long as remaining articles together, with setulate setae (2 on inner distal margin and 3 on or near distal outer corner). Ischium unarmed. Merus 0.6 as long as carpus, with 2 setulate setae on dorsal surface and 1 on outer distal angle. Carpus 1.3 times as long as propodus, with 9 setulate setae on inner margin and 1 setulate seta on outer distal angle. Propodus with many setulate setae on inner margin (some of them not drawn), 1 setulate seta on outer distal angle and 1 setulate seta on dorsal surface. Dactylus 0.45 as long as propodus with simple distal setae (larger one distinctly longer than article).

Third maxilliped ( Fig. 4B ). Basis slightly longer than remaining articles together, with setulate setae on both margins and a row of 4 short simple setae on ventral surface. Ischium unarmed. Merus 0.63 as long as carpus, with 4 setulate setae on inner margin and 2 setulate setae on outer distal angle (longer seta extending slightly beyond halfway along carpus). Carpus 1.14 times as long as propodus, with 9 setulate setae arranged in two rows on inner margin, and 2 setulate setae on outer margin. Propodus 2.5 times as long as dactylus with 12 setae (with two rows of setulae basally, see detail) on inner margin and setulate setae on outer margin and ventral surface. Dactylus with 3 simple setae on inner margin, and 3 setae distally (longer one 1.6 times as long as article). Exopod flagellum with 8 articles.

First pereopod ( Fig. 4C ). Basis 0.8 as long as remaining articles combined, with setulate setae on both margins and distally. Ischium with 2 short setulate setae on distal inner corner. Merus 0.73 as long as carpus, with a crown of setulate setae distally. Propodus 1.4 times as long as carpus and 1.85 times as long as dactylus. Carpus, propodus and dactylus with simple setae only. Exopod flagellum with 8 articles.

Second pereopod ( Fig. 5A ). Basis (broken) as long as remaining articles combined, with setulate setae on both margins and distally. Ischium and merus with a large serrulate robust seta on distal outer angle and simple setae. Carpus 1.6 times as long as propodus and dactylus combined, with 19 serrulate robust setae on outer margin. Dactylus twice as long as propodus with simple setae. Exopod flagellum with 8 articles.

Third pereopod ( Fig. 5B ). Basis 1.6 times as long as remaining articles combined. Merus 2.1 times as long as carpus. Carpus 0.7 as long as propodus and dactylus combined. Basis with setulate setae; carpus and propodus with 2 and 1 large setae, respectively; dactylus terminal seta with tiny setulae distally, remaining setae simple. Exopod flagellum with 8 articles.

Fourth pereopod ( Fig. 5C ) as third pereopod except for: Merus 1.5 times as long as carpus, Exopod flagellum with 9 articles. (The material is quite damaged, making it difficult to corroborate differences in the number and position of setae, if any, with third pereopod).

Fifth pereopod ( Figs. 1E and 5D ) as long as its pereonite, and 0.5 as long as basis of pereopod 4. Basis as long as remaining articles combined, with 1 long barely setulate seta. Remaining articles with simple setae. Exopod absent.

Penial papillae ( Figs. 1E and 5D ), without setae or elaboration, extending from the genital pores.

Pleopods 1–3 ( Fig. 5E ). Basis inner margin with a row of coupling setae (barely setulate, carrying a serrula distally), followed by a row of setulate setae, 5–5, 5–4 and 4–3 on pleopods 1, 2 and 3, respectively. Endopod with one article, with 8 setulate setae (only basal part drawn), outer edge with a finger-like process carrying 2 broom setae. Exopod with two-articles, distal article with 6 setulate setae (only basal part drawn).

Uropod ( Fig. 5F ). Peduncle 1.48 times as long as telson and 0.96 as long as endopod, inner margin with 28–31 robust setae. Endopod 1.1 times as long as exopod, of 3 articles, first article 1.85 times as long as remaining articles combined, with 4 large robust setae settling between 4 groups of small robust setae (composed of 6, 4–5, 7 and 7 setae, respectively). Second article slightly longer than the third, inner margin with 5–6 small robust setae and 1 large robust seta distally. Third article with 3–4 small robust setae on inner margin, and 3 setae (2 large, 1 minute) distally. Exopod with simple setae on both margins and 2 robust setae (1 broken) distally.

3.1.2. Description of the ovigerous female (habitus and appendages based on the paratype MACN-In. 44069a)

Total length: (pleonite 6, telson, and uropods missing): 15.1 mm. Total length estimated with missing distal parts: approximately 17.6 mm.

Carapace ( Figs. 6A and B ) approximately as long as wide. Mid-dorsal carina simple, even or finely denticulated (teeth microscopic, only visible under high magnification); marginal carina with flat, truncate teeth, more developed on the anterior half of carapace (see detail Fig. 6B ). Other aspects as in male.

First antenna ( Fig. 6C ). Peduncle, article 1 1.39 times as long as articles 2 and 3 together; article 2 1.22 times article 3; all three articles with setulate setae. Main flagellum shorter than peduncle, composed of 6 articles, article 5 with an aesthetasc distally; article 6 minute, with an aesthetasc halfway along article. Accessory flagellum 0.7 as long as main flagellum, composed of 4 articles, last one minute. Variation: ovigerous female (paratype MACN-In. 44068b). Right antenna, main flagellum with 6 articles (last one minute). Left antenna, main flagellum with 7 articles (first two badly separated, last one minute).

Fifth pereopod ( Fig. 6A ; see also Fig. 8B ) slightly shorter than its pereonite, approximately 0.3 as long as basis of pereopod 4, with setae.

3.1.3. Description of the manca (based on paratype MACN-In. 44067a)

Total length: 7.0 mm.

Carapace ( Fig. 6D ) as male excepting for: mid-dorsal carina simple, very low, rounded, only noticeable by rotation of the specimen. Marginal carina with flat truncate teeth, which are more developed on anterior half of carapace (many teeth broken in the specimen drawn).

3.1.4. Distribution

Off Argentina, off east of USA, 457-1712 m (see Fig. 1 , Table 1 ).

3.1.5. Etymology

This species is dedicated to Ute Mühlenhardt-Siegel, in recognition for her valuable work on deep sea cumaceans.

Figures

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.)

Fig. 2. Platytyphlops uteae n. sp. Adult male (Holotype MACN-In. 44066): A. Habitus in lateral view (fifth pereopod, basis only); B. Cephalothorax in dorsal view. C-E, Adult male (Paratype MACN-In. 44068a): C. First antenna; D. Second antenna, arrow points the squama; E. Last thoracic segment and fifth pereopods; arrow points penial papilla. Scale bars: A, B, 3 mm; C-E, 0.5 mm.

Fig. 3. Platytyphlops uteae n. sp. Adult male (Paratype MACN-In. 44068a): A Left mandible (distal part only); B. First maxilla; C. Second maxilla; D. First maxilliped. Scale bars: A-D, 0.2 mm.

Fig. 4. Platytyphlops uteae n. sp. Adult male (Paratype MACN-In. 44068a): A. Second maxilliped; B. Third maxilliped, with detail of a prodopal setae; C. First pereopod. Scale bars: A-C, 0.5 mm.

Fig. 5. Platytyphlops uteae n. sp. Adult male (Paratype MACN-In. 44068a): A. Second pereopod; B. Third pereopod; C. Fourth pereopod; D. Fifth pereopod, arrow points penial papilla; E. Second pleopod, exopod drawn separated for the sake of clarity; F. Last pleonite, telson and uropod, with detail of a robust seta. Scale bars: A-F, 0.5 mm.

Fig. 6. Platytyphlops uteae n. sp. Ovigerous female (Paratype MACN-In. 44069a): A. Habitus in lateral view, fifth pleonite, telson and uropods missing; B. Cephalothorax in dorsal view, with detail of anterior margin of carapace; C. First antenna. Manca (Paratype MACN-In. 44067a): D Carapace in dorsal view. Scale bars: A, B, 3 mm; C, 0.5 mm; D, 1 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.