Bairdoppilata hirsutella Maddocks, 2022

Maddocks, Rosalie F., 2022, Taxonomic applications of the esophageal flapper valve in Bairdoppilata and Glyptobairdia (Bairdiidae, Ostracoda), with comments on anatomy, ontogeny, and geography, Zootaxa 5175 (3), pp. 301-342 : 322-325

Bairdoppilata hirsutella Maddocks , n. sp.

( Figures 11 , 12A–M , 13A–F , 14A )

? 1969 Bairdoppilata ( Bairdoppilata ?) hirsuta (Brady) .—Maddocks, p. 79, fig. 43A–I, pl. 2, figs. 1, 2 [specimens USNM 121353 and 121355 from the Gulf of Mexico, only, with uncertainty].

1973 Bairdoppilata hirsuta (Brady) .—Maddocks, p. 42, figs. 5B–G, 6A–E.

Material Examined: Eleven specimens, including USNM 139893, 139895–139900 ( Maddocks 1973).

Types: Holotype male specimen 634M, USNM 139891 ; illustrated paratype female USNM 635 F, USNM 139892 ; illustrated paratype, molting juvenile specimen 689J, USNM 139894 .

Type locality: Eltanin Station 25 in the Pacific Ocean, east of the Galapagos Islands ; 04 o 53’N, 80 o 28’W, depth 2489 m.

Dimensions: Male specimen 634M (USNM 139891): LVL 1.700 mm, LVH 1.070 mm, RVL 1.680 mm, RVH 0.980 mm. Female specimen 635F: USNM 139892: LVL 1.836, LVH 1.238, RVL 1.836 mm, RVH 1.083 mm. Molting juvenile specimen 689J: USNM 139894: LVL 1.447 mm, LVH 0.930 mm, RVL 1.434 mm, RVH 0.853 mm. See also Fig. 11 .

The RV dimensions of juvenile specimen 689J are close to those reported for the RV lectotype of B. hirsuta by Puri & Hulings (1976), but the latter was described as an adult .

Esophageal Valve: The plate ( Fig. 13C ) is broad, thin, and gently curved with smooth contours. There are about 18 low, thin, conical to subcylindrical teeth, which are widely spaced around the perimeter; the middle teeth are the smallest, and sizes increase somewhat toward the corners. There are no corner teeth, and the corners are smoothly rounded.

Anatomical Remarks: The rotund carapace is inflated, thickest at mid-height near the AMS, and smooth, glossy, with NPC but no surface sculpture ( Figs. 12H–M ). In lateral outline it is broadly oval and upright in posture, with evenly curved dorsal and ventral margins. Both the anterodorsal corner and the caudal process are located distinctly above mid-height. Bairdoppilatan dentition is well developed ( Figs. 12F–G ). The calcified inner lamella of the A-1 instar is fairly broad ( Figs. 12A, C ) but weakly calcified and easily damaged.

The adult A2 and walking legs are extraordinarily long and thin, as usual in deep-sea animals. The distal claws of the A2 ( Fig. 13D ) are equal in size, long and very thin. The fused claw is perfectly smooth and tapers to a sharp point.

Maddocks (1973, fig. 5B–G, 6A–E) published a full suite of drawings for male specimen 634M, USNM 139891 , which is here designated as the holotype. The drawing of the hemipenis showed the non-erect condition, with several overlapping processes enveloped by the hood-like distal appendage. Photographs of the same specimen are provided here as Figs. 13A–D .

The conspicuous carapace sensilla ( Fig. 12H ) for which B. hirsuta was named are not unique to this species or genus but are seen in many bairdioids (for example, fig. 19N of Brandão, 2008). They are more noticeable in deepsea forms, because the dark color contrasts with the stark white valves. The number of NPC increases for each instar in bairdiids ( Smith & Kamiya 2002). At each molt, the existing sensilla are retained, although their exocuticular covering is discarded with the exuvia. The inherited sensilla are thicker, longer, and darker in color than those newly added. On the adult carapace there are numerous NPC of different sizes, bearing sensilla of several ontogenetic ages, as indicated by length, thickness and color. One may speculate that this canopy of sensilla allows a small animal to claim a large volume of space, confers buoyancy, provides early warning of predation, and protects the carapace from abrasion and siltation.

Taxonomic Remarks: Maddocks (1973) identified these specimens as B. hirsuta (Brady) , but that identification requires re-examination. The soft parts of B. hirsuta are unknown, the lectotype may be a juvenile, the type locality is many thousands of kilometers distant, and no geographically intermediate populations have been reported. Brandão (2008) demonstrated that the diversity of deep-sea bairdioids has been greatly under-estimated, and it is best to be more conservative with identifications of Brady’s species. For clarity of communication, the population collected at Eltanin station 25 is named here as a new species.

B. hirsutella is similar to the two females collected from the Gulf of Mexico, which were identified as B. (B.?) hirsuta by Maddocks (1969) (specimens 468F, 469F, USNM 121353 , 121355 ). Their identity is considered uncertain at present. Larger assemblages, including males, will be required to evaluate the relationship of these distant populations .

Figures

FIGURE 11. Bairdoppilata hirsutella Maddocks, n. sp. H:L scatter plot for 4 specimens from Eltanin station 25: Holotype specimen 634M (USNM 139891), and paratype specimens 635F (USNM 139892), 636W, and 689J (USNM 139894).Also plotted here are specimen 468F (SUM 121353), which was collected in the Gulf of Mexico and is of uncertain species identity, and the Lectotype RV of Bairdia hirsuta Brady.

FIGURE 12. Bairdoppilata hirsutella Maddocks, n. sp. A–C, molting juvenile specimen 689J, USNM 139894, instar A–1: A, LV interior in reflected light, with narrow infold, broad but weakly calcified inner lamella, and vestibules partly filled with fluid; B, LV interior in reflected light, with AMS, showing striated, hummocky texture of inner chitinous lining, as sensilla and cuticle are being withdrawn from older valve; C, anterior margin of RV interior in reflected light, showing narrow (normal) infold. D–K, holotype adult male specimen 634M, USNM 139891: D–E, LV and RV interiors in reflected light, with broad calcified inner lamella, shallow vestibules separated ventrally, prominent selvage and fringes; F, RV interior, posterodorsal edge with denticles of supplemental dentition; G, LV interior, posterodorsal edge with locules of supplemental dentition beneath dorsal overhang; H–I, RV and LV exteriors in transmitted light, with broad (normal) inner lamellae, fairly deep vestibules, NPC, sensilla, and AMS; J–K, RV and LV exteriors in reflected light, showing smooth surface and sensilla; RV caudal process is damaged. L–M, adult female specimen 635F, USNM 139892: RV and LV exteriors in transmitted light, with AMS and sensilla. Scale bar = 50 µm.

FIGURE 13. Bairdoppilata hirsutella Maddocks, n. sp. A–D, holotype adult male specimen 634M, USNM 139891: A, dorsal view of zygum, both furcae, and left hemipenis; B, distal element, copulatory tube, and terminal appendages of left hemipenis; C, dorsal view of esophageal valve with ring, collar, belt, plate, and both braces; D, A2 distal claws. E, adult female specimen 635F, USNM 139892: genital lobe. F, molting juvenile specimen 689J, USNM 139894, A–1: detail of antennal claws to show how ramus and claws are withdrawn during molting. Scale bar = 50 µm.

FIGURE 14. Bairdoppilata hirsutella Maddocks, n. sp. A, molting juvenile, female A–1, specimen 689J, USNM 139894: posterior region of body with zygum, genital lobes, furca, and postabdominal seta. Scale bar = 50 µm.