Careproctus argosgeorgiae, Villarroel-Perez & Chernova & Weston & Vukasin & Shcherbich, 2026

Careproctus argosgeorgiae sp. nov. Villarroel-Perez & Chernova urn:lsid:zoobank.org:act:

( Figures 1–5 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 ; Table 1)

Holotype. MNHN- ICT 7645, female 294 mm TL, 255 mm SL. Falkland Plateau northeast of Falkland Islands, 50°32’ S, 53°54’ W, depth 1680 m, 10.10.2024 (UTC-3), F/ V CFL Hunter, longline (umbrella), line 3476/station 1815, FIFD grid XL-AW; collector Martin L. Villarroel-Perez. GoogleMaps

Diagnosis. Careproctus argosgeorgiae sp. nov. is distinguished from congeners by the following combination of characters: vertebrae 47; dorsal-fin rays 42; anal-fin rays 34; pectoral-fin rays 37; pleural ribs in three pairs, two of which are strongly developed; teeth simple; gill slit long, about half HL and reaching pectoral-fin ray 18; pelvic disk large, about 33% HL; distance from disk to anus greater than or equal to disk length; pectoral-fin upper lobe 67% HL; skin naked, with thick subcutaneous gelatinous tissue; color uniformly light orange, with deep orange margins of disk and pectoral fins.

Description. Dorsal-fin rays 42, first ray between neural spines 2 and 3. Anal-fin rays 34, with three anterior rays before the first haemal spine. Caudal-fin principal rays 12 (6 upper and 6 lower); procurrent rays 3 (2 upper and 1 lower) ( Fig. 3 View FIGURE 3 ); caudal-fin formula 15 (2+6/6+1). Hypural plate structure indistinguishable on radiographs. Vertebrae 47 (pre-caudal 12 + caudal 35, including urostylar center). Pleural ribs in three pairs: two strong pairs on vertebrae 10 and 11 ( Fig. 2D View FIGURE 2 ); and a third pair thin and short (hardly visible) on vertebra 12. Counts and measurements are provided in Table 1.

Body stout and not humpback ( Fig. 1 View FIGURE 1 ). Head large, 3.5 in SL; pre-caudal part of body almost half of SL (48%). Maximal body depth equal to head length (99% HL), depth at A-fin origin almost equal to head depth (16 and 19% SL), depth at caudal peduncle 2% SL (8% HL).

Head not deep at occiput, depth (66% HL) somewhat less than width (74% HL). Snout, 42% HL in length, not protruding above upper jaw. Nostrils one pair; tube width 2.1% HL. Mouth horizontal, terminal; width between corners of mouth about half of head length (54% HL). Teeth simple, conical, and sharp ( Fig. 2C View FIGURE 2 ), in numerous oblique rows, 6–7 teeth in a row near jaw symphysis. Eye small; diameter 4.6% SL ( 6.2 in HL); pupil round. Interorbital width 11.2% SL (2.4 times eye diameter). Postorbital length 14% SL (3.0 times eye diameter). Gill slit long, 13% SL (2.8 times eye diameter), almost equal to half the head length (45% HL) and reaching pectoral-fin ray 18, ventral end about level with mouth cleft. Opercular flap prominent, tip rounded when fresh and angled after fixation ( Fig. 1C View FIGURE 1 ). Pore formula 2–6–7–1 ( Fig. 2A View FIGURE 2 ). Chin pores closely spaced (~2 pore diameters), preoperculomandibular pores 2–4 separated by ~4 pore diameters.

Dorsal fin not deep, with 3 or 4 anterior rays obviously erectile, tips standing out from fin membrane ( Fig. 1A View FIGURE 1 ). Caudal fin length 27% SL. Dorsal and anal fins overlap caudal fin by about three quarters of its length.

Pectoral fin distinctly notched, with 37 rays: 29 in upper lobe, including shortest in notch, and 8 in lower lobe. Pectoral fin upper lobe rather long (67% HL), reaching anal-fin origin; lower-lobe rays no longer than upper-lobe rays, almost reaching anus. Pectoral girdle broken, lower part missing ( Fig. 4 View FIGURE 4 ); scapula and two upper radials present; scapula and radials notched, with fenestrae in the cartilaginous plate between adjacent elements.

Pelvic disk longitudinally oval (length 1.2 times width), located below gill slit. Disk length 32.6% HL ( 3.1 in HL), disk width 27.2% HL. Anterior fold of disk and segmental pads in central part not differentiated, central part of disk not depressed, diameter larger than width of marginal part ( Fig. 2B View FIGURE 2 ). Disk to anus distance about equal to disk length (10.0% and 9.2% SL). Anus opening well behind head (pre-anal length 128% HL), on vertical line near end of longest ray of the pectoral-fin. Distance from anus to anal-fin origin 1.8 times distance from posterior margin of disk to anus. Stomach and pyloric caeca not examined; otoliths not extracted.

Gelatinous subcutaneous tissue (=subdermal extracellular matrix sensu Eastman et al. 1994) quite thick when fresh; dorsal-fin rays covered by this tissue on proximal one-third of fin length; anal-fin rays completely embedded in tissue along anterior half of fin length. Skin naked, prickles absent. Female with large light-yellow eggs of approximately equal size, averaging 5 mm diameter, largest 5.7 mm.

Color when fresh uniform light orange with rose tint; margins of disk and ends of pectoral-fin rays orange. Oral cavity pale; gill cavity orange brown; gills reddish brown. Peritoneum brown with darker dispersed pigments. Coloration after fixation in formaldehyde and after preservation in alcohol pale ( Fig. 1C View FIGURE 1 ).

Etymology. The specific epithet argosgeorgiae honors the F/V Argos Georgia, a longliner that sank in the South Atlantic near the Falkland Islands on 22 July 2024, resulting in the loss of 13 lives and 14 survivors, including two fisheries observers. The response to the tragedy reflects the resilience and compassion of the South Atlantic islands community and underscores the human risks of deep-sea fishing in subantarctic and Antarctic waters. The epithet is a Latin feminine genitive meaning “of the Argos Georgia ”, commemorating the vessel, its crew, and all those connected to it.

Distribution. Known from a single specimen captured on the Falkland Plateau, northeast of the Falkland Islands, at a bathydemersal depth of 1680 m.

Capture and associated fauna. The fish was incidentally recovered during hauling of umbrella-type longline gear targeting Dissostichus eleginoides Smitt, 1898 in waters northeast of the Falkland Islands, at depths of approximately 1040–1790 m. The individual was unhooked at the time of collection and exhibited a ruptured abdominal wall with extruded ripe eggs. The bycatch composition (%) was dominated by deep-sea fish species, including the elasmobranchs Antarctic starry skate Amblyraja georgiana Norman, 1938 and butterfly skate Bathyraja papilionifera Stehmann, 1985 ( Rajiformes : Rajidae ) (41%), the Southern sleeper shark Somniosus antarcticus Whitley, 1939 ( Squaliformes : Somniosidae ) (2%) and the osteichthyans, mainly big-eye grenadier Macrourus holotrachys Günther, 1878 ( Gadiformes : Macrouridae ) (35%) and blue antimora Antimora rostrata Günther, 1878 ( Gadiformes : Moridae ) (22%). Benthic invertebrates, including cold-water corals and sponges that are VME indicator taxa ( Huvenne et al. 2011; Robert et al. 2020), together with lithodid crabs, collectively accounted for only 0.02% of the total bycatch weight recorded across all hauls.

Biology. The holotype is a ripe female (maturity stage V), weighing 392 g (wet weight at sea), with large eggs; the specimen was collected in October ( Southern Hemisphere). An elongate, worm-like ectoparasite was attached to the caudal region on the left side of the body .

Comparisons. Of the eighteen species of Careproctus known from southern South America and adjacent waters, C. atakamensis Andriashev, 1998 , C. aureomarginatus , C. macranchus Andriashev, 1991 , and C. magellanicus Matallanas & Pequeño, 2000 have more vertebrae (51–59) than C. argosgeorgiae sp. nov. (47). In contrast, C. falklandicus , C. fueguensis Matallanas & Piacentino, 2019 , C. pallidus Vaillant, 1888 , and C. patagonicus Matallanas & Pequeño, 2000 have fewer vertebrae (36–40). Unlike C. argosgeorgiae sp. nov., most of the other listed species lack pleural ribs, including C. acaecus Andriashev, 1991 , C. aculeolatus , C. armatus , C. cactiformis Andriashev, 1990 , C. minimus and C. stigmatogenus .

By the presence of two pairs of strong pleural ribs, C. argosgeorgiae sp. nov. is similar only to C. atrans , C. herwigi Andriashev, 1991 , and C. smirnovi . It differs from C. atrans in having a higher number of pectoral-fin rays (37 vs. 26). Of the remaining two species, C. argosgeorgiae sp. nov. differs from C. herwigi , described from northern Argentina ( 41°13’ S, 1250 m), by the presence of simple teeth (vs. three-tuberculated teeth), a higher number of vertebrae (47 vs. 45), a longer gill slit reaching the 18th pectoral-fin ray (vs. 7–8 rays), and a gill slit approximately half of head length (vs. one-third). Additional differences include a smaller eye ( 6.2 in HL vs. 4.4), and a distance from disk to anus approximately equal to disk length (vs. about half of disk length).

The new species is most similar to C. smirnovi , which is known from waters north of the Falkland Islands at depths of 1500–1580 m based on two specimens of 204 and 186 mm SL ( Andriashev 1991 a, 2003; this paper: Fig. 5 View FIGURE 5 ). Careproctus argosgeorgiae sp. nov. is larger in size and agrees with C. smirnovi in the presence of pleural ribs, simple teeth, a similar number of vertebrae, dorsal-, pectoral- and caudal-fin rays, a similar gill slit size ( Table 1), and in the peritoneum coloration. However, it differs in having a less humpbacked occiput, an opercular flap positioned below the level of the eye, the upper pectoral-fin ray at mouth-cleft level, and a thicker, well-developed subcutaneous layer covering the origins of the dorsal and anal fins.

Additional differences between C. argosgeorgiae sp. nov. and C. smirnovi include fewer anal-fin rays (34 vs. 36–37), a greater maximal body depth (28.0 vs. 25.8–26.2% SL), a shorter pre-dorsal length (32.3 vs. 34.4–35.0% SL), greater distances from chin to disk (15.3 vs. 13.3–14.0% SL) and from chin to anus (32.1 vs. 26.5–30.1% SL), and a longer upper lobe of the pectoral-fin (67 vs. 58–60% HL). The anus is positioned more posteriorly, with the distance from disk to anus larger (10.0 vs. 3.5–7.5% SL) and exceeding disk length (vs. less than disk diameter). In addition, the central part of the disk by diameter is larger than the width of its marginal part (vs. smaller than the marginal part), and the interorbital width is greater (39.7 vs. 34.2–35.8% HL). Color differences are also distinct with the body uniformly light orange and the disk and pectoral fins having deep orange margins (vs. rose-lilac coloration, darker posteriorly).

Some of the observed differences between C. argosgeorgiae sp. nov. and C. smirnovi may be influenced by specimen condition at fixation, particularly pre-dorsal-fin length and chin-to-disk distance. Nevertheless, most characters are interpreted as interspecific differences, supporting the recognition of C. argosgeorgiae sp. nov. as a distinct species.

A comparison is also provided with C. solovjevae Balushkin, 2012 , originally described in the genus Volodichthys Balushkin, 2012 , because it was considered by its author to be closest to C. smirnovi ( Balushkin 2012) , to which the new species is also most similar. Available data ( Table 1) indicate that Careproctus argosgeorgiae sp. nov. resembles C. solovjevae in vertebral number and the presence of pleural ribs, but differs in having a gill slit reaching anterior to the 18th pectoral-fin ray (vs. 10–13), a smaller eye (16.2 vs. 20.6–25.2% HL), a smaller disk (32.6 vs. 37.2–42.4% HL), a shorter distance from anus to anal-fin origin (17.9 vs. 20.2–20.4% SL), and distinct coloration (body light orange vs. gray-lilac, darker posteriorly; peritoneum brown vs. brown with a greenish tint).

Except as noted above, six other species of Careproctus possessing two or three pairs of long pleural ribs are known from the Southern Hemisphere, all of which differ from C. argosgeorgiae sp. nov. Three species have higher vertebral counts: C. albescens Barnard, 1927 from South Africa (60–63), C. novaezelandiae Andriashev, 1990 from bathyal depths of the New Zealand Plateau (53–54), and C. paxtoni Stein, Chernova & Andriashev, 2001 from waters off New South Wales (58–59). Two species have similar vertebral (46–47) but differ in tooth morphology (three-lobed or with shoulders) and in having a shorter gill slit reaching only to the 5th–6th pectoral-fin rays in C. catherinae from the Ross Sea, or to the 7–11th rays in C. parini from the South Shetland Islands ( Andriashev 2003).

solovjevae ; diagnostic characters of the new species are marked in bold. F=female; M=male.

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