Mystriophis caboverdensis Da Luz, Lopes, Jimenez & Psomadakis, 2025

Luz, Alciany Nascimento Da, Correia, Sandra Margarida, Lopes, Evandro P., Jimenez, Jose Gonzalez, Traore, Diafodé & Psomadakis, Peter Nick, 2025, A new species of the genus Mystriophis (Anguilliformes: Ophichthidae) from Cabo Verde (Eastern Central Atlantic), with notes on two Mystriophis specimens documented on the R / V Dr. Fridtjof Nansen, Zootaxa 5632 (2), pp. 293-308 : 295-307

publication ID	https://doi.org/10.11646/zootaxa.5632.2.4
publication LSID	lsid:zoobank.org:pub:33B2ADE8-12ED-48A5-9283-2196177351B5
DOI	https://doi.org/10.5281/zenodo.15376067
persistent identifier	https://treatment.plazi.org/id/E3799972-FFBB-FFF3-C0A4-0408FC2CA6C7
treatment provided by	Plazi
scientific name	Mystriophis caboverdensis Da Luz, Lopes, Jimenez & Psomadakis
status	sp. nov.

Treatment

Mystriophis caboverdensis Da Luz, Lopes, Jimenez & Psomadakis , sp. nov.

urn:lsid:zoobank.org:act:37740D65-0C8F-49E6-A518-F73DE487B370

New English name: Cabo Verde spoon-nose eel

( Figs. 1–4 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 , 6 View FIGURE 6 , Tables 1–3 View TABLE 1 View TABLE 2 View TABLE 3 )

Holotype. IEO1662, 723 mm TL, on the shelf between Boa Vista and Maio islands, Cabo Verde Archipelago , Eastern Central Atlantic Ocean (15°40’58.19”N, 23°01’10.81”W), R / V Dr. Fridtjof Nansen , Station 30, bottom trawl, 195 m depth, 30 November 2021. GoogleMaps

Diagnosis. The following combination of characters distinguishes Mystriophis caboverdensis sp. nov. from its congeners: dorsal-fin origin in front of pectoral-fin tip; inner and outer maxillary teeth subequal in size; head length 11.7 % of TL; snout length 16.1 % of HL (1.9 % of TL); interorbital width narrow, 6.8 % of HL (0.8 % of TL); predorsal length 13.7 % of TL; pectoral-fin length 22.9 % of HL (2.7 % of TL); distance between upper edge of gill opening and origin of dorsal fin 18.4 % of HL (2.1 % of TL); pectoral-fin rays 12; lateral-line pores to anus 64/63 (65/65 to anal-fin origin); vertebral formula 9–64–153; colouration dark brown with white streaks on the sides of head and distinct white spots along lower jaw and below eye; dorsal fin with wide black margin; surface sensory papillae on the nape, visible as a faint pale band crossing the head.

Description. Morphometric and meristic data are presented in Table 1 View TABLE 1 . Body moderately elongate, its depth 26.1 and 34.3 in TL at gill opening and anus, respectively. Branchial basket moderately expanded. Head and trunk shorter than tail; head and trunk 2.2, head 8.6, and tail 1.8 in TL. Head elongate and pointed, its dorsal and ventral profiles nearly straight (nape slightly convex); head ogive-shaped when viewed from above, its width 4.3 in HL. Snout short, blunt, laterally constricted near tip, overhanging beyond tip of lower jaw; snout subconical when viewed from above. Lower jaw included in upper jaw, its tip reaching beyond base of anterior nostril tube. Upper-jaw length 2.2 in head. Center of eye situated in anterior third of upper jaw. Lips well developed. Anterior nostril a short tube, laterally directed, inserted at deepest point of snout constriction ( Fig. 2 View FIGURE 2 ); posterior nostril opens along outer edge of upper lip, entirely covered by a flap whose center lies beneath anterior margin of eye. Eye relatively large, 10.6 in HL ( Table 1 View TABLE 1 ), positioned dorso-laterally on head. Interorbital space flat and narrow, less than eye diameter. Median fins well developed, folding back into a deep dermal furrow, and ending about an eye diameter before the tail’s finless tip. Vertical through dorsal-fin origin slightly behind mid-pectoral fin length; Pectoral-fins moderate, oval in shape; upper edge of pectoral base inserted slightly above upper end of gill opening; the base lying posteroventrally at about 45° and ending well above upper half of gill opening. Gill opening crescent-shape, on lower half of body, slightly inclined backwards. Interbranchial distance about equal to unstretched gill opening.

Cephalic pores ( Fig. 3 View FIGURE 3 ): SO 1+4; IO 3+3; POM 6+2 (7+2 on right side); STC 3; F 1. Surface sensory papillae well developed and contained within the white pigmented streaks and lines present on sides and top of head (see Fig. 5B View FIGURE 5 ). Lateral-line pores well-developed; 9 before gill opening in a high arching sequence, 64/63 before anus (pores not visible on posterior part of tail).

Teeth conical, slightly recurved, quite robust, and unequal. Upper and lower jaw biserial, vomerine teeth uniserial. Intermaxillary ( Fig. 3A View FIGURE 3 ) composed of 1 central and 3 fang-like teeth on each side at tip of snout (anteriormost central tooth and first 2 lateral teeth largest; the smaller lateral likely regenerating), followed a little farther back on the mesial line by a pair of smaller teeth placed in front of the first vomerine tooth. Vomerine teeth in a single row consisting of 2 widely separated, large fang-like teeth (the largest in the mouth) followed by 5 more closely set teeth (partially embedded by soft tissue), decreasing in size posteriorly ( Fig. 3A View FIGURE 3 ). Maxillary with 38/36 and 28/30 teeth on inner and outer row, respectively; teeth on inner and outer rows subequal in size, the outer teeth more pointed and beginning at level of fifth (left) and third (right) inner tooth (4A). Dentary ( Fig. 3B View FIGURE 3 ) with 37/34 and 26/22 teeth on inner and outer row, respectively; outer row much larger, consisting of 2/3 large, widely spaced teeth anteriorly (each preceded by a smaller replacement tooth on the left side) followed by 9/4 smaller, similar-size, closely-set teeth, these followed by 13/16 very small teeth progressively decreasing in size. The inner teeth beginning at level of third (left) and between the second and third (right) outer tooth ( Fig. 3B View FIGURE 3 ).

Fresh colouration (after defrosting). Nearly uniform dark brown, head and ventral side somewhat paler ( Fig. 1 View FIGURE 1 ); distinctive white oblique lines on sides of head: the first from corner of mouth onto cheek (to about mid-eye level), the second from the apical tip of the first line running posteriorly as a short dotted line (the two lines forming an angle <90°), the third as an irregular/dotted oblique line on the branchial region; distinct white spots or marks along lower jaw, on posterior nasal flap and posteroventral corner of eye ( Fig. 4A View FIGURE 4 ); a faint pale dotted band on top of head at level of nape and a pair of white oblong patches diverging posteriorly on each side of ventral midline of throat and a single white patch, (overlain by pin point melanophores) at level of isthmus extending onto anterior part of abdomen ( Fig. 4C View FIGURE 4 ); all white markings (i.e. spots, dotted lines and bands) associated to cephalic pores or surface sensory papillae; pattern of fine longitudinal wavy lines of darker tone forming the deep part of dermal folds on sides and top of head; supratemporal and anterior lateral-line pores white prominently encircled in dark brown ( Fig. 4B View FIGURE 4 ); dorsal fin white basally, distal half black ( Fig. 6 View FIGURE 6 ); basal half of pectoral fin whitish, light brown on distal half ( Fig. 4A View FIGURE 4 ); anal fin colour pattern mostly similar to dorsal fin.

Colouration in preservative. Similar to fresh colouration but body lighter and white lines on the head less distinct.

Size. Known from the holotype, a 72.3 cm TL adult female and a photographic record of a 100 cm specimen misidentified as Mystriophis rostellatus uploaded on FishBase www.fishbase.org (version 03/2025) by Pedro Niny Duarte.

Etymology. Named for Cabo Verde, the type locality of the new species.

Distribution ( Fig. 5 View FIGURE 5 ). Known from the holotype, collected by bottom trawl at 195 m depth in the southeastern part the Cabo Verde Archipelago (between Boa Vista and Maio Islands) and from a photographic record of a 100 cm TL specimen (see above) captured from Grande Islet, located in the southern part of the Cabo Verde Archipelago.

Comparisons. Mystriophis caboverdensis sp. nov. is unique among Mystriophis species in having the dorsal-fin origin slightly behind mid-length of pectoral-fin (vs. above or behind pectoral-fin tip in M. rostellatus and M. crosnieri ) ( Figs. 1 View FIGURE 1 , 6 View FIGURE 6 , 7A View FIGURE 7 , 8A View FIGURE 8 , 11A). It is also distinguished from its congeners in having 153 total vertebrae (vs. 154–158 in M. rostellatus and 136–144 in M. crosnieri ); 12/12 pectoral-fin rays (vs. 13 in M. rostellatus and 13–14 in M. crosnieri ); 64/63 lateral-line pores before anus (vs. 55–58 in M. rostellatus and M. crosnieri ); inner and outer row of maxillary teeth subequal in size (vs. teeth on outer row larger; see p. 208 in Blache 1971); predorsal length 117.4 % HL (vs. 123.9–135.3 % in M. rostellatus and 134.1–147.8% HL in M. crosnieri ); distance between upper end of gill opening and origin of dorsal fin 18.4 % HL (vs. 23.9–35.3 % in M. rostellatus and 34.1–47.8 % in M. crosnieri ).

The new species is further distinguished from M. rostellatus in having a larger preanal length 45.8 % (vs. 40.4–44.3%) TL and eye diameter 9.4 % (vs. 6.7–8.7 %) HL and a greater width at isthmus 10.8 % (vs. 5.2–8.3 %) HL, as well as teeth tips ungrooved (vs. grooved; see fig. 3 in Blache 1971).

Likewise, it is further distinguished from M. crosnieri in having a smaller HL 11.7 % (vs. 12.2–12.8 %) TL, snout length 16.1 % (vs 18.3–20.6 %) HL, interorbital width 6.8 % (vs. 8.7–11.8 %) HL and pectoral fin length 22.9 % (vs. 28.2–35.6 %) HL, body depth at anus 2.9 % (vs. 3.1–3.8 %) TL. Furthermore, based on comparisons with the M. crosnieri specimen examined by us, the new species has a narrower head (see Figs. 4B View FIGURE 4 , 7C View FIGURE 7 ), its greatest width 2.7 (vs. 3.6 %) TL.

In pigmentation, M. caboverdensis sp. nov. is distinguished from M. rostellatus and M. crosnieri in having an overall darker brown body when fresh (vs. dark ochre to light reddish brown) with white streaks and short dotted lines on the sides of head and distinct white spots along lower jaw and posteroventral corner of eye (vs. no white markings on head and body); dorsal fin with wide black margin (vs. dorsal fin with narrow black margin) ( Fig. 6 View FIGURE 6 ), also see Blache (1971: figs. 1, 6); sensory papillae on the nape individually undistinguishable, visible only as a faint pale band crossing the head (vs. sensory papillae on nape visible as a pale dotted-line crossing the nape with 2 shorter parallel branches running forward perpendicular to the main row) ( Figs. 4B View FIGURE 4 , 7C View FIGURE 7 , 10A View FIGURE 10 ).

The new species is further distinguished from M. rostellatus in having wavy longitudinal lines of darker tone (vs. lighter tone) forming the deep part of dermal folds on anterior part of body and from M. crosnieri in lacking yellowish tinge on top and sides of head ( Figs. 6 View FIGURE 6 , 7 View FIGURE 7 , 8 View FIGURE 8 ).

Finally, M. caboverdensis sp. nov. is distinguished from Mystriophis sp. A (an undescribed species known from off Angola) in having a shorter predorsal length 13.7 % (vs. 24 %) TL and more total vertebrae 153 (vs. 141).

Molecular analysis. The ML tree inferred from the COI sequences resolved into three major clades ( Fig. 9A View FIGURE 9 ), largely with support bootstrap values. The sequences of the two Mystriophis species generated in this study are in a group that includes Ophisurus macrorhynchos Bleeker and that this group is sister to Echiophis punctifer (Kaup) . This group in its turn forming a sister relationship with Echelus uropterus (Temminck & Schlegel) that includes all species of the subfamily Ophichthinae . Ahlia egmontis Jordan and Scolecenchelys macroptera (Bleeker) nest together to form a basal distinct clade including all species of the subfamily Myrophinae ( Fig. 9A View FIGURE 9 ). Despite the low (64) support node depicting the sister-group relationship between Mystriophis spp. and O. macrorhynchos — most probably due to the lack of intermediate species in our analysis—the haplotype network (see Fig. 9B View FIGURE 9 ) shows 18 mutational steps between the two Mystriophis species, slightly less than found between M. caboverdensis sp. nov. and O. macrorhynchos (22 mutational steps). Furthermore, the pairwise estimate of evolutionary divergence between species (see Table 2 View TABLE 2 ) clearly shows that our new species from Cabo Verde belongs to the genus Mystriophis as indicated by the lower genetic divergence value (3.6%).

Despite this study has for the first time provided inference of the phylogenetic placement of the genus Mystriophis from the perspective of 552 COI nucleotides, additional analysis with a larger number of species and specimens, including M. rostellatus , from a wider geographic area is needed to reliably resolve the relationships of species of the genus Mystriophis with the other Ophichthinae species.

Remarks. Even though some overlap, especially with M. rostellatus (see comparisons) may occur when more specimens of Mystriophis caboverdensis sp. nov. become available, its peculiar morphological characteristics and mtDNA sequence are such that we have no doubt as to its uniqueness. In Cabo Verdean waters, this new species has been misidentified as M. rostellatus as shown by a photo uploaded on FishBase www.fishbase.org (version 03/2025) by Pedro Niny Duarte of a large individual (100 cm TL) from Grande Islet ( Fig. 5 View FIGURE 5 ) collected by longline at 100–150 m depth on 07 November, 2000 (Menezes et al. 2021). This additional information supports the idea that similarly to M. crosnieri , also the new species is a deepwater species. Whereas M. rostellatus is a coastal (including lagoons) species not exceeding 40 m depth ( Blache et al. 1970; Blache 1971; McCosker 1986; McCosker 2016).

Mystriophis crosnieri is known to occur in the Western Mediterranean, Canary Islands and from Senegal to Angola between 75 and 400 m depth ( Blache 1971; Böhlke 1981; McCosker 2016), but it was never recorded from Cabo Verde. Conversely, M. rostellatus , a coastal species (not exceeding 40 m depth) ranging from Mauritania to Namibia ( Blache 1971; Böhlke 1981; McCosker 2016) has been reported for Cabo Verde by Reiner (1996) and Wirtz et al. (2013). However, M. rostellatus has only been listed/cited by these authors without vouchers available for confirmation. Therefore, we cannot exclude that M. rostellatus has been misidentified with our new species in Cabo Verde waters.

The M. crosnieri specimen examined by us agrees well with the morphological features provided by Blache (1971) except for having a slightly smaller snout (see Table 1 View TABLE 1 ). Detailed colouration of M. crosnieri is provided based on fresh and defrosted photos of the specimen examined by us ( Figs. 6 View FIGURE 6 , 7 View FIGURE 7 , 8 View FIGURE 8 ).

Notably, Blache (1971) mistakenly reported that the distance from upper pectoral-fin base to dorsal-fin origin is equal to 1/3 of HL in M. crosnieri . As attested by measurements of 10 specimens (597–965 mm TL) presented by Blache (1971: 218) himself and from the M. crosnieri specimen examined by us ( Table 1 View TABLE 1 ), the distance from upper pectoral-fin base to dorsal-fin origin is on average 41.0 % of HL.

While preparing this paper we became aware of photographs of a freshly caught Mystriophis specimen, 122 cm TL (not retained) trawled between 56–60 m depth off São Tomé during a Nansen survey. We tentatively identify this specimen ( Fig. 10 View FIGURE 10 ) as Mystriophis cf. rostellatus based on the depth of capture and on the wavy longitudinal lines of lighter tone (vs. darker tone in M. crosnieri ) forming the deep part of dermal folds on anterior part of body. This feature is included among the characteristics separating M. rostellatus from M. crosnieri (see Blache 1971: 217). Interestingly, on the sides of the head, the above mentioned wavy horizontal lines appear as dark brown irregular broken lines in M. cf. rostellatus (see Fig. 10B View FIGURE 10 ) and as nearly-continuous horizontal lines in M. crosnieri ( Figs. 6 View FIGURE 6 , 7B View FIGURE 7 , 8B View FIGURE 8 ) and M. caboverdensis sp. nov. ( Figs. 4A View FIGURE 4 , 6 View FIGURE 6 ). If confirmed, this newly found colour feature may be used, together with other diagnostic characters, to distinguish M. rostellatus from its congeners. However, the observed colouration differences and distinctive depth range (intermediate between M. rostellatus and M. crosnieri , M. caboverdensis sp. nov.) of the São Tomé specimen may be indicative of an undescribed taxon.

As remarked by McCosker (2016), the biodiversity and taxonomy of ophichthid eels in the region is still incomplete and several undescribed species are likely to occur. Among them is Mystriophis sp. A , a spoon-nose eel yet to be described, known to occur off Angola ( McCosker 2016) and possibly also the specimen from São Tomé documented in the present paper. For this reason, it is important that unidentified specimens, particularly from deep water, are retained and deposited in museum collections for further study.