Holohalaelurus favus, Brett A. Human, 2006

Brett A. Human, 2006, A taxonomic revision of the catshark genus Holohalaelurus Fowler 1934 (Chondrichthyes: Carcharhiniformes: Scyliorhinidae), with descriptions of two new species., Zootaxa 1315, pp. 1-56 : 36-43

Holohalaelurus favus sp. nov.

(Figs. 11-12, Table 4)

Holohalaelurus regani : Smith, 1949: 60 (in part); Bass, 1973: 6 (in part); Bass et al., 1975: 25 (in part); Compagno, 1984b: 338 (in part); Bass, 1986: 93 (in part); Compagno, 1988: 152 (in part); Compagno et al., 1989: 54 (in part); Compagno, 1999: 98 (in part); Richardson et al., 2000: 553 (in part).

Holohalaelurus punctatus : Compagno & Human, 2003: 12.

Holohalaelurus regani favus subsp. nov.: Human, 2003: 92.

Holohalaelurus regani northeastern subspecies Compagno et al., 2005: 237.

Type Series and Locality. Holotype, RUSI 6139 (previously ORI 1482 (erroneously listed as ORI 1485 in the RUSI database)) , mature male 515mm TL, off Durban , kwaZuluNatal, South Africa, approx. 29°51'S 31°00'E, collected by the Keurboom, February, 1965, in fair condition, colour and patterning somewhat faded (Fig. 11).

Paratype, RUSI 6138 (previously ORI 1002) , mature female 423mm TL, collected from Durban to Tugela River Mouth , kwaZulu-Natal, RUSI data gives location 29°51’S 31°03’E, by Keurboom, 17th July, 1964, in fair condition, colour and pattern faded, and tail incompletely broken at the caudal peduncle (Fig. 12).

Diagnosis. A relatively large member of the genus, H. favus has the following distinguishing features: denticles on dorsal midline greatly enlarged from snout to second dorsal origin; denticles on pectoral fin dorsal surface greatly enlarged in adults; clubshaped papillae not present on the distal tip of the clasper; buccal papillae in mouth large and prominent on upper and lower surfaces; moderate vertebral count, 124 total vertebrae in the holotype (123 in the paratype, mean 117.8); relatively high tooth counts, 65 upper teeth in total in the holotype (66 in the paratype, mean 66.3), 70 lower teeth in total in the holotype (58 in the paratype, mean 60.3). Covered in irregularly shaped spots and reticulations on a brown background, resembling a honeycomb pattern; white spots rarely present and inconspicuous when present.

Description. Morphometric and meristic data are given in Table 4. Holotype, mature male 515mm TL (paratype, mature female 423mm TL, mean of all specimens examined in Table 4, including the type series, see Study material): body slender and elongate; head compressed, head width 2.86 (1.86, 2.25) times its height at the posterior margin of the orbit, and head width 2.25 (1.45, 1.71) times its height at the pectoral fin origin; trunk depressed, trunk width 1.51 (1.33, 1.39) times its height; abdomen slightly depressed, abdomen width 1.08 (1.25, 1.13) times its height; tail slightly depressed or not, tail width 1.02 (1.0, 1.04) times its height; caudal peduncle compressed, caudal peduncle height 1.37 (1.35, 1.50) times its width; ventral sensory pores not conspicuously black in preserved specimens, although likely to be so in fresh or live specimens; head long, head length 0.21 (0.20, 0.20) times the precaudal length; snout short, broadly rounded and not coming to a point, preoral length 0.24 (0.30, 0.31) times the snout to first gill slit distance; mouth short and narrow, relatively broadly arched, buccal papillae in mouth large and prominent on upper and lower surfaces, mouth width 2.55 (3.75, 3.36) times its length; eye slit like, eye length 1.76 (1.76, 1.60) times its height, distance from snout to the anterior origin of the orbit 0.64 (0.64, 0.65) times the snout to spiracle length; spiracle length 0.27 (0.16, 0.19) times the eye length; area around gill slits naked, lacking denticles; distance from snout to first dorsal fin origin 0.70 (0.67, 0.68) times the distance from the snout to the second dorsal fin origin; denticles on dorsal midline greatly enlarged from snout to second dorsal origin; first dorsal fin length 1.76 (2.0, 2.06) times its height, length of the base of first dorsal fin 0.72 (0.67, 0.68) times the length of the base of second dorsal fin; second dorsal fin length 1.66 (2.24, 2.53) times its height; snout to pectoral origin length 0.45 (0.46, 0.45) times the snout to pelvic fin origin length; pectoral fin large and winglike, enlarged denticles on the dorsal surface in adults, in the centre of the fin and towards the posterior margin of the fin, pectoral fin length 1.21 (1.55, 1.66) times its height; height of the pectoral fin 2.76 (2.74, 3.28) times the height of the pelvic fin; distance from pectoral insertion to pelvic origin 1.19 (1.25, 1.09) times the distance between the insertion of the second dorsal fin and the caudal fin dorsal origin; pelvic fin long and low, pelvic fin length 3.02 (3.58, 4.24) times its height, pelvic fin free rear tips variably fused, but never completely fused; claspers elongate without papillae on the distal tips, clasper inner margin length 8.25 (N/A, 8.63) times their base; snout to anal origin length 5.18 (3.91, 3.91) times the distance between the anal fin insertion and the origin of the ventral caudal fin; anal fin long and low, anal fin length 5.36 (4.94, 6.12) times its height; length of anal fin base 1.88 (1.82, 2.0) times the length of the second dorsal fin base; caudal dorsal margin length 1.33 (1.92, 1.71) times the interdorsal space, caudal ventral lobe weakly developed. Vertebral counts: 31 (30, 29.5) monospondylous, 55 (55, 55.3) precaudal diplospondylous and 38 (38, 33) caudal diplospondylous vertebrae. Dental formula: upper jaw (left) 31 (32, 32.0), symphyseal 1 (0, 0.7), (right) 33 (34, 33.7); lower jaw (left) 35 (28, 29.7), (symphyseal) 0 (1, 0.7), (right) 35 (29, 30.0).

Size and Sexual Maturity. Holohalaelurus favus sp. nov. is a large species of Holohalaelurus shark and attains at least 515mm TL, with the heaviest specimen examined in this study weighing 301.3g (Fig. 1 and Table 4). Males are immature at 193mm TL and mature at 515mm TL. Females are adolescent at 291mm TL and mature at 423mm TL.

Colouration. Dorsal background colouration of H. favus sp. nov. is pale brown to grey brown covered with many relatively large, irregularly shaped, solid spots, these sometimes fused into short bars and small reticulations giving rise to a honeycomb pattern; spots faint on pectoral fins and not present on pelvic fins or dorsal fins (possible preservation artefact), white spots rarely present and inconspicuous; no white spot above the pectoral fin base, or white spot at dorsal fin origins. Ventral colouration uniformly grey brown, fin webs darker and red brown, sensory pores black in fresh specimens.

Comparison with other species. Enlarged denticles are present along the dorsal midline in H. favus , from the snout to the origin of the second dorsal fin. Adult H. favus have enlarged denticles on the dorsal surface of the pectoral fins, a trait shared with adult H. regani . Buccal papillae are present, but not as large as in H. punctatus and H. regani . The fusion of the spots into bars and reticulations is not as evident as in H. regani and H. melanostigma . Holohalaelurus favus is smaller than H. regani and is equivalent in size to H. melanostigma before maturity, but grows to a larger size as an adult. Holohalaelurus favus is closest to H. regani in overall morphology and intermediate between H. punctatus and H. regani in colouration.

Remarks. Although no locality is provided on the ORI data sheet for the holotype (RUSI 6139), the following is provided, “off Keurboom. Arr[ival] date 15-2-1964 ”. From other ORI data sheets, it appears that the Keurboom regularly trawled on grounds to the southeast of Durban, not far offshore (usually 8 to 9 miles). Locality data from the RUSI database for this specimen gives the coordinates for Durban Bluff, however, this appears to be an approximation. Although the exact location is not known, there is little doubt that this specimen came from off Durban.

Morphometric proportions given by Bass et al. (1975) are a combination of “Natal” (= H. favus sp. nov.) and “Cape” (= H. regani ) specimens that they placed under the name of H. regani . Although comparisons of their data with the data collected during this study are similar, this is probably due to the morphological conservation displayed by these two species. Meristic data of Bass et al. (1975) came from “Natal” sharks and agrees with the meristics given here. The dentition and denticles described and illustrated by Bass et al. (1975) are probably referable to H. favus . According to Bass et al. (1975), H. favus has a total vertebral count of 123 to 136 (mean = 129.1), from a sample of 28 “Natal” H. regani (= H. favus ).

Bass (1973) showed that the “Natal” form of H. regani (= H. favus sp. nov.) displays an enormous amount of ontogenetic allometry across a number of measurements, as well as illustrating a juvenile compared to a mature H. favus (under the name H. regani ) to show proportional differences. Bass (1973) illustrated for H. regani , that the pectoral fin to pelvic fin measurement was greater in males than in females, regardless of the size of the individual, and is probably referable to H. favus . Strong sexual dimorphism is present in H. favus , with males growing much larger than females, and has been noted by Bass (1973) and Bass et al. (1975).

Bass et al. (1975: 26) describe for H. regani “…a row of white spots down each side… these spots… fade rapidly with growth”, however this is referable to H. favus sp. nov. as the author has not observed these spots on H. regani , even on freshly caught specimens while aboard the vessel R.V. Africana (Fig. 6A).

Bass et al. (1975) were the first to recognise a different form of Holohalaelurus occurring in the waters off northern kwaZulu-Natal and southern Mozambique. Although they placed it under the name of H. regani , they separated it from the more commonly occurring form, which they called the “typical” or “Cape” form ( H. regani as defined here), by referring to it as the “Natal” form (= H. favus n. sp.). The “Natal” form has subsequently been recognised by Compagno (1984b, 1988, 1999), Bass (1986), Compagno et al. (1989, 2005), and Richardson et al. (2000). Holohalaelurus favus has also been illustrated several times (see Bass, 1973; Bass et al., 1975; Bass, 1986). It was also illustrated in Smith (1949) but wrongly identified as a juvenile H. regani .

The author has examined all of the ORI data sheets referable to “ H. regani ” sharks collected off kwaZulu-Natal and Mozambique. Many of the specimens are described as having a honeycomb pattern, and are probably referable to H. favus sp. nov., although it is not possible to verify this without examining the actual specimens. Similarly, ORI have many specimens recorded from off Durban, northern kwaZulu-Natal, and into Mozambique (ORI data sheets) however, it is not possible, for the most part, to determine whether these records refer to “Cape” or “Natal” H. regani , because H. regani does occur at least as far north as Durban (see account of H. regani ).

This species may have suffered the same fate as H. punctatus in the region from Durban to southern Mozambique (see account for H. punctatus ). Specimens under the name H. regani were regularly caught in that area, and yet very few exist in collections today, and none have been collected from that area since Bass et al. (1975). An investigation is desperately needed in the region of kwaZulu-Natal and southern Mozambique to establish the status of Holohalaelurus there.

Distribution. Holohalaelurus favus sp. nov. is a regional endemic with a very limited range (Fig. 13), confined to five degrees of latitude. From this study, its range was verified from off of Durban, kwaZulu-Natal, South Africa, to just northeast of Maputo, Mozambique, in the subtropical western Indian Ocean. Two of the specimens examined were recorded with latitude and longitude data that places them at Durban Bluff, however these specimens were probably collected in deeper water off Durban Bluff.

Holohalealurus favus sp. nov. appears to have a preference for water deeper than 200m and shallower than 1000m. Bass et al. (1975) state that H. regani has a depth range from 200m to 420m off kwaZulu-Natal, and a depth range from 240m to 740m in southern Mozambique, both records are probably attributable to H. favus . They further state that the depth range may be greater than that reported by them because juveniles appear to be adapted to living in deeper waters compared to adults. If it is true that the juveniles of H. favus live in deeper water than the adults (Bass et al., 1975; Bass, 1986), then this is the reverse of that observed in H. regani , where the juveniles apparently occur in shallower water than the adults (Richardson et al., 2000).

Etymology. The specific name comes from the Latin word, favus (masculine), meaning honeycomb, and is reference to the colour pattern of fresh specimens of this species. Indeed, the ORI data sheet for the holotype (measured by N. Naicki), describes the colour pattern as “…light brown honeycomb pattern”.

Common name. Honeycomb Izak or Natal Izak.

Study material. RUSI 6138, designated paratype of H. favus sp. nov., see under Type Series and Locality for details; RUSI 6139, designated holotype of H. favus sp. nov., see under Type Series and Locality for details; RUSI 6140, previously ORI 2571 , adolescent female 291mm TL, off Maputo , Mozambique, 25°15'S 35°10'E ; RUSI 6271, previously ORI 2688 , immature male 193mmTL, off Durban Bluff , kwaZulu-Natal, South Africa, approx. 29°52'S 31°22'E .

To the authors knowledge, these specimens are all of the known specimens referrable to this species.