Holohalaelurus regani (Gilchrist 1922)

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 : 18-27

Holohalaelurus regani (Gilchrist 1922)

(Fig. 5, Table 2)

Scylliorhinus regani Gilchrist, 1922 : 5.

Scylliorhinus regani : Barnard, 1925: 42.

Not Scyliorhinus regani Fowler, 1925 : 188; Fowler, 1926: 32; Barnard, 1927: 1013 (= Poroderma marleyi Fowler 1934 ).

Halaelurus (Holohalaelurus) regani : Fowler, 1934: 235; Fowler, 1941: 42.

Holohalaelurus regani regani subsp. nov.: Human, 2003: 95.

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

Type Series and Locality. Neotype, designated herein, and type species for the genus Holohalaelurus , SAM 32448 , mature male 628mm TL, R.V. Africana Cruise 079, station A9830 082-3162 (erroneously recorded as 082-3160 on label) , 30°57’S 16°46’E, from southeast of Hondeklip Bay, Northern Cape Province, South Africa, from 234m, 27th January, 1990, in excellent condition.

Diagnosis. Holohalaelurus regani is the largest species of Holohalaelurus , and the following distinguishes H. regani from other Holohalaelurus sharks: denticles on dorsal midline from snout to second dorsal fin origin greatly enlarged; denticles on dorsal surface of pectoral fins greatly enlarged in adults; club-shaped papillae not present on the distal tip of the clasper; buccal papillae in mouth large and prominent on upper and lower surfaces; relatively high vertebral count, 126 total vertebrae in the neotype (mean 121.2); relatively high tooth counts, 71 upper teeth in total in the neotype (mean 64.5), 72 lower teeth in total in the neotype (mean 59.8). Adults with large horseshoe shaped markings, larger than eye diameter, on yellow-brown background; juveniles with large, irregularly shaped spots, ontogenetically fusing into the adult pattern; white spots never present.

Description. Morphometric and meristic data are given in Table 2. Neotype, mature male 628mm TL (mean of all specimens examined in Table 2, including the neotype, see Study material): body slender and elongate; head depressed, head width 2.33 (2.60) times its height at the posterior margin of the orbit, and head width 1.86 (2.14) times its height at the pectoral fin origin; trunk depressed, trunk width 1.46 (1.48) times its height; abdomen slightly depressed, abdomen width 1.08 (1.21) times its height; tail slightly compressed, tail width 0.86 (0.98) times its height; caudal peduncle compressed, caudal peduncle height 1.14 (1.44) times its width; ventral sensory pores conspicuously black; head moderately long, head length 0.22 (0.22) times the precaudal length; snout short, rounded and coming to a point, preoral length 0.22 (0.30) times the snout to first gill slit distance; mouth moderately long and relatively wide, moderately arched, buccal papillae in mouth large and prominent on upper and lower surfaces, mouth width 2.42 (2.85) times its length; eye slit like, eye length 2.07 (1.88) times its height, distance from snout to the anterior origin of the orbit 0.66 (0.68) times the snout to spiracle length; spiracle length 0.31 (0.19) times the eye length; area around gill slits naked, lacking denticles; distance from snout to first dorsal fin origin 0.69 (0.67) times the distance from the snout to the second dorsal fin origin; enlarged denticles on the dorsal midline from snout to second dorsal fin origin; first dorsal fin length 1.97 (2.18) times its height, length of the base of first dorsal fin 0.90 (0.73) times the length of the base of second dorsal fin; second dorsal fin length 2.44 (2.37) times its height; snout to pectoral origin length 0.46 (0.47) 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 1.28 (1.34) times its height; height of the pectoral fin 3.03 (2.64) times the height of the pelvic fin; distance from pectoral insertion to pelvic origin 1.16 (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 3.73 (3.42) 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 9.0 (8.33) times their base; snout to anal origin length 4.85 (4.38) times the distance between the anal fin insertion and the origin of the ventral caudal fin; anal fin long and low, anal fin length 4.97 (4.87) times its height; length of anal fin base 1.88 (1.84) times the length of the second dorsal fin base; caudal dorsal margin length 1.52 (1.51) times the interdorsal space, caudal ventral lobe weakly developed. Vertebral counts: 30 (30.4) monospondylous, 58 (54.3) precaudal diplospondylous and 38 (36.5) caudal diplospondylous vertebrae. Dental formula: upper jaw (left) 32 (31.9), symphyseal 6 (2.0), (right) 33 (30.8); lower jaw (left) 33 (28.8), (symphyseal) 6 (2.7), (right) 33 (28.4).

Size and Sexual Maturity. Holohalaelurus regani is the largest of the Holohalaelurus sharks. The largest total length recorded here was 631mm and the largest weight recorded was 691.3g, for males (Fig. 1 and Table 2). In the current study, males were found to be juvenile at 232mm to 420mm TL, and mature at 598mm to 631mm TL. Females were found to be juvenile at 140mm to 254mm TL, adolescent at 224mm to 351mm TL, and mature at 425mm to 515mm TL. The heaviest female examined in this study weighed 320g.

Colouration. The colour pattern of adult H. regani is very striking and unique amongst Holohalaelurus , dorsal background colouration pale yellow to pale yellow brown, also pale yellow grey, yellow brown to mustard, pale brown, but these may be preservation artefacts. Ontogenetic progression of dorsal patterning is as follows: juveniles (Fig. 6B) with moderately large irregularly shaped solid dark brown spots that increase in size and begin to fuse in larger individuals to form small bars, blotches and reticulations, several indistinct saddles may be variably present or absent; in adolescent and mature animals (Figs. 5 & 6A), the patterning is a maze of large bold reticulations and horseshoe shaped markings, with spots virtually absent, when present, found only on the caudal peduncle or on fin webs, saddles absent; pattern on pectoral and pelvic fins identical to that of the dorsal patterning corresponding to the stage of maturity; white spots never present, no white spot above pectoral base or white spots at dorsal fin origins. Ventral colouration uniformly white, or off white in fresh or well preserved specimens, ranging to dull grey or brown in preserved specimens; with sensory pores conspicuously black on underside of head, trunk, pectoral and pelvic fins.

Comparison with other species. Holohalaelurus regani has greatly enlarged denticles on the dorsal midline, equivalent to H. favus and more so than other Holohalaelurus species. Adult H. regani have enlarged denticles on the dorsal surface of the pectoral fins, as do adult H. favus . The buccal papillae are large and conspicuous, but less so than in H. punctatus . Adults of H. regani have a unique dorsal patterning of large bold reticulations and horseshoe shaped markings, with spots few or absent, and no white spots. The dorsal patterning of juveniles is similar to that found in H. favus , H. grennian and H. punctatus , but distinguishable from these in the absence of white spots, absence of a white spot above the pectoral fin bases, and the absence of a honeycomb pattern. Holohalaelurus regani grows to a larger size than any other shark in this genus. Holohalaelurus regani is closest to H. favus and H. melanostigma in overall morphology, with adult colouration closest to H. melanostigma , and juvenile colouration closest to H. favus .

Remarks. Two forms of H. regani have been described (Bass et al., 1975) and generally recognised prior to this study. These forms include the “Cape” or “typical” form, and the “Natal” or “northeastern” form. The “Natal” form was diagnosed as a taxon warranting the rank of species, here described as H. favus sp. nov., whereas the “Cape” or “typical” form represents the true H. regani as originally described by Gilchrist (1922).

There are two juvenile female specimens in the SAIAB collection (RUSI 952) that are currently recognised as the syntypes for H. regani . Both of these animals are at the minimum extreme of total length for free swimming animals of this species. Gilchrist (1922) lists locality stations without reference to any specimens, and there is no reference to these localities anywhere within the species description. The only specimen referred to by Gilchrist in his description of H. regani was of a male 50cm long, clearly not referable to either of the female RUSI 952 specimens, which were measured by the author as being 205mm TL and 254mm TL. Gilchrist (1922) also describes “horseshoe-shaped bands”, which are absent on both of the syntypes because the horseshoe patterning only develops in H. regani at a much larger size than the RUSI 952 specimens. The catalogue for the SAIAB collection does not contain any details of who deposited these specimens or how they came to be syntypes, and Recommendation 72D states that labelling accompanying a type should unmistakably denote their status (ICZN, 1999).

Eschmeyer (1998) lists these specimens as the type series for H. regani based on Compagno (1984b), Bass (1986) and Compagno et al. (1991), however, Compagno (1984b) lists them as “probable syntypes”, Bass (1986) makes no mention of any type series, and Compagno et al. (1991) only list the S.S. Pickle stations from Gilchrist (1922) without reference to the RUSI specimens. Article 72.4.7 (ICZN, 1999) states that the recognition of putative type material in publications other than in the original description, labels accompanying the putative type series, or museum catalogue entries, are not necessarily evidence that a putative type series is legitimate, as is the case with the RUSI 952 specimens. Although these specimens are currently recognised as syntypes (Eschmeyer, 1998), scrutiny reveals that these specimens are invalid type material for H. regani due to the lack of reference to these specimens in the original species description and lack of corroborating evidence. Barnard (1925) refers to a type specimen for H. regani in the Collection of the Government Marine Survey, with no further details. If indeed a H. regani type existed in this collection, it has since been lost.

This issue was referred to the ICZN (case 3364) - BZN 62(4), 16 December 2005. New Applications. CASE 3364: Scylliorhinus regani Gilchrist, 1922 (currently Holohalaelurus regani ; Chondrichthyes, Carcharhiniformes SCYLIORHINIDAE ): proposed conservation of current usage by designation of a neotype. B.A. Human. Their conclusion was “…when no name-bearing type specimen is believed to be extant [since there is no evidence to support the validity of the RUSI 952 specimens as type material], no ruling of the Commission is needed to designate a neotype of Scylliorhinus regani Gilchrist, 1922 … following the provisions of the Code (Article 75)… Therefore, the Secretariat is prepared to close the case” (S. Nikolaeva, pers. comm.).

Given the state of the type series for Holohalaelurus sharks, and to promote the stability of nomenclature for species within this genus, the designation of a neotype for H. regani would be warranted in accordance with Articles 75.1 and 75.3 (ICZN, 1999). The designation of a neotype (SAM 32448) from southeast of Hondeklip Bay, Northern Cape, results in the type locality changing to southeast of Hondeklip Bay, Northern Cape, in accordance with Article 76.3 (ICZN, 1999).

The type locality for H. regani given in Gilchrists’ original description, was “Cape Seas… in 95 to 175 fathoms”, and not 95-131 fathoms as listed by Eschmeyer (1998). The type locality data that accompanies the syntypes of H. regani , listed four possible S.S. Pickle stations from off of Table Bay, Western Cape (stations 234, 235, 241, or 243), with the possibility that the specimens may have also come from stations 324 or 359, presumable S.S. Pickle stations (exact location unknown). In any event, these localities are sufficiently ambiguous that the proposed type locality does not violate the requirement that the neotype be collected from the type locality (Article 75.3.6, ICZN, 1999), and furthermore, the proposed neotype type locality still falls into the type locality defined by Gilchrist, i.e. “Cape Seas”.

A source of taxonomic confusion in this genus is that there is marked ontogenetic allometry (as noted by Bass, 1973) and patterning in this species. In juveniles, the caudal peduncle is extremely elongated and the body and head are very short compared to adults (Fig. 6B). Also, although the colour observed in the juveniles is similar to that of immature and adult H. regani , albeit somewhat duller (possible preservation artefact), the patterning in juveniles is of large diffuse spots and short bars, with no signs of reticulations. The reticulations that are characteristic of the adults, take form in late juveniles and immature specimens. This ontogenetic shift may be present in other members of the genus and caution must be used when attempting to identify juveniles.

Fowler (1934) states that he erroneously described Poroderma marleyi (= P. pantherinum ) under the name Scyliorhinus regani in Fowler (1925, 1926), which was followed by Barnard (1927). In both publications, Fowler illustrates specimens that are readily recognisable as P. pantherinum (Human, 2006).

Morphometric proportions given by Bass et al. (1975) are a combination of H. favus sp. nov. and H. regani , and although their proportions are similar to those given here, they should be used with caution. Strong sexual dimorphism is present in H. regani , with males growing much larger than females, and has been noted by many authors (Bass, 1973; Bass et al., 1975; Springer, 1979; Richardson et al., 2000; Human, 2003). Meristics and dentition given by Bass et al. (1975) are referable to H. favus and should not be used for comparison to H. regani as defined here and by Gilchrist (1922). Compagno (1988) defines Holohalaelurus as having seven turns in the spiral valve. In this study, spiral valve counts for H. regani ranged from three to six in specimens not in the type series.

Distribution. Holohalaelurus regani is a near endemic of South Africa and endemic to southern Africa (Fig. 7). This species prefers temperate to cool temperate waters, although it is also found in the subtropical waters of kwaZulu-Natal (Bass et al., 1975; Compagno et al., 1991; Richardson et al., 2000; present study). Holohalaelurus regani occurs in the Indian Ocean from about Durban, kwaZulu-Natal, South Africa, southwards and westwards to Cape Agulhas, continuing westwards into the Atlantic Ocean, and then northwards to southeast of Lüderitz, Namibia (Compagno et al., 1991; Richardson et al., 2000; present study).

Holohalaelurus regani is common to abundant on the continental shelf and upper slope down to at least 1075m (the deepest record yet published for this species), although it is more common between around 150 to 300m, and rare above 100m (Compagno et al., 1991; Richardson et al., 2000; present study). Holohalaelurus regani appears to prefer depths between 200m and 300m on the west coast, and depths between 100m and 200m on the south coast (Richardson et al., 2000). This species is a common bycatch of demersal trawlers (Compagno & Smale, 1989; Richardson et al., 2000) and was the most frequently encountered cartilaginous fish in the study by Compagno et al. (1991).

Compagno et al. (1991) also report this animal as far north in the Atlantic Ocean as southeast of Lüderitz, Namibia, and reasoned that this is the northern most limit of this sharks range in the Atlantic Ocean, as H. regani was not caught in Spanish research cruises that trawled the entire length of the Namibian coastline. It appears that Galeus polli replaces H. regani (and Scyliorhinus capensis ), north of the Atlantic limit of H. regani , possibly occupying the same niche that H. regani occupies in southern Africa (Compagno et al., 1991; L. Compagno, pers. comm.).

Bass et al. (1975) give the distribution of H. regani as from South Africa, Zanzibar and Somalia. Their records of H. regani in Zanzibar are based on H. grennian sp. nov. and H. melanostigma , and the source of their Somalian record is Fraser-Brunner (1952 in Bass et al., 1975). It is highly unlikely that H. regani occurs this far north, and it is more likely that the Somalian record is based on H. grennian or possibly H. melanostigma . The occurrence of Holohalaelurus north of Kenya needs further investigation.

Etymology. This catshark is “[n]amed after Mr Regan, who has described many South African fish” (Gilchrist, 1922).

Common name. Izak or Izak catshark have been used as common names for H. regani . Gilchrist (1922) called it a “Mottled Dog-fish”.

Study material. BAH 20020110.01 , mature male 630mm TL, R.V. Africana Cruise 165, A20476 3403-015 , 35°36'S 19°36'E ; BAH 20020414.06 , mature male 598mm TL, R.V. Africana Cruise 167, A20804 3028-001 ; BAH 20020414.07 , mature female 460mm TL, R.V. Africana Cruise 167, A20804 3028-001 ; BAH 20020414.08 , mature female 483mm TL, R.V. Africana Cruise 167, A20804 3028-001 ; BAH 20020414.09 , gravid female 455mm TL, R.V. Africana Cruise 167, A20804 3028-001 ; BAH 20020414.10 , mature female 428mm TL, R.V. Africana Cruise 167, A20804 3028-001 ; BAH 20020414.11 , gravid female 431mm TL, R.V. Africana Cruise 167, A20804 3028-001 ; BAH 20020414.12 , mature male 598mm TL, R.V. Africana Cruise 167, A20804 3028-001 ; BAH 20020419.02 , mature male 600mm TL, R.V. Africana Cruise 167, A20814 4053-010 ; BAH 20020419.03 , mature female 515mm TL, R.V. Africana Cruise 167, A20814 4053- 010 ; BAH 20020419.04 , gravid female 466mm TL, R.V. Africana Cruise 167, A20815 3270-011 ; LJVC 860111 , juvenile female 140mm TL, R.V. Africana Cruise 39, A3340 3404-017 , 35°57'S 19°42.4'E ; RUSI 952 , invalid syntypes, 2 specimens, both juvenile females, 254mm TL and 205mm TL, off Table Bay? Western Cape, South Africa, S.S. Pickle sta. 234?, 235?, 241?, or 243? ; RUSI 2800 , juvenile female 349mm TL, off Knysna , Eastern Cape, South Africa, 34°02'S 23°02'E ; RUSI 25726 , mature male 598mm TL, R.V. Africana Cruise 39, A3337 2662-014 , 35°42'18"S 19°44'24"E ; RUSI 38280 , adolescent female 351mm TL, [[ off Durban ]] 29°57'05"S 31°14'30"E ; RUSI 48813 , immature female 224mm TL, Namibia , 29°56'00”S 16°23'18"E ; RUSI 53725 , mature male 604mm TL, Namibia, R.V. Africana Cruise 59, A6949 0219-88 , 27°27'24"S 14°25'00"E ; SAM 12986 , adolescent male; SAM 12987 , 3 specimens, juvenile males, 270mm TL and 420mm TL, immature male, 270mm TL, [[ S of Cape Town ]] 34°43'15"S 18°30'00”E ; SAM 12988, previously PF 12684 , gravid female 425mm TL, NW½N 18mi off East London , Eastern Cape, South Africa, S.S. Pieter Faure, 33°15'S 28°09.5'E ; SAM 12989 , juvenile male 270mm TL, NE½N 19mi off Cape Point , Western Cape, South Africa, S.S. Pieter Faure, 34°36'S 18°18'E ; SAM 12990 , 5 specimens, 4 juvenile females, 176mm TL, 200mm TL, 230mm TL, and 254mm TL, and one juvenile male, 232mm TL, NE by E¾E 8mi off Cape Point , Western Cape, South Africa, S.S. Pieter Faure, 34°24.5'S 18°23'E ; SAM 12991 , adolescent female ; SAM 24408 , 2 specimens, one adolescent female, one mature male ; SAM 27027 ; SAM 31695 ; SAM 32448, designated neotype of H. regani , see under Type Series and Locality for details; SAM 32619 , mature female, R.V. Africana Cruise 86, A10600 , 35°04'S 20°44'E ; SAM 32995 , R.V. Africana Cruise 60, A7045 , 35°07'S 19°28'E ; SAM 33287 , R.V. Africana Cruise 111, A14748 , 36°09'S 20°7'E ; SAM 34500 , R.V. Africana Cruise 139, A18578 2606-083 , 35°06.5'S 19°08.5'E ; SAM 34648 , R.V. Africana Cruise 109, A14673 , 33°19'S 16°35.5'E .