Pterygosquilla capensis Manning, 1969a

Brokensha, Rouane, Landschoff, Jannes & Griffiths, Charles, 2025, Taxonomic guide to the mantis shrimps (Crustacea: Stomatopoda) of South Africa, Zootaxa 5713 (1), pp. 1-93 : 73-77

Pterygosquilla capensis Manning, 1969a

( Fig. 28 )

Squilla armata .— Stebbing, 1902: 45; 1910:.405.— Tattersall, 1913: 879.— Balss, 1916: 51.— Calman, 1923: 1.— Barnard, 1950: 845, fig. 1d, f.— Lebour, 1954: 231, fig. 6 [larvae].

Squilla armutus .— Stebbing, 1914: 257, 300.

Pterygosquilla armata capensis Manning, 1969a: 8–13 , figs. 2, 3.

Pterygosquilla capensis .— Ahyong, 2012: 92 (key).

Material examined. Northern Cape: SAMC-A079447 , 1 ♂ (TL 55 mm), off Holgatrivier mouth, 28°59.90’S 16°38.87’E, 18 Jun 1986, 56 m, bottom trawl, SFI. SAMC-A079477 , 1 ♀ (TL 49 mm), west coast, 31°09’00.0”S 17°19’60.0”E, 28 June 1987, 177 m, stat. A5901-054-037-2317 . Western Cape: SAMC-A019431 , 1 ♀ (TL 138 mm), False Bay, 33°52’59.9”S 18°27’00.0”E, depth and date unknown, coll. Duminy; SAMC-A001343 , 1 ♂ (TL 155 mm) , Cape Town docks, 33°52’59.9”S 18°22’59.9”E, depth unknown, Oct 1911, coll. L. Peringuey; SAMC- A079593, 2 ♀ (TL 80 mm), False Bay 34°23’17.9”S 18°40’18.1”E, 31 Jan 1959, stat. FAL 351F; SAMC-A045105 , 1 ♀ (TL 66), 4 ♂ (TL 47–72 mm), 32°04’59.9”S 18°06’00.0”E, 21 Sep 1960, rock dredge at 108 m, coll. R. B. Manning; SAMC-A012008 , 1 ♂ (TL 126 mm), Paarden Island , 34°02’59.6”S 23°03’00.0”E, depth unknown, Aug 1963, coll. K. Emerson; SAMC-A079438 , 1 ♀ (TL 110 mm) Paarden Eiland Power Plant outlet , Cape Town , Jul 1973, shallow intertidal; SAMC-A079407 , 1 ♀ (TL 115 mm) Table Bay power plant, 33°54’14.7”S 18°27’37.4”E, 26 June 1974, shallow intertidal; SAMC-A079522 , 1 ♀ (TL 74 mm), Table Bay, 33°49’00.1”S 18°27’00.0”E, 23 rd May 1980, depth unknown, stat. TBD 74, dredge; SAMC-A079403 , 1 ♀ (TL 96 mm), Oliphantsbos Beach , 34°15’25.5”S 18°22’52.1”E, 1981, shallow intertidal, coll. W. R. Liltved; SAMC-A079405 , 6 ♂ (TL 36–71 mm), 5 ♀ (TL 32–64 mm), Danger Bay, Saldanha, 33°00’12.0”S 17°53’12.0”E, 22 May 1983, 0–50 m, stat. A 009-54-01, RMT-8 , DSF; SAMC-A079417 , 2 ♂ (TL 41 mm), 1 ♀ (TL 35 mm), Saldanha, 33°02’26.4”S 17°46’28.8”E, 22 May 1983, 0–100 m, stat. A 009-54-02, RMT 8 and Neuston, SFI; SAMC-A79471 , 1 ♂ (TL 80 mm), off Saldanha , 33°07’00.0”S 17°59’24.0”E, 23 May 1983, 40 m, stat. A 009-56-01A, RMT 8 , DSF; SAMC-A079402 , 1 ♂ (TL 81 mm), Misty Cliffs , Cape Town , 34°11’57.6”S 18°17’13.2”E, 26 May 1983, 100 m, stat. A 009-72-02, RMT 8 and Neuston, SFI; SAMC-A079408 , 1 ♀ (TL 82 mm), off Hout Bay, 34°02’48.0”S 18°15’41.4”E, 26 May 1983, depth unknown, stat. A 009-70-01, SFI; SAMC-A079406 , 1 ♂ (TL 78 mm), off Hout Bay, 34°05’19.2”S 18°13’00.0”E, 26 May 1983, 100 m, stat. A 009-70-02, SFI; SAMC-A079419 , 1 ♂ (TL 76 mm), Saldanha Bay, 33°07’00.0”S 17°59’24.0”E, 23 May 1983, 40 m, stat. A 009-56-01, RMT-8 , SFI; SAMC-A077772 , ♀ (TL 79 mm), off De Hoop Nature Reserve , 35°43’00.0”S 20°55’00.0”E, 2 Jun 1988, 105 m, stat. A722; SAMC-A079478 , 1 ♂ (TL 150 mm), off the Western and Eastern Cape border, 31°15’06.0”S 17°39’30.0”E, 6 Aug 1989, depth unknown, stat. A9053-075-039-2331, SFI; SAMC-A079481 , 4 ♂ (TL 100–140 mm) 4 ♀ (TL 88–130 mm), off Elands Bay, 32°13’60.0”S 18°13’60.0”E, 68 m, stat. A10434 -084-041-1070; SAMC-A079458 , 4 ♂ (TL 135–161 mm), 31°30’00.0”S 17°56’00.0”E, 6 Aug 1989, 98 m, midwater trawl, stat. A9055-075-040-1058, RV Africana , West coast Hake biomass survey; SAMC-A079459 , 3 ♂ (TL 76–125 mm) 1 ♀ (TL 86 mm), 31°15’00.0”S 17°30’00.0”E, 6 Aug 1989, 145 m, stat. A 9052-075-038-2324, RV Africana , West coast Hake biomass survey; SAMC-A079480 , 4 ♂ (TL 49–94 mm) 7 ♀ (TL 48–89 mm), off Elands Bay, 32°27’60.0”S 17°49’00.0”E, 25 Jul 1990, 139 m, stat. A10431-084-038-3456; SAMC-A079473 , 3 ♂ (TL 158–176 mm), off Standfontein, 31°51’00.0”S 17°58’00.0”E, 27 Jul 1990, 111 m, stat. A10438 -084-043-2393; SAMC-A079506 , 1 ♂ (TL 92 mm), 25 Sept 1991, off George , 34°04’00.0”S 23°10’00.0”E, 64 m, stat.A12056-095- 050-2262 . Eastern Cape: SAMC-A079404 , 3 ♂ (TL 85–90 mm), 1 ♀ (TL 100 mm), Tsitsikamma National Park MPA, 34°04’00.0”S 23°51’00.0”E, 12 Apr 2004, 121 m, stat. A23068 -028-1054, bottom trawl. Unknown location: SAMC-A079460 , 1 ♂ (TL 108 mm) 1 ♀ (TL 90 mm), 6 th Nov. 1984, 33 m, stat. 24-02A, DSF; SAMC-A079455 , 1 ♂ (TL 77 mm), stat. A2935-036-017, shark gut; SAMC – A079487 1 ♂ (TL 69 mm), stat. SL 11; SAMC-A079456 , 2 ♂ (TL 70–97 mm), stat. A2936-036-018, shark gut .

Diagnosis. Rostral plate triangular to linguiform; apex narrowly rounded. Distance between SM carinae onequarter distance between IM carinae. SM carinae of AS 1–5 present in juveniles and small adults, indistinct to absent in specimens exceeding TL 90 mm. Posterior margin of AS 5 usually without accessory spinules. Telson with postanal carina, can be faint in smaller specimens.

Colour in alcohol. Closely resembles Barnard’s (1950) colour description as overall “horny amber” with cornea green and dactylus pale. However, specimens can appear dusky to salmon pink while still exhibiting the white dactylus Barnard described. Several specimens with squarish dark brown spot on each abdominal segment between IM and LT carinae and on AS 2 between LT and MG carinae. Posterior margin of AS 1–4 dark brown as well as tips of all pleopods, uropodal exopod and endopod and antennal scales. Mid-marginal brown strip on carapace. Dark dots distally positioned by articulation of pereopod segments on pereopods 1–3. Dark red outlining anterior SM tubercles of telson.

Colour in life. Two colour morphs are given in the regional offshore guide ( Atkinson & Sink 2018). Overall honey coloured with pereopods and dactylus white; uropodal exopod distal segments and telson posterior margin bright yellow for several individuals found on the south and east coasts. The second and more common colouration can be pinkish purple to grey and maroon with abdominal and telson carinae, as well as telson posterior margin trimmed with orange-red to maroon; all limbs pale.

Measurements. ♂ (n = 48) TL 36–176 mm, ♀ (n = 30) TL 32–138 mm.

Distribution and habitat. Only known from southern Africa, Namibia to southern KwaZulu-Natal. While abundant on the west coast of South Africa, specimens have been collected from off Namibia as far up as Walvis Bay. Several specimens have been reported as being collected from shark and tuna stomachs of unspecified species. The species occurs on level sand or mud substrates suitable for their burrowing lifestyle. Specimens have been recorded at depths 34–584 m, with most from around 100 m (DFFE, unpublished data).

Remarks. Commonly known as the Cape Mantis Shrimp, this species is the only stomatopod species known from the west coast north of St. Helena Bay in South Africa and spanning the entire coast of Namibia ( Abelló & Macpherson 1990). High abundances of P. capensis have been reported in certain coastal areas between St. Helena Bay and the South African border with Namibia, and the species is known as an important prey species of many predatory fish and seabirds ( Griffiths & Blaine 1988). As one of just three species of mantis shrimp known from the west coast of South Africa, P. capensis is the one frequently caught in large numbers during trawl and dredge surveys. In their investigation into mantis shrimp distribution and population biology, Griffiths & Blaine (1988) P. capensis was the only stomatopod species collected by trawl surveys along the west coast of South Africa between Port Nolloth and Cape Agulhas, with the highest concentration of individuals at St Helena Bay. The present study reports on the large number of Pterygosquilla specimens collected between 1875 and 2004 and housed in the Iziko South African Museum.

Pterygosquilla armata , P. capensis , P. gracilipes , and P. schizodontia make up the four species of Pterygosquilla currently recognised. Manning (1969a) defined three subspecies of Pterygosquilla armata : P. a. armata (H. Milne Edwards, 1837) from southern South America; P. a. schizodontia ( Richardson, 1953) from New Zealand and P. a. capensis Manning, 1969a , from South Africa. Subsequently, in his study of P. schizodontia, Ahyong (2012) recognised the subspecies of P. armata as three separate species substantiated by their characteristic morphologies, as well as their distinct geographical distributions. For specimens TL ≥ 100 mm, Manning (1969a) distinguished his subspecies, Pterygosquilla armata capensis , by the size of the lobe between the terminal spines of the uropodal protopod, the degree of definition for the abdominal SM carinae and distance between the abdominal SM carinae. Ahyong (2012) found Manning’s use of the former character to be unreliable but validated the use of the distinctiveness of, and distance between, the abdominal SM carinae as features with which to distinguish P. schizodontia from P. armata .

The present series agrees with Manning (1969a) and the distance between the abdominal SM carinae is consistent as a diagnostic feature. Pterygosquilla capensis is distinguished from P. schizodontia by the distance between SM carinae being one-fourth rather than one-third the distance between IM carinae. Distinctions between P. armata and P. capensis are more subtle and are based on size-related characteristics for both species. Meanwhile, morphological variation in P. capensis is marked, especially in the number of teeth on the dactylus of the raptorial claw and condition of the IM denticles of the telson. Ranging in number from 6–11 teeth on the dactylus of the raptorial claw, the majority of examined specimens had 7 or 8 teeth with five specimens exhibiting differing teeth numbers on either dactylus: 7 and 9, 9 and 10, 10 and 9 and two specimens with 7 and 8 teeth of the right and left dactyli of the raptorial claw respectively. As previously recorded in P. armata and P. schizodontia , at least one IM denticle of the telson is usually secondarily bifurcated, with no obvious pattern in number or orientation. An unusual feature never recorded for Pterygosquilla is the addition of a small apical spine on the rostral plate illustrated herein for P. capensis ( Fig. 28J ) and observed for several specimens. Other minor variation includes varying shapes of the rostral plate from the length being slightly longer or shorter than the width and the sternal keel of the TS8 with an apex ranging from rounded to sharp.

The most accessible and utilized method to identify the species of Pterygosquilla is via their discrete distributions: P. armata from southern South America, P. gracilipes from the west coast of Patagonia, P. schizodontia from New Zealand and P. capensis from South Africa ( Ahyong 2012). However, the variation of certain features found in the present material calls into question the use of distinct population localities to identify P. capensis . The species not taken into consideration by Manning (1969a) in his revision of P. armata is the highly understudied Pterygosquilla gracilipes Miers, 1881 from Chile. After its original description, P. gracilipes has been revisited briefly by Kemp (1913) and more recently by Hendrickx & Rivas (2016) using specimens from southern Chile. In his key to the genus, Ahyong (2012) distinguished P. gracilipes via the absence of a postanal carina, as well as the presence of more than 18 SM denticles on the telson in adults. However, in the present study the distinctness of the postanal carina varies from a well-defined ridge to a faintly raised line and in one specimen the postanal carina is absent. The incongruity of the features found in the present series of P. capensis casts some doubt on the taxonomic utility of the feature.

The second feature used to distinguish P. gracilipes is the greater number of triangular to spinular SM denticles (>18) of the telson compared to other species in the genus (1 or 2 rounded to subquadrate denticles and occasionally up to 10 tiny spinules) ( Ahyong 2012). However, multiple specimens of the present series exhibited more than 18 SM denticles of the telson and appear spinular in structure ( Fig. 28I, K ). Overall, 12 of the 78 specimens examined were found to have more than 18 SM denticles, accounting for 15 % of the present material. These specimens are all a similar midrange size ( 62–108 mm TL) and were collected in the 1980s during surface and midwater trawl surveys between Saldanha Bay and the Cape Peninsula .

The species of Pterygosquilla are distinguished from other Squillidae genera by their ocular scales being produced into strong anteriorly-directed spines. However, 13 (roughly 17%) of the 78 specimens of Pterygosquilla examined displayed rounded ocular scales ( Fig. 28G ). Moreover, this feature is usually observed in combination with the other varying characters mentioned above. Specimens with rounded ocular scales were usually found to exhibit more than 18 denticles between the SM teeth of the telson [9 of the 13 had>18 SM denticles]. As previously mentioned, this feature is considered characteristic to P. gracilipes . Furthermore, this feature combination was observed in specimens with a greater number of teeth on the dactylus of the raptorial claw (9–11 teeth). The specimens with rounded ocular scales were stored in assorted jars containing P. capensis material with the ‘normal’ complement of characteristics. This variation observed for a genus defining feature puts into question the stability of the feature as diagnostic.

The high variation found in this local species suggests that a global revision of Pterygosquilla is required. The variation in P. capensis raises the question of whether there is more than one species present in this highly abundant and perhaps most common South African stomatopod. Such questions should be explored by future studies incorporating molecular tools.

Figures

FIGURE 28. Pterygosquilla capensis Manning, 1969a: A–F, ♂ TL 72 mm, SAMC-A045105; G, I, K, ♀ TL 82 mm, SAMC- A079408; H, ♂ TL 155 mm, SAMC-A001343; J, ♂ TL 150 mm, SAMC-A079470. A, anterior cephalothorax, dorsal; B, right raptorial claw, lateral; C, left pleopod 1 endopod, anterior; D, TS5–8, left dorsal; E, right uropod, ventral; F, AS4–6, left uropod and telson, dorsal; G, ocular scale variation, dorsal; H–I, telson variations, dorsal; J, rostrum variation, dorsal; K, SM denticle variation, dorsal. Scale A–B, D–F = 2 mm; C = 1 mm; H = 4 mm; K = 0.5 mm.