Oratosquillina interrupta ( Kemp, 1911 )

Masunari, Setuko, Lopes, Odete Lopez & Ahyong, Shane T., 2025, Introduction of the Indo-West Pacific mantis shrimp, Oratosquillina interrupta (Kemp, 1911) (Stomatopoda, Squillidae), to Brazil, Zootaxa 5637 (1), pp. 180-184 : 181-183

Oratosquillina interrupta ( Kemp, 1911)

( Fig. 1 )

Material examined. 1 male (TL 101.9 mm), 1 female (TL 115.5 mm), Paraná State, southern Brazil, 25°54’36”S, 48°33’13”W, 9–10 m, sandy substrate, coll. V. Liandro, 8 July 2023; 1 male (TL 87.7 mm), 13 females (TL 64.4–120.0 mm), Paraná State, southern Brazil, 25°54’36”S, 48°33’13”W, 9–10 m, sandy substrate, coll. V. Liandro, 10 July 2024; 2 males (TL 89.8–107.8 mm), 21 females (TL 81.8–137.2 mm), Paraná State, southern Brazil, 25°54’36”S, 48°33’13”W, 9–10 m, sandy substrate, coll. V. Liandro, 15 August 2024.

Diagnosis. Rostral plate broader than long, without median carina ( Fig. 1A, B ). Carapace anterior width about 0.5 carapace length; median carina interrupted at base of anterior bifurcation, branches of bifurcation distinct ( Fig. 1B ). Raptorial claw dactylus with 6 teeth, occlusal margin of propodus pectinate; carpus with two triangular lobes on dorsal margin; merus with inferodistal spine ( Fig. 1C ). Thoracic somites 5–7 lateral processes distinctly bilobed ( Fig. 1D ). Telson without carinae on dorsolateral surface ( Fig. 1A, E ). Uropodal protopod with convex lobe on outer margin of inner spine; 7–9 movable spines along outer margin of exopod proximal article ( Fig. 1E ).

Coloration ( Fig. 1 ). The overall coloration in live specimens is light olive green or straw-colored. However, the following structures are dark olive green: carapace grooves, posterior margin of body somites, submedian carinae of last abdominal somite, all carinae of telson, inner margin of proximal article of uropod exopod and proximal third of inner margin of distal article of uropod exopod. Diffuse, dark gray oval spot in the center of the carapace in most individuals. Furthermore, brownish-red coloration is present in carapace median carina including anterior bifurcation branches, around anterior pit and posterior bifurcation, gastric grooves of carapace, submedian carinae of all body somites except abdominal somite 6, transverse bar in abdominal somite 2, short longitudinal bar in middle line of abdominal somites 2–5. Telson with a spot resembling a broad arrow in the proximal third of median carina of telson, distal article of uropodal exopod yellowish (most individuals), most spines of telson and uropods pale red.

Remarks. The specimens agree in all respects with the description and published accounts ( Kemp 1911; Manning 1995: figs. 140, 141; Ahyong 2001: fig. 142; Ahyong 2016: fig. 5B; Dudiya et al. 2022: figs 1, 2). Oratosquillina interrupta is readily distinguished from all other Brazilian squillids by the combination of bilobed lateral processes of thoracic somites 5–7 and 6 teeth on the dactylus of the raptorial claw.

We are unaware of exactly when O. interrupta invaded the waters off the Paraná State coast and no previous specimens are present in the albeit small stomatopod collection (about 30 specimens total) of the Museu de História Natural do Capão da Imbuia. However, the trawl fisherman who collected the current series of O. interrupta, Mr Valdinei Liandro , indicates that the species has been present in trawl by-catch for the past 40 years. The bright, distinctive coloration of Oratosquillina interrupta , with the deep-marron spot on the median carina of the telson and yellow uropods, is unlike that of any other squillid in the region. In the trawling grounds, only one other stomatopod, Gibbesia neglecta , is present, which not only is a dull gray-brown, but is also most common at a different depth. Oratosquillina interrupta is part of the bycatch of the White Shrimp fishery [ Litopenaeus schmitti ( Burkenroad, 1936) ] that operates at 9–10 m depth. Conversely, G. neglecta is bycatch of the Seabob Shrimp fishery [ Xiphopenaeus kroyeri ( Heller, 1862) ], which typically works in shallower sublittoral depths of 3– 4 m. Thus, Oratosquillina interrupta is unlikely to have been mistaken for other species of stomatopod, even if the species name was not known to Mr Liandro at the time. This suggests that O. interrupta was introduced during or prior to the 1980s but has gone undocumented because of the lack of study of the stomatopods of Paraná State. The capture of specimens of both sexes, across a wide size-range over many years, corroborates our contention that O. interrupta is well established in southern Brazilian waters. To date, O. interrupta has only been collected in trawls at 9–10 m depth; intertidal and other habitats remain to be properly surveyed for the presence of the species.

The strong numerical dominance of females in the present samples of O. interrupta is notable (4 males vs 35 females) resulting in a very high sex ratio of 0.1:1.0. Although females are generally more abundant in squilloids, the sex ratio is usually much lower, typically in the range 0.8–1.0:1.0, and never as high as recorded here ( Hamano 2005; Maulidanti et al. 2024). Given that the present series of O. interrupta was not collected using a standardized sampling design, the abnormally high sex-ratio is more likely to be an artefact of sampling, rather than a reflection of actual population dynamics.

Oratosquilla interrupta is the fourth squillid to have become established outside of its natural range. The species is sometimes locally harvested as part of commercial trawl by-catch throughout much of its range but it (or its close relatives) are nowhere part of the aquarium or live seafood export trade ( Manning 1998; Ahyong, pers. obs.), so translocation of adults to South America is highly unlikely. Therefore, given the lack of biogeographic or oceanographic connectivity between tropical southern Brazil and the tropical Indo-West Pacific, it is unlikely that O. interrupta reached Brazil by natural dispersal. The larval stages of O. interrupta are as yet incompletely known ( Alikunhi 1967), but closely related squillids with known life histories have a pelagic larval period of one to two months ( Ahyong et al. 2014). Thus, the most likely mode of translocation of O. interrupta to Brazil is pelagic larvae in shipping ballast water, as with the introduction of Oratosquilla oratoria from East Asia to Australia and New Zealand ( Ahyong & Wilkens 2011).

Distribution. Indo-West Pacific from the northwestern Indian Ocean to the western Pacific including the Persian Gulf, Pakistan, India, Australia, Vietnam, Malaysia, Thailand, Hong Kong and Taiwan ( Manning 1995; Ahyong et al. 2008; Ahyong 2016; Dudiya et al. 2022), and for the first time from the western Atlantic off southern Brazil (present study).

Figures

FIGURE 1. Oratosquillina interrupta (Kemp, 1911), female (TL 124.3 mm), Guaratuba, Paraná State, southern Brazil, 15 August 2024, MHNCI_INV 0054/2025: A, dorsal habitus; B, carapace dorsal surface; C, right raptorial claw; D, right lateral processes of thoracic somites 5–8; E, right uropod, dorsal view.