Mesacturoides fimbriatus ( Lenz, 1905 )

Mesacturoides fimbriatus ( Lenz, 1905)

( Fig. 17 View FIGURE 17 )

Gonodactylus fimbriatus Lenz, 1905: 388 , pl. 47 fig. 2 [ type locality Zanzibar].

Mesacturoides fimbriatus .— Manning, 1962a: 7, 8, 10, fig. 2b.— Cappola & Manning, 1995: 279–280. — Ahyong, 2005: 163.

Material examined. KZN: SAMC-A015621 , 1 ♂ (TL 21 mm), Sodwana Bay, 27°31’00.1”S 32°40’59.9”E, 27 Jul 1976, 13.5 m, RW 14, coll GoogleMaps . R. Winterbottom, det. S. Ahyong.

Diagnosis. Rostral plate distinctly trispinous with anterior margins concave; anterior angles spiniform; lateral margins convex; slender median spine longer than base. Carapace with anterior margins convex, extending anteriorly beyond base, but not beyond anterior angles of rostral plate. A2 protopod dorsally with fixed, anteriorly directed spine. Mandibular palp 3-segmented. 5 epipods present. AS 6 unarmed, LT carina produced posteriorly as a blunt, triangular lobe. Telson with two pairs of primary teeth well-formed; SM teeth with movable apices and 6–11 SM slender denticles; IM teeth apices shorter than SM teeth with 5–8 IM denticles. Telson dorsal surface with 3 mid-dorsal carinae; MD carina broad with two posteriorly appressed swellings; MD carina flanked by two low carinae. Uropod protopod outer spine broader and longer than inner. Uropodal exopod proximal segment with 5 movable spines on outer margin, 2 proximal spines straight, 3 distalmost enlarged and strongly recurved anteriorly; proximal segment with dorsal patch of setae, distal segment dorsal surface completely setose. Uropod endopod outer margin fully setose, inner margin at most sparsely setose; ventral surface completely setose.

Measurements. ♂ (n = 1) TL 21 mm. At TL 31 mm, a female specimen from Somalia is the largest recorded ( Cappola & Manning 1995).

Colour in alcohol. Completely faded. The only mention of species colouration in life is ‘dark brown’ ( Lenz 1905).

Distribution and habitat. Arabian Sea, Pakistan, Persian Gulf to Western Indian Ocean, Somalia, Seychelles, Zanzibar and South Africa [KZN]; 0–13.5 m ( Ahyong 2005); associated with live and dead coral.

Remarks. The examined specimen agrees with the original species description by Lenz (1905), as well as the more recent report by Manning (1962a). Mesacturoides fimbriatus is most similar to M. brevisquamatus ( Paulson, 1875) and can be distinguished by the shape and setation of the uropods, as well as the number and form of the SM and IM denticles of the telson ( Manning 1962a, 1969c). However, the type material of both M. fimbriatus from Zanzibar and M. brevisquamatus are lost. Due to the two species distributional overlap in the Indian Ocean, the erection of neotypes for both species is recommended ( Ahyong 2005).

In South African waters, this reef-associated species has only been found once in Sodwana Bay, KZN ( Ahyong 2005). The species appears to be restricted to the northern and western Indian Ocean, ranging from Pakistan and the Persian Gulf to Somalia and extending south to the Seychelles, Zanzibar and South Africa. A targeted study of coral reef related mantis shrimps would likely find this species in coastal waters between Zanzibar and South Africa. The species inhabits live as well as dead coral and has been recorded as a host to the parasitic gastropod Caledoniella montrouzieri Souverbie, 1869 ( Cappola & Manning 1995). Species of Mesacturoides are suspected to use their highly modified uropods for securing themselves in their reef borrows, but this has yet to be observed ( Manning 1962a, 1978b).

LYSIOSQUILLOIDEA Giesbrecht, 1910 View in CoL

Diagnosis (after Ahyong 2012). Cornea mid-band with 6 (rarely 2) rows of hexagonal ommatidia. A1 somite dorsal processes spiniform or dorsoventrally flattened, not anteriorly compressed and rounded laterally. MXP3–4 with propodi subquadrate, ribbed or beaded. Body flattened, loosely articulated or compact. Raptorial claw with ischiomeral articulation terminal, dactylus inflated or uninflated basally. Telson rarely with distinct MD carina; primary teeth apices all fixed or at most with movable SM teeth. Uropodal protopod with at most two primary spines; articulation of exopod segments terminal.

Composition. Coronididae Manning, 1980 ; Lysiosquillidae Giesbrecht, 1910 ; Nannosquillidae Manning, 1980 ; Tetrasquillidae Manning & Camp, 1993 .

Remarks. Typically inhabiting deep burrows in soft sediment, lysiosquilloids rarely leave their shelters, but instead ambush prey from the mouths of their burrows. Lysiosquilloids are predominantly ‘spearers’ with only some species in family Coronididae possessing a smashing claw. Of the four families recognised, two are known from South Africa, both of which possess a raptorial claw adapted for spearing prey.

Key to the South African families of LYSIOSQUILLOIDEA View in CoL

1. Antennular somite with ventral carina. Telson IM denticles obsolete, at most low, rounded. Abdominal somites loosely articulated............................................................................... Lysiosquillidae View in CoL

– Antennular somite without ventral carina. Telson IM denticles pointed. Abdominal articulation compact.... Tetrasquillidae View in CoL

LYSIOSQUILLIDAE Giesbrecht, 1910 View in CoL

Diagnosis. Cornea strongly bilobed, set obliquely on stalk. Antennular somite with ventral carina.A2 protopod with 1 mesial and 2 ventral papillae. Raptorial claw with dactylus uninflated basally; propodus with 4 proximal movable spines. MXP1–5 with epipod. Abdominal segments depressed, loosely articulated. Pereopods 1–3 with slender or ovate endopods. Proximal margin of uropodal endopod without strong dorsal fold. Telson with IM and LT primary teeth fused into margin, presenting at most appearance of short projections; IM denticles obsolete, at most low, rounded.

Composition. Lysiosquilla Dana, 1852 ; Lysiosquilloides Manning, 1977a .

Remarks. Until recently, three genera, Lysiosquilla Dana, 1852 , Lysiosquilloides Manning, 1977a and Lysiosquillina Manning, 1995 , were recognised. Manning (1995) distinguished Lysiosquillina from Lysiosquilla based on antennal scale morphology and erected Lysiosquillina for three species with a broad antennal scale (length less than 3.0 times greatest width) and that lack the mesial dorsal spine on the antennal protopod. Meanwhile, Lysiosquilla was restricted to species with a mesial dorsal spine on the protopod of the antennae and having a slender antennal scale (length 3.0 or more times greatest width). However, with the description of more species, some exhibited characteristics intermediate between Lysiosquilla and Lysiosquillina (Ahyong 2001; Ahyong & Lin 2022). Subsequently, Lysiosquillina was synonymised with Lysiosquilla and phylogenetic analysis of all known species of Lysiosquillidae found species of the previously recognised Lysiosquillina to be monophyletic, but nested within Lysiosquilla , making the latter paraphyletic ( Ahyong & Lin 2022). The Lysiosquillidae include the largest known mantis shrimps, with all species exceeding 100 mm in total length. The largest known specimen of L. maculata is recorded as up to 385 mm ( Roxas & Estampador 1930). One characteristic of the group shared with nannasquillids is the loosely articulated abdominal somites, which allows for better movement within their vertical burrows. One genus is known from South Africa.