Achaeus monodi (Capart 1951)

Achaeus monodi (Capart, 1951)

Podochela monodi Capart, 1951:95, fig. 31, pl. 1: figs. 8, 11, pl. 2: figs. 17, 18, 20 [Cabinda, Zaire, Angola].

Achaeus monodi.—Monod, 1956:548, figs. 782–810 [Senegal, Guinea, Sierra Leone, Gabon].—Longhurst, 1958:89 [Sierra Leone].—Rossignol, 1962:122 [Congo].—Forest and Guinot, 1966:109 [Guinea, Ivory Coast, Nigeria, Principe, São Tomé].—Le Loeuff and Intès, 1968, table 1 [Ivory Coast].

DISTRIBUTION.—West Africa, from Senegal to Angola, including the offshore islands of the Gulf of Guinea, Principe, and São Tomé; sublittoral, 0–4 to 100 m.

Achaeus trifalcatus Forest and Guinot, 1966

Achaeus sp.—Monod, 1956:547, figs. 777–781 [Annobon].

Achaeus trifalcatus Forest and Guinot, 1966:110, figs. 15–17, [Principe, São Tomé, Annobon].

DISTRIBUTION.—Known only from the offshore islands of the Gulf of Guinea, Principe, São Tomé, and Annobon, in depths from 0–6 to 37 m.

*Achaeus turbator, new species

MATERIAL EXAMINED.—Pillsbury Material: Nigeria: Sta 248, 33 m, 9 (includes holotype), 2 ov (L, W).

DESCRIPTION.—Carapace (Figure 67a,c) elongate triangular, width 0.64–0.72 (mean 0.68) times length, strongly narrowed anteriorly, slightly constricted behind orbits, neck appearing elongate, branchial regions swollen, regions well defined. Surface appearing smooth, not markedly granular.

Rostrum (Figure 67a,c) consisting of 2 very short, slender spinules with distinct posterior or basal shoulder, arising from truncate lobe or from 2 lobes separated by very shallow median emargination. Rostral spines directed anteriorly, not upturned in lateral view (Figure 67b).

Supraorbital eave (Figure 67a,b) smooth or lightly tuberculate, not armed with spinules. Postorbital margin smooth, unarmed. Eyestalks stout, width about half length, expanded distally, anterior margin sinuous, lacking well-marked projection. Narrow process on anterior margin of stalk extending to rounded tubercle over cornea. Latter large, oval, obliquely terminal.

Hepatic region moderately expanded, produced into acute or subacute unarmed lobe, anterior margin almost perpendicular to body line, occasionally with lateral tubercle but lacking apical spine. Width at hepatic lobes subequal to or less than distance from gastric protuberance to anterior margin.

Dorsal surface of carapace with 2 prominences on midline, gastric prominence an inflated tubercle, smaller and lower than cardiac prominence, neither spined dorsally. Protogastric region with low, unarmed tubercle. Branchial region smooth, with low mesobranchial tubercle centered dorsally. Epibranchial swelling, if present, low, inconspicuous. Low swelling present on metabranchial region above posterior pereiopods. Posterior and posterolateral margins unarmed, tubercles present anteriorly on margin above chelipeds.

Basal antennal article (Figure 67d) usually smooth, lightly tuberculate or with 1 or 2 low spinules in some specimens. Antennal segments unarmed.

Antennular fossae large, longitudinally subovate, lateral margins of fossae irregularly crenulate along border with basal antennal segment. Basal antennular segment bearing irregular line of tubercles ventrally. Interantennular process slender, terminating posteriorly in thin, blunt, obtuse, triangular lobe. Anterior process of epistome very slender.

Epistome (Figure 67d) appearing elongate, actually broader than long, widening posteriorly, most of surface smooth, with single sharp tubercle present anterolateral to opening of antennal gland. Pterygostomian region with sharp tubercle on lateral border.

Third maxillipeds not meeting in midline, hairy, not heavily spined. Ischium with 2 parallel lines of small tubercles, mesial margin tuberculate, erect spines present on margin in some specimens. Merus largely smooth, with few surface tubercles, narrow, unarmed mesially or with tubercles or small spines. Palp with slender dactylus, shorter than stout carpus and propodus combined; carpus and propodus each with distal spine mesially.

Chelipeds (Figure 67e) long and stout, not heavily armed or setose. Ischium with several spines ventrally. Merus inflated, with row of large spines on ventrolateral border, inner distal spine mesially, upper surface largely smooth, with seta-tipped tubercle near midlength and small distal, dorsal spine. Carpus with proximal outer spine, row of spines of varying size dorsally, shorter row distolaterally, terminating in large distal spine. Chela shorter than remainder of cheliped, fingers shorter than palm. Palm with row of spines dorsally and ventrally, outer surface smooth, inner surface spinulose in males, nearly smooth in females. Fingers flattened, without prominent gape, cutting edges crenulate, proximal tooth of movable finger largest, not markedly enlarged. Chela largely naked, with few long and short hairs scattered over surface.

Walking legs very long and slender, merus and propodus of first each longer than carapace, with curled hairs arising singly on dorsal surface of carpus and propodus, longer hairs arising distally on propodus. First walking leg longest, remainder decreasing in length posteriorly. Proximal segments of walking legs unarmed, merus with distal dorsal spine. Dactylus of first walking leg straight proximally, slightly curved distally, unarmed ventrally, slightly more than half as long as propodus, latter slightly shorter than merus. Dactylus of second walking leg shorter than that of first, slightly curved, with 1 or 2 subdistal teeth ventrally, length across arc about half that of propodus, latter shorter than merus. Dactylus of third walking leg falciform, with about 12 sharp ventral teeth, length across arc less than half that of propodus, latter shorter than merus. Dactylus of fourth walking leg (Figure 67f) falciform, with about 12 sharp teeth ventrally, length across arc more than half that of propodus, latter shorter than merus.

Sternum unarmed or with few, low tubercles, and with short, oblique carina in males posterior to articulation of cheliped.

Abdomen in male of 6 somites (Figure 67g). All somites wider than long, third widest. Distal somite not expanded laterally, not markedly wider than fifth, apex obtuse, rounded. Surface with broad elevation on first and third to fifth somites. Male pleopod as illustrated (Figure 67h).

MEASUREMENTS.—Carapace lengths of males 5.8 to 7.8 mm, of ovigerous females 6.0 mm.

DISTRIBUTION.—Known only from the type-locality, off Nigeria.

TYPE-SPECIES.—Achaeus calypso Forest and Guinot, 1966.

ETYMOLOGY.—The name is derived from the name of the vessel Calypso in combination with the generic name Achaeus; gender of the name is masculine.

DIAGNOSIS.—Carapace subtriangular, longer than broad, narrowed behind orbit, largely smooth dorsally, margins spinulous. Rostrum of 2 elongate, anteriorly truncated lobes, apex and margins spinulous. Orbit with only supraorbital eave above, lined with long spinules. Postorbital spine absent. Eyestalks long, nonretractile, cornea obliquely subterminal, slightly ventral, large, ovoid. Interantennular septum produced ventrally into cupped process with distal sharp spine, visible in dorsal view. Basal antennal article slender, channelled longitudinally, depression flanked on each side by line of tubercles, with strong distolateral spine. Merus of third maxilliped ovate, not notched distally, narrower than ischium, palp articulating at summit. Chelipeds spinous, slightly enlarged in adult male, palm strongly compressed, cristate dorsally and ventrally. Walking legs long and slender, dactyli of posterior 2 falciform, ventrally spinulated. Abdomen of 6 free somites in both sexes, male abdomen widest at third somite. Male first pleopod bluntly pointed, aperture terminal in groove.

MATERIAL EXAMINED.—Pillsbury Material: Liberia: Sta 68, 70 m, broken shell, 2 (L).

Ghana: Sta 17, 48 m, fine sand and green mud, 1, 2 (1 ov)(W). Sta 22, 51 m, rough bottom, 1 (W).

Nigeria: Sta 248, 33 m, 3, 1 ov (L).

Cameroon: Sta 260, 46 m, 1 (W).

Other Material: Dahomey: Off Grand-Popo, 30 m, Petersen grab, 23 Feb 1964, Guinean Trawling Survey, Tr 34, Sta 2, 2 (L).

DESCRIPTION.—Carapace (Figure 68a) pyriform, width 0.75 to 0.87 (mean 0.82) times length, constricted behind orbit, branchial regions only slightly inflated, not extending over lateral margin, latter spinulous, regions not well defined. Surface sparsely granular, with scattered long, hooked hairs, especially laterally and anteriorly.

Rostrum (Figure 68a,c) consisting of 2 broad projections, separated by broad V- or U-shaped emargination, inner margins extending ventrally to sharp interantennular spine, clearly visible in dorsal view. Margins and blunt apices of rostrum spinulous, apices raised dorsally.

Orbital margin (Figure 68c) including supra orbital eave, completely lined with denticles or strong spinules. Distinct postorbital spine absent. Eyestalks slender, elongate, anterior or anteroventral margin with prominent, thin, blade-like, obtuse projection, as wide as or wider than stalk, with anterior spinules. Narrow process from anterior margin extending to rounded, setiferous tubercle over cornea. Latter broad, oval, obliquely terminal.

Hepatic region well defined, strongly projecting laterally, smooth or with apical spine or with apical row of spinules flanked anteriorly by spinular crest on hepatic lobe. Carapace width at hepatic lobes subequal to or greater than distance from gastric prominence to anterior margin.

Dorsal surface of carapace with 2 prominences in midline, gastric slender, usually an erect spine, often obsolete or broken, much the higher, cardiac prominence a low, obtusely rounded, conical lobe. Branchial regions smooth, unarmed, subregions not well marked. Lateral and posterior margins of carapace completely lined with tubercles or erect spinules.

Basal antennal article longitudinally sulcate, with inner and outer lines of spinules, fewer in smaller specimens, outer line terminating in enlarged distolateral tooth. Free segments of antennal peduncle variably tuberculate or spinulose.

Antennular fossae elongate-triangular, margins unarmed, lacking anterior rim, each fossa grading anteriorly into rostral spine. Basal antennular segment with patch or line of spiniform tubercles. Interantennular process strongly produced (Figure 68b), projecting well beyond level of basal antennal segment, expanded laterally to form broad, anteriorly cupped lobe, curved anteriorly, apically acute or spiniform. Inner, dorsal margin of cupped lobe grading evenly into inner surfaces of rostral horns. Anterior process of epistome thin, rounded, blade-like, projecting ventrally.

Epistome subrectangular, broader than long, most of surface smooth, with spinulose crest or patch of spinules lateral to opening of antennal gland. Pterygostomian region with stalked projection, apically spinulose, on lateral border.

Third maxillipeds not meeting in midline, hairy, heavily spined. Exopod lined with spinules. Ischium with 2 divergent rows of sharp denticles, mesial margin spinulose, tuberculate. Merus with line of sharp denticles on surface, spined mesially, with spinules laterally and distally. Palp with slender dactylus, shorter than stout carpus and propodus combined. Carpus and propodus each with distal spine mesially.

Chelipeds slender in both sexes, longer and slightly inflated in males, merus extending beyond eye in males, not extending to eye in females and juveniles. Ischium very spinous, largest spine set distoventrally. Merus with line of erect spines on sharp ventral border, outer surface smooth, upper border cristate, smooth or with line of tubercles, inner surface with some lines of tubercles. Palm strongly compressed, cristiform dorsally and ventrally, upper margin with spaced spines and tubercles, lower margin smooth, inner surface of lower margin with line of spines and denticles, outer surface smooth, inner surface tuberculate. Fingers longer than palm, flattened, lacking prominent gape, cutting edges crenulate, lacking enlarged proximal tooth on movable finger. Chelae largely naked, with few hooked hairs on outer surface, upper and lower borders with few long, stiff hairs interspersed between spines.

Walking legs long and slender (merus of second pereiopod longer than carapace, propodus subequal to or slightly longer than carapace), with curled hairs arising in groups on dorsal surface of distal 4 segments and longer hairs scattered over surface, especially on propodus and dactylus. Second pereiopod longest, remainder decreasing in length posteriorly. Merus of walking legs with distal arc of spinules or low tubercles dorsally. Dactylus of second pereiopod straight proximally, curved distally, unarmed ventrally, more than half as long as propodus, latter shorter than merus. Dactylus of third pereiopod as long as that of second, slightly more curved distally, unarmed ventrally, more than half as long as propodus, latter subequal to merus. Dactylus of fourth pereiopod falciform, ventral margin with numerous triangular teeth, some swollen, proximally tuberculate, length across arc subequal to that of propodus, latter shorter than merus. Dactylus of fifth leg falciform, armature similar to that of fourth, length across arc subequal to that of propodus, latter shorter than merus.

Male abdomen narrowed distally, apex broadly rounded, with median tubercle on each somite, sixth somite with 2 subapical tubercles or spinules. Male pleopod as figured by Forest and Guinot (1966, fig. 19c,d).

Sternum granular in both sexes, in male ornamented with anteriorly convex arc of strong spines and tubercles, with 1 enlarged spine near base of each cheliped.

MEASUREMENTS.—Carapace lengths of males 5.7 to 9.0 mm, of females 4.8 to 9.3 mm, of ovigerous females 8.6 to 9.3 mm. The male holotype has a carapace length of 10.0 mm (Forest and Guinot, 1966).