Fennerosquilla heptacantha Chace 1939

Fennerosquilla heptacantha (Chace, 1939)

(Fig.1)

Chloridella heptacantha Chace 1939: 52.— Manning 1968: 129 [list].

Squilla heptacantha.— Manning 1959: 19; 1969: 171; 1978: 40.—Camp 1983: 55–57. Fennerosquilla heptacantha.— Manning & Camp 1983: 317 –322, fig. 1.— Manning 1991: 14 [tab.].— Herrera-Moreno & Betancourt 2003: 276.— Ahyong 2005: 206 [appendix 1].— Perez-Gelabert 2008: 29.— Reaka et al. 2009: 917 [table].— Schram 2010: 235.

Diagnosis. Carapace median carina with distinct, uninterrupted anterior bifurcation; posterolateral margins obtusely angular, not evenly rounded. Mandibular palp present. Maxillipeds 1–4 with epipod. Raptorial claw with opposable margin of propodus pectinate, with three movable proximal spines; carpus dorsal carina irregular; dactylus with seven teeth including terminal tooth. Thoracic somite 5 with lateral process a single broad lobe with sharp apex. Thoracic somite 6 lateral process strongly bilobed, with anterior and posterior lobes of similar size. Thoracic somites 6–7 lateral processes sharp posterolaterally. Thoracic somite 7 lateral process with small angular anterior lobe. Abdominal somites 1–5 without median carina. Telson submedian teeth with fixed apices; prelateral lobe present; dorsolateral surface without supplementary carinae or tubercles.

Material examined. MOUFPE 15062, 1 adult female, total length 149 mm; Station BPot–Talude #MT51, initial trawl 04°48.4436'S 036°10.8739'W, finish trawl 04°48.6166'S, 036°9.9897'W, 178– 193 m.

Measurements (mm). CL 22.8; CW 17.2; TeW 20.0; TeL 18.38; DrL 3.4; DrD 3.2; PL 27.3; PD 6.4; CoL 2.0; CoW 4.0; EL 3.8; AW 23.1.

Indices (mm). AWCLI 101.31; CI 570.00; PI 83.51; PLDI 426.56.

Geographic distribution (Fig. 2). Northwest Atlantic: Gulf of Mexico –Florida; Straits of Florida; Bahamas; Cuba; Caribbean Sea– Dominican Republic; Puerto Rico; Virgin Islands; Honduras; Panamá (Manning 1969; Schram 2010). Southwest Atlantic: Brazil –Rio Grande do Norte (present study).

Habitat. The specimen was collected from a rubble bottom at 178–193 m depth, bottom temperature 19°C, and salinity 36.14 ppt. Previews information related the species solely to a benthic soft bottom (Reaka et al. 2009). Fennerosquilla heptacantha seems to have a slope distribution at depths of 105–458 m in the tropical western Atlantic Ocean (see also Manning 1991; Reaka et al. 2009).

Remarks. The specimen is an adult female, and with a total length 149 mm, is the largest recorded for the species. The largest prior records do not exceed a total length of 100 mm (Manning 1969, 1983, Schram 2010). The corneal index (CI) of the present specimen is within the reported range (412–576 mm by Manning & Camp, 1983). The lateral process of seventh thoracic somite is faintly bilobed, with a small, low anterior lobe. Thoracic somites 5–8 have an anterior tubercle between submedian and intermediate carinae. The intermediate carina on all abdominal somites terminates in acute angle or spine, although Chace (1939) describes the first abdominal somite not ending in right angle. The telson is slightly wider than long (1.08 ×) like that figured by Manning & Camp (1983: fig. 1) (1.04 ×), rather than wider as long according the original description (Chace 1939). According to Ahyong (pers. comm.), in squillids, the telson generally becomes proportionally slightly wider as the specimen becomes larger. The telson median carina is prominent anteriorly (swollen) as illustrated by Manning & Camp (1983: fig 1). Eleven intermediate denticles on posterior margin of telson, within previous results by Manning (1969) (8–13 denticles). The presence of the ventral carina below the lateral tooth (stridulatory keel) is now recognized (Ahyong 2005). Although minor differences are noted between the present specimen and previous works, the pigmentation zone on each side of telson median carina and all main diagnostic characters are still preserved.

The present study reports for the first time F. heptacantha from the south Atlantic Ocean and thus extends the southern distribution to the Rio Grande do Norte State, in Brazil (Fig. 2). This trawl depth of this specimen (178–193 m) accords with the literature (Chace 1939; Manning 1991; Reaka et al. 2009). The present paper brings some new information about the ecological aspects, as type of bottom, salinity and temperature (see Habitat). Fennerosquilla heptacantha apparently has a disjunct deep water distribution (more than 100 m), but this species will probably be found to occur widely in the tropical Western Atlantic. Few deep water surveys have been conducted outside off Caribbean Sea and Gulf of Mexico and further deep water surveys along the Atlantic coast should provide further information about this species, and further increase its known distribution.