Atya crassa (Smith)

Atya crassa (Smith)

Evatya crassa Smith, 1871:95–97 [type-locality: “Fresh water streams, Polvon, and the ‘Rio Fulva, two and a half miles northwest of Realejo,’ Occidental Department, Nicaragua”; types: (?)USNM 84261, 1; (?)PM 6038, 1, 1].—Kingsley, 1878b:57.—Holthuis, 1955b:26.

Euatya crassa.—Koelbel, 1884:318, 320.

Euatya (Evatya) crassa.—Koelbel, 1884:318.

Atya (Evatya) crassa.—Ortmann, 1895:408, 410, 415.—Doflein, 1900:127.

Atya (Euatya) crassa.—Ortmann, 1897:184, 186.

Evatya crassus.—Sheldon, 1905:343 [erroneous spelling].

Atya crassa.—Bouvier, 1905:110, 113, 124; 1925:26–28, 293, 319–323, figs. 54, 68.—Pesta, 1931:173, 178.—Oliveira, 1945:178.—Holthuis, 1951:9; 1955b:26, fig. 9.—Balss, 1955, fig. 1050.—Kaestner, 1970, figs. 13–18f.—Burukovsky, 1974, fig. 85.

REVIEW OF LITERATURE.—Smith (1871) described this shrimp along with Atya rivalis and A. tenella from freshwater streams at El Polvón in the western part of Nicaragua; he also cited a second locality for A. crassa, “Rio Fulva, two and a half miles northwest of Realejo.” Kingsley (1878b) added no new information but listed the species and cited it from the west coast of Nicaragua. Koelbel (1884), in describing Euatya sculptilis (= Atya gabonensis Giebel, 1875) and emending the spelling of Evatya, assigned Smith's species to the same genus and reported its occurrence in Río Presidio (perhaps near Mazatlán, Sinaloa), Mexico. Ortmann (1895) recognized two subgenera of the genus Atya and placed A. crassa in the monotypic subgenus Evatya; no new data relative to the species were included. Doflein (1900), who followed Ortmann in the subgeneric assignment, listed this shrimp from the Atlantic side of Panama. In the meantime, Ortmann (1897) had employed the combination Atya (Evatya) crassa, presented a diagnosis of the species, and included Nicaragua and Mexico in his summary of distribution. Sheldon (1905) added no new information. Bouvier (1905), not recognizing the subgeneric designations of Ortmann, provided a key to the species of the genus, and pointed out the similarity in the serrate rostra of A. crassa and A. (= Micratya) poeyi Guérin-Méneville (1855). In his monograph of the Atyidae, Bouvier (1925) emphasized the relationships of A. crassa with A. gabonensis, considering them to be the most advanced members of the genus. A key to the species was provided along with a summary of the locality records (those just cited), an illustration, in lateral aspect, of a male, and another of the telson. Pesta (1931), reporting on the Austrian expedition of 1930 to Costa Rica, added a new locality for the species: Río Nuevo that flows into Golfo Dulce. Oliveira (1945), in his study of Atya scabra in northeastern Brazil, mentioned A. crassa but added nothing to our knowledge of the species, nor did Holthuis (1951); however, the latter (1955b) cited this shrimp as the type of Smith's Evatya and included the illustration of the entire animal that appeared in Bouvier's monograph. Balss' (1955) figure was also taken from Bouvier, Kaestner's (1970) from Balss, and Burukovsky's (1974) from Holthuis.

PUBLISHED ILLUSTRATIONS.—The only illustrations of this shrimp are a dorsal view of the telson and a lateral one of an entire animal included in Bouvier (1925). The latter figure was reprinted by Holthuis (1955b) and Balss (1955), and indirectly by Kaestner (1970) and Burukovsky (1974).

DIAGNOSIS.—Cephalic region of carapace strongly sculptured and bearing many rows of corneous-tipped spines and tubercles. Rostrum with margins tapering from base and studded with median dorsal row of corneous-tipped spines. Pterygostomian angle produced in prominent spine. Ventral margin of abdominal pleura lacking sclerotized denticles; caudoventral angle of fourth and fifth pleura usually produced in spines. Fifth abdominal segment with median tubercle on sternum moderately to strongly developed; sternum of sixth abdominal segment less than half as long as wide. Preanal carina in form of subconical spine directed caudally to caudoventrally. Telson 1.2 to 1.4 times as long as broad and bearing paired arched dorsal rows of 4 to 6 spines. Antennular peduncle with dorsal surface of proximal article lacking sclerotized spinules proximal to transverse distal row; penultimate article 1.5 to 2.2 times as long as wide and bearing dorsolateral longitudinal row of spinules. Coxa of third and fourth pereiopods with prominent ventrolateral spine, that of third also with strong mesial caudoventral prominence. Third pereiopod with merus subplane ventrally, 1.5 to 2.3 times as long as high, ventromesial margin subangular and parallel to that of corresponding podomere of other third pereiopod, and lateral surface bearing irregular rows of spines, many of which with flattened corneous extremities; propodus 1.3 to 1.6 times as long as broad, studded with scalelike tubercles on extensor surface and with few similar ones of flexor surface, latter largely obscured by conspicuous tufts of long plumose setae; dactyl apparently inflexibly fused with propodus and bearing 1 or 2 small scalelike tubercles on flexor surface just proximal to corneous tip.

MALE (Río Chucunaque, Darién Province, Panama).—Rostrum (Figure 16a,c) with margins tapering from base to corneous, acute apex, latter almost reaching distal end of antennular peduncle; dorsal median carina rounded and bearing row of 7 corneous-tipped spines, 4 of which situated behind orbit, directed dorsally, and decreasing in size posteriorly; those on rostrum subequal in size, 2 more posterior ones directed dorsally, and anteriormost anterodorsally. Ventral surface of rostrum evenly rounded transversely, lacking clearly defined carina; lateral carinae very small, becoming obsolete at base of anteriormost spine. Ocellar beak upturned and so well concealed beneath rostrum and between eyes that hardly noticeable. Antennal and pterygostomian spines acute, and cephalic border of carapace between them bearing 2 large, acute, corneous-tipped spines. Entire surface of carapace densely punctate, and cephalic half very ornate dorsally and dorsolaterally, bearing paired ridges studded with rows of corneous-tipped spines; ventrolateral punctations bearing conspicuous setae.

Pleura of first and second abdominal segments (Figure 16i) with rounded posteroventral extremities, corresponding parts of third obtuse, and those of fourth and fifth acute with corneous apices; anteroventral angle of sixth also with acute, corneous, caudoventrally directed tip. All pleura lacking corneous denticles on ventral margin, but fourth and fifth with row of prominent plumose setae. Fourth abdominal tergum approximately 1.2 times as long as fifth, length of sixth subequal to that of fifth and almost 0.9 as long as telson. Sternum of fifth abdominal segment (Figure 1m) with very prominent, corneous-tipped, acute median spine directed caudoventrally; sternum of sixth segment about 0.42 times as long as broad. Preanal carina (Figure 16k) represented by strong, caudally directed, corneous-tipped spine. Telson (Figure 16b) about 1.3 times as long as wide, its dorsal surface bearing paired rows of 6 corneous denticles and with posteromedian tubercle slightly overhanging caudal margin.

Proximal podomere of antennule (Figure 16a,l) with strong stylocerite overreaching midlength of segment, dorsal surface with few setae but lacking corneous spinules; distal margin studded with row of 5 corneous spinules; penultimate segment of peduncle 1.5 times as long as wide and provided with 4 spinules on dorsolateral surface and row of 3 (right) or 4 (left) on distal margin; ultimate podomere with no spinules on dorsal surface but with row of 5 flanking dorsal base of lateral flagellum and 2 at dorsal base of mesial flagellum. Antenna with ventrolateral spine on basis reaching proximal end of penultimate podomere of antennular peduncle, distinctly overreaching stylocerite; lateral spine on scaphocerite strong, extending to level of tip of rostrum; lamella overreaching peduncles of antennule and antenna; flagellum of antenna reaching caudal margin of telson.

Third maxilliped overreaching antennular peduncle by 0.25 length of ultimate segment of endopod; tip of exopod almost reaching midlength of penultimate podomere of endopod; penultimate segment about 1.6 times as long as ultimate.

First pereiopod reaching level of base of ultimate podomere of antennule, second reaching base of distal fifth of dactyl of first pleopod; terminal brush of setae of both appendages lacking scraping denticles. Except for coxa, third pereiopod (Figure 16d,g,j) lacking spines and when extended anteriorly, overreaching antennular peduncle by length of propodus and dactyl. Merus with ventromesial margin straight, almost 1.5 times as long as high, 14.1 times length of carpus, and 4.4 times as long as propodus; latter slightly longer than wide and 0.48 as long as carpus; distoventral margin of coxa strongly scalloped, distolateral surface with strong spine, and mesial caudoventral prominence strongly developed and studded with prominent setal clusters. Lateral, dorsal, and ventral surfaces of merus bearing longitudinal rows of conspicuous, corneous tubercles of which apices of most somewhat flattened and bearing sharp free edge; paired clusters of plumose setae flanking distal base of most tubercles; tubercles on ventral surface largely concealed by dense, shaggy beard of setae; mesial extremity of podomere slightly produced at level of mesial articular condyle of carpus; strong tubercle on distal mesioventral angle opposing tubercle on carpus. Ventral and ventromesial surface of carpus heavily bearded. Flexor surface of propodus with few widely spaced tubercles, almost all obscured by tufts of setae borne proximally on podomere; dactyl fused with propodus, its flexor surface bearing median cluster of small, corneous denticles flanked by pair of setal clusters.

Fourth pereiopod with dactyl reaching base of distal third of merus of third pereiopod; length of merus slightly greater than twice that of carpus, latter 1.1 times longer than propodus; coxa with strong distolateral spine. Fifth pereiopod reaching end of basal fifth of carpus of fourth; merus about 1.5 times as long as carpus, and latter 0.86 as long as propodus. Ornamentation of merus, carpus, and propodus of fourth pereiopod similar to that of third except ventral surface of merus with 3 articulated spines, and ventrolateral surface of carpus with 1; only 2 such spines present on merus of fifth pereiopod, and flexor surface of dactyl with row of many more spinules, ornamentation otherwise similar to that of fourth.

Diaresis of lateral ramus of uropod flanked proximally by 16 articulated corneous denticles and slightly larger fixed lateral spine.

SIZE.—The largest specimen for which measurements are available is a male from Río Presidio, Mexico, which has a carapace length of 60.0 mm. The largest female, one from northwestern Ecuador, has a corresponding length of 41.4 mm. No ovigerous females have been reported or examined by us.

DISTRIBUTION AND SPECIMENS EXAMINED.—This species ranges along the Pacific slope from Presidio (probably Sinaloa), Mexico, southward to Ecuador, and in Panama it has been found on the Caribbean slope (Doflein, 1900) (Figure 17).

Records for the known localities are listed below. Collections that we have examined are marked with an asterisk if they have been previously reported and with a dagger if they are reported herein for the first time. Numbers following the specimens listed are measurements, in mm, of the carapace length or, if followed by “t.l.,” total length. Some listings lack dates and/or collectors; if so, these could not be determined.

MEXICO: (1) *BM, Río Presidio (?Sinaloa) (Koelbel, 1884:318), 1 (60.0), 2 (17.7, 23.3), A. Forrer; MHNP, 1 specimen (35.5). (2) †USNM, Río Tehuantepec, Oaxaca, 1 (50.5), T. Mac-Dougall.

EL SALVADOR: †USNM, Río Lempa at Suchitoto, 2 (29.3, 28.7), 1 (29.0), 9 Feb 1924, C.A. Hildebrand and Foster; USNM, 2 (22.6, 32.8), 5 Feb 1924, CAH and F.

NICARAGUA: (1) *USNM, freshwater streams, E1 Polvón (12°27′N, 87°05′W) or Río Fulva, 2.5 mi NW of Realejo (Smith, 1871), 1 (40.0), syntype, 1869, J.A. McNeil. (2) †PM, “Rio Frilo,” (probably Río Frío), about 1.8 km NW of Realejo, 1 (11.2), 2 (8.5, 15.0), 1869, J.A. McNiel.

COSTA RICA: Río Nuevo (Halbinsel Osa), Golfo Dulce (Pesta, 1931:178), 1 (120, t.l.), 4 juv, 1 Apr 1930.

PANAMA: (1) “Atlantic side” (Doflein, 1900:127). (2) †USNM, Río Chucunaque near Río Sansón, Provincia de Darién, 3 (47.5, 50.8, 56.3), 27 Apr 1958, C.E. Bennett, Jr. (3) †USNM, Río Chucunaque above Membrillo, Provincia de Darién, 1 (38.9), 4 (15.3–38.6), 7 Apr 1924, J.L. Baer. (4) †LGA, Río Bayano at ford, Provincia de Panamá, 1 (6.3), 6 Mar 1973, R.L. Dressler. (5) †LGA, headwaters of Río Bayano 1 (28.0), 1 (9.6), Dec 1974, L.G. Abele.

COLOMBIA: †USNM, Río Dagua at bridge, 0.25 km from Buenaventura, 6 (30.8–41.0), 5 (28.7–39.3), 17 Jul 1939, Karl P. Schmitt.

ECUADOR: (1)†BM, NW Ecuador, alt 136 m, 2 (38.1, 39.0), 4 (32.1–41.4). (2) †MCZ, Ríos Cayapas, Hoja Blanca, and San Miguel, in immediate vicinity of village of San Miguel, Provincia de Esmeraldas, 2 (32.9, 37.9), Miyata and Rand. (3) †USNM, junction of Río Cayapas and Río San Miguel, Provincia de Esmeraldas, 1 (37.2), Jun 1977, Andris Rankis.

VARIATIONS.—The following few remarks are based on such a limited series of specimens, 11 constituting the greatest number from a single locality, that they should not be considered as conclusive. The specimens from Colombia and Ecuador differ from those from the Middle American region in possessing fewer tubercles on the lateral surface and dorsal margin of the merus of the third pereiopod. In the South American specimens, the dorsal row consists of 12 to 14 (rarely 13 or 14) and in those from Middle America, 15 to 19. Six to 10 spines constitute the median row on the rostrum, and, whereas in the specimens from Ecuador, Colombia, and Panama there are usually six or seven, as contrasted with eight to 10 in the more northern part of the range, the numbers are not consistent, for specimens from both E1 Salvador and Nicaragua have as few as seven and at least one from each of Colombia and Panama exhibit eight or nine. Of the other features compared in specimens from throughout the range, there seems to be no correlation of a variation with a limited part of the area occupied by the species.

ECOLOGICAL