Ameroculodes miltoni, a new species of estuarine amphipod (Crustacea: Malacostraca: Peracarida: Oedicerotidae) from the southeastern United States Author Foster, John M. Author Heard, Richard W. text Zootaxa 2002 2002-04-12 28 1 12 journal article http://doi.org/10.5281/zenodo.4620161 1d53d267-f236-45da-b852-56b4cf3525d6 1175­5326 4620161 2EB3FDF9-76B5-44D9-90BD-AEEF4C1E94FC Ameroculodes miltoni , new species ( Figs. 1­5 ) Monoculodes edwards Holmes, 1905 : 487 .– Heard , 1975 : 22,25,27; Howard, 1975 : 14 ; Howard et al., 1975 : 188 ; Sikora et al., 1972 : 519,524 ; Stickney et al., 1974 : 519, 525 ; Stickney et al., 1975 : 519 . Ameroculodes edwardsi : Camp, 1998 : 130 . Monoculodes sp . ­­ Dorjes & Howard, 1975 : 152 ; Overstreet & Heard , 1982 : 139 . Monoculodes sp. A : Rakocinski et al., 1996 ; Gaston et al., 1996 : 675 , 677, 678. Monoculodes n. sp. : Saloman, 1976 : 49 Material Examined .– Holotype : Ovigerous, female , 5.0 mm, USNM 1001720 , Mississippi Sound adjacent to Biloxi Lighthouse and Lighthouse Pier , Biloxi , Jackson Co. , Mississippi , depth 1.0 meter, fie­medium sand substratum , 5 Jan 1992 , coll. David Hard . Paratypes : Mississippi , Biloxi , type locality, collection Bba­ 10 ovigerous females , 4.0­6.0 mm USNM 1001721 ; collection BBb­ 10 males , 4.5 ­ 5.5 mm , USNM 1001722, 25 Jan 1994 , coll. Jan Boyd ; collection Bbc­ 50 ovigerous females and 10 males , USNM 1001723 , type locality, coll. David Hard , 0 5 Jan 1992 ; collection Bbd­ 45 ovigerous females and 9 males , GCRL 2031 , coll. David Hard .– Louisiana : collection LPa­ 5 ovigerous females , 5.0 ­ 7.0 mm, USNM 1001724 , Lake Pontchartrain , Tchefuncta River , March 1991 , salinity 0.0 ppt, coll. R.W. Heard .– Georgia : collection SIa­ ovigerous female , 3.5 mm , USNM 1001725 , Sapelo Island , 14 May 1988 , coll. R.W. Heard .­ Florida : collection PBa­ ovigerous female , 5.5 mm , USNM 1001726 , Pensacola Bay , roadside park at the north base of the bridge causeway , depth 1.5 meters, sand substratum, mesohaline conditions , coll. R.W. Heard , 25 Jan 1991 . SBa­ 10 ovigerous females , 5.0 ­ 6.5 mm USNM 1001727 , SBb­ male , 5.0 mm, USNM 1001728, 29 Nov 1993 , sandy sediments, <1.0 meter, Sulphur Point at Hathaway Bridge , St. Andrew Bay , coll. J. M. Foster . Other materials examined : [? Ameroculodes miltoni ] NMCC acc # 1991 ­ 1902, 26 Feb 1976 , Courtney Campbell Causeway , Tampa Bay , Florida , muddy, shelly­sand substratum , coll. E. L. Bousfield ; 1 male , 3 female , NMCC acc # 1991 ­ 1905 , 0 5 Feb 1976 , subtidal sand , Panacea, Florida , coll. E. L. Bousfield ;. 3 females A . nr. miltoni AMNH 16578 , Swan Point , New Jersey , coll. K. Gosner . Comparative materials examined : Holotype , Ameroculodes (= Monoculodes ) edwardsi (Holmes 1905 ) , USNM 29243 , male , 9 mm , Woods Hole , MA , coll. V. N. Edwards ;– A. edwardsi , 4 females , USNM 107800 , York River , Virginia , Feb. 1960 ;.– A. emarginatus Barnard, 1962 , several females , USNM 106507, 109352 , and 108867 , 10 ­ 20 meters, Southern California , coll. J. L. Barnard . Diagnosis – Postero­ventral epimeral plates 1­3 rounded; rostrum blunt, stout, short; uropod 2 with relatively few dorsal spines; telson rounded posteriorly. Description – adult female.– Head: rostrum blunt, moderately deflexed, slightly recurved, not reaching end of first peduncle article of antenna 1 , lateral lobe blunt; eyes dorsal, ommatida compact. Antenna one (setation as illustrated) – longer than peduncle of antenna two; peduncle, article two longer than articles one or three; flagellum shorter than peduncle with eight articles, penultimate and antepenultimate articles bearing aesthetascs. Antenna 2 (setation as illustrated) – peduncle, article 5 equal to or slightly longer than 4 ; flagellum shorter than peduncle, with 7 articles. Upper lip – ovate, slightly expanded distally, apically setose. Lower lip – outer lobes laterally expanded, recurved posteriorly, medially and apically setose; inner lobe separate, smaller than outer, setose apically. FIGURE 1 : Ameroculodes miltoni , n sp. , paratype female BB­a, 4.5 mm (A) whole animal (B) head (C) head, antenna 1­1, female (D) paratype male BB­b, 5.0 mm ­ head, antenna 1­2 male Mandible – Left mandible incisor process bearing 4 jagged teeth ( 1 depressed, blunt), 4 serrate spine­setae; lacinia mobilis with 5 teeth; molar process encircled with overlapping subacute cusps, triturative; palp, article 2 longest, twice length article 3 , with double row of long, distally tapered spine­setae, article 3 with row of 8­10 short spine­setae on distal half, with 4 long, simple terminal setae. Right mandible, incisor bicuspidate, bearing broad blade proximally; lacinia mobilis with several small, proximal teeth; 5 serrate, spine­setae present; molar and palp same as left mandible. FIGURE 2 : Ameroculodes miltoni n. sp. , paratype female BB­a (A) mandibular palp, article 2­3 (B) left molar and incisor (C) right incisor (D) maxilla 1 (E) maxilliped (F) maxilla 2 (G) lower lip Maxilla 1 – Inner plate with 2 simple terminal setae, 1 finely plumose terminal seta, surface with very fine hair­like setae; outer plate with 9 terminal spines, 3 bifurcate distally, 3 serrate, 3 blunt; palp with terminal spines and setae. Maxilla 2 – Inner and outer plates equal in length, each with 2 rows of terminal setae; inner plate with 9 strong setae, 3 bifurcate distally. Maxilliped – Inner plate slightly over half width of outer plate at widest point, with 10 distal spine­setae; outer plate large, not reaching end of palp article 2 , inner margin with 11 spines and several setae; palp article 2 truncate, widened distally, strong inner marginal, facial, and inner distal setae, article 3 short, terminal setae, with large, curved terminal claw about half length of article 3 . FIGURE 3 : Ameroculodes miltoni n. sp. , paratype female BB­a (A) gnathopod 1 (B) gnathopod 2 (C) pereopod 3 (D) pereopod 4 (E) pereopod 5 Gnathopod 1 – Article 2 long, slender, with most marginal and facial setae clustered distally; articles 3 and 4 with posterior marginal setae; article 5 , carpal lobe 44 % ( 37­ 55 %) length of article 6 , barely reaching palmar angle of palm, with 8 posterior marginal and terminal spines and several simple setae; palm gently convex, with 2 rows of short and long setae on either side of finely serrate medial ridge, with strong spine at junction with posterior margin of article 6 ; article 7 (dactyl) fitting palm, with 8 short, flattened spines on inner margin. Gnathopod 2 – Coxa with 2 posteromarginal spines and simple ventral setae; article 2 long, slender, with long, simple posterior and anterior marginal simple setae, articles 3 and 4 with posterior setae; article 5 with long, slender carpal lobe bearing long medial and terminal simple setae, with 1 short, stout terminal spine, lobe reaching or exceeding palmar angle of article 6 ( 100­115 %); article 6 longer and more narrow than article 6 of gnathopod 1 , palmar angle with stout spine, palmar margin bearing finely serrate medial ridge bearing rows of short and long simple setae on either; article 7 as in gnathopod 1 . Pereopod 3 – Coxa quadrate, with posterior and ventral setae, posterior setae thin, spine­like; oostegite longer and broader than coxal plate; article 2 , posterior margin with 4 clusters of long, thin simple setae, anterior margin with a large cluster of setae near anterodistal angle; article 3 short, with cluster of posterodistal setae; article 4 90 % of length of article 5 , with numerous long, simple setae in rows and clusters on posterior and anterior margin and facially, posterior setae distally tapered; article expanded distally; article 5 strongly setose posteriorly, with long, distally curved setae, anterior and facial margins with thinner, simple setae; article 6 over half the length ( 61­75 %) of article 5 , anterior margin oblique, with several strong rows of long, distally curved setae, with a dense row of similar setae near posterior margin; article 7 , short, stout, with 1 accessory seta, one third length [ 32 % ( 27­43 %)] of article 6 . Pereopod 4 – Coxa broad, widened distally with distal marginal setae and with 1 long seta at posterodistal angle; article 2 shorter than coxal plate, with anterior, posterior and facial setae, with clusters of setae at anterodistal angle, distomesial area with several long plumed setae; article 3 with 2 anterodistal spines and one plumed setae; article 4 posterior margin with long, distally tapered setae, outer facial margin with 3 clusters of long setae, anterior margin without setae except for a large cluster of very long, tapered setae subdistally, length of article 4 subequal to article 5 ; article 5 with dense posterior marginal and anterodistal setae, 3 facial setae; article 6, 75 % length ( 66­85 %) of article 5 , anterior margin with 6 rows of long, simple setae, posterior and facial margins with fewer, stouter, distally tapered setae; article 7 , short, stout, approximately one­third length of article 6 , with 1 short proximal seta. Pereopod 5 – Coxal plate wider than long, slightly bilobed distally with ventral and posterior marginal setae; gill plate shorter than coxa width; article 2 subovate, widened medially, tapering distally with two rows of simple, anteromarginal setae, posterior margin with submarginal row of long plumose, outer posterior margin with double row of simple setae; article 3 short with anterodistal setae; article 4 , posterior margin with 5 clusters of thin, simple and plumose marginal setae, posterodistal angle with clusters of longer, distally tapered setae, mesial anterodistal and posterodistal margins with a cluster or long plumed setae; article 5 , anterior margin with 4 stout, tapered setae, posterior margin with a posterodistal cluster of simple setae setae; article 6 longer than article 5 with 4 groups of setae on anterior margin, posterior margin with a 5 clusters of simple setae; article 7 short, stout, tapered distally, approximately half length of article 6 . FIGURE 4 : Ameroculodes miltoni n. sp. , paratype female BB­b (A) pereopod 6 (B) pereopod 7 (C) detail of article 6­7, gnathopod 2 (D) epimera 1­2­3 Pereopod 6 – Coxal plate about as wide as deep, posterior margin with 4 spines, distal margin and distal half of anterior margin with short setae; article 2 subovate, anterior margin, proximal half with simple setae, distal half with long plumed setae, outer surface with submarginal row of simple setae, posterior margin with short simple setae, with medial submarginal row of long plumose setae; article 3 , short, with anterodistal setae; article 4 posterior margin with simple setae increasing in length distally, with plumed setae distally, anterodistal angle with plumed and simple setae, anterior margin with simple setae; article 5 shorter than article 6 , with long, curved setae on posterodistal margin, anterior margin with simple setae; article 6 with long, tapered setae on posterior margin, sparse on anterior margin; article 7 short, stout, tapered distally, approximately half length of article 6 . Pereopod 7 – Coxa short and wide with short posterior spines; article 2 , expanded posteriorly, posterior margin with short, thin spines, mesial surface with row of long plumose setae, anterior margins with 4­5 short spines; anterodistal angle with a cluster of 4­5 spines; article 3 with 5 strong anterodistal spines; article 4 , anterodistal angle with 4 spines, posterior margin with 3 clusters of spines, article 5 subequal to article 4 in length, with 2 groups of 2 spines on posterior margin and 3 groups of 2­4 spines on anterior margin, anterodistal and posterodistal angles with spine clusters; article 6 subequal to article 5 in length with 4 clusters of 2­3 anterior marginal spines, distal margin ringed with spines; article 7 subequal to article 6 in length, anterior margin with 4 spine groups, distal margin with 2­4 long, plumose setae (often lost in preserved specimens). Oostegites – Present on gnathopod 2 through pereopod 5 , densely setose marginally. Epimeral plates – Epimeron 1 with gently curved ventral margins and corners, without setae; epimeron 2 ventral margin almost convex, broadly rounded posteriorly and anteriorly with submarginal setae; epimeron 3 , ventral margin straight, with marginal and submarginal setae, corners abruptly rounded. Pleopods – Pleopods 1­3 of equal length, peduncle shorter than rami, with finely plumose marginal setae, simple facial setae, 2 retinacula (coupling hooks) distally on each peduncle, rami with 13­15 setose articles. Uropod 1 – Peduncle longer than rami, two proximoventral spines near articulation with urosome, one dorsodistal spine at the base of each ramus; outer margin with a row of 6­9 short spines, inner margin with 2­4 thin marginal spine­setae; inner ramus longer than outer, both with 2­4 marginal spine setae, inner margins of both rami minutely serrate, terminal spines absent. FIGURE 5 : Americulodes miltoni n. sp. , paratype female BB­b (A) uropods 1­2­3, lateral view (B) telson Uropod 2 – Peduncle subequal to outer ramus in length, with 1­2 inner marginal spines, 4­5 outer marginal spines, outer distal margin with a short stout spine; inner ramus longer than outer, both rami with 2­4 marginal spines on both outer margins, inner margins of both rami minutely serrate, terminal spines absent. Uropod 3 – Peduncle about half length of inner ramus, with several distal spines, inner ramus longer than outer with 2 marginal spines; outer ramus with 1 spine, terminal ramal spines absent. Telson – Tapering to gently rounded distal margin with 2 posterodorsal marginal setae. Adult male – Similar to female in most aspects, but distinctly smaller. Antenna 2 much longer than antenna 1 , with 11­13 articles bearing aesthetascs. Length of pereopod 7 in relation to body length much longer in male than in female. Etymology – This species is named in honor of the late Milton Foster, naturalist and father of the senior author. FIGURE 6 : Ameroculodes edwardsi (Holmes, 1905) holotype, 9 mm, USNM 29243 (A) gnathopod 2 (B) gnathopod 1 (C) head, lateral (D) pereopod 3 (E) pereopod 6 Remarks – In southeastern waters, Ameroculodes miltoni has been confused with its distinctly larger relatives, Ameroculodes edwardsi and Deflexilodes intermedius , both reliably known only from the cold temperate waters of northeastern North America (north of New Jersey ). Besides its much smaller size, A. miltoni differs from A. edwardsi (see Fig. 6 ) by having the ( 1 ) epimeral plates 1­3 rounded (quadrate in A. edwardsi ), ( 2 ) rostrum blunt, stout, and short (more flattened and longer in A. edwardsi ), ( 3 ) uropod 2 peduncle with larger and fewer dorsal spines (numerous smaller spines in A. edwardsi ), and ( 4 ) telson subovate and rounded posteriorly (truncate in A. edwardsi ), ( 5 ) basis of pereopod 7 relatively narrow (broad in A. edwardsi ). Deflexilodes intermedius , like A. miltoni , has rounded epimeral plates; it is, however, readily distinguished by the dactyls of the 3 rd and 4 th pereopods, which are well­developed and elongate (those of A. miltoni are reduced and short). In the northern Gulf of Mexico , Ameroculodes miltoni occasionally co­occurs with Hartmanodes (= Monoculodes ) nyei (Shoemaker, 1933 ) . The two species are immediately distinguishable by the distinctly longer carpal lobes of gnathopods 1 and 2 and the longer more “hooked” rostrum of H. nyei , as well as by setation of the uropods and the shape of the telson. The only other shallow water oedicerotid known from the waters of the southeastern United States , which occasionally co­occurs with A. miltoni , is Americhelidium (= Synchelidium ) americanum ( Bousfield, 1973 ). However, this species is characterized by having a chelate second gnathopod. Actually, A. miltoni may have its closest affinities to the eastern Pacific species A. hartmani and A. emarginatus . Ecological observations – Ameroculodes miltoni is normally associated with estuarine and coastal bay habitats in a wide range of salinities (< 1 °/ to 35 °/), occurring on medium to fine sand or sand­silt substrata. It appears to be an important bionomic component of estuaries of the northern Gulf of Mexico . At its type locality, a shallow sand bottom adjacent to the Biloxi Lighthouse Pier, A. miltoni is an important component in the diet of juvenile spot, Leiostomus xanthurus Lacèpéde during March, April, and May (R. Heard , per. obs.). Under the name “ Monoculodes edwardsi ” it also has been reported in the diets of other estuarine fishes ( Sikora et al. 1972 , Stickney et al. 1974, 1975 , Heard 1975 ). Ameroculodes miltoni is an excellent swimmer and enters the water column at night. In Georgia and Mississippi estuaries, it can represent an important part of the hypoplankton in night plankton tows (R. Heard , pers. obs.).