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Alpheus angulatus, a new species of snapping shrimp from the Gulf of Mexico and northwestern Atlantic, with a redescription of A. heterochaelis Say, 1818 (Decapoda: Caridea, Alpheidae)
| Content Provider | Semantic Scholar |
|---|---|
| Author | Mcclure, Matthew R. |
| Copyright Year | 1995 |
| Abstract | -Two species of the Edwardsii-group of snapping shrimp, Alpheus heterochaelis Say and A. estuariensis Christoffersen, have been recorded from coastal estuarine habitats of the Gulf of Mexico and Atlantic coasts of the United States. A new species, A. angulatus, has been discovered to inhabit these habitats across this range and is described and illustrated. Thenew species is morphologically similar to A. armillatus, the latter being a tropical species. A redescription with illustrations of A. heterochaelis is also provided herein. The Edwardsii species group of Alpheus consists of at least 10 western Atlantic species (Chace 1972; Christoffersen 1979, 1984; Williams 1984; Abele & Kim 1986), of which Alpheus heterochaelis Say, 1818, is the most abundant and widely distributed. Alpheus heterochaelis was originally described from Amelia Island, Nassau County, Florida, and has been reported to range from the lower Chesapeake Bay to Aransas County, Texas, Cuba, Curagao, Surinam, and possibly to Slo Paulo, Brazil (Chace 1972, Williams 1984). A variety of studies have been done concerning the biology of A. heterochaelis (for example, Wilson 1903, Nolan & Salmon 1970, Knowlton 1973, Conover & Miller 1978, Mellon &Stephens 1978). Despite the abundance of studies on A. heterochaelis, the geographic limits and the systematic status of this species remain problematic. Based on apparent misidentifications of West Indian and Brazilian specimens, Chace (1 972) questioned the occurrence of A. heterochaelis south of Surinam. Knowlton (1973) noted differences in egg size between laboratory reared A. heterochaelis from North Carolina and south Florida, and proposed that A. heterochaelis comprised two or more species. From a reevaluation of Alpheus inhabiting shallow-estuarine environments of the western Atlantic, Christoffersen (1 984) suggested the existence of a species complex, and described a new species, A. estuariensis (holotype from the Rio Potengi estuary, Rio Grande do Norte, Brazil), ranging from the east coast of Florida into the Gulf of Mexico from Mississippi to Texas; Cuba; Dominican Republic; Trinidad; Curagao; and from Cearh to Paranh, Brazil. Christoffersen (1 984) further concluded that the Alpheus occurring in the northern Gulf of Mexico represents A. estuariensis, and described the range of A. heterochaelis to be from North Carolina to Paraiba, Brazil. However, using Christoffersen's (1984) key, specimens from Galveston were identified by the author as A. heterochaelis. Thus, plus a reexamination of museum specimens of A. estuariensis from the northern Gulf of Mexico suggest the existence of taxonomic ambiguity concerning the Edwardsii group of Alpheus from the coastal waters of the Gulf of Mexico and northwestern Atlantic. VOLUME 108, NUMBER 1 8 5 An assessment of allozymic variation of specimens of Alpheus from Texas revealed the existence of two discrete and markedly different gene pools (McClure & Greenbaum 1994). Additional allozymic data (unpublished) indicate that these forms are sympatric throughout the northern Gulf of Mexico and Northwestern Atlantic coasts as far north as Beaufort, North Carolina. The present study was designed to provide morphological descriptions and identifications of the two electrophoretically identified species. Materials and Methods Snapping shrimps were collected at low tide by dip net in intertidal and shallow subtidal habitats consisting of sand or mud bottoms covered with oyster clumps or rocks. Shrimps were collected in coastal waters from south Texas to North Carolina (see Appendix for localities). Shrimps were stored at 80°C to fully preserve color patterns. Starch-gel electrophoresis (McClure & Greenbaum 1994) was used to sort the individuals into discrete electromorphic classes. Morphological characters were then assessed and compared with museum material and descriptions in the literature. Total Length (TL) of specimens is the combined measurements of the carapace, abdominal, and telson lengths. Museum specimens of A. heterochaelis, A. estuariensis, A. nuttingi, and A. armillatus were obtained from the following institutions: Marine Research Division, Florida Department of Natural Resources, St. Petersburg, Florida (FBSC); Marine Environmental Sciences Consortium, Tuscaloosa, Alabama (MESC); Texas A&I University, Kingsville, Texas (TAI); National Museum of Natural History, Smithsonian Institution, Washington, D.C. (USNM); Museum national D'Histoire naturelle, Paris, France (MNHN); Lamar University collection, Beaumont, Texas (LU). The original type material of A. heterochaelis and A. armillatus is not available; it is likely that the specimens have been lost. As the only detailed descriptions of A. heterochaelis are from the Carolinas (Christoffersen 1984), comparisons to this species were from material from the type locality and from the Carolinas. For A. arrnillatus, specimens from the type locality (Antilles) were used as a reference. Type material of the two species described here have been deposited in the USNM. Alpheus angulatus, new species Figs. 1, 2 Crangon armillatus. -Hay & Shore, 19 18: 386, fig. 9. (not Alpheus arrnillatus MilneEdwards, 1837). Alpheus estuariensis. -Christoffersen, 1984: 19 1 (in part, see discussion). Alpheus arrnillatus. Chace, 1972:62 (in part, see discussion). Ho1otype.-Male, 28 mm TL, on mud under rocks and rubble, South Padre Island, Texas, Laguna Madre just north of BrazosSantiago Pass, coll. M. K. Wicksten, 4 Jul 1992, USNM 266804. Material examined. -See Appendix. Diagnosis. -Rostra-orbital depressions abrupt posteriorly. Ventral margin of carapace pronounced at an angle ventrally posterior to second pereopods. Minor claw of male not balaeniceps-shaped. Spine present on merus offirst pereopod. Third and fourth pereopods with movable spine on ischium, lacking on fifth pereopod. Description of holotype. -Rostrum reaching 0.5 length of first antennular segment; in form of raised crest extending beyond base of eyestalks and widening into flat triangular area (Fig. 1 A). Ocular hoods prominent and unarmed, separated from rostrum by adrostral depressions abrupt posteriorly (Fig. 1A). Ocular hood width 0.27 times length of carapace. Carapace as figured (Fig. lC), 0.35 times TL (range 0.31-0.40 for all specimens examined). Carapace smooth, posterior of carapace with cardiac notch; 86 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON Fig. 1. A l p h m angulatus, new species. Adult male (holotype) from South Padre Island, Texas (TL = 28 mm). A, anterior carapace and antennae, dorsal; B, sixth abdominal somite, telson and uropods, dorsal; C, carapace and antennae, lateral; D, abdominal pleura, lateral. Bar indicates 5 mm. . VOLUME 108, NUMBER 1 ventral margin acute ventrally just posterior to articulation of second pereopod. Abdomen as figured (Fig. ID), 0.55 times total length (range 0.44-0.56). Pleura of abdominal somites 1 through 5 with ventral margins rounded. Sixth abdominal pleura with ventral margin acute posteroventrally. Telson (Fig. 1 B) 0.1 1 times total length (range 0.09-0.14). Proximal telson width 0.67 of length, distal width about 0.5 of length; 2 pairs of dorsal spines, anteriormost pair positioned about 0.4 of telson length, posteriormost pair positioned at 0.67; posterior margin convex, with 2 pairs of lateral spines, space between spines with double row of setae. Antennular peduncle with stylocerite dorsally flattened, terminating anteriorly at sharp point which reaches anterior margin of first antennular segment; second antennular segment longer than first and about 1.5 times as long as third (Fig. lA, C). Antenna1 spine reaching end of antennal peduncle, and just overreaching antennal scale; concave at middle and faintly convex at distal tip. Basal segment of antennal peduncle armed with spine ventrolaterally (Fig. 1 A, C). Mandible with 10 teeth. Third maxilliped reaching just beyond end of antennal peduncle; terminal article setose. First pereopods (Fig. 2A, B, C) strongly chelate and unequal; merus armed with spine distoventrally. Major chela thick, setose distally; propodus length 0.5 1 times total body length (range 0.28-0.56); upper and lower margins deeply notched proximal to articulation of dactyl, upper notch width about 0.04 of propodus length, lower notch width about 0.1 1 of propodus length; maximum propodus height about 0.46 times length; dactyl length about 0.36 times propodus length; hand height with dactyl closed about 0.35 times propodus length; dactyl with entire upper and distal margins rounded, with setae arranged in tufts; opposable margin of dactyl with molar process tilted at angle to axis of dactyl; sculpture of propodus as figured (Fig. 2A, B), with upper and lower notches forming saddle-like depressions (extending about 0.07 and 0.1 1 times length of propodus, respectively) into the lateral surfaces of propodus; upper notch positioned about 0.5 the length of propodus, lower notch positioned about 0.61, having tuft of setae on proximal end oflower notch; angular area of upper mesial surface of fixed finger rounded, having granular texture and tufts of setae; distal end of propodus rounded, with tufts of setae. Minor chela robust and setose, with setal tufts increasing distally on both propodus and dactyl (Fig. 2C); not sexually dimorphic, lacking balaeniceps setose crest on dactyl; propodus 0.33 times total body length (range 0.15-0.37 for specimens examined); propodus height about 0.30 times length in both sexes; dactyl length about 0.5 times that of propodus length in both sexes. Second pereopods slender and weakly chelate (Fig. 2D); carpus subdivided into 5 articles decreasing in length as follows (numbered from the proximal end); 1, 2, 5, 3 = 4. Third and fourth pereopods with ventral movable spine on ischium (Fig. 2E, F); dactyli simple; third pereopod propodus with 7 stout spines and 3 or 4 smaller alternating lateral spines, fourth with 8 stout spines and 5 or 6 alternating lateral |
| Starting Page | 84 |
| Ending Page | 97 |
| Page Count | 14 |
| File Format | PDF HTM / HTML |
| Volume Number | 108 |
| Alternate Webpage(s) | https://research.nhm.org/pdfs/26177/26177.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
