Synalpheus mexicanus Coutière, 1909

Salazar, Margarita Hermoso, Wicksten, Mary & Morrone, Juan J., 2005, Redescriptions and taxonomic notes on species of the Synalpheus townsendi Coutière, 1909 complex (Decapoda: Caridea: Alpheidae), Zootaxa 1027 (1), pp. 1-26 : 13-20

Synalpheus mexicanus Coutière, 1909

Figures 5–6

Synalpheus townsendi mexicanus Coutière, 1909: 34 , fig. 17.— Chace, 1937: 123.— Carvacho & Ríos, 1982: 284.— Wicksten, 1983: 38.—Villalobos et al., 1989: 15.— Ríos, 1992: 12.— Villalobos­Hiriart, 2000: 82, fig. 41.— Wicksten & Hendrickx, 2003: 66.

Material examined: GULF OF CALIFORNIA, MEXICO: 4 males and 3 females (types, USNM 038393 USNM). Isla Espíritu Santo , Canal de San Lorenzo, 23 m, coral. 15 March 1949, Velero IV station 1738­49, 1 female ( LACM). Bahía de La Paz, 7 males, 5 females, and 6 ovigerous females ( CCUBCS). Roca Shepard, Cabo San Lucas, 8–15 m, year 1974, Donald G. Lindquist, 1 female ( LACM 322­05 ) . COLOMBIA: Ensenada de Utría , 1 male and 1 female ( USNM 244261 ) .

Description

Rostrum slender, with several setae at apex, straight in lateral view, 3.3 times longer than wide at base, reaching 0.6 times as long as visible part of first segment, not overreaching level of the orbital teeth in lateral view. Anterior margin between orbital teeth and base of rostrum almost straight, orbital hoods separated from rostrum by marked, depressed anterior slope of carapace. Orbital hoods slightly inflated dorsally; orbital teeth slender, acute, tip slightly directed mesially in dorsal view, straight in lateral view, shorter than rostrum, with one or two setae at apex, reaching 0.4 times as long as visible part of first segment of antennular peduncle. Ventral rostral process short, ventral margin rounded. Pterygostomial margin produced as broad, subtriangular, acute lobe.

Antennular peduncle short, 3.9 times longer than wide, first segment 1.1 times as long as second and third segments combined, 1.8 times as long as second segment, second segment 1.3 times as long as third segment. Stylocerite slender, reaching to 0.4 times as long as second segment.

Blade of scaphocerite well developed, 3.6 times longer than wide, 0.8 times as long as third segment of antennular peduncle; disto­lateral tooth straight, lateral margin concave, surpassing blade by 1.1 length of third segment, overreaching antennular peduncle and carpocerite by more than half length of third segment. Basicerite with very short dorsal tooth, 0.1 times as long as ventro­lateral spine; lateral tooth long, reaching 0.9 times as long as visible part of first segment of antennular peduncle, eight times as long as dorsal spine. Carpocerite short and slender, 4.6 times as long as wide, almost reaching distal end of antennular peduncle.

Apex of third maxilliped with five strong, dark spines; ultimate segment 3.6 times as long as penultimate segment.

Ischium of major first pereopod 0.6 times as long as wide. Merus thick, 2.1 times as long as wide, 0.53 times as long as palm, dorsal margin convex, ventral margin almost straight, distal end of dorsal margin with strong tooth with apex pointed downward. Carpus with dorsal distal margin rounded, ventral margin bilobed. Chela long and slender, 2.8 times as long as wide; palm slightly compressed laterally, twice as long as wide, 2.5 times as long as fingers, dorso­distal margin with slender tooth, slightly directed downward; fingers short, 0. 3 times as long as palm.

Ischium of minor first pereopod 0.3 times as long as merus. Merus 2.5 times as long as wide, dorsal and ventral margin slightly convex, dorsal distal margin with small tooth. Carpus half as long as palm, dorsal distal margin with small tooth. Palm of chela 1.8 times as long as wide, 1.7 times as long as fingers, with numerous setae.

Ischium of second pereopod 0.8 times as long as merus. Merus 6.6 times as long as wide, 0.8 times as long as carpus. Carpus slender, with 5 segments having ratios of lengths from first to fifth as follows: 4:1:1:1:2. Palm of chela 1.6 times as long as wide, 0.7 times as long as fingers, fixed finger with tuft of scarce setae, dactylus with scarce setae.

Ischium of third pereopod 2.5 times as long as wide. Merus 4.5 times as long as wide. Carpus 2.7 times as long as wide, 0.5 times as long as propodus, with spine at distal end of ventral margin. Propodus 7.6 times as long as wide, 4.9 times as long as dactylus, ventral margin with 9–10 movable spines and pair at distal end. Dactylus slender, 3.5 times as long as basal width, ungui approximately equal in width at base, following main axis of dactylus. Fourth and fifth pereopods similar but shorter, fifth pereopod with tufts of setae along flexor margin of propodus.

Pleura of first abdominal somite sexually dimorphic, in male with broad tooth on posterior ventral margin; pleura of second abdominal somite broadly rounded in both sexes; pleura of third to fifth abdominal somites with acute tooth on posterior half of ventral margin in male, rounded in female. Second pleopod with appendix interna. Telson broad, 1.3 times as long as wide at anterior margin, 2.4 times as long as wide at posterior margin; dorsal surface with slight longitudinal median depression, lateral margins sinuous, posterior margin convex; with 2 pairs long dorsal spines, both pairs of spines slightly removed from lateral margin, anterior pair situated at 0.3 times length, posterior pair at mid­length; posterolateral angles projecting and slightly acute; posterior margin armed with 2 slender lateral spines; mesial spines 1.5 times as long as lateral spines. Uropodal exopod with lateral margin convex anteriorly; diaeresis with 2 lateral teeth; lateral tooth longer, one spine between these.

Carapace length to 3.7 mm.

Color in life. —Not reported.

Type locality. — Southern Gulf of California .

Habitat. — Rock coral and sand; intertidal to 35 m ( Wicksten, 1983).

Geographic distribution and depth range.— Angel de Guarda island to Cabo San Lucas, Gulf of California; Revillagigedo Islands ( Wicksten and Hendrickx, 2003); Estero de Utrías, Colombia (this paper). Several authors ( Coutière, 1909; Chace, 1937; Steinbeck & Ricketts, 1941; Carvacho & Ríos, 1982; Wicksten, 1983; Rodríguez de la Cruz, 1987; Villalobos­Hiriart et al., 1989; Hendrickx, 1992, 1993; Rodríguez Alámarz et al., (2002) considered S. mexicanus to be endemic to the Gulf of California, but the record from Colombia extends its distribution southwards.

Remarks.— The type material of S. mexicanus consists of seven damaged specimens. The most complete one was chosen for the redescription. This species is morphologically variable, although its variability was not discussed previously in the literature. In the studied material, we observed variation in the length and width of the rostrum. The anterior margin of the carapace, between the orbital teeth and the rostrum, may be concave or almost straight. The relative length of the carpocerite varies from almost reaching the end of the antennular peduncle to slightly surpassing it. The dorsal tooth of the basicerite is more marked in some specimens. Its proportion in relation to the length of the lateral spine varies from 0.1 to 0.2 times. In the third pair of pereopods the length/width proportions of its articles are variable: dactylus 3.5–4, propodus 7.1–8.3, carpus 2.2–2.8, and merus 4.2–4.7. The longitudinal median depression of the telson is less conspicuous in some specimens.

We were unable to examine all of the specimens discussed by Wicksten (1983). Some of these specimens may be misidentified.

Synalpheus peruvianus Rathbun, 1910

Figures 7–8

Synalpheus townsendi peruvianus Rathbun, 1910:563 , fig. 4, Plate 5.— Méndez, 1981: 92.— von Prahl 1986: 96.—Lemaitre & Álvarez­León, 1992:43.

Material examined: Matapalo , Peru: 1 ovigerous female (Holotype, USNM 40503 ) .

Description

Rostrum very short, slender, straight, with several long setae at apex, 2.5 times longer than wide, reaching to 0.3 times length of visible part of first segment of antennular peduncle, overreaching level of orbital teeth in lateral view; anterior margin between orbital tooth and base of rostrum broad, almost straight; orbital hoods separated from rostrum by marked depressed anterior slope of carapace. Orbital hoods slightly inflated dorsally; orbital teeth short, acute, apex directed slightly laterally in dorsal view, slightly upward in lateral view. Rostrum and orbital tooth equally long, with scarce setae at apex of rostrum. Ventral rostral process short and slightly bilobed. Pterygostomial margin produced as subtriangularly, short and distally acute lobe.

Antennular peduncle long, slender, 5.8 times longer than wide; visible part of first segment 0.9 times as long as second and third segments combined, 1.5 times as long as second segment; second segment 1.4 times as long as third segment. Stylocerite elongated, reaching to 0.5–0.6 times length of second segment.

Blade of scaphocerite well developed, 3.2–3.3 times as long as wide, reaching to 0.2 times length of third segment of antennular peduncle; disto­lateral tooth slender, apex slightly directed laterally, lateral margin slightly concave, overreaching blade by approximately 0.8 length of third segment of antennular peduncle, reaching or surpassing antennular peduncle by 0.1 length of third segment, shorter than carpocerite by 0.4 length of third segment. Basicerite without dorsal tooth; lateral tooth broad proximally, reaching to 0.7 times length of visible part of first segment of antennular peduncle. Carpocerite broad, broader at mid­length, 3.8 times as long as wide, surpassing antennular peduncle by 0.5 times length of third segment of antennular peduncle.

Apex of third maxilliped with six dark spines; ultimate segment approximately 4 times as long as penultimate segment.

Ischium of major first pereopod 0.5 times as long as wide. Merus broad, twice as long as wide, 0.4 times as long as palm, dorsal margin almost straight, ventral margin slightly sinuous, distal end of dorsal margin with spine. Carpus with subtriangular lobe on dorsodistal margin, ending in small, acute tooth; ventral margin bilobed. Chela long and slen­ der, 2.6 times as long as wide; palm 1.6 times as long as wide, dorso­distal margin with acute distal tooth, directed ventrally; fingers 0.4 times as long as palm.

Ischium of minor first pereopod 0.2 times as long as merus, 1.5 as long as wide. Merus 3.1 times as long as wide, dorsal margin slightly convex, ventral margin almost straight, dorso­distal margin with small tooth. Carpus 0.5 times as long as palm, small spine on dorso­distal margin. Palm 1.9 times as long as wide, 1.4 times as long as fingers; fingers with scarce tufts of long setae.

Ischium of second pereopod 0.8 times as long as merus. Merus 5.7 times as long as wide, 0.9 times as long as carpus. Carpus slender, with five segments having ratios of lengths from first to fifth as follows: 4:1:1:1: 2. Palm of chela 1.5 times a long as wide, 0.9 times as long as fingers, fingers and palm with several tufts of setae and single setae.

Ischium of third pereopod 2.3 times as long as wide. Merus 4.4 times as long as wide. Carpus half as long as propodus, with pair of spines at distal end of ventral margin. Propo­ dus 7.5 times as long as wide, 4.7 times as long as dactylus, ventral margin with nine pairs of spines and pair of spines at distal end. Dactylus long, slender, 3.2 times as long as basal wide, ungui approximately equal in width.

Pleura of first fifth abdominal somites rounded. Second pleopod with appendix interna.

Telson broad, 1.3 times as long as wide at anterior end, 2.5 times as long as wide at posterior margin; dorsal surface with slight longitudinal median depression; lateral margins sinuous, posterolateral angles rounded; posterior margin convex; with two pairs of long dorsal spines situated at some distance from lateral margin; anterior pair situated at 0.4 times length of telson, posterior pair at 0.7 times length of telson. Posterolateral spines broken in this specimen. Uropodal exopod with lateral margin convex anteriorly; diaeresis with two lateral teeth, lateral tooth longer, one long spine between these two teeth.

Carapace length to 4.0 mm.

Color in life.—Not reported.

Type locality.— Matapalo , Peru .

Habitat.— Found among oysters ( Rathbun, 1910) or coral reefs ( von Prahl, 1986).

Geographic distribution and depth range. Ensenada de Utría, Colombia to Matapalo, Peru, less than 10 m ( von Prahl, 1986; Lemaitre & Álvarez León 1992).

Remarks. Many species of Synalpheus present a wide range of intraspecific variation. Even the same specimen may present differences when sides are compared. Frequently, the variation in the cephalic appendages is correlated to both the position of the major chela of the first pair of pereopods. In the holotype of S. peruvianus , the major chela is on the left side and incidentally the left appendages are smaller than the appendages on the right side.

We do not agree with some of the characters listed by Rathbun (1910). According to her, the rostrum exceeds slightly the length of the orbital teeth; however, we observed that they have the same length. Rathbun (1910) mentioned that the scaphocerite reaches the apex of the antennular peduncle, but we found that in the holotype, the scaphocerite reaches only to about 0.2 times the length of the third segment of the antennular peduncle. She also stated that the carpocerite surpassed slightly the antennular peduncle, but we found that the carpocerite reached only slightly beyond half the length of the third segment of the antennular peduncle. These discrepancies may be because Rathbun measured the holotype in a different position or at a different angle.

Synalpheus peruvianus has been poorly collected. Lemaitre and lvarez León (1992) recorded the species from Isla Gorgona, Colombia. The only other record of this species is Rathbun’s specimen from the type locality. Méndez (1981) did not report any other specimens from Peru.

Figures

FIGURE 5. Synalpheus mexicanus Coutière, 1909. A, frontal region in dorsal view. B, carapace. C, abnormal rostrum. D, major cheliped. E, minor cheliped. F, second pereopod.

FIGURE 6. Synalpheus mexicanus. A, third pereopod. B, abdomen of male. C, second pleopod. D, telson and uropods.

FIGURE 7. Synalpheus peruvianus Rathbun, 1910. A, frontal region in dorsal view. B, carapace. C, ventral rostral process. D, female abdomen. E, major cheliped. F, carpal junction with major chela.

FIGURE 8. Synalpheus peruvianus. A, minor cheliped. B, second pereopod. C, third pereopod. D, second pleopod. E, telson and uropods.