Macrobrachium santanderensis, Garcia-Perez, Alfredo & Villamizar, Jorge, 2009

Garcia-Perez, Alfredo & Villamizar, Jorge, 2009, Macrobrachium santanderensis, new species of freshwater prawn (Crustacea: Decapoda: Palaemonidae) from the northeastern Andes mountains of Colombia, Zootaxa 2061, pp. 61-68 : 62-68

Macrobrachium santanderensis , new species

All the specimens of the new species were collected during the dry season in a farm premises located approximately 70 km on an east to west road connecting the cities of Bucaramanga and Barrancabermeja (Department of Santander, Central East of Colombia, South America) and located at 900 m above the mean sea level (07°06’15” latitude North, 73°24’44” longitude West, Figure 1 ). The collected specimens were preserved in 50% isopropyl alcohol solution. All drawings were made by hand and using a binocular stereomicroscope.

Material and methods: During the field survey, several small sized freshwater prawn (total length mean ± SD=36 ± 3 mm), including berried female specimens (n=30) were collected carrying few (mean ± SD=117 ± 44) and large oval eggs (2.6–2.8 mm in diameter). The holotype (1 male, tl 40 mm, May 1995; collected by Alfredo García-Peréz, Sara Cristina Sierra , and Martha Cecilia Rincón), and paratypes (5 males, 5 females; May 1995; collected by Alfredo García-Peréz, Sara Cristina Sierra , and Martha Cecilia Rincon) are deposited under registration number CHJ076 in the Entomology Laboratory collection at the Museum of Natural History of the Universidad Industrial de Santander (MHNUIS for its convention name in Spanish), Bucaramanga, Santander, Colombia. As used in this paper, carapace length (cl) is measured from the posterior margin of the cephalothorax to the tip of the rostrum and total length (tl) is measured from tip of rostrum to tip of telson.

Carapace ( Fig. 2 A): Carapace smooth, rostrum (rostral formula 8–9/2–3) well developed with tip as long as or slightly shorter than antennal scale, lancet-shaped with 8–9 teeth on upper edge regularly distributed and 0–1 tooth behind posterior limit of orbit, 2–3 teeth on lower edge reaching proximal third of rostrum. Setae short, fine and hair-like or non-plumose in space between teeth on upper rostrum and covering totally distal third of lower rostrum. Antennal and hepatic spines distinctly present with antennal conspicuously larger than hepatic. Antenna ( Fig. 2 C): Scaphocerite well developed, reaching tip of the rostrum or slightly shorter than rostrum, about four times as long as broad with one anterolateral spine strongly acute, rounded distally and fringed along almost entire inner margin with hair-like dense setae, proximal area with one pair of strias; basicerite stout, with acute ventrolateral tooth; multisegmented flagellum longer then total body length.

Antennule ( Fig. 2 D): Peduncle 3-segmented reaching the distal tooth in the lower margin of rostrum; stylocerite long, reaching half zone of intermediate segment; proximal segment rounded distally, fringed with hair like setae and reaching stylocerite, scale with one dorsal spine, cluster setae in the distal zone and statocyst; intermediate and distal segments almost equal size, together are equal size to length of proximal segment; distal margin of intermediate segment with sharply pointed lateral spine, reaching half zone of distal segment (inner spine) and setae in outer spine reaching proximal area of endopod; exopod divided into two rami consisting of six basal segments, at least 50-segmented outer ramus and 22-segmented inner ramus; endopod at least 60-segmented, longer than outer ramus of exopod and some segments bearing distal setae.

Mandible ( Fig. 3 A): Mandible has a 3-segmented palp, distal segment rounded with three bifid setae marginally; incisor and molar parts distinctly separated, forming a “V” shaped structure on a long base; incisor process stout, distal margin truncate with three major and three minor teeth; molar process cylindrical, truncated distally, with five crushing teeth and molar surface surrounded by many slender teeth.

Maxillule ( Fig. 3 B): Structure well developed. Coxal endite narrower than basal and fringed with naked setae distally; basal endite broader than coxal, convex apex, with 2-terminal and 1-subterminal rows of stout spinules and sparse setae laterally; palp distinctly bilobed, with 2 naked setae distally in upper lobe and short cluster setae in lower lobe.

Maxilla ( Fig. 3 C): Unsegmented endopod without setae; scaphognatite well developed with dense long naked setae at apex, smooth outer marginal and surface shows longitudinal venation pattern; endites elongated, 3-lobated and deeply clefted with several distal and sub distal naked setae.

First maxilliped ( Fig. 3 D): Basis and coxa separated by a notch, with numerous setae marginal and sub marginal; endopod unsegmented, palp naked and pointed distal end; exopod naked with a well developed caridean or Boas’ lobe, flagellum slender and large; epipod bilobed, distal endite larger than proximal and pointed marginally, proximal endite rounded.

Second maxilliped ( Fig. 3 E): Developed and pediform; 3-segmented endopod; distal segment widened, margin distally truncated, bearing many naked setae; exopod naked much longer than endopod; epipod bilobed ending with a large podobranch on the upper lobe and small podobranch on the lower lobe, opposite margin to upper lobe with naked setae.

Third maxilliped ( Fig. 3 F): 3-segmented endopod and about twice as long as exopod, naked setae on each segment, distal segment covered with naked setae and naked spine at apex; exopod naked as long as first segment of endopod and appears to be unsegmented.

Pereiopods: Exopod absent; first pair of pereiopods ( Fig. 4 A) stout, reaching distal apex of antennal scale; well developed chelae with dactyl and fixed fingers showing numerous naked setae and sensory hairs; carpus two and one third times as long as chelae and slightly longer that merus; basis with setae on ventral margin. Second pair of pereiopods ( Fig. 4 B) robust, similar in size and shape, and longer that rest of pereiopods; completely smooth and naked with merus as long as carpus; carpus beyond antennal scale with few setae in distal apex, and longer than well-developed chelae with cutting edges having three proximal teeth without denticles, and a few setae at the distal end of the fingers. Third ( Fig. 4 C), fourth ( Fig. 4 D) and fifth ( Fig. 4 E) pairs of pereiopods fully developed similar in size and shape, with exception of fifth pair showing a row of spines on outer margin of carpus and the dactylus covered with naked setae.

Pleopods: Pleopods well developed; exopod distinctly broader and longer than endopod; both exopod and endopod weakly pointed distally with dense long naked setae, and surface shows a leaf venation pattern. First pair of pleopods ( Fig. 4 F) with naked protopodite; endopod reduced and the appendix interna is absent. Second, third, fourth and fifth pair of pleopods fully developed similar in size and shape, protopodite with broad distal end and outer margin with dense setae. Appendix interna well developed in second, third, fourth and fifth pair of pleopods reaching half size of endopod, apex rounded with stamen-like setae. Appendix masculina in second pair of pleopods ( Fig. 4 G) is located between appendix interna and endopodite, rounded distally, twice the size that appendix interna, and slightly shorter than endopodite, distal end and margins covered with dense setae.

Telson and uropods ( Fig. 2 B): Telson very elongated, much longer than broader with setae and one spine present at base of median process and two pairs of dorsal spines at the last middle of the telson. Posterior portion narrow with an intermediate protrusion longer and robust than one pair of small external spinules flanked by an internal pair of spinules overreaching midpoint and external pair, and one pair of long posteriormarginal plumose setae between internal spinules. Uropods longer than telson, rounded distally and fringed with dense hair like setae on outer and inner margins of endopods and inner margin of exopods. Distal fourth of outer margin in uropodal exopod produced to form stout spine with a spine inside. Uropodal exopods are slightly larger and broader than endopods.

Abdomen ( Fig. 4 H): Body sub-cylindrical without lateral ridges. The abdominal somites are smooth and different sizes. The sixth abdominal somite is twice as long as the fifth and 0.4 times as long as carapace. Color, size, and eyes: Body color in living animal is translucent; small sized prawn (total length mean ± SD=36 ± 3 mm); eyes stout and well developed, with large, globular and pigmented cornea. Cornea rounded, much longer and slightly broader than eyestalk.

Etymology: The specific name santanderensis is derived from the name of the Department of Santander, one of the political subdivisions of Colombia where the new species was found.

Water Quality: Physical-chemical water properties, field tested at the time of collection was as follows: pH 5.0 standard units, water temperature 23°C, dissolved oxygen concentration 2.3 mg/L and water visibility using the Secchi disk 21 cm.

Discussion: Due to the restricted studies and scarcity of published data on Macrobrachium species for this region of Colombia, the comparative studies with other local species of Macrobrachium is difficult. However; morphology comparison with other Colombian Macrobrachium species which inhabit the nearby Orinoco river basin such as M. brasiliense , M. cortezi , M. heterochirus , and M. reyesi , and the only species reported for the Catatumbo region ( M. praecox ), reveals characters indicative of a new freshwater prawn species.

Remarks: The anterolateral surface of the carapace in M. brasiliense is covered with spinules whereas it is completely smooth in M. santanderensis . Rostrum curved downward overreaching antennal scale with 2–4 teeth completely Post-orbital in M. cortezi ; sinuous and shorter than antennal scale with 4–5 teeth completely post-orbital in M. heterochirus ; straight and shorter than the antennal scale with 1–2 teeth completely postorbital in M. precox ; straight and as long as or slightly longer than antennal scale with 2–3 teeth completely post-orbital in M. reyesi ; whereas rostrum reaching antennal scale and 0–1 tooth behind posterior limit of orbit in M. santanderensis . Second pair of pereiopods slightly or completely different in size, and covered with conspicuous spines in M. brasiliense , M. cortezi , and M. heterochirus ; merus as long as carpus and shorter than chelae with fingers thickly pubescent ( M. praecox ) or naked ( M. reyesi ); whereas second pair of pereiopods are similar in shape, and completely smooth with merus as long as carpus and longer than chelae, and few setae at the distal end of the fingers in M. santanderensis . Eggs large and few are characteristics of M. brasiliense , M. cortezi , M. reyesi , and M. santanderensis as opposed to the small and numerous eggs found in M. heterochirus and M. praecox .

Roux (1928) has the only morphological description for the unique species ( M. praecox ) found and reported for this Colombia region. Pearse (1916), Escobar (1979), Von Prahl and Rios (1984), and Bowles et al. (2000) described specific Colombian biotopes inhabited for different Macrobrachium species. The collection of the Smithsonian National Museum of Natural History (2008) has twelve Palaemonidae records reported for Colombia under four Macrobrachium species: M. carcinus , M. hancocki , M. rathbunae , and M. transandicum .

Holthuis (1952) reported that 13 species of Macrobrachium live in the Atlantic ( acanthurus , brasiliense , carcinus , olfersii , praecox , surinamicum ) and Pacific ( americanum , diguetti, hancocki , panamense , rathbunae , tenellum , transandicum ) coasts of Colombia. Martinez (1973) recorded M. crenulatum and faustinum ; Medina and Sobrino (1975) listed M. amazonicum ; Escobar (1979) added M. heterochirus ; and Campos (1997) included M. nattereri . Valencia-López and Rocha de Campos (2004, 2007) examined, determined, revised and confirmed taxonomically the specimens of six Colombian Macrobrachium collections. They found a total of 21 native Macrobrachium species registered and reported for the Colombia collections. The species M. cortezi , M. ferreirai , and M. reyesi were registered for the first time, and M. praecox is still the only species registered for the Catatumbo region, which is part of the northeastern Andes mountains of Colombia.

However, Macrobrachium rosenbergii , endemic species from Southeast Asia should be reported for Colombia after its introduction was approved by the Colombia government in the early 80’s for aquaculture purposes ( National Oceanic Atmospheric Administration, 1991). Currently, data is not available about Colombian companies, research institutes, public or private universities or individuals who are culturing this freshwater prawn. After almost 30 years of its introduction, the scientific literature has not published reports of M. rosenbergii being catch in either the wild in Colombia.

According to the classification done by Shokita (1985) using the eggs as a reference, this new species can be classified as large-eggs and land-locked life-cycle prawn. Macrobrachium species usually need saline water to complete their development. However, species with totally or partially abbreviated larval development (1–3 larval stages) have essentially developed an adaptation to the strictly freshwater habitat, and usually they have few large eggs ( Pereira and Garcia, 1995). Anger (1995) considers that species inhabiting fast-flowing or stagnant freshwater bodies have a restricted geographical range, thus the current species described here would have a restricted geographical distribution to Santander.

At present the following twenty three (23) Macrobrachium species are known and reported in the literature from Colombia: acanthurus , amazonicum , americanum , brasiliense , carcinus , cortezi , crenulatum , digueti , faustinum , ferreirai , hancocki , heterochirus , nattereri , olfersii , panamense , praecox , rathbunae , reyesi , rosenbergii (introduced species), santanderensis (new species), surinamicum , tenellum and transandicum . We hope this new species record and description will assist in clarifying collections of freshwater specimens to increase the knowledge and habitat protection of Macrobrachium species for this Colombian region.

The inaccessibility to some remote areas has not allowed these tropical zones to be adequately surveyed, considering the variety of habitats. Some of the poorer known zones are unexplored systems of small creeks, ditches, streams or ponds direct or indirectly connected to rivers.

Figures

FIGURE 1. Map of Colombia indicates the location (●) where specimens of the new species of Macrobrachium santanderensis were collected.

FIGURE 2. Macrobrachium santanderensis, new species, holotype, tl. 40 mm. A. Carapace; B. Telson; C. Antenna; D. Antennule. Scale bars equal 1.0 mm.

FIGURE 3. Macrobrachium santanderensis, new species, holotype, tl. 40 mm. A. Mandible; B. Maxillula; C. Maxilla; D. First Maxilliped; E. Second Maxilliped; F. Third Maxilliped. Scale bars equal 1.0 mm.

FIGURE 4. Macrobrachium santanderensis, new species, holotype, tl. 40 mm. Pereiopods (A. First; B. Second; C. Third; D. Fourth; E. Fifth); Pleopods (F. First; G. Second showing appendix masculina); H. Abdomen. Scale bars equal 1.0 mm.