Pipefishes (Syngnathinae) are found in all tropical and warm-temperate marine waters, but out of approximately 219 known species, only about 20 are restricted to freshwater (most in the Indo-Pacific genus Microphis) (Nelson, 2006; Kuiter, 2009). Although many syngnathids are threatened by human activities (e.g., Foster and Vincent, 2004) and freshwater fishes are especially vulnerable due to the small size of their habitat (Moyle and Leidy, 1992), not much information is available on the ecology of these freshwater pipefishes.
One pipefish and one seahorse species are known from coastal waters of Suriname (Uyeno et al., 1983), but until now syngnathids were not known to occur in freshwater in that country (Ouboter and Mol, 1993). Freshwater pipefish were also neither listed for the fish fauna of French Guiana (Planquette et al., 1996; Keith et al., 2000) nor in a recent checklist of freshwater fishes of the Guiana Shield (Vari et al., 2009). However, Moonen (2006) reported a Pseudophallus species from the Approuague River basin in French Guiana.
Eschmeyer (2010) recognizes two valid Pseudophallus species in drainages of the Western Atlantic (from Mexico to Brazil): P. mindii (Meek and Hildebrand, 1923) and P. brasiliensis Dawson, 1974. Two additional Pseudophallus species are also known from Pacific drainages. The taxonomy of the two Atlantic species is confusing. Dawson (1974) described P. brasiliensis from Rio Tocantins, but later (1982), based on examination of additional material, he considered that differences between the two species were due to local population variations. He therefore placed P. brasiliensis in the synonymy of P. mindii. Ferraris (2003) also includes P. brasiliensis in P. mindii, but Menezes et al. (2003) consider P. brasiliensis a valid species. The differences between the two species are minor (Dawson, 1974) and their current distributional limits are unclear.
In March 2007, I collected specimens of a small pipefish at a sheltered beach in Corantijn River, Suriname, during conditions of low water level (Hydrobiology, 2007). The collection locality, Sand Landing, was situated approximately two kilometres upstream of the Amerindian village Apura and 155 km from the river mouth (here defined as the 15 m low-tide depth contour), in a reach well upstream of the 300 mg Cl/L limit of salt water intrusion located at km 40 during peak flow and km 82 during low flow (Crul and Reyrink, 1980; Amatali, 1993). With these specimens representing the first record of a freshwater pipefish in Suriname, I conducted two additional surveys for collecting additional specimens and ecological information in order to record the occurrence and habitat of the pipefish in the study area. Comments on the identity of the Corantijn River pipefish and observations on its behaviour in a field aquarium are also presented here.
MATERIAL AND METHODS
Following the initial collect of four pipefish specimens at Sand Landing in March 2007, 16 additional sampling stations (Fig. 1) were selected accordingly in lower Corantijn River, for two subsequent surveys in May 2007 (high water) and September 2007 giving special attention to riverine sites with aquatic macrophytes and to substrate. At the sampling stations, water temperature and conductivity were measured with a YSI Model 30 meter, dissolved oxygen was measured with a YSI Model 50B meter, pH was measured with an Oaklon pH testr3+DJ meter, surface water current velocity was measured with a Global water FP101/FP102 meter and turbidity was measured with a HACH DR 890 colorimeter.
In September 2007, I collected (1) bottom substrate samples in shallow water for analysis of sediment particlesize distribution, and, at Sand Landing, (2) the small grass-like aquatic macrophyte and (3) two zooplankton samples, the first by pouring 100 litre water through a plankton net (80 [micro]m mesh size) and the second by slowly towing the plankton net behind a boat during one minute. Analysis of sediment particle-size distribution was based on the ash-free dry mass of the bottom sediment (Van Reeuwijk, 1992). The aquatic macrophyte of Sand Landing was stored in 80% ethanol, and subsequently sent to the herbarium of Utrecht University (Utrecht, the Netherlands) and the herbarium of Anton de Kom University (Paramaribo, Suriname) for identification. Zooplankton samples were analysed by A. Haripersad-Makhanlal, Hydraulic Research Division of the Ministry of Public Works (Paramaribo, Suriname), using a Reichert MeF2 inverted microscope.
Fishes (pipefishes and other small-sized fishes) were collected with a 3 x 1.2 m small-meshed seine net (2 mm knotto-knot mesh size) in shallow water. In May 2007, three pipefishes were collected under unfavourable, high-water conditions with an adjusted collection method: the fine-meshed seine was attached to two 3-m long poles held by two persons positioned on both sides of the boat and then pushed gently through deep water with the boat moving slowly towards or along shore. In September 2007, I kept three male pipefishes for two days alive in a small field aquarium (37 x 23 x 22 cm) in order to make behavioural observations; these pipefishes were fed with freshly hatched Artemia nauplii ad lib.
Fishes were initially fixed in 4% formaldehyde and later transferred to 70% ethanol for long term storage. Pipefishes were deposited at the National Zoological Collection of Suriname (NZCS, Anton de Kom University, Paramaribo), Field Museum of Natural History (FMNH, Chicago), and California Academy of Sciences (CAS, Los Angeles). Measurements of length and wet mass of pipefishes were to the nearest mm and 0.1 mg, respectively. Tissue samples of pipefishes from the sites Sand Landing, Potoka Bank and Pigeon Island were collected and stored in 80% ethanol for analysis of DNA sequences. Four mitochondrial genes: cytochrome oxidase I (COI), 12S rRNA (12S), 16S rRNA (16S), and NADH dehydrogenase, subunit 1 (ND1), and two nuclear genes: Myosin Heavy Chain 6 (Myh6) and S7 ribosomal protein (S7) were analysed by Graham Short (CAS). The sequences will be deposited in GenBank after publication.
Fishes were identified with regional monographs like Eigenmann (1912), Planquette et al. (1996), Keith et al. (2000) and Le Bail et al. (2000), and taxonomic publications specific to Suriname. Fish names follow Eschmeyer (2010). The Corantijn River pipefish was first identified by Phil Willink (FMNH), and then by Graham Short and Beth Moore (CAS) using two publications of Dawson (1974, 1982).
Pipefish specimens collected and identification
A total of 12 small adult pipefishes (< 7.5 cm total length, < 0.3 g wet mass) was collected at three sites in the lower Corantijn River: 4 out of 9 adult specimens collected at Sand Landing were preserved (N 05[degrees]09'10.4", W 57[degrees]10'54.0"; NZCS F-7069, 2 pregnant males; FMNH-119605, 1 pregnant male and 1 female; CAS-230534, 4 newborns), 2 at Potoka Bank (N 05[degrees]03'21.3", W 57[degrees]18'56.9"; NZCS F-7070, 1 pregnant male; CAS-230532, 1 pregnant male) and a single specimen at Pigeon Island (N 04[degrees]59' 17.4", W 57[degrees]25'26.9"; CAS-230533, 1 pregnant male) (Fig. 1). At Sand Landing an average of three adult pipefishes was collected per survey, while at both Potoka Bank and Pigeon Island only one pipefish was collected per survey. Pipefishes were not collected at 17 other sites in the lower Corantijn River between the first rapids at Cow Falls and the village Orealla (Fig. 1, Tab. I).
Pipefish specimens collected in Corantijn River represent a single species, as confirmed by DNA sequences analyses of the mitochondrial and nuclear genes. It is a species belonging to the small genus Pseudophallus based on the configuration of body ridges (superior trunk and tail ridges discontinuous near rear of dorsal fin; inferior trunk and tail ridges continuous; lateral trunk ridge continuous with lateral tail ridge and confluent with superior tail ridge), the absence of an anal fin, 13-15 trunk rings, and the brood pouch of the male below tail rings 11-22. Females of the genus have an enlarged anal papilla (present in a female from Sand landing). The brood pouch of the male is on the abdomen and highly complex, with bilateral, inverted pouch folds that grow together in a closed pouch (i.e., Urophori type A4i; Herald, 1959; Dawson, 1985; Wilson et al., 2003). Based on the low number of rays in the dorsal fin (<30) and the small size of the Corantijn pipefish (< 7.5 cm total length), I here use the name Pseudophallus cf. brasiliensis Dawson, 1974 for the freshwater pipefish of Corantijn River.
Habitat of Pseudophallus cf. brasiliensis
The Sand landing site was characterized by a silty bottom substrate (in a reach with predominantly coarse sandy bottom sediments) and a meadow of a small grass-like, aquatic macrophyte that was exposed during low water conditions (Fig. 2).
The upper reaches of the lower Corantijn River, between the village Orealla (km 110) and the first rapids Cow Falls (km 235) (Fig. 1), had fresh water with low conductivity (< 30 [micro]S/cm) year round (i.e., in March, May and September 2007), a pH of 5.9-6.5, dissolved oxygen concentrations varying between 3.7 and 7.3 mg/l, low turbidity (7-20 NTU), and water temperature of 26.7-32.1[degrees]C (Tab. I). River width varied between 350 (at orealla) and 2500 m and water depth along the thalweg, the line joining the lowest points along the entire streambed defining its deepest channel, varied between 30 (at orealla) and 3 m. The water level in this reach showed both seasonal and diurnal (tidal) variation. In March 2007, the water level was low (Fig. 2A), while in May 2007 the water level was high. In September 2007, at intermediate water level, current velocity varied between 0.0 and 2.5 m/s at the sampling stations. Tributaries like Kaburi Creek and Kabalebo River had a somewhat higher conductivity (> 30 [micro]S/cm) than Corantijn River. In general, these results agree well with more extensive water quality data for orealla, Apura and Matapi in the reach orealla-Cow Falls (Crul and Reyrink, 1980).
The sediment in the upper 10-cm layer of the river bed in the reach orealla-Cow Falls was dominated by sand (Tab. II). However, at sheltered sites such as Sand landing the bottom substrate was more diverse with finer particles like silt and clay well represented in addition to sand (Tab. II). Downstream orealla extensive mudflats show up along the shores at low water conditions and, in general, finer particles (silt and clay) start to dominate the bottom sediments (Mol, unpubl.).
The underwater meadow at Sand landing comprised a spatially restricted area of approximately 150 by 40 m (Fig. 2). The grass-like, aquatic macrophyte making up the meadow was identified as the dwarf Amazonian sword plant Helanthium tenellum (Alismataceae) (for nomenclature see lehtonen and Myllys, 2008); H. tenellum was also collected at station P9, a beach 300 m downstream of Sand landing, and station P6, a mid-river bank downstream Sand landing. H. tenellum showed extensive root masses (Fig. 2B), suggesting that uptake of nutrients from the bottom substrate was important for this aquatic macrophyte.
In September 2007, only few zooplankton organisms were collected above the H. tenellum meadow at Sand landing: one Diaptomus (Copepoda, Calanoida) individual and two nauplius larvae in the 100 L sample, and one cylopoid copepod and one nauplius larvae in the tow-sample. No rotifers or cladocerans were observed in the two samples.
Corantijn River fish communities associated with P. cf. brasiliensis habitat at Sand Landing, Potoka Bank and Pigeon Island were dominated by Anchoviella lepidentostole, Hemiodus unimaculatus, Hemigrammus spp., Jupiabapolylepis, Moenkhausia grandisquamis, Moenkhausia lepidura, Pristella maxillaris, Brycon falcatus (juveniles), Aphyocharax erythrurus, Rineloricaria sp., Tomeurus gracilis, Crenicichla nickeriensis (juveniles), Geophagus brachybranchus (mainly juveniles), and Evorthodus lyricus. The species Anchoviella guianensis, Lycengraulis batesii, Cyphocharax spilurus, Leporinus friderici (juveniles), Astyanax bimaculatus, Poptella brevispina, Acestrorhynchus microlepis, Copella arnoldi, Corydoras cf. bicolor, Hypostomus sp. (juveniles), and Eleotris pisonis were present in low numbers.
At Sand landing eight males and one female P. cf. brasiliensis were collected; all eight males had eggs in their brood pouch, indicating that the Corantijn River pipefish is a true freshwater fish, i.e., the species is reproducing in fresh water. The female was identified by its elongated anal papilla, the absence of any pouch plates or folds, and a vividly striped coloration (Fig. 3; coloration not visible in the alcohol-preserved specimen). Male pipefishes had a mottled, brown colour (Fig. 4). Mature males with ripe brood pouch measured 53-72 mm total length and weighed 94-289 mg; the female was only 43 mm long and weighed 21 mg (Tab. III). At Potoka Bank and Pigeon Island, only male pipefishes were collected (three in total). Pregnant male pipefishes were collected in the low-water season (March), the high-water season (May) and at intermediate water levels (September) suggesting that reproduction takes place year-round. one pregnant male P. cf. brasiliensis that was collected 14 September 2007 at Sand Landing and kept alive in a bucket for aquarium observations released approximately 20 young pipefishes from its pouch during the night of 14/15 September. The transparent, newborn pipefishes measured 7-9 mm TL, weighed 0.6-0.9 mg (Tab. III) and had their fins fully formed. Three days later two other male pipefishes also released their offspring (approximately 20 newborns per male).
In the aquarium, three males P. cf. brasiliensis remained most of the time rather inactive on the bottom (Fig. 4) or in a clump of H. tenellum macrophytes. No signs of aggression among the males were observed. After adding live Artemia nauplii to the aquarium the pipefishes became more active, first moving with their head, and finally swimming through the tank in search of Artemia prey. Newborns P. cf. brasiliensis also showed benthic behaviour, resting for most of the time on the bottom of the aquarium. They did not accept Artemia nauplii and died after two or three days.
Freshwater pipefish of the genus Pseudophallus are widely distributed along the tropical eastern coast of South America (Dawson, 1982) and the occurrence of P. cf. brasiliensis in Suriname is therefore not unexpected. However, the Pseudophallus pipefish seem rare as they are apparently not represented in collections of freshwater fishes of the Guiana Shield (Vari et al., 2009) and not much is known about their ecology (but see De Leon, 1975, cited in Dawson, 1982). More work needs to be done on Pseudophallus taxonomy in order to resolve the indecision regarding conspecificity of P. brasiliensis and P. mindii. Molecular analyses of P. brasiliensis and P. mindii from their respective type localities (and comparison with DNA sequences of the Corantijn pipefish) would help to settle the question. In this respect it is important that tissue samples have been collected of three Corantijn River pipefish specimens and that 6 DNA sequences have been analysed. In addition the distribution of both species, if proved valid, also needs to be investigated. Suriname is geographically located in a prime position to help figure out the distribution problem. A Pseudophallus species has indeed been discovered in small tributaries of Approuague River, French Guiana, where it occurred in calm water between stems of the emergent macrophyte Montrichardia arborescens (Moonen, 2006), and recently a single female of P. cf. brasiliensis has been collected in a second Surinamese river (Suriname River; CAS-230535) (pers. obs.).
Seahorses and pipefishes are extraordinary among fishes in their remarkable adaptations for paternal care (male pregnancy) and frequent occurrences of sex-role reversals (i.e., female-female competition for mates) (Vincent et al., 1992). The differences in coloration suggest sex-role reversion in P. cf. brasiliensis. The sex ratio of the catch of P. cf. brasiliensis at Sand Landing (eight males, one female) also suggests that the females of this species live in a sex-role reversed harem structure with territorial females competing for males that brood their eggs (e.g., Vincent et al., 1992; Wilson et al., 2003; Nelson, 2006), although an alternative explanation for the observed sex ratio is that females and pregnant males have different habitat preferences (e.g., Roelke and Sogard, 1993). Syngnathids with complex brooding pouches (sensu Herald, 1959) may spend more energy on their offspring than do those with less complex brooding structures and, with an increase of male parental investment relative to females, more frequent sex-role reversals would be expected in species with more complex brood pouches. However, Wilson et al. (2003) showed that sex-role reversal in Syngnathidae is positively associated with polygamous mating patterns and not necessarily with the complexity of the male brooding structure. For example, sex-role reversal has not yet been documented in monogamous seahorses (genus Hippocampus), although these species have the highest degree of pouch development with placenta-like structures (Vincent and Sadler, 1995). Taking into account the apparent harem structure of the Sand Landing population and sexual dimorphism in coloration in P. cf. brasiliensis, it would be of interest to investigate the genetic mating system of the Corantijn pipefish by analysis of microsatellite markers (e.g., McCoy et al., 2001) or underwater observations in the low-water season (e.g., Vincent and Sadler, 1995).
Based on the catch per unit effort, the Sand Landing site apparently had a higher pipefish population density than the Potoka Bank and Pigeon Island sites. Thus the Sand Landing pipefish population may function as a source population from which pipefishes disperse to other sites in the lower Corantijn River upstream and maybe also downstream of Sand Landing (Fig. 5). Positive rheotropism was reported in the related freshwater pipefish Pseudophallus starksii (De Leon, 1975, cited in Dawson, 1982). Sand Landing showed medium to low flow velocities and this is likely due to its sheltered location immediately downstream a right-handturn of the river. The medium to low flow velocity at Sand Landing can plausibly explain the mixed sand:silt:clay bottom substrate in clear water and these conditions, in turn, have probably favoured extensive growth of H. tenellum macrophytes. The dwarf Amazonian sword plant H. tenellum is known to be light-demanding (Kasselmann, 2003). It also has a well-developed root system (Fig. 2B) and, like other Amazon sword plants (Kasselmann, 2003), probably needs a nutrient-rich substrate. A sandy bottom with low nutrient content or a clay bottom substrate in turbid water (and limited light penetration) would not represent favourable growth conditions for H. tenellum macrophytes. Benthic newborn P. cf. brasiliensis pipefish may find shelter against the current and predators between leaves of the little H. tenellum plants. Taking into account the low zooplankton (food) densities in Corantijn River (above, also see Crul and Reyrink, 1980), the H. tenellum meadow may also provide a good habitat for periphyton-associated food organisms (e.g., protozoans and rotifers) for newborn and adult P. cf. brasiliensis. In addition, the medium to low flow velocities at the sheltered Sand Landing site may have a direct positive impact on the Corantijn pipefish as these fish are not strong swimmers (pers. obs. in aquarium). Stands of H. tenellum were not observed at Potoka Bank and Pigeon Island, but at both sites pipefishes were collected between submersed plant leaves and at the exact collection sites current velocity was not strong.
Although the collection of only three Corantijn pipefishes in May 2007 is perhaps not surprising given the difficult, high-water conditions during that survey, the total number of pipefishes collected at 20 sampling stations during three surveys was low with only 12 specimens caught at three stations; nine of these were collected at Sand Landing. The number of collected pipefishes is small when compared to the total number of 1,833 fishes collected during the three surveys in 2007. Because other small-sized fish species (e.g., Hemigrammus spp, Tomeurus gracilis) were collected in much larger numbers and pipefishes are not particularly fast-moving fishes (as observed for P. cf. brasiliensis in the aquarium), it is here concluded that the Corantijn River pipefish occurs in low abundance and in specific habitats. For example, no pipefish was collected in tributary creeks or exposed sandy beaches/banks without aquatic vegetation. In addition, P. cf. brasiliensis was also not collected during extensive surveys (including numerous rotenone collections) of the lower Corantijn River and tributaries in 1979-1980 by R. Vari (1982), and in sections of the Corantijn River upstream of Cow Falls, including Sipaliwini River, by ichthyologists of the Natural History Museum of Geneva and the author (R. Covain, pers. com.; Mol, unpubl.).
Foster and Vincent (2004) pointed out that syngnathid fishes have certain life-history characteristics, such as a sparse distribution, low mobility, small home range, low fecundity, male pregnancy, and lengthy parental care that make them vulnerable to human-induced disturbance. In addition, freshwater habitats (and their fish species) are among the most threatened in the world (Moyle and Leidy, 1992; Bruton, 1995). The Sand Landing beach with its relatively high pipefish population density was proposed as the best site for the construction of a jetty for shipment of bauxite (Hydrobiology, 2007). In addition, there are old plans (that recently received renewed attention) for a hydroelectric dam in the Kabalebo River (e.g., Vari, 1982), a large tributary of Corantijn River about 20 km upstream Sand Landing; this proposed dam would affect the hydrology of the middle Corantijn River including the Sand Landing site. Although construction of the jetty has recently been postponed indefinitely (the mining company having left Suriname) and the Kabalebo Dam may not be constructed after all, the Sand Landing site clearly needs legal protection. However, in the long term protection of the Sand Landing site alone may not be sufficient to protect the habitat and associated pipefish, and a more comprehensive, whole-catchment management strategy may be necessary (e.g., Saunders et al., 2002).
Acknowledgments.--I thank Ross Smith, Frank van der Lugt, Paul ouboter, Kenneth Wan Tong You and Joep Moonen for help with field work. Jeff Armaketo organized river transportation. Phil Willink (Chicago Field Museum) and Beth Moore (California Academy of Sciences) both identified the Corantijn River pipefish. Graham Short (CAS) established the sex of a female specimen. Olaf Banki (Utrecht University Herbarium), Andre van Proosdij (hortus botanicus Amsterdam) and Gisla Jairam-Doerga identified the dwarf Amazonian sword plant. Two anonymous reviewers provided comments that improved a previous version of this manuscript. BHP-Billiton financed the three pipefish collection surveys on Corantijn River.
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Jan H. MOL (1)
(1) Center for Agricultural Research in Suriname (CELOS) and Department of Biology, Anton de Kom University of Suriname, CELOS building, Leysweg, Paramaribo, Suriname, South America. [firstname.lastname@example.org]
Table I.--Sampling stations (P1-P20), dates, water quality, and site characteristics for three pipefish surveys (March, May, and September 2007) in the reach Orealla-Cow Falls, Corantijn River, Suriname. NA: data not available. Distance from Sampling station river mouth Habitat type (km along thalweg) P1 122 Clear-water creek P2 134 River beach P3 139 Black-water creek P4 145 Clear-water creek P5 149 Disturbed shore P6 150 Midriver bank P7 154 Disturbed shore with grasses P8 154 Disturbed shore at small wharf P9 155 Sheltered river beach P10/Sand Landing 155 Sheltered river beach P10/Sand Landing 155 Sheltered river beach P10/Sand Landing 155 Sheltered river beach P11 161 Backwater channel P12 163 Backwater channel P13 169 Midriver bank P14 172 Midriver bank P15 174 Clear-water creek P16 178 Clear-water creek P17/Potoka Bank 185 River beach & bank P17/Potoka Bank 185 River beach & bank P18 NA--Kabalebo River beach River P19/Pigeon Island 210 Small river island P20 211 Small river island Sampling station Date Time Water temperature ([degrees]C) P1 18 May 2007 1215 25.4 P2 26 Mar. 2007 1230 29.3 P3 18 May 2007 1350 25.4 P4 18 May 2007 1600 NA P5 17 May 2007 1430 27.0 P6 20 May 2007 1230 30.7 P7 17 May 2007 1350 27.0 P8 26 Mar. 2007 1030 29.3 P9 10 Sep. 2007 1545 31.8 P10/Sand Landing 26 Mar. 2007 800 28.7 P10/Sand Landing 17 May 2007 820 26.7 P10/Sand Landing 10 Sept. 2007 1305 32.1 P11 19 May 2007 1000 26.8 P12 24 Mar. 2007 930 28.9 P13 24 Mar. 2007 1030 30.1 P14 17 May 2007 1030 NA P15 17 May 2007 1040 26.9 P16 17 May 2007 1145 24.7 P17/Potoka Bank 19 May 2007 1130 26.8 P17/Potoka Bank 11 Sep. 2007 1500 31.4 P18 11 Sep. 2007 1230 28.6 P19/Pigeon Island 14 Sep. 2007 1015 30.1 P20 14 Sep. 2007 1100 30.4 Sampling station Conductivity Dissolved pH Turbidity ([micro]S/cm) oxygen (pH-units) (NTU) (mg/L) P1 20 NA NA NA P2 10 4.2 6.5 11.0 P3 43 NA NA NA P4 NA NA NA NA P5 20 NA NA NA P6 26 6.7 6.2 11.0 P7 19 NA NA NA P8 10 4.2 6.2 8.0 P9 25 6.1 5.9 NA P10/Sand Landing 10 3.7 6.4 7.2 P10/Sand Landing 19.5 NA NA NA P10/Sand Landing 26 6.7 5.9 14.0 P11 19 NA NA NA P12 10 4.1 6.3 13.0 P13 10 4.6 6.3 10.0 P14 NA NA NA NA P15 18 NA NA NA P16 35 NA NA NA P17/Potoka Bank 19 NA NA NA P17/Potoka Bank 15 6.1 6.0 21.0 P18 39 6.7 6.1 14.0 P19/Pigeon Island 24 6.4 6.2 16.0 P20 23 7.3 6.0 14.0 Sampling station Current velocity (m/s) P1 NA P2 NA P3 NA P4 NA P5 NA P6 2.5 P7 NA P8 NA P9 0.0 P10/Sand Landing NA P10/Sand Landing NA P10/Sand Landing 0.0 P11 NA P12 NA P13 NA P14 NA P15 NA P16 NA P17/Potoka Bank NA P17/Potoka Bank 1.8 P18 3.2 P19/Pigeon Island 0.0 P20 0.0 Table II.--Particle size distribution of upper 10-cm of Corantijn River bottom sediment at nine sampling stations. Sediment particle size distribution Large-grain Fine-grain Sand silt silt Clay Sampling stations (2000-50 um) (50-20 um) (20-2 um) (< 2 um) P6 92.45 4.47 1.15 1.93 P9 53.25 35.50 5.43 5.82 P10 / Sand Landing 42.56 37.46 8.44 11.54 P13 98.68 0.22 0.40 0.70 P14 99.43 0.17 0.02 0.37 P17 / Potoka Bank 98.95 0.20 0.30 0.55 P18 98.87 0.40 0.50 0.23 P19 / Pigeon Island 84.17 2.57 3.38 9.88 P20 95.28 0.91 0.40 3.41 Table III.--Length and wet mass of four adults and six newborns (1-day-old) Pseudophallus cf. brasiliensis from Corantijn River, Suriname. Collection Collection date/ Specimens locality birth date female P10 / Sand landing 26 Mar. 2007 male P10 / Sand landing 26 Mar. 2007 male P17 / Potoka Bank 11 Sep. 2007 male P19 / Pigeon Island 14 Sep. 2007 newborn P10 / Sand landing 14/15 Sep. 2007 newborn P10 / Sand landing 14/15 Sep. 2007 newborn P10 / Sand landing 14/15 Sep. 2007 newborn P10 / Sand landing 14/15 Sep. 2007 newborn P10 / Sand landing 14/15 Sep. 2007 newborn P10 / Sand landing 14/15 Sep. 2007 Total Standard Wet length length mass Specimens (mm) (mm) (mg) female 43 42 21.1 male 53 52 93.7 male 71 70 277.0 male 72 71 289.1 newborn 8 NA 0.6 newborn 7 NA 0.6 newborn 8 NA 0.7 newborn 8 NA 0.9 newborn 9 NA 0.8 newborn 9 NA 0.6