Pedro-Luis Ardisson

Intertidal and shallow water amphipods (Amphipoda: Gammaridea and Corophiidea) from Isla Pérez, Alacranes Reef, southern Gulf of Mexico

Tropical coral reefs are known to exhibit high levels of biodiversity. Amphipod crustaceans are successfully adapted to a wide range of marine habitats in coral reefs, but some regions, such as the Campeche Bank in southern Gulf of Mexico, are poorly studied or even unsurveyed for amphipods. To begin to address this paucity of information, the present study records amphipod species from Isla Perez, an island of the Alacranes Reef National Park, southern Gulf of Mexico. Twenty sites were sampled in the intertidal zone and shallow water adjacent to the island. Thirty-one species of amphipod were identified, 15 of which represented a geographical range extension to the northern Yucatan Peninsula, with four new records for the Mexican south-east sector of the Gulf of Mexico; nine for the Gulf Coast of Mexico; and two for the entire Gulf of Mexico. Significantly, a difference in faunal composition between windward and leeward areas of the intertidal zone was found.

Benthic infauna variability in relation to environmental factors and organic pollutants in tropical coastal lagoons from the northern Yucatan Peninsula.

We examine the abundance and species composition variability of benthic infauna from tropical coastal lagoons in relation to environmental factors and organic pollutants. Sediment samples were collected at 40 sites in four lagoons in the northern Yucatan Peninsula. A total of 7985 individuals belonging to 173 species were sampled. While the eastern lagoons were dominated by polychaetes, the western ones were dominated by crustaceans. Overall, polychaetes had the highest abundance (48%), followed by crustaceans (42%). According to canonical correspondence analysis, species attributes were correlated with water salinity, pH and temperature, but also with sediment pentachlorobenzene, trichlorobenzene, and low molecular weight polycyclic aromatic hydrocarbons. Some pollutants exceeded sediment quality guidelines, representing a potential environmental risk to benthic infauna. Together, environmental factors and pollutants explained 52% of the variance in abundance and species composition among sites.

Dulichiella celestun, a new species of amphipod (Crustacea: Amphipoda: Melitidae) from the Gulf of Mexico, with a key and zoogeographic remarks for the genus in the western Atlantic

The discovery of a new melitid amphipod in the Celestun Biosphere Reserve (northern Yucatan peninsula, SE Gulf of Mexico) is reported. Dulichiella celestun sp. nov. differs from its congeners by an unique set of characteristics: truncated lateral cephalic lobe, mandibular palp article 1 having inner margin produced distally, carpus longer than the propodus of gnathopod 1, gnathopod 2 propodus distolateral crown with four spines, pereopods 3-7 dactylar unguis anterior margin with two accessory spines, and urosomite 3 bearing four dorsal spines. A key to species and zoogeographical affinities among members of the genus in the western Atlantic are also provided.

Caprellids (Crustacea: Amphipoda) from the Gulf of Mexico, with observations on Deutella mayeri, redescription of Metaprotella hummelincki, a taxonomic key and zoogeographical comments

Seventeen species of caprellid amphipods have been recorded so far in the Gulf of Mexico. New distributional and habitat data are included for 12 species. Pseudaeginella biscaynensis has been recorded again in the Gulf of Mexico for the first time since it was originally described 45 years ago. New morphological information based on the development of Deutella mayeri and a redescription of Metaprotella hummelincki are also provided, along with a key for species identification and zoogeographical comments at the regional and global scales.

Morphological variation of Thalassia testudinum in two shallow coastal environments from the southeastern Gulf of Mexico

Abstract Total biomass, shoot density, leaf length and leaf width of the dominant seagrass Thalassia testudinum were compared between two coastal environments in the northeastern part of the Yucatan peninsula (Mexico). The coastal environments were (a) an exposed sublittoral zone (<1 km from the shoreline) and (b) a sheltered coastal lagoon. Plant morphology was monitored at monthly intervals from June 2001 to May 2002. There was a clear morphological variation between coastal environments throughout the period of study. In the exposed sublittoral zone, total biomass and shoot density were lower and leaves were longer and wider. In contrast, in the sheltered lagoon, total biomass and shoot density were higher and the leaves shorter and narrower. Overall, high values of total biomass, shoot density and leaf width were observed during the warm weather seasons (rainy and dry) whereas the low values were observed during the cold fronts weather season (nortes); leaf length followed a reverse trend. Results presented here stress the need to take into account the natural pattern of morphological variation in the design of sampling and monitoring programs.

On the phylogenetic position of Pseudophilomedinae within Sarsielloidea (Ostracoda, Myodocopida), with a description of one new Harbansus from Ningaloo Reef and redescription of H. paucichelatus from Yucatan

Abstract Previous studies have suggested incongruence between current systematics and molecular phylogenies of Sarsielloidea, with a possible polyphyly of the family Philomedidae. Here, we provide molecular phylogenetic analyses based on 18S rDNA and 28S rDNA. The former includes five new sequences and 12 from the GenBank, and the latter two new and six sequences from the GenBank. We use three methods, maximum likelihood, maximum parsimony, and neighbor joining, and all reconstructed phylogenies support previously suggested polyphyly, indicating a closer relationship of the subfamily Pseudophilomedinae with one subfamily of Sarsiellidae than with the nominotypical subfamily of Philomedidae. Morphological characters that may be key indicators of the phylogenetic relationships between three Sarsielloidea families are discussed. We also describe the 21st representative of the Pseudophilomedinae genus, Harbansus Kornicker, (Smith Contrib Zool 260:75, 1978), Harbansus ningalooi n. sp., from the Ningaloo Reef, Western Australia. This is the first Harbansus reported from the Australian west coast and the second from the Australian coral reef systems. It differs from all other congeners by peculiar claw-like processes on the posterior infold. Most Harbansus species have relatively restricted distributions, except Harbansus paucichelatus (Kornicker, in Inst Mar Sci 5:195–300, 1958), which has also been postulated to represent a species complex. We present a detailed morphological redescription of this species, based on the freshly collected material from the Yucatan Peninsula, as well as four mitochondrial COI sequences. These become the first COI sequences of the entire superfamily Sarsielloidea available on the GenBank. To facilitate future identification, we include a key to species of Harbansus.

DIFFERENTIAL USE OF THALASSIA TESTUDINUM HABITATS BY SYMPATRIC PENAEIDS IN A NURSERY GROUND OF THE SOUTHERN GULF OF MEXICO

Density of Penaeidae was assessed in habitats of Thalassia testudinum with different relative location (inshore zone and coastal lagoon) and sediment type (fine sand and coarse sand) during three weather seasons in the Yucatan peninsula, Mexico. A total of 26,847 penaeids were collected on a fortnightly basis from June 2001 to May 2002. A differential habitat use was observed in juveniles of three species of penaeids. Densities of Farfantepenaeus brasiliensis (mean size ± SD: 8.3 ± 3.8 mm CL, carapace length) and Farfantepenaeus notialis (5.5 ± 2.2 mm CL) were highest in the coastal lagoon in T. testudinum on fine sand, while density of Metapenaeopsis goodei (6.7 ± 1.7 mm CL) was also highest in T. testudinum on fine sand, but in the inshore zone. This spatial distribution pattern varied little during the three sampling seasons. A unimodal temporal distribution pattern was observed for juveniles of each species of penaeid, the abundance peaks of F. brasiliensis and M. goodei overlap in the nortes season, while the abundance peak of F. notialis was distinct, peaking in the rainy season. In contrast to juveniles, epibenthic Farfantepenaeus spp. postlarvae (3.2 ± 0.5 mm CL) had a more uniform spatial distribution with a bimodal temporal distribution pattern, a highest abundance peak in the late rainy-early nortes seasons and other minor in the dry season. A redundancy analysis indicated that densities of penaeids were related primarily with water salinity, sediment grain size, and aboveground biomass and structural complexity of T. testudinum, which are variables closely linked with the spatial arrangement of the habitats along the inshore zone and coastal lagoon. The use of different T. testudinum habitats allows coexistence of sympatric penaeids in the nursery ground with minimal inter-specific interactions.

Climatological, annual, and seasonal variability in chlorophyll concentration in the Gulf of Mexico, western Caribbean, and Bahamas using NASA colour maps

This study investigates climatological, seasonal, and interannual variability in chlorophyll concentration (Chl) throughout the Gulf of Mexico (GM), the western Caribbean Sea (WC), and the Bahamas (BI). For this purpose, Coastal Zone Color Scanner (CZCS) (1979–1986), Ocean Color and Temperature Scanner (OCTS) (1996–1997), and Sea-Viewing Wide Field-of-View Sensor (SeaWiFS) (1997–2008) NASA climatology, yearly, and seasonal Level-3 Standard Mapped Image series were used. Inspection of the original Chl and the obtained fuzzy unsupervised classified maps show the existence of a transition zone between the already known coastal and open waters. The extension (total number of pixels) and form of polygons representing these water masses vary both annually and seasonally, showing their greatest differences during spring and autumn in the northeastern and northwestern GM, Campeche Sound, and the Honduras coast in the Caribbean. In contrast, the BI present polygons having an almost invariant extension and form. The seasonal averaged Chl values up to 0.8 mg m−3 present a cyclic variation, showing the highest Chl during winter months and the lowest Chl during summer months, independent of the basin or the sensor under consideration. The CZCS and OCTS products must be considered with care; however, they provide results that are compatible with findings from the SeaWiFS time series. Annual and winter/autumn trends – a decrease in Chl – were identified in the GM and BI. The Caribbean reports constant Chl values during the two periods under study. Possible interpretations of these trends will come from detailed interpretation of local data.

MORPHOMETRIC RELATIONSHIPS OF JUVENILE METAPENAEOPSIS GOODEI (SMITH, 1885) (DECAPODA, PENAEIDAE) IN THE YUCATAN PENINSULA , MEXICO

The small penaeid shrimp Metapenaeopsis goodei (Smith, 1885) is widely distributed along the Atlantic Ocean, yet information on its morphometric features is scarce or non-existent. This study evaluated differences in the morphometric relationships between sexes of juvenile (carapace length mean: 6.8 mm, range: 3 to 10.5 mm) in a nursery ground of northeastern Yucatan peninsula, Mexico. The morphological features studied were carapace length (CL), total length (TL), rostrum length (RL), relative rostrum length (RL∕CL ratio), and total wet weight (W). About 19% of females ( n = 207 ) and 54% of males ( n = 167 ) had size classes of complete sexual maturity reported for this species, i.e., >8 and >6 mm CL, respectively. Analysis of covariance detected significant differences between sexes for the TL-CL, RL-CL, RL/CL-CL and CL-W relationships. The coefficient b (slope) of the morphometric relationships decreased about 4 to 20% in females relative to males. The TL-CL, RL-CL and CL-W relationships showed positive allometry for both sexes, but more strongly in males, suggesting that as juveniles increase in CL the males become larger, heavier, and with longer rostrum than females, although males did not reach the same maximum mean CL as females. The positive allometric growth for the CL-W relationship suggests that weight increases more than length, probably because of the abundant food supply on the nursery ground. Results from the current study indicate that separation of morphometric relationships for females and males is necessary for M. goodei that inhabit nursery grounds. Sexual dimorphism in morphometry appears to reflect development to sexual maturity of juveniles in shallow inshore nursery grounds, before migrating to offshore adult habitats.

Intra-Annual Variability of a Benthic Amphipod Assemblage (Crustacea: Amphipoda) in a Tropical Shallow Coastal Environment

The community structure of tropical soft-bottom macrofauna is generally considered temporally stable. Here, we document the intra-annual variability of an amphipod assemblage from a tropical benthic habitat. The study was carried out in a shallow coastal environment of the southern Gulf of Mexico, based on historical data obtained from monthly samplings from June 2007 to May 2008, which encompassed three seasons: rainy, cold fronts and dry. Water and sediment variables were recorded to characterize the habitat, and amphipods were collected to assess changes in composition, density, and feeding modes. Using habitat characteristics, the predefined climatic seasons were examined with a discriminant analysis to order the sampling months into the three seasons. A nested analysis of variance showed that, at monthly and seasonal scales, the assemblage is more variable than expected. The species richness and density varied significantly over time, mostly at the monthly scale. Furthermore, a correspondence analysis showed that the species composition was distributed seasonally; this ordination was validated by a permutational multivariate analysis of variance. Finally, a redundancy analysis between species and habitat characteristics revealed seasonal relationships between the environmental conditions and the amphipod fauna. We propose a conceptual model to summarize the joint variation of environmental and biological factors. The present study suggests that an ecological turnover occurs at the site, along with habitat partitioning among the species through time, which depends on the species and its trophic preferences.