Fiddler Crab Uca Minax Research Articles

Simple model of megalopal transport in narrow river-dominated estuaries

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 452:179-191 (2012) - DOI: https://doi.org/10.3354/meps09605 Simple model of megalopal transport in narrow river-dominated estuaries Stephen A. Borgianini1,*, Richard Styles2, Renae J. Brodie3 1Department of Mathematics and Sciences, University of South Carolina Beaufort, Bluffton, South Carolina 29909, USA 2U.S. Army Corps of Engineers, Coastal and Hydraulics Laboratory, Engineer Research and Development Center, Vicksburg, Mississippi 39180, USA 3Department of Biological Sciences, Mount Holyoke College, South Hadley, Massachusetts 01075, USA *Email: borgians@uscb.edu ABSTRACT: In river-dominated estuaries such as Winyah Bay at the base of the Pee Dee River in South Carolina, USA, the net movement of water and pelagic larvae is toward the ocean. Larvae of many decapods are hypothesized to recruit back into estuaries using a complex behavior termed flood-tide transport (FTT). A pattern of late-stage larval behaviors in concert with daily tidal rhythms yields net larval transport upstream into the estuary. Tidal currents in narrow river channels exhibit little distortion of flow, resulting in near linear flows. This means that there is a linear decay in tidal current amplitude over the last few kilometers of the upper estuary that can be easily modeled with a simple 1-dimensional (1D) model. With our 1D model, we demonstrate that ebb and flood currents can be modeled accurately near the limit of maximum upstream tidal influence within narrow river-dominated estuaries. Our model predicts the damping of flood tidal current in the face of river discharge. This dampening restricts the upriver migration potential of larvae that use FTT to return to adult habitats, or colonize new habitat. When our model is coupled with FTT behavior, we can predict the ability of red-jointed fiddler crab Uca minax (LeConte 1855) larvae to recruit back to the freshwater reaches of the Pee Dee River estuary for any combination of river discharges or tidal amplitudes. The flow model we developed can be used to assess the potential impacts of changing river flow and sea level on larval recruitment to upstream areas of coastal rivers. KEY WORDS: Larval transport · Decapod larvae · Tidal currents · River discharge · Tidal freshwater · Modeling · Uca minax · Global warming Full text in pdf format PreviousNextCite this article as: Borgianini SA, Styles R, Brodie RJ (2012) Simple model of megalopal transport in narrow river-dominated estuaries. Mar Ecol Prog Ser 452:179-191. https://doi.org/10.3354/meps09605 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 452. Online publication date: April 25, 2012 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2012 Inter-Research.

Reduced Cuticular Permeability Promotes Inland Habitat Expansion and Freshwater Survival in the Fiddler Crab Uca Minax but not in its Less Terrestrial Counterparts U. Pugilator and U. Pugnax

We report a two-fold suppression in activation energy for water loss in adult Uca minax males compared to co-occurring species, U. pugilator and U. pugnax, that overlap in salt marsh/estuary habitats, implying a water-tight cuticular modification that is unique to U. minax. This is further reflected by a drop in Arrhenius frequency (steric) factor A as an integrated measure of cuticular effectiveness. U. minax is also distinguished by an enlarged body size (approximately 5× as large as the other two species) and an enhanced capacity for water retention by a pronounced 4-5 fold decrease in net transpiration rate, presumably as a result of surface area to volume properties and the reduction in cuticular permeability. High net transpiration rates correspond to high activation energies in U. pugilator and U. pugnax, suggesting that they are more porous; the values for U. pugnax were the highest indicating that this species is the most prone to water stress. Features that these crab species have in common are a 67% body water content, twice the amount of water as their dry mass (size), and absence of a critical transition temperature (CTT) that safeguards them against an abrupt, lethal water loss. Lack of a CTT agrees with previous descriptions of crabs having no water-proofing epicuticular lipids and matches their rapid water loss rates and limitation to wet habitats. The ability by U. minax to conserve water by restricting water loss, however, makes them less dependent on a moisture-rich habitat, and this parallels field data that account for the differential capacity of U. minax to thrive in terrestrial inland locations by resisting desiccation and to survive in fresh water by being less porous to water entry. Results are consistent with the view that placing a priority on investigating what crabs are actually doing in the field (they operate on a smaller scale; i.e., microhabitat) is more important to application of net transpiration rate than as a general indicator of moisture-requirements for a species. Une diminution de 2 fois de l'energie d'activation pour la perte d'eau chez les adultes d'Uca minax compares aux deux especes U. pugilator et U. pugnax, qui coexistent dans les habitats lagunaires et estuariens a ete observee, impliquant des modifications cuticulaires pour empecher l'entree d'eau. Ceci est aussi reflete par une chute du facteur A de la frequence d'Arrhenius, en tant que mesure integree de l'efficacite de la cuticule. U. minax se distingue aussi par, une taille plus grande (approximativement ×5 par rapport aux deux autres especes) et une capacite plus grande pour retenir l'eau grâce a une diminution par 4-5 du taux net de transpiration, probablement une consequence de la proportion surface volume et d'une reduction de la permeabilite cuticulaire. Des taux eleves de transpiration correspondent a une energie d'activation elevee chez U. pugilator et U. pugnax, suggerant que ces especes sont plus permeables; les valeurs pour U. pugnax etaient les plus elevees, indiquant que cette espece est la plus sensible au stress aqueux. Les caracteristiques que ces especes de crabes ont en commun sont 67% de contenu en eau corporelle, deux fois plus d'eau que leur poids sec (taille) et l'absence de temperature critique de transition (CTT), ce qui les protege contre une perte d'eau brutale et letale. L'absence de CTT est en accord avec des descriptions precedentes de crabes ne possedant pas de lipides cuticulaires impermeabilisants, leur taux rapide de perte d'eau et leur restriction a des habitats humides. La capacite de U. minax a conserver l'eau en restreignant les pertes, le rend cependant moins dependant d'un habitat riche en humidite, et ceci rejoint les donnees de terrain qui indiquent une capacite differente de U. minax a prosperer a l'interieur des terres en resistant a la dessiccation et a survivre en eau douce en etant moins permeable a l'entree d'eau. Les resultats sont en accord avec l'opinion que, placer la priorite sur les observations de terrain (micro-habitats) est plus important que l'application du taux net de transpiration en tant qu'indicateur general des exigences d'humidite pour une espece.

Developmental shift in the selective tidal-stream transport behavior of larvae of the fiddler crab Uca minax (LeConte)

Following hatching, larvae of the fiddler crab Uca minax (La Conte) are exported from the adult habitat in estuaries to coastal and shelf waters where they undergo development prior to re-entering estuaries as postlarvae (megalopae). Studies of the spatial distribution of both newly hatched zoeae (Stage I) and megalopae indicate they undergo rhythmic vertical migrations associated with the tides for dispersal and unidirectional transport (selective tidal-stream transport) both within estuaries and between estuaries and the nearshore coastal ocean. We tested the hypothesis that U. minax zoeae possess a circatidal rhythm in vertical migration that facilitates offshore transport in ebb tidal flows, while postlarvae (megalopae) return to estuaries using a similar flood-phased endogenous rhythm. We also determined if the expression of the rhythm was influenced by the salinity conditions zoeae and megalopae experience as they transition between low-salinity regions of estuaries and high-salinity coastal waters. Stage I zoeae were collected by holding ovigerous female crabs in the lab until hatching. Megalopae were collected from the plankton and identified to species using molecular techniques (PCR-RFLP). Under constant laboratory conditions, both zoeae and megalopae exhibited endogenous circatidal rhythms in swimming that matched the principal harmonic constituent of the local tides (12.39 ± 0.07 h; X¯ ± SE). Upward swimming in Stage I zoeae occurred 2.5-4 h after high tide near the time of expected maximum ebb currents in the field. Rhythmic swimming of megalopae occurred slightly earlier in the tide (2.5 ± 0.09 h after high tide; X¯ ± SE) but was not entirely synchronized with flood currents, as expected. Salinity conditions had no apparent effect on the expression or pattern of the rhythms. Results indicate that this circatidal rhythm forms the behavioral basis of selective tidal-stream transport (STST) in early stage U. minax zoeae, but does not undergo a sufficient phase shift to account for vertical distribution patterns exhibited by megalopae in the field.

Larval mortality during export to the sea in the fiddler crab Uca minax

Dense populations of the fiddler crab Uca minax (Le Conte 1855) are common along tidally influenced freshwater rivers and streams >50 km from the sea. Adults do not migrate from inland sites to release larvae, but instead release them directly into an environment where the zoeae cannot survive. Laboratory salinity tolerance experiments were used to determine how long larvae from the inland-most population of U. minax along the Pee Dee River, South Carolina, USA can survive zero salinity compared to larvae from a brackish water population (salinity 5) near the mouth of Winyah Bay in the same estuary. Larvae from the brackish water population were also exposed to a salinity of 5 and their survival tracked. These experiments were conducted from May to August 2004 and 2005. To determine if inland larvae suffered significant mortality in transit due to salinity stress, current profiles were measured in the field and used to model the time taken by a larva using ebb-tide transport to travel to permissive salinities. The laboratory tolerance experiments showed that larvae from the inland freshwater population had LT50’s of 4–5 days at 0 salinity, which were significantly longer than those of the brackish water zoeae (2–3 days). Zoeae from the brackish water population survived for at least one larval molt at a salinity of 5 with LT 50’s of ∼12 days. Estimated travel times to reach permissive salinities from the inland-most population based on current profiles were 3–5 days for larvae using night-time only ebb-tide transport and 1.5–2.5 days for those using ebb-tide transport both day and night. Previously published field data indicate that U. minax larvae do use both day- and night-time ebb-tide transport, and are found in high densities in the water column during the day. These results lead to the conclusion that U. minax stage I zoeae do not undergo significant salinity-induced mortality during their 50+ km trip to the sea.

Molting of fiddler crab Uca minax megalopae: stimulatory cues are specific to salt marshes

Waterborne chemicals can be habitat cues for pelagic larvae of benthic invertebrates by stimulating settlement and metamorphosis. Less clear is whether cue effectiveness declines with increasing distance from the source. We examined whether the ability of seawater to stimulate meta- morphosis (molting) of fiddler crab Uca minax megalopae to the first-crab stage is restricted to water overlying marshes. Laboratory-reared megalopae were enclosed in situ for 3 d within nylon mesh cages in both a marsh and a river site 15 m away from the marsh. Even in the absence of contact with sediment, megalopae in the marsh had high rates of molting, whereas those in the river molted at very low rates similar to control megalopae enclosed in glass jars containing filtered seawater and deployed in the marsh habitat. In a second experiment, we tested for a dose-dependent molting re- sponse from the presumed source of the cue. We hypothesized a negative linear relationship in molt- ing frequency with increasing distance from the marsh. Megalopae were enclosed for 3 d in cages within the marsh and at distances of 2, 5, and 15 m away from the marsh edge, and in jars within the marsh. Molting response was greatest in the marsh, intermediate 2 and 5 m away from the marsh, and lowest 15 m from the marsh and in the control jars (test of regression slope, F1, 25 = 13.290, p= 0.001, r 2 = 0.321). Therefore, chemical cues for molting of fiddler crab megalopae originate in marshes and decline in effectiveness within a short (<15 m) distance of the marsh habitat.

Comparison of fish and macroinvertebrate use ofTypha angustifolia, Phragmites australis, and treatedPhragmites marshes along the lower Connecticut River

Since 1965 large areas of lower Connecticut River tidelands have been converted from high diversity brackish meadow andTypha angustifolia marsh to near monocultures ofPhragmites australis. This study addresses the impact ofPhragmites invasion on fish and crustacean use of oligohaline high marsh. During spring tides from early June through early September 2000, fishes and crustaceans leaving flooded marsh along 3 km of the Lieutenant River, a lower Connecticut River tributary, were captured with Breder traps at 90 sites, equally distributed amongPhragmites, Typha, and treated (herbicide and mowing)Phragmites areas. Pit traps, 18 per vegetation type in 2000 and 30 each inPhragmites andTypha in 2001, caught larvae and juveniles at distances of up to 30 m into the marsh interior. There were no significant differences in fish species compositions or abundances among the vegetation types. Size distributions, size specific biomasses, and diets ofFundulus heteroclitus, the numerically dominant fish, were also similar. The shrimpPalaemonetes pugio was more abundant inPhragmites than in other types of vegetation, whereas the fiddler crabUca minax was least numerous inPhragmites. Mean numbers ofF. heteroclitus andP. pugio caught per site event were positively correlated with increasing site hydroperiod. Significantly moreF. heteroclitus were captured along the upper reach of the river where marsh elevations were lower than farther downstream. MoreF. heteroclitus and fewerP. pugio andU. minax were captured during the day than at night. A relatively small number of larval and juvenileFundulus sp. were captured in pit traps, but consistently fewer inPhragmites than inTypha, suggesting thatTypha and brackish meadow marshes may provide better nursery habitat. Vegetation was sampled along a 30 m transect at each trap site in 2000. Plant species diversity was greatest in treatedPhragmites areas and lowest inPhragmites sites.

Buffer zones promoting oligotrophication in golf course runoffs: fiddler crabs as estuarine health indicators

Nitrogen pollution above a threshold level induces a eutrophication process in coastal creek ecosystems and consequently impacts on the water quality. The remedy for this scenario is the introduction of methods to enhance oligotrophication by means of constructed wetlands and buffer zones. This paper discusses new data on nitrogen flux and population changes in the primary consumers in the Bradley Creek ecosystem, adjacent to the Duck Haven Golf Course in southeastern North Carolina. In 1998-99, over different seasons, density distribution of the field populations of the fiddler crab Uca minax, was monitored as an indicator of environmental health. A control site at Whiskey Creek, adjacent to the University Center for Marine Sciences, was monitored in the same period since this site is not influenced by any golf course nutrient flux. The results pointed out that threshold level for optimum population density in Spartina grandiflora salt marsh is 0.1 mg/L of nitrates. A dense crab population, adjacent to the golf course with a buffer zone, was indicative of restoration of the estuarine ecosystem. A model, involving the use of constructed wetlands for oligotrophication, is being prepared on the basis of studies conducted by the University of South Alabama for a stormwater wetland constructed adjacent to the university's golf course.

Chemoreception by the red‐jointed fiddler crab Uca minax (Le Conte): Spectral tuning properties of the walking legs

The red‐jointed fiddler crab Uca minax is one of the most abundant macroinvertebrates inhabiting the temperate western Atlantic salt marshes, along the eastern and southern coasts of the United States. Dactyl chemoreception is the primary sensory modality involved in food detection. Ninety‐six chemoreceptor cells from 69 male and female second and third legs were tested with 20 compounds known to be stimulatory in other decapods. Each compound was tested as 1 s pulses at 10‐3M. Overall, chemoreceptor cells on the dactyls responded strongest to glutamate and ammonium chloride followed by citric acid. Glutamate‐ and ammonium chloride‐best cells formed the most prominent cell populations and were relatively narrowly tuned. Individual cells exhibited a range of tuning breadths based on responses to single compounds. Amines were moderately stimulatory. Surprisingly, hexose sugars which cause strong behavioural responses in U. minax elicited only weak physiological responses. Glutamate sensitivity separates U. minax from other species of fiddler crabs. The results indicate that the chemical response spectrum of U. minax includes compounds that occur naturally in salt marshes as algal and animal constituents, exudates, and decomposition products.

Adaptive significance of hatching rhythms and dispersal patterns of estuarine crab larvae: avoidance of physiological stress by larval export?

Estuarine crabs commonly display two larval dispersal patterns in which larvae are either exported from or retained within estuaries. The semiterrestrial fiddler crab Uca minax (LeConte, 1855) hatches on nocturnal spring high tides in the upper estuary and larvae are rapidly transported downstream. The mud crab Rhithropanopeus harrisii (Gould, 1841) hatches on nocturnal high tides of any amplitude and larvae are retained behaviorally in the upper estuary throughout development. If larvae are exported from the estuary to avoid environmental stress, then exported larvae should be less tolerant of high temperatures and low salinities than retained larvae. Larvae of these two species of estuarine crabs were hatched at 20‰ and 25 °C and subjected to salinities of 0, 5, 10,20, and 30‰, temperatures of 25 and 35 °C, and exposure times of 2, 6, 12, and 48 h. Larvae of both species reared at 30 or 20‰ survived well, while those reared in fresh water all died within 2 h regardless of temperature. Mud crab larvae reared at 5 and 10‰ survived better at the lower temperature (25 °C), higher salinity, and shorter exposure times. There was no significant effect of temperature or salinity on the survival of fiddler crab larvae, although survival decreased with increasing exposure time. Thus, the hypothesis that fiddler crab larvae are exported into stable coastal waters to reduce physiological stress is not supported. However, fiddler crab larvae may have evolved to be very tolerant of extreme temperature and salinity stress because they, unlike mud crabs, often release their larvae into shallow creeks. Most fiddler crab larvae are released on nocturnal spring high tides, which facilitates dispersal from tidal creeks. However, freshwater runoff and heat transferred from the marsh surface to flooding waters may still create stressful conditions for larvae soon after they are released. Larval release on spring high tides may facilitate dispersal from tidal creeks.

Na + regulation and (Na ++ K +)ATPase activity in the euryhaline fiddler crab Uca minax (Le conte)

1. 1. Specific activity and kinetic characteristics of the (Na + + K +)ATPase have been investigated in the gill epithelium of the hyper-hypoosmoregulator crab Uca minax. 2. 2. (Na + +K +)ATPase activity is shown to be at least three times higher in the posterior gills. 3. 3. The kinetic study supports the hypothesis of the existence of two different (Na + + K +)ATPases: the enzyme activity in the posterior gills could be involved in the transepithelial transport of Na + while the activity of the anterior gills could be responsible for the intracellular regulation of Na + and K +. 4. 4. Significant and specific changes in (Na + +K +)ATPase activity occur upon acclimation to media of various salinities.

Certain organism-substrate relationships affecting the distribution of Uca minax (Crustacea: Decapoda)

The involvement of substrate in the ecology of the fiddler crab Uca minax was investigated by means of both field and laboratory studies. These included determination of the oxygen-holding capacities of five types of substrates on which this organism lives, as well as experiments to determine if there is substrate selection. The effect of population density on burrowing was also studied to determine the optimum number of individuals needed in the selection experiments, and to delineate the mechanisms these organisms use for avoiding dispersion onto less favorable substrates.

Influence of X-Rays on Limb Regeneration in Urodele Amphibians

Influence of X-Rays on Limb Regeneration in Urodele Amphibians