Luis M. Mejía-Ortíz

MODIFICATIONS OF EYE STRUCTURE AND INTEGUMENTAL PIGMENT IN TWO CAVE CRAYFISH

Abstract Eyestalk length, internal eye structure, pigmented eye area, and pigments in eyes and exoskeleton were studied in two stygobiont crayfish, Procambarus cavernicola and Procambarus oaxacae reddelli. Results were compared with the epigeal crayfish Procambarus olmecorum, all three species inhabiting the karstic region of Acatlan, Oaxaca, Mexico. The stygobite species have shorter eyestalks and reduced pigmented areas compared with the epigeal species. For both eye and integument pigments, the stygobite species have a reduction in their total absorbance spectra compared to the epigeal species. Internal eye structure and organisation are reduced in both stygobite species, but to a greater extent in Procambarus cavernicola. These results are discussed in relation to the time of cave colonisation, the degree of adaptation, and the energy economy hypothesis.

A new use for useless eyes in cave crustaceans

[Cave animals show various adaptations to survival in their unusual environment, involving their physiology, behaviour, life history, and morphology. The morphological adaptations include enlargement of the sensory and ambulatory appendages, reduction or lack of pigment in the integument, and reduction or loss of eyes. In general, the eyes of cave animals show only non-constructive adaptations: however, we have found setae on the corneal surfaces in three different genera of cave decapods (Potamalpheops, Macrobrachium, and Procambarus) where setae are normally never present. We suggest that this constitutes the development of a new function for the obsolescent eyes, either tactile or chemosensory. This obviously underscores the general hypertrophy of non-visual sensory systems in cave organisms. Los animales cavernicolas muestran singulares adaptaciones para sobrevivir en sus ambientes, involucrando principalmente caracteristicas de su fisiologia, comportamiento, historia de vida. Las adaptaciones morfologicas frecuentemente comprenden el alargamiento de los apendices sensoriales y ambulatorios, reduccion o carencia total de pigmentos en el integumento, asi como una disminucion o perdida total de los ojos. En general los ojos de los animales cavernicolas solo tienen adaptaciones no constructivas; sin embargo, nosotros hemos encontrado setas sobre las superficies de la cornea en tres generos diferentes de decapodos cavernicolas (Potamalpheops, Macrobrachium, y Procambarus) donde las setas normalmente nunca estan presentes sobre la cornea. Sugerimos que esto constituye el desarrollo de una nueva funcion para los ojos obsoletos, ya sea tactil o quimioreceptora. Esto obviamente subraya la hipertrofia general de los sistemas sensoriales no visuales en los organismos de cueva., Cave animals show various adaptations to survival in their unusual environment, involving their physiology, behaviour, life history, and morphology. The morphological adaptations include enlargement of the sensory and ambulatory appendages, reduction or lack of pigment in the integument, and reduction or loss of eyes. In general, the eyes of cave animals show only non-constructive adaptations: however, we have found setae on the corneal surfaces in three different genera of cave decapods (Potamalpheops, Macrobrachium, and Procambarus) where setae are normally never present. We suggest that this constitutes the development of a new function for the obsolescent eyes, either tactile or chemosensory. This obviously underscores the general hypertrophy of non-visual sensory systems in cave organisms. Los animales cavernicolas muestran singulares adaptaciones para sobrevivir en sus ambientes, involucrando principalmente caracteristicas de su fisiologia, comportamiento, historia de vida. Las adaptaciones morfologicas frecuentemente comprenden el alargamiento de los apendices sensoriales y ambulatorios, reduccion o carencia total de pigmentos en el integumento, asi como una disminucion o perdida total de los ojos. En general los ojos de los animales cavernicolas solo tienen adaptaciones no constructivas; sin embargo, nosotros hemos encontrado setas sobre las superficies de la cornea en tres generos diferentes de decapodos cavernicolas (Potamalpheops, Macrobrachium, y Procambarus) donde las setas normalmente nunca estan presentes sobre la cornea. Sugerimos que esto constituye el desarrollo de una nueva funcion para los ojos obsoletos, ya sea tactil o quimioreceptora. Esto obviamente subraya la hipertrofia general de los sistemas sensoriales no visuales en los organismos de cueva.]

Seasonal Patterns in the Distribution of Three Species of Freshwater Shrimp, Macrobrachium spp., along an Altitudinal River Gradient

The distribution of different species belonging to the freshwater shrimp genus Macrobrachium was studied along an altitudinal gradient in the Huitzilapan River, Veracruz, Mexico. Population surveys of M. heterochirus, M. carcinus and M. acanthurus were conducted along an 80 km long river stretch that started at 1045 m above sea level (asl) and ended at the estuary. In the dry and rainy seasons, sampling was conducted, at eight sampling sites along the river. The animals were collected with traps and casting nets. Five abiotic variables: temperature, salinity, water velocity, pH, and dissolved oxygen (DO) were measured. An altitudinal species segregation was observed: Macrobrachium heterochirus was most widely distributed in the dry season, from 1045 to 105 m asl, and most numerous at altitudes between 500 and 100 m; M. carcinus occurred at altitudes ranging from 280 to 5 m asl in both seasons; and M. acanthurus was restricted to the estuary below 5 m asl. Temperature decreased whereas water velocity increased with altitude, as was registered in both seasons. Our results indicate that seasonal differences shaped the distribution patterns of the three species. During the dry season, the distributions of the shrimp extended along the entire river, whereas in the rainy season their distribution was mainly in the lower area of river, and the main variables measured that have major influence in their abundance, seemed to be DO and water velocity. En este trabajo reportamos la distribucion de diferentes especies de langostinos del genero Macrobrachium a lo largo de un gradiente latitudinal en el rio Huitzilapan, Veracruz, Mexico. Un analisis poblacional de M. heterochirus, M. carcinus y M. acanthurus fue realizado a lo largo de un transecto de 80 km que inicio a los 1045 metros sobre el nivel del mar (msnm) y finalizo en donde el rio es un estuario. Se realizaron cuatro muestreos en las estaciones de secas (2) y en lluvias (2); ocho lugares fueron muestreados a lo largo del rio. Los animales fueron colectados con trampas y atarrayas, asimismo fueron medidos cinco variables abioticas (temperatura, salinidad, velocidad del agua, pH y oxigeno disuelto). Una segregacion altitudinal fue observada: Macrobrachium heterochirus fue la especie con una distribucion mas amplia en la estacion de secas desde los 1045 a los 105 msnm, prefiriendo areas a altitudes entre los 500 y los 100 m; M. carcinus ocurre a altitudes desde 280 a 5 m en ambas estaciones; y M. acanthurus estuvo restringida a la zona del estuario por debajo de los 5 msnm. La temperatura disminuyo donde la velocidad del agua se incremento con la altitud, esto fue registrado en ambas estaciones. Nuestros resultados indican que las diferencias estacionales marcan las distribuciones de las tres especies. Durante la epoca de secas, las distribuciones se extienden a lo largo de todo el rio. Mientras en la estacion de lluvias esta fue principalmente sobre el area mas baja del rio, y las principales variables medidas aqui que tienen una mayor influencia en sus abundancias fueron el oxigeno disuelto y la velocidad del agua.

ARE THERE ADAPTATION LEVELS TO CAVE LIFE IN CRAYFISH

Abstract The stygobitic crayfish Procambarus cavernicola and Procambarus oaxacae reddelli and the epigeal crayfish Procambarus olmecorum were maintained in laboratory conditions in order to compare their oxygen consumption rates by measuring the decreasing oxygen concentration. These closely related species belong to the same subgenus and live in nearby caves and surface streams located in the same karstic region found in northern Oaxaca, Mexico. The consumption rates were monitored in laboratory conditions during fifteen hours in water maintained at 20°C without food. Significant differences among the species were found. Although these species live in similar conditions of total darkness during their life cycles, P. cavernicola had the higher oxygen consumption rate; this is a result of being slightly conditioned to oxygen partial pressures of the experimental bottle. Procambarus oaxacae reddelli showed a lower oxygen consumption rate strongly correlated to the oxygen partial pressure of the water. The epigeal P. olmecorum was used as a control and showed a consumption rate slightly conditioned to oxygen partial pressures that was lower than the consumption rate of P. cavernicola. The differences in consumption rates between the stygobitic species in relation to the characteristics of the caves where they live and their adaptation degree to cave life are discussed.

Freshwater Prawns of the Genus Macrobrachium (decapoda, Palaemonidae) with Abbreviated Development from the Papaloapan River Basin, Veracruz, Mexico: Distribution and New Species

In the Papaloapan River two freshwater prawns with abbreviated development have been recorded: Macrobrachium villalobosi (a stygobitic species) and Macrobrachium totonacum (an epigeal species). In this paper we describe four new species from this genus, and the distribution of these six species along the river basin. M. oaxacae nov. sp. occurs in the River La Junta, and together with M. cosolapaense nov. sp. is geographically close to the stygobitic species and M. totonacum, but differs from these in the following aspects: pigmentation, the number of rostral spines, and the relative proportions of the articles of the second pereiopod, of appendix masculina and appendix interna, and the number of spines on the appendix masculina. Macrobrachium mazatecum nov. sp. lives in two streams in Veracruz: the first close to Tierra Blanca Veracruz and the second on the Zapotal Veracruz near Mpio. Lerdo de Tejada. This species was also recorded in two springs near Valle Nacional Oaxaca, and differs from M. oaxacae nov. sp. and M. cosolapaense nov. sp. in the number of rostral spines, and the relative proportions on the articles of second pereiopod, of appendix masculina and appendix interna, and of the spines on the appendix masculina. Finally, Macrobrachium jacatepecense nov. sp. occurs only in a spring near Jacatepec, Oaxaca. This species differs from the other species in the relative proportions of the articles of the second pereiopod: however, it is very close to Macrobrachium oaxacae nov. sp. in the number of rostral spines, but based on the geographical distribution of both species and other features, it is clearly a different species. In this Papaloapan River basin, the distribution of this complex of species is very limited, because the various populations live in very restricted areas associated with springs or small streams, and without direct interconnections. All these new species are comparable with the epigeal Macrobrachium species in the southeast of Mexico that have abbreviated larval development.

Progressive troglomorphism of ambulatory and sensory appendages in three Mexican cave decapods

Sensory and ambulatory appendages were compared between epigeal and cave species of prawn and crayfish from Mexico. The cave prawn Macrobrachium villalobosi was compared with the epigeal M. totonacum. The cave crayfish Procambarus cavernicola and P. oaxacae reddelli were compared with the epigeal P. olmecorum. In both Macrobrachium and Procambarus the antennules and antennae of the cave species were longer in proportion to carapace length than in epigeal species. In the crayfish the cave species had a longer and narrower first pereiopod, and also showed a greater development of setation on the antennules, antennae, and carapace. These are all considered examples of progressive troglomorphism. They will improve non‐visual sensory capability in the aphotic and resource‐poor cave environment.

Morphological adaptations to anchialine environments in species of five shrimp families (Barbouria yanezi, Agostocaris bozanici, Procaris mexicana, Calliasmata nohochi and Typhlatya pearsei)

Anchialine systems are unusual among aquatic habitats in that they are subterranean karst systems in which marine and overlying groundwater are separated by distinct haloclines and characterized by high sulphur content, darkness and low nutrient availability. In this study, we examine how the antennulae, antennae, eyes and integument morphology of five anchialine species of decapods (Barbouria yanezi, Agostocaris bozanici, Procaris mexicana, Calliasmata nohochi and Typhlatya pearsei) are adapted for anchialine environments. Our examination of sensorial structures shows that while these species appear to have convergent adaptations for anchialine environments, degrees of specialization in antennular and antennal structures vary, with Barbouria yanezi showing the greatest setation. The eyes of all five species show pores at their tips, but only Calliasmata nohochi also exhibits setae on the eyes. We propose that these additional setae and pores function to enhance the ability of these decapods to sense mechanical and chemical stimuli in the water. In overview, these anchialine crustaceans have evolved anatomical/morphological attributes that appear to function to help detect predators, congeners, food, or refugia.

Arthropods Host Intracellular Chemosynthetic Symbionts, Too: Cave Study Reveals an Unusual Form of Symbiosis

Mutualisms with chemosynthetic microbes are surprisingly rare in arthropods and their relatives. Despite the evolutionary benefit assumed in retaining symbionts through growth cycles, this molting group also lacks intracellular mutualisms. The current study provides evidence of the first chemosynthetic intracellular symbiosis in Arthropoda (Crustacea), discovered in extreme anchialine cave. These unusual groundwater systems enclose a landlocked marine layer, are typified by sharp salinity and oxygen gradients and are analogous to better studied extreme environments (hydrothermal vents, methane seeps). Our investigations via electron microscopy, stable isotope analysis and an enrichment experiment reveal that shrimp harbor endosymbiotic mutualistic bacteria. As intracellular mutualisms require more morphological and genetic adaptations than their extracellular counterparts, our findings shed light on the selective pressures towards endosymbiosis in extreme ecosystems. Intracellular symbiosis may serve as an innovation for maintenance of mutualistic bacteria through molt cycles in systems that are sparsely populated with low concentrations of chemosynthetic substrates.

The abbreviated larval development of Macrobrachium totonacum Mejía, Alvarez & Hartnoll, 2003 (Decapoda, Palaemonidae), reared in the laboratory

Abbreviated larval development is described and illustrated for Macrobrachium totonacum Mejia, Alvarez & Hartnoll, 2003, a recently described freshwater prawn with three larval stages. The study is based on laboratory-reared material. Females carry 18 eggs on average, with a maximum of 28. The average egg diameter is 2.1 mm. The first larval stage has sessile eyes, and all appendages are developed except the uropods; however, the chelae on pereiopods 1 and 2, and the pleopods, are non-functional. In stage 2 the eyes are articulated, and the chelae and pleopods are functional. In stage 3 the uropods are developed. The larvae are lecithotrophic in the first two stages, and start feeding in stage 3. The larval development of this species is compared with other Mexican and South American species of Macrobrachium with abbreviated development: it has the same number of stages as M. vicconi Roman, Ortega & Mejia, 2000, another Mexican species. El desarrollo larval abreviado es descrito e ilustrado para Macrobrachium totonacum Mejia, Alvarez & Hartnoll, 2003, una especie de langostino recientemente descrita con tres estados larvales. Este estudio esta basado en material obtenido en laboratorio. Las hembras llevan en promedio 18 huevos y un maximo de 28. El diametro promedio del huevo es de 2,1 mm. El primer estadio larval tiene ojos sesiles y todos los apendices estan desarrollados excepto los uropodos; sin embargo, la quela de los pereiopodos 1 y 2 y los pleopodos no son funcionales. En el estado dos, los ojos estan articulados y la quela y pleopodos son funcionales. En el estado tres los uropodos estan desarrollados. Las larvas son lecitotroficas en los primeros dos estadios e inician su alimentacion en el estado tres. El desarrollo larval de esta especie es comparada con otras especies de Macrobrachium de Mexico y Sudamerica con desarrollo abreviado, esta especie tiene el mismo numero de estados que otra especie mexicana: M. vicconi Roman, Ortega & Mejia, 2000.

EL DESARROLLO SUSTENTABLE Y LA INSTRUMENTACIÓN DEL PARADIGMA EN MÉXICO

Through this paper we aim to illustrate the latest proposals within EU legislation regarding airports, which are facing some difficulties in the EU legislative iter of approval. Airports, due to the liberalization and deregulation process, shifted from an appendix facility of air transport into a self-standing industry. The whole process was imprinted by the massive privatization and is leading now into a competitive and common market, at least in EU level. These proposals, regarding slot allocation, groundhandling and procedure for restriction of the noise related operations, are to be considered as a serious effort for a comprehensive regulation. In our view, de lege ferenda it is a welcome initiative which yet represents difficulties in reaching uniformity within Union airport market. Furthermore, it is time for the Commission to launch new package related to the State Aids in the Air Transport sector and specifically, those which deals with airports.