José A. Viccon-Pale

FECUNDITY AND DISTRIBUTION OF FRESHWATER PRAWNS OF THE GENUS MACROBRACHIUM IN THE HUITZILAPAN RIVER, VERACRUZ, MEXICO

[Three aspects of the reproductive biology (fecundity, size of ovigerous females, and egg size) of the freshwater prawns Macrobrachium acanthurus , M. heterochirus , and M. carcinus , in the Huitzilapan river, Veracruz, Mexico, were studied. Adults of Macrobrachium acanthurus and M. carcinus occupied the lower part of the river in the estuarine area, while reproductive M. heterochirus were distributed from 105 to 535 m altitude. Macrobrachium acanthurus exhibited significant differences in fecundity, mean size of ovigerous females, and egg size, according to the time of year. For M. heterochirus , egg size varied depending on the time of year and on their position in the river. Finally, for M. carcinus , egg size varied only depending on the time of year. Tres aspectos de la biologia reproductiva (fecundidad, talla de hembras ovigeras y tamano de huevo) de los camarones de agua dulce Macrobrachium acanthurus , M. heterochirus y M. carcinus , en el rio Huitzilapan, Veracruz, Mexico, fueron estudiados. Adultos de Macrobrachium acanthurus y M. carcinus ocuparon las partes bajas del rio en la zona estuarina, mientras que organismos reproductivos de M. heterochirus se distribuyeron de los 105 a los 535 m de altitud. Macrobrachium acanthurus exhibio diferencias significativas debidas a la epoca del ano en fecundidad, talla promedio de hembras ovigeras y tamano de huevo. Para M. heterochirus el tamano del huevo vario dependiendo de la epoca del ano y de la posicion dentro del rio. Finalmente, para M. carcinus , el tamano del huevo vario solamente debido a la epoca del ano., Three aspects of the reproductive biology (fecundity, size of ovigerous females, and egg size) of the freshwater prawns Macrobrachium acanthurus , M. heterochirus , and M. carcinus , in the Huitzilapan river, Veracruz, Mexico, were studied. Adults of Macrobrachium acanthurus and M. carcinus occupied the lower part of the river in the estuarine area, while reproductive M. heterochirus were distributed from 105 to 535 m altitude. Macrobrachium acanthurus exhibited significant differences in fecundity, mean size of ovigerous females, and egg size, according to the time of year. For M. heterochirus , egg size varied depending on the time of year and on their position in the river. Finally, for M. carcinus , egg size varied only depending on the time of year. Tres aspectos de la biologia reproductiva (fecundidad, talla de hembras ovigeras y tamano de huevo) de los camarones de agua dulce Macrobrachium acanthurus , M. heterochirus y M. carcinus , en el rio Huitzilapan, Veracruz, Mexico, fueron estudiados. Adultos de Macrobrachium acanthurus y M. carcinus ocuparon las partes bajas del rio en la zona estuarina, mientras que organismos reproductivos de M. heterochirus se distribuyeron de los 105 a los 535 m de altitud. Macrobrachium acanthurus exhibio diferencias significativas debidas a la epoca del ano en fecundidad, talla promedio de hembras ovigeras y tamano de huevo. Para M. heterochirus el tamano del huevo vario dependiendo de la epoca del ano y de la posicion dentro del rio. Finalmente, para M. carcinus , el tamano del huevo vario solamente debido a la epoca del ano.]

Synchronization by light of the circadian rhythm of motor activity in the crayfish

Abstract We have studied the pattern for resetting the circadian rhythm in the spontaneous motor activity of the crayfish. Spontaneous motor activity was recorded continously at a constant temperature and under free running conditions in complete darkness. The effect of single light pulses applied at different circadian times, on the circadian rhythm of motor activity was measured in both transient stage and steady state. The results led us to construct a phase‐transition curve and phase‐response curve which were analyzed to obtain information about the oscillators which underlie the circadian rhythm of motor activity.

About the Existence of Circadian Activity in Cave Crayfish

Evidence of a circadian clock mechanism was found in the cave crayfish Procambarus cavernicola. Analysis of motor activity recorded in this species during 12 consecutive days in either free running (constant darkness, DD or constant light, LL) or entrainment conditions (12 h of light alternated with 12 h of darkness, 12 : 12 LD) showed a well recognized circadian rhythm. In this rhythm however, the absence of synchronization by periodical external signals was notorious. The comparison between the motor circadian rhythm in cave crayfish and epigeous crayfish Procambarus clarkii (these last studied during juvenile and adult stages), evidenced strong similitude between the motor circadian rhythm of cave crayfish and juvenile epigeous crayfish.

Circadian rhythm in locomotor activity in the burrower crayfish Procambarus acanthophorus (Villalobos 1948)

Crayfish Procambarus acanthophorus is a burrower that spends long periods building deep tunnels to reach the water table during the dry season; thus, its survival entertains a close ecological relationship with the sediment. The aim of this work was to determine whether the properties of the circadian rhythm of locomotor activity could be modified by the sediment availability. Experiments were conducted in both aquaria filled with sediment or filled with water, under cycles of Bright and Dim Illumination (BI:DI, 12:12 h) or under continuous DI:DI. The rhythm of locomotor activity was entrained with the photoperiod in aquaria with sediment or water; however, statistical differences between conditions were obtained comparing the period and the level of activity under free-running. These data suggest that the substrate’s sensorial perception could be encoded as a significant ecological parameter that exerts influence in the physiological mechanisms that control the temporal order in P. acanthophorus.

Distribution and Abundance of Diacyclops Sp. (Crustacea: Copepoda) in Gabriel Cave, Oaxaca, Mexico

The distribution and abundance of the stygobiont copepod Diacyclops sp., as well as values of some environmental variables (depth of the pools, temperature, dissolved oxygen, pH, percent saturated oxygen and organic matter content) in Gabriel Cave are reported for the first time. The copepods were collected in 12 pools using traps and plankton nets with a 10 μm mesh opening. The highest abundance of Diacyclops sp. was observed in the central zone of the cave and it was related to the organic matter content. The depth of the pools ranged from 10 to 100 cm, temperature from 20.1 to 24 °C, dissolved oxygen from 0.1 to 7 ml/l, pH ranged 6.3 to 8.3 and organic matter content ranged from 0.001 to 21.3 %. Water quality as well as the amount of available food determine the distribution and abundance of this planktonic stygobiont cyclopoid in the cave.