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Hansen (1897), dealing with only fragmentary material, erected the genus Bathygyge with B. grandis as its type-species as one of the earliest bopyrid species known from the eastern Pacific Ocean. [...]

Two abdominal molts representing a small cymothoid isopod are described from the marine late Miocene Gram Formation of southern Denmark. Abdominal molts are generally regarded as being difficult or even impossible to assign to genus of family due to overlap of morphological characters. A preliminary study supported by statistical and multivariate analysis of the genera most closely resembling the specimens reveals that although some overlap in characters do occur, the genera can to a large extent be defined by a diagnostic set of features. The Danish Miocene taxon described herein is assigned to Aega Leach, 1815 as the only known fossil of this important cosmopolitan genus.

Four species of isopod characteristic of salt marsh habitats, Tylos ponticus, Porcellio lamellatus, Halophiloscia couchii and Armadillidium album coexist in the upper reaches of the Ria Formosa lagoon salt marsh system in southern Portugal. In this locality, T. ponticus is the most abundant of the four species with mean annual densities of 2,950 [m.sup.-2] and a peak density of 10,387 [m.sup.-2] in July 1998 which is very much higher than what has previously been recorded for any isopod in any habitat. The mean annual densities for the other species were lower: P. lamellatus 36 [m.sup.-2], A. album 19 [m.sup.-2] and H. couchii 3 [m.sup.-2], indicating a less significant role in this ecosystem. Tylos ponticus and A. album started to breed on May, 24 and 12 months after release from the marsupium, respectively, where as other species start to breed in March, 12 months after their release from the marsupium. Tylos ponticus has a relative growth rate (RGR) of 0.23 between release from the marsupium and time of first breeding in July of its second year and breeds at a mature mass of 3.6 mg AFDM whereas the other three species mature after 10-12 months, have more than double this RGR but because of the shorter pre-reproductive period breed at masses of 1.8 mg AFDM for P. lamellatus, 1.0 mg AFDM for H. couchii, and 1.1 mg AFDM for A. album, respectively. The mass specific fecundity of all three of the less abundant species was higher than that of T. ponticus but the offspring of T. ponticus were ten times heavier than those of the next largest species, P. lammellatus. The difference in abundances between the species is interpreted as being due to the larger mass of the offspring of the most successful species. This larger mass confers an adaptive advantage due to larger size being associated with reduced juvenile mortality for isopods under abiotically stressful conditions., Introduction Salt marshes are highly productive but abiotically stressful habitats (Odum 1970; Kneib 1984; Chapman 1992; Vernberg 1993). The combination of desiccation risk, osmotic variability, and temperature fluctuations make it [...]