Shrimps from the genus Lysmata are known because of their wide diversity of lifestyles, mating systems, symbiotic partnerships, and conspicuous coloration. They can occur in crowds (large aggregations), in small groups, or as socially monogamous pairs. Shrimps from this genus are rare, if not unique among crustaceans, because of their unusual sexual system. To date, the sexual system of all species investigated comprises a protandric simultaneous hermaphroditism: shrimps initially mature and reproduce as males and later in life turn into functional simultaneous hermaphrodites. The evolutionary relationships of the species within the genus are unsettled. A molecular phylogeny of the group may shed light on the evolutionary origins of the peculiar sexual and social systems of these shrimps and help resolve standing taxonomic questions long overdue. Using a 647-bp alignment of the 16S rRNA mitochondrial DNA, we examined the phylogenetic relationship of 21 species of shrimps from the genus Lysmata from several biogeographical regions; the Atlantic, Pacific, and Indo-Pacific. The resulting phylogeny indicates that the genus is paraphyletic and includes the genus Exhippolysmata. The constituent species are subdivided into three well supported clades: one group exclusively composed of neotropical species; a second clade comprising the Indo-Pacific and Atlantic symbiotic fish cleaner shrimps; and a third clade including tropical and temperate species from the Atlantic and Pacific. The molecular phylogeny presented here does not support a historical contingency hypothesis, previously proposed to explain the origins of protandric simultaneous hermaphroditism within the genus. Furthermore, the present study shows that monogamous pair-living is restricted to one monophyletic group of shrimps and therefore probably evolved only once.

Crabs from the Mithrax-Mithraculus species complex are known for their diversity of lifestyles, habitats, and coloration. This group includes small, colourful, symbiotic species and much larger, reef-dwelling crabs targeted by fishermen. The evolutionary relationships between the species within this complex are not well-defined. Previous studies based upon morphological characters have proposed the separation of this complex into two genera (Mithrax and Mithraculus), but cladistic analyses based upon larval characters do not support this division. A molecular phylogeny of the group may help to resolve this longstanding taxonomic question and shed light on the ecological conditions driving the diversity of these crabs. Using a 550-bp alignment of the 16S rRNA mitochondrial DNA segment we examined the phylogenetic relationships between 8 species within the Mithrax-Mithraculus complex native to the Caribbean. The resulting phylogeny indicates that this complex is paraphyletic, as it includes the genus Microphrys. The analyses revealed a well-supported, monophyletic group containing four species of Mithraculus (M. cinctimanus, M. coryphe, M. sculptus and M. forceps) and supported one pair of sister species from the genus Mithrax (M. caribbaeus and M. spinosissimus). No complete segregation of species, according to genera, was evident, however, from tree topologies. Bayesian-factor analyses revealed strong support for the unconstrained tree instead of alternative trees in which monophyly of the two genera was forced. Thus, the present molecular phylogeny does not support the separation of the species within this complex into the genera Mithrax and Mithraculus. A review of the literature demonstrated considerable phenotypic variation within monophyletic clades in this group.

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Since 2002 two areas in southern Louisiana (Caernarvon Breton Sound estuary and Atchafalaya basin region) were studied regarding the occuiTence of the invasive and potentially harmful cyanobacterium Cylind1•ospemzopsis raciborskii. In the Caernarvon Breton Sound estuary, the species was detected for the first time in Louisiana in July 2002 in Grand Lake during monthly phytoplankton monitoring surveys. The species occulTed again in the estuary in summer and fall 2003 and 2004. Three distinct morphotypes (straight, curved, curled) were present, with the curved or curled varieties usually most abundant (> 80%). During summer 2003 the cell numbers in Grand Lal 20 X10 6 cells liter-1). In 2004 the species was a rare sight in the estuary and was not detected any more in 2005. In the Atchafalaya basin region, C. racibm•skii was frequently detected in fall 2004. The greater Lake Fausse Pointe area was especially a hot spot, with critical level abundances up to 30 X 10 6 cells liter-I. In both areas C. mciborskii occulTed only in summer and fall at elevated water temperatures (> 25-33 C). It was more frequently detected in the southern, less diversion-influenced part of the Caernarvon Breton Sound estuary, whereas it occurred more often in the northetn part of the Atchafalaya basin. The species was present in a conductivity range from !iS em-I 700 to 10,000 within the Caernarvon Breton Sound estuary. Samples containing Cylindrospennopsis generally were significantly higher in total and cyanobacterial chlorophyll compared to samples without Cyli11dmspemzopsis.