Biology and systematics of western Atlantic peppermint shrimp, Lysmata spp. (Decapoda: Caridea: Hippolytidae).

摘要

In recent years, considerable efforts have been focused on the minimization of negative impacts caused by the harvest of marine ornamental species from the wild. Nevertheless, the marine segment of the aquarium trade industry still predominantly relies on wild collected specimens, with over 90% of the traded species being taken from coral reefs.;The western Atlantic peppermint shrimps, mostly traded as "Lysmata wurdemanni," have been used for many years to control pest anemones (Aiptasia spp.), Concerns due to potential over-harvesting and increased market demand of decapods and other marine ornamental species have induced extensive research in developing aquaculture protocols for the most demanded species. However, unexplained differences in length of larval period between research groups prompted questions about the true identity of L. wurdemanni. As laboratory-rearing work progressed, I began to doubt these identifications.;The present study investigates the various aspects of biology and systematics of the western Atlantic peppermint shrimp complex Lysmata wurdemanni (Gibbes) and L. rathbunae. Lysmata wurdemanni , originally described from Florida and South Carolina, is redescribed. Gibbes' types of L. wurdemanni are considered as lost, therefore, a neotype is selected from specimens collected near Key West, Florida. Lysmata rathbunae Chace is rediagnosed; the locality of this species is restricted to Florida and Yucatan; Chace's sponge dwelling "variety" of L. rathbunae is separated from L. rathbunae and assigned to a new species. In addition a second "variety" of L. rathbunae was identified as a new species. In total, five new species are recognized. Each species may be most easily recognized by the unique color pattern. Lysmata pederseni, n. sp. also differs ecologically in being associated with tube sponges. Lysmata rathbunae appears to be a deep-water species, while the other five species are found mostly in shallow waters.;The phototactic response of the larvae of two sympatric species of caridean shrimp (Lysmata wurdemanni and L. boggessi) to a range of light spectra and intensities were examined. The larvae were less sensitive to light than some other decapod crustaceans. Both species displayed similar spectral preference shifting from 480 to 520 nm as they developed from early to late zoeal stages. Spectral preference shifts during ontogeny are previously unknown in crustaceans or, to our knowledge, other taxa. The phototaxis of these larvae is interesting in light of our recent reevaluation of the taxonomic status of western Atlantic Lysmata.;The population structure and interbreeding ability of Lysmata wurdemanni across its range was examined to determine if the "species" is genetically homogeneous or consisted of isolated, distinct populations. Four populations were sampled, North Carolina (NC), Florida east coast (FLE), Florida Keys (FLK), and Texas (TX). Of the three populations tested for interpopulation breeding (FLE, FLK, TX), only two crosses failed to successfully hybridize: TX female failed to cross with males of either FLK or FLE shrimp; furthermore, hybridization was limited in TX male and Florida female crosses. A 615 by portion of the mitochondrial cytochrome c oxidase I gene (COI) was amplified using PCR, sequenced for analysis after editing the DNA traces. Sequence data from the COI region was obtained from 35 L. wurdemanni specimens collected from four localities. From these populations a total of 16 unique haplotypes were identified. AMOVA results underline the distinct nature of the L. wurdemanni populations, revealing that 95.73% of the variance is distributed among the four populations. Neighbor joining and maximum parsimony tree analysis based on COI data support a strong divergence between all populations except NC and FLE, in which NC haplotypes were nested inside a clade from FLE. These analyses demonstrated a lack of gene flow and strong isolation between the populations on the east coast of the United States (NC and FLE) and those on the Gulf coasts (FLK and TX).;The presented research highlights the need for extensive review of other species of Lysmata that has a wide geographic range coupled with noticeable variations. Taxonomic reexaminations must take into account the living color pattern of the species. Lysmata shrimp provide an interesting model for contrasting different modes of development, duration in the plankton, population structure and habitat use. Caution should be used when assessing species as complexes unless biological breeding data is provided as proof of divergence. The reclassification of the Western Atlantic peppermint shrimp makes it possible to examine the evolution of the "unique" reproductive system, protandric simultaneous hermaphroditism (PSH) within genus Lysmata and related taxa.