Tentative species-level determinations were made herein. However, despite the Hawaiian marine amphipod fauna being well described and the sample location being well studied, it is possible that one or both are undescribed species. For instance, Perioculodes aequimanus tentatively reported from Australia (Barnard 1931; Lowry and Stoddart 2003) was subsequently described as a new species, P. talboti (Hughes and Lowry 2009). Final determination of the Hawaiian specimens will require further analyses (e.g., comparison with type specimens from the type locality, molecular characterization).
Because they exhibit six of the 10 predicted attributes of introduced peracarid species (Chapman and Carlton 1991), both genera are likely to be recent introductions to Hawai‘i. Each attribute is discussed below.
Both genera were previously unknown in the local region. Neither genus was detected in 1997 or 2008 surveys designed to detect nonindigenous marine species introductions in Honolulu Harbor (Coles et al. 2009; Coles et al. 1999).
There is a likely human mechanism of introduction. For centuries, ship fouling has been the primary human mechanism of dispersing marine organisms (Chapman and Carlton 1991); Honolulu Harbor is the Hawai‘i’s principal seaport.
Both genera were collected with known introductions. Also collected by the ARMS unit were the cryptogenic tanaid Chondrochelia dubia (Krøyer 1842) and unidentified cumaceans. The latter were unknown in Hawai‘i prior to 1996, suggesting that all cumaceans are introduced (Carlton and Eldredge 2009).
Both genera are associated with new or artificial environments. Dredge and fill activities have resulted in extensive modifications to and very little natural substrate remaining in Honolulu Harbor (Coles et al. 2009). Additionally, the ARMS unit from which the genera were collected are anthropogenic structures.
Assuming the species determinations herein are correct, both species have a disjunct global distribution. Autonoe seurati was described from the Pacific Ocean at French Polynesia (Chevreux 1907b). It was subsequently reported from Fiji (Schellenberg 1938) and New Caledonia (Ledoyer 1984). It was tentatively identified (Moore 1988), and later confirmed (Myers 2009) from Australia. Perioculodes aequimanus was described from the Red Sea (Kossmann 1880). It was later reported from the Suez Canal (Schellenberg 1928), then from the Mediterranean coast of France (Ledoyer 1972). It was subsequently reported throughout Mediterranean waters (Esquete et al. 2010). It was tentatively identified from Brazil (Serejo 1998), and confirmed to occur in Atlantic waters when reported from Spain (Esquete et al. 2010). Perioculodes aequimanus was first reported from the Pacific when found in the Cook Islands (Myers 1990).
Neither genus has a sufficient life history adaptation for global dispersal. It is well known that all peracarid crustaceans brood their young to a juvenile stage (Strathmann and Strathmann 1982). Thus, neither genus has the ability to undergo long-range larval dispersal.
Two additional attributes, post-introduction range expansion and discontinuous regional distribution, could not be assessed by the identification of amphipods collected from a single ARMS unit. Monitoring Hawai‘i’s other harbors, as well as non-harbor habitats, would allow the evaluation of those attributes.