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A taxonomic study on the Phtisicidae (Crustacea: Amphipoda) of New South Wales, Australia

abstract The present study reviews the taxonomy of the Phtisicidae (Crustacea: Amphipoda) from the coast of New South Wales, Australia. The following seven species are described; Dodecas decacentrum Stebbing, 1910b, Dodecas hexacentrum Mayer, 1903, Hircella cornigera (Haswell, 1879b), Metaproto novaehollandiae (Haswell, 1879a), Notoprotomima smithi gen. nov., sp. nov., Paraproto sp. and Perotripus sp. Generic diagnoses of Notoprotomima gen. nov., Dodecas, Hircella and Metaproto are provided based on the present materials. Notoprotomima smithi is fully described as a new species of the new genus. Dodecas decacentrum differs from Dodecas hexacentrum by the presence of paired dorsodistal projections on pereonite 2, paired mid-dorsal projections on pereonites 3 and 4 and shorter gill length on pereonites 2 and 3. Hircella cornigera and Metaproto novaehollandiae are described in detail. The larger mature males of M. novaehollandiae possess the unusual massive type of the propodus of gnathopod 2. The extended distribution of Perotripus to the New South Wales coast is noted. A key for these phtisicid amphipods from New South Wales, Australia is provided.


Introduction
The Phtisicidae (Crustacea: Amphipoda) are one of the dominant groups of caprellid amphipods called "skeleton shrimps" inhabiting mainly shallow water ecosystems, especially in the tropical to temperate regions of the northern hemisphere and all over the southern hemisphere including Antarctica (see McCain and Steinberg 1970;Takeuchi 1993;De Broyer et al. 2004). The Phtisicidae of New South Wales, Australia were first recorded in two papers published by Haswell (1879aHaswell ( , 1879b. He reported Hircella cornigera (Haswell, 1879b) and Metaproto novaehollandiae (Haswell, 1879a) from Port Jackson, an inner bay situated in the Greater Sydney area. Mayer (1903) reported Dodecas hexacentrum Mayer, 1903 from off Watsons Bay, Port Jackson in his monographic work that covered the Caprellidae of the world. Stebbing (1910b) reported Dodecas decacentrum Stebbing, 1910b from Botany Bay and off Wattamolla. Hence, four species have been recorded from New South Wales from the late nineteenth century to the beginning of the twentieth century. The type specimens of the Phtisicidae species deposited in the Australian Museum were listed by Springthorpe and Lowry (1994). However, modern taxonomic descriptions have not been published on the Phtisicidae of this area for nearly a century, leading to the unclear status of each species of the Phtisicidae. In the present study, we report the results of our taxonomic study on representatives of the family Phtisicidae in New South Wales, Australia including detailed descriptions of seven species: Dodecas decacentrum Stebbing, 1910b;Dodecas hexacentrum Mayer, 1903; Hircella cornigera (Haswell, 1879b); Metaproto novaehollandiae (Haswell, 1879a); Notoprotomima smithi gen. nov., sp. nov.; Paraproto sp. and Perotripus sp. A key for these species of the Phtisicidae is provided.

Material and methods
The materials used in the present study, are based mainly on two sources. One is the type and additional specimens of the Phtisicidae which have been accumulated by the Australian Museum and by Dr S.D.S. Smith's laboratory, then of the University of New England, through various taxonomic, ecological and environmental surveys. The other specimens were obtained from field surveys during the 1995/96 austral summer along the coasts of New South Wales, from Jervis Bay and adjacent areas to the Solitary Islands. Mouthparts, gnathopod 1 and pereopods 5 to 7 of described individuals were dissected and mounted on slides in polyvinyl-lactophenol. The lateral body view of somites, antennae, respective appendages and mouthparts were drawn under a microscope equipped with a camera lucida. All descriptive text was generated from a DELTA database (Dallwitz 2005) to the world genera and Australian species of caprellid and phtisicid amphipods. The setal formulae (1-x-y-1 or 1-x-1) for the setae on mandibular palp article 3 are used for descriptions, as described by McCain (1968). All material is lodged in the Australian Museum, Sydney (AM). Standard abbreviations on the plates are: A, antenna; ABD, abdomen; F, female; G, gnathopod; LL, lower lip; M, male; MD, mandible; MX, maxilla; MXP, maxilliped; P, pereopod; UL, upper lip; LT, lateral; V, ventral; L, left; R, right. Takeuchi (1993) showed 12 coded generic diagnostic characters based on a literature survey of the Phtisicidae, Caprellidae, Paracercopidae and Caprogammaridae. These characters were expanded to include several new characters, especially features of the head with pereonite 1, features of the mandible, features of the maxillipedal palp including the size of the inner plate (basal endite) to the outer plate (ischial endite) and a feature of pereonite 4. The fundamentally same generic diagnosis was also used for the genera of the Caprellidae in Takeuchi and Lowry (2007),  and Takeuchi et al. (2014) and that for Phtisicidae in . The familial classification of the present study follows Takeuchi (1993Takeuchi ( , 1999, Guerra-García and Takeuchi (2003,  and Takeuchi (forthcoming 2015).

Type locality
Botany Bay and off Wattamolla, New South Wales, Australia, 69-108 m depth.
Upper lip notched, forming rounded quadrilateral projections. Mandible right side incisor with six teeth; lacinia mobilis a reverse trapezoid plate followed by one smaller plate; accessory setal row with 10 setae; palp article 2 with one lateral seta; palp article 3 setal formula 1-16-1; left side incisor with five teeth; left side lacinia mobilis with five teeth, followed by one trapezoid plate; left side accessory setal row with one bundled seta and 10 setae; palp article 2 with five lateral setae; palp article 3 setal formula 1-17-1. Lower lip finely setose on inner and outer lobes. Maxilla 1 outer plate with six stout apical setal-teeth; palp distal margin with six triangular projections, each with one slender or robust seta, with a row of slender setae. Maxilla 2 inner plate triangular with nine apical robust setae; outer plate elongate with 12 apical setae. Maxilliped inner plate (basal endite) oval, with three stout serriform setae on expanded inner half of distal margin, with one or two setae on outer half; outer plate (ischial endite) oval, 0.5 × length of inner plate (basal endite), inner margin smooth, with four setae on inner margin; palp article 2 setose on inner margin; palp article 3 with moderately dense distal setae; palp article 4 weakly falcate.

Remarks
Of the seven species of Dodecas, two species, D. decacentrum Stebbing, 1910b andD. hexacentrum Mayer, 1903, have been reported along the coasts of New South Wales and redescribed in the present study. Guiler (1954) synonymized D. decacentrum with D. hexacentrum based on the Tasmanian specimens.
Dodecas decacentrum is, however, easily distinguished from D. hexacentrum, which coexists along the New South Wales coasts by the following diagnosis: (1) in D. decacentrum pereonite 2 possesses a pair of dorsodistal projections in addition to mid-dorsal projections on pereonite 2, while in D. hexacentrum the pereonite 2 lacks the dorsodistal ones; (2) in D. decacentrum pereonites 3-4 possess a pair of mid-dorsal projections, while in D. hexacentrum pereonites 3-4 lack these projections; (3) gills on pereonites 2 and 3 of male D. decacentrum are half the length of the corresponding pereonites, whereas those of male D. hexacentrum are longer than the corresponding pereonites; (4) in D. decacentrum the carpus of pereopods 6 and 7 are elongated with four or five spines along the anterior margin, while in D. hexacentrum the carpus of pereopods 6 and 7 lacks anterior spines.
The other five species have been reported so far from Tasmania and sub-Antarctic and Antarctic regions. Especially, D. grandimanus Guiler, 1954 andD. tasmaniensis Guiler, 1954 were established based on specimens which were collected from off Mountain Creek, Tasmania by Guiler (1954). Guerra-García and  showed the lateral view of a male and a mature female of D. tasmaniensis Guiler, 1954 from Tasmania. The male, 9.41 mm in body length, is a little smaller than a mature female, 9.47 mm in body length, in both Guerra-García and . The figure of the male indicates the presence of paired posterodorsal projections on pereonite 1, midlateral projection, paired anteriorly curved mid-dorsal projections, and anteriorly curved dorsodistal projection on pereonite 2 and paired mid-dorsal projections on pereonite 3 (see Guerra-García and Takeuchi 2004, fig. 3A). These characteristics show the close relationship of D. tasmaniensis to D. decacentrum (Guerra-García and . However, the male specimen of D. tasmaniensis might not be a fully grown male, which fits precisely the species diagnosis of the present study, since in D. decacentrum and D. hexacentrum males grow larger than females (see Figures 1 and 4) similar to Caprella (see Takeuchi and Hirano 1991;Nakajima and Takeuchi 2008). Moreover, the lateral figure of a mature female of D. tasmaniensis lacks the posterodorsal projections on pereonite 1 and paired anteriorly curved mid-dorsal projections on pereonite 2 (see Guerra-García and Takeuchi 2004, fig. 3B), while an immature female, 5.22 mm in body length, collected from King George Sound, Western Australia possessed paired anteriorly curved middorsal projections and anteriorly curved dorsodistal projection on pereonite 2, paired mid-dorsal projections and shallow dorsodistal projection on pereonite 3, a middorsal projection on pereonite 4 and a shallow mid-dorsal projection on pereonite 5 (see Guerra-García 2004a, fig. 7). These differences indicate that it is necessary to find fully adult males to clarify the species diagnosis of "D. tasmaniensis" collected from off Mountain Creek, Tasmania. Mayer, 1903 (Figures 4-6) Dodecas hexacentrum Mayer, 1903: 29-30, pl. 1, figs 14-15, pl. 6 figs 33-34. -Stebbing, 1910b: 652. -K.H. Barnard, 1932: 306, fig. 169a. -Guiler, 1954: 539-542, figs 8-9. -McCain and Steinberg, 1970: 49. -Lowry and Stoddart, 2003.

Type locality
Off Watsons Bay, Port Jackson, New South Wales.

Other records
New South Wales: East of North Head and east of South Head, Port Jackson, east of Long Reef. Victoria: Griffiths Point.
Upper lip notched, forming shallow quadrilateral projections. Mandible right side incisor with five teeth; lacinia mobilis a reverse trapezoid plate followed by a smaller plate; palp article 2 with eight lateral setae; palp article 3 setal formula 1-9-1; left side incisor with five teeth; lacinia mobilis with five teeth, followed by a trapezoid plate; palp article 2 with six lateral setae; palp article 3 setal formula 1-10-1. Lower lip finely setose on inner and outer lobes. Maxilla 1 outer plate with six stout apical setal-teeth; palp distal margin with five triangular projections, each with one robust seta, with a row of slender setae. Maxilla 2 inner plate triangular with one apical robust and eight slender setae; outer plate elongate with eight apical setae. Maxilliped inner plate (basal endite) quadrilateral, with three stout serriform setae on expanded inner half of distal margin, with one seta on outer half; outer plate (ischial endite) oval, 0.25 × length of inner plate (basal endite), inner margin smooth, with three or four setae on inner margin; palp article 2 setose on inner margin; palp article 3 not expanded, with six lateral to distal setae; palp article 4 weakly falcate.

Remarks
See remarks of Dodecas decacentrum.

Remarks
The genus Hircella was established specifically for H. cornigera (Haswell, 1879b) by Mayer (1903). Recently, Guerra-García and  described the second species of Hircella, H. inermis Guerra-García and Takeuchi, 2004 from the Tasmanian coast. Mayer (1903) mentioned that pereopod 5 of Hircella was completely degenerate, and the diagnosis of Takeuchi (1993) followed his conclusion. Since the type specimen deposited in the Australian Museum is lost (Springthorpe and Lowry 1994), this new diagnosis is based on recently collected specimens from the Solitary Islands, New South Wales. Observation revealed that pereopod 5 is composed of one tiny article and the number of articles in the flagellum of antenna 2 increases from two to three during growth (see Figure 10). Hence, the generic diagnosis of the present genus is revised as above.

Remarks
Mayer (1882) established the genus Hircella based on the single species, Caprella cornigera Haswell, 1879b, which was collected from Clark Island, situated in the middle of Port Jackson. The type specimens are lost (Springthorpe and Lowry 1994). The field survey during 1995/96 as well as the survey of the deposited specimens at the Australian Museum failed to find H. cornigera from Port Jackson. However, H. cornigera was found from Spilit Solitary Island, Korffs Islet, and North Solitary Island, the Solitary Islands, Corambirra Point, Coffs Harbour, and south of Governor Head, out of Jervis Bay, New South Wales. In addition to the coast of New South Wales, H. cornigera was recorded from North Stradbroke Island, which is situated near the southern border of Queensland (Guerra-García 2006). These indicate that H. cornigera is still distributed widely along the east coast from Jervis Bay, the New South Wales to North Stradbroke Island, Queensland facing the Pacific Ocean, while the species seems to have disappeared from Port Jackson and the inner parts of Jervis Bay. Hence, in the present study, a mature male and a mature female collected from the Solitary Islands have been described in detail.
Close observation of the present specimens shows that article numbers in the flagellum of antenna 2 increase from two to three during growth ( Figure 10). Of the 11 males measured, all males larger than 7.4 mm in body length posses a 3-articulate flagellum. Of females, most have two articles in the flagellum, but the third largest mature female has three articles in the flagellum.
In addition to H. cornigera, two additional species of Hircella have been recorded recently; H. inermis Guerra-García and Takeuchi

Remarks
The genus Metaproto was established specifically for M. novaehollandiae (Haswell, 1879a) by Mayer (1903). The generic diagnosis of the present genus is provided based on the present description of M. novaehollandiae (Haswell, 1879a).        Upper lip notched, forming shallow quadrilateral projections. Mandible right side incisor with five teeth; lacinia mobilis with four large teeth; accessory setal row with seven setae; palp article 2 with three setae; palp article 3 setal formula 1-7-1-0; left side incisor with six teeth; lacinia mobilis with two reverse-trapezoid plates; accessory setal row with one bundled seta and seven setae; palp article 2 with six lateral setae; palp article 3 setal formula 1-5-1-1. Lower lip finely setose on inner and outer lobes. Maxilla 1 outer plate with six stout apical setal-teeth; palp distal margin with four triangular projections, each with one slender seta. Maxilla 2 inner plate triangular with seven apical robust setae; outer plate elongate with five apical setae. Maxilliped inner plate (basal endite) round, with one large and two small nodular setae; outer plate (ischial endite) oval, subequal to inner plate (basal endite), with seven setae on inner margin; palp article 2 scarcely setose on inner margin; palp article 3 not expanded, four distal setae; palp article 4 falcate.

Remarks
The syntypes of the present species deposited in the Australian Museum consisted of three samples, registered as P3387, P3388 and G2556. Although the sample registered as P3388 contains about 20 specimens, all specimens except for two dissected ones, were once dried up. A male and a mature female from the sample registered as P3387 were redescribed and illustrated for the present study under the new register numbers of AM P46915 and AM P87331.
The morphology of gnathopod 2 of larger males is unique within the Phtisicidae. The macrobenthic infaunal survey of Botany Bay by NSWSPCC during 1976 to 1977 contained about 200 individuals of M. novaehollandiae which were originally identified as "Metaproto haswelliana" in the catalogue of the Australian Museum and this named species was listed in the project studying effects of dredging on the macrobenthic infauna of Botany Bay (Jones and Candy 1981). Close examination of these individuals from Botany Bay shows the morphological development of gnathopod 2 during growth (Figures 15 and 16). In males smaller than 9.0 mm in body length and in the females of all stages, the characteristics of the propodus are typical of the family. In smaller males, the palm between the grasping robust setae followed by two smaller subgrasping robust setae and the distal end is slightly convex with no crumpled parts near the palm (Figure 16). The features of the propodus in females are similar to those of smaller males, but in mature males larger than around 8.0 mm body length, the propodus of the gnathopod 2 becomes massive. The widest part of the palm is about 2/3 the length of the palm; the lateral part of the propodus is extended into a curving edge covering about 2/3 of the lateral side of the palm and the lateral part between the curving edge and the palm forms several crumpled lines (Figure 16). The morphology of the propodus of gnathopod 2 is likely to change largely in just one moult.
In addition to this unique sexual dimorphism in gnathopod 2, in males, the propodus of pereopods 3 and 4 carries three to four robust setae on the middle of the shallow convex palm, while females have a straight palmar face on the propodus of the pereopods.
As in Hircella cornigera (Haswell, 1879b), article numbers in the flagellum of antenna 2 increase from two to three during growth (Figure 15). In males collected from Botany Bay by NSWSPCC, all males larger than 4.0 mm in body length possess a 3-articulate flagellum, while in females article numbers increase from two to three at around 4-6 mm in body length.
In addition to New South Wales, Australia, Metaproto novaehollandiae has been reported from tropical areas of the Indo-Pacific: Banda Sea (Mayer 1903 Close observation of NSWSPCC specimens shows that the numbers of articles in the flagellum of antenna 2 are restricted to two to three even in the larger mature males having the massive type propodus of gnathopod 2 ( Figure 15). Mayer (1903) reported five articles in the flagellum on the male from Banda Sea. The lateral view of M. novaehollandiae from the tropical Indo-Pacific area in Guerra-García (2002, 2003, 2004a, 2004b, 2006, García and Lowry 2009 shows article numbers ranging from 2 to 4 (or 5).
The propodus of gnathopod 2 figured in Laubitz (1991) and Guerra-García (2002, 2003, 2004a, 2004b, 2006 is rather elongated as in typical species of Phtisicidae. However, as far as we know, there are no taxonomic descriptions on M. novaehollandiae from tropical areas of Indo-Pacific referring to the massive propodus of gnathopod 2. The morphological diversity in antenna 2 and in the propodus of gnathopod 2 of M. novaehollandiae from tropical areas of the Indo-Pacific indicates the presence of multiple species differing from the M. novaehollandiae of New South Wales. In our opinion M. novaehollandiae reported from areas outside New South Wales, especially tropical waters, needs to be reanalysed. Hence, we do not include the records of M. novaehollandiae in the tropical region of the Indo-Pacific ( (Mayer 1903;Laubitz 1991, Guerra-García 2002, 2003, 2004a, 2004b, 2006Guerra-García and Lowry 2009) in the synomym list. Recently, Takeuchi and Oyamada (2013) studied in detail Caprella californica Stimpson, 1857 [sensu lato] which is widely distributed on both sides of the North Pacific as a common species, and reported that the differences of Japanese C. californica [sensu lato] from California ones are at species level. In their opinion the Japanese species identified as C. californica [sensu lato] is actually Caprella scauroides Mayer, 1903. Genus Notoprotomima gen. nov.

Remarks
This new genus, Notoprotomima, is most closely related to Pseudoprotomima McCain, 1969 andSymmetrella Laubitz, 1995. Three The present new genus, Notoprotomima, differs from Pseudoprotomima (see McCain and Gray 1971;Takeuchi 1993) in the following generic characters: (1) the flagellum of antenna 2 in Notoprotomima is restricted to two articles even in mature males, while that in Pseudoprotomima varies from two to four articles; and (2) in Notoprotomima the third article of the mandibular palp has two to three large distal setae, while in Pseudoprotomima the setal formula is 1-x-1.
The genus Symmetrella was established for Symmetrella arnaudi Laubitz, 1995 collected from bathyal depths, 2200 m, from the southern Indian Ocean (Laubitz 1995). The present new genus, Notoprotomima, differs from Symmetrella (see Laubitz 1995) in the following generic characters: (1) in Notoprotomima the third article of mandibular palp has two to three large distal setae, while in Symmetrella the setal formula is 1-x-1; (2) in Notoprotomima pereopod 4 is composed of seven articles, while Symmetrella lacks pereopod 4; and (3) in Notoprotomima the abdomen lacks pleopods, while in Symmetrella the abdomen possesses a pair of tiny pleopods.
Hence, we establish the new genus, Notoprotomima, based on the present species. The description and figures for P. grandimana Guerra-García, 2004a(Guerra-García 2004a agree well with the present species in the above generic diagnosis of Notoprotomima and P. grandimana is here moved to Notoprotomima.
Upper lip notched, forming shallow quadrilateral projections. Mandible right incisor with six teeth, lacinia mobilis with two teeth, with two trapezoid plates decreasing in size, accessory setal row with seven setae; palp article 3 with two long apical setae and distal marginal fringing setae; left incisor with five teeth, lacinia mobilis with two teeth, with three trapezoid plates decreasing in size, accessory setal row with three setae; palp article 3 with two long apical setae and distal marginal fringing setae. Lower lip finely setose on inner and outer lobes. Maxilla 1 outer plate with five stout apical setal-teeth; palp distal margin with two triangular projections and four robust seta. Maxilla 2 inner plate triangular with three apical robust setae; outer plate elongate with five apical setae. Maxilliped inner plate (basal endite) round, with two stout serriform setae on inner half of distal margin, with two setae on outer end; outer plate (ischial endite) oval, 0.8 × length of inner plate (basal endite), inner margin smooth, with three or four setae on inner margin; palp article 2 setose on inner margin; palp article 3 with five distal setae; palp article 4 weakly falcate.
Pereopod 3 very slender; gill similar to gill 2; basis to carpus cylindrical; basis longer than other pereopod articles, 2/5 × pereopod length; propodus with distal palm, delimited by two robust setae. Pereopod 4 very slender; shorter than pereopod 3; gill similar to gill 2; propodus with distal palm, delimited by two robust setae. Pereopod 5 slender; dactylus short, straight, with one seta in the middle. Pereopod 6 basis longest followed by merus; carpus with two setae on posterior margin; propodus with two pairs of robust setae on posterior margin, with two robust setae along palm, with trapezoid comb on distal part of palm; dactylus falcate. Pereopod 7 similar to pereopod 6; merus longer than basis.

Etymology
This species is named in honour of Dr S.D.A. Smith, who first found the present species and enthusiastically supported the present study.

Remarks
The present species, N. smithi sp. nov., differs from N. grandimana (Guerra-García, 2004a), which was recorded from shallow waters of Western Australia, in the following ways: (1) in N. smithi, antenna 1 is shorter than the body length, while in N. grandimana, antenna 1 is about half of the body length; (2) in N. smithi, gills are about half of the corresponding pereonite length, while in N. grandimana, gills are 1/3 to 1/2 of the body length; (3) in N. smithi, there are two triangular projections situated near distal end of palm of gnathopod 2, while in N. grandimana, the middle projection on the palm is rectangular (based on Guerra-García 2004a: 19, Figure 16); (4) in pereopods 6 and 7 of N. smithi, the trapezoid comb is present on the distal part of the palm of the propodus, while in N. grandimana, the propodus of pereopods 6 and 7 lack the comb; (5) in N. smithi, the third article of the mandibular palp has two large setae, while in N. grandimana the third article has three large setae.

Remarks
Four species of Paraproto have been recorded from the Australian coasts before the present study: P. condylata (Haswell, 1885a) from Australia, P. gabrieli Stebbing, 1914 from Victoria, P. spinosa (Haswell, 1885a) from Victoria and P. tasmaniensis Guerra-García and  Of the four species of Paraproto, P. condylata and P. tasmaniensis have the body smooth, as in the present species. However, because of the lack of a modern description of P. condylata from Australia we hesitate to identify this small individual.
Paraproto condylata was first reported by Haswell (1885a) as Proto condylata Haswell, 1885a. He never noted the specific locality for this species in Australia unlike the record for P. spinosa (Haswell, 1885a) that was recorded as "only in one locality-Port Western, Victoria." Dr William A. Haswell served the University of Sydney around that period (Morison 1983). If P. condylata was collected from Victoria or other states, there is a high possibility that he would have recorded the locality as for P. spinosa (Haswell, 1885a). Hence, P. condylata might have been collected from Sydney or adjacent areas along the coasts of New South Wales, Australia. Mayer (1903) also noted "Paraproto condylata ?" in the species list of "Sydney (Port Jackson and Broken Bay)". The type material of P. condylata described by Haswell (1885a) is missing (Springthorpe and Lowry 1994). McCain and Gray (1971) reported the occurrence of "P. condylata" from South Shetland Islands, Antarctica with several illustrations. Guerra-Garcia and Coleman (2001) redescribed and figured "P. condylata" based on the specimens collected by the Polarstern cruise ANT XIV/2 from South Shetland Islands. Their description and figures in general agree with the description by McCain and Gray (1971). De Broyer et al. (2004) identified Antarctic "P. condylata" as Paraproto sp. due to several morphological differences between the Australian and Antarctic specimens. Based on Antarctic "P. condylata" a new species is proposed (Takeuchi, forthcoming 2015).

Locality
New South Wales: Long Reef (this study).

Remarks
The genus Perotripus was established based on the single species, P. brevis (La Follette, 1915), which is distributed along the Californian to Alaskan coasts of the northeastern Pacific (Dougherty and Steinberg 1953;Laubitz 1970). Two additional species, P. keablei Of them, the present species, Perotripus sp., differs from P. brevis in the following distinctive characters: pereonite 2 is longer than pereonite 3 in Perotripus sp. from New South Wales, while pereonite 3 is longer than pereonite 2 in P. brevis. However, we have not described the present specimens as a new species because the specimens collected from New South Wales are only two small individuals. This indicates the possibility that these are juveniles, which have not developed specific diagnostic characters.
Perotripus keablei was recorded from Lizard Island, on the northern part of the Great Barrier Reef, Queensland. Unlike P. brevis, P. koreanus and Perotripus sp. in the present study, pereopod 3 of P. keablei has one tiny article with two apical setae, which is very similar to that of pereopod 4. Recently,  established the genus Microtripus which differs from Perotripus by 3-articulate flagellum of antenna 1 with three articles and pereopod 3 with one article. While P. brevis and P. koreanus have preopod 3 with three articles, corresponding pereopod of P. keablei with one article. Hence, this indicates that P. keablei possibly belongs to a different new genus from Perotripus.
In addition to these three species of Perotripus and Perotripus sp. reported in the current study, an undescribed species of Perotripus was recorded in the ecological and phylogenic studies and checklist from the Pacific coasts of central Japan (Takeuchi et al. 1987;Takeuchi and Hirano 1995;Takeuchi 1999;Aoki and Takeda 2006).