The caprellidean Amphipoda from the subantarctic islands of New Zealand and Australia with the description of a new genus and two new species *

Recently, there has been a general effort to contribute to the knowledge of Antarctic and Subantarctic fauna. For example, the “Polarstern” surveys, carried out within the framework of the international EASIZ (Ecology of the Antarctic Shelf Ice Zone) Programme, are helping to improve our understanding of the Southern Ocean fauna, including caprellids (Guerra-García, 2001; Guerra-García and Coleman, 2001). From 1963 to 1992 the Smithsonian Oceanographic Sorting Center (SOSC) received and sorted more than 20,000 samples of benthic invertebrates, plankton, algae and fish collected by researchers associated with the United States Antarctic Program (USAP). The project “Synopses of the Antarctic Amphipods”, devoted to amphipod crustaceans, is another example of improving the knowledge of Antarctic marine invertebrates through the Antarctic Amphipodologists Network, which is assisted by the Royal Belgian Institute of Natural Sciences, Brussels. SCI. MAR., 67 (2): 177-194 SCIENTIA MARINA 2003


INTRODUCTION
Recently, there has been a general effort to contribute to the knowledge of Antarctic and Subantarctic fauna.For example, the "Polarstern" surveys, carried out within the framework of the international EASIZ (Ecology of the Antarctic Shelf Ice Zone) Programme, are helping to improve our understanding of the Southern Ocean fauna, including caprellids (Guerra-García, 2001;Guerra-García and Cole-man, 2001).From 1963 to 1992 the Smithsonian Oceanographic Sorting Center (SOSC) received and sorted more than 20,000 samples of benthic invertebrates, plankton, algae and fish collected by researchers associated with the United States Antarctic Program (USAP).The project "Synopses of the Antarctic Amphipods", devoted to amphipod crustaceans, is another example of improving the knowledge of Antarctic marine invertebrates through the Antarctic Amphipodologists Network, which is assisted by the Royal Belgian Institute of Natural Sciences, Brussels.The majority of the above projects and sampling programmes focus on Antarctic fauna, and few studies have been carried out along Subantarctic areas, which are very important as transitional zones between temperate and Antarctic waters.However, we can point out the important scientific effort undertaken by the "Joint Magellan" Expedition (Chilean-German-Italian) in 1994 on board the Victor Hensen in the Magellanic region; the collection of the Amphipoda from the "Joint Magellan" expedition were investigated by De Broyer and Rauschert (1999).
The Australian Museum, as a part of a general shallow-water amphipods collection, carried out several sampling programmes along the Subantarctic Islands of New Zealand and Australia (Aucklands Islands, The Snares and Campbell Island).Additionally, caprellids were collected by the USAP Program (National Museum of Natural History, Smithsonian Institution) from the Antipodes Islands, Campbell Island and Macquarie Island.The collections of the Australian Museum focused on shallow water amphipods, while the Smithsonian Collections focused on deeper waters (around 100 m).The caprellids from both collections are studied in the present paper.
The gammaridean collections of the Australian Museum around these Subantarctic Islands have recently been studied (families Melitidae and Hadziidae by Lowry and Fenwick (1983), family Lysianassoidea by Lowry and Stoddart (1983)) but the caprellidean collections were still awaiting identification.Before these extensive works of Lowry and Fenwick (1983) and Lowry and Stoddart (1983), only a few studies had been carried out along the islands south of New Zealand and Australia.Lowry and Fenwick (1983) gave a general account of previous amphipod studies from this area, plus a description and maps of the sampling areas where the Australian Museum staff collected the material, an account of collecting methods, and a detailed station list.
Only four caprellid species had been reported from the area before this study: Caprella equilibra Say, 1818, a cosmopolitan species reported from the Auckland Islands (McCain, 1969) and the Antipodes Islands (McCain, 1979), Caprella manneringi McCain, 1979 associated with a starfish from Antipodes Island (McCain, 1979), Caprellina longicollis (Nicolet, 1849) found at the Antipodes and Auckland Islands (McCain, 1969(McCain, , 1979) ) and Caprellinoides mayeri (Pfeffer, 1888), an Antarctic species which has been recorded from Macquarie Island (McCain and Gray, 1971).The present collection studied in this paper contained these four species that had already been recorded in the area, plus one new genus, Caprellaporema, and two new species, Caprellaporema subantarctica sp.nov.and Pseudaeginella campbellensis sp.nov., which are described as new for science in the present paper.Together with the complete descriptions of the new taxa, a full redescription of C. manneringi and lateral views of the remaining species are given.A key to the six species reported so far in the study area is also provided.

STUDY AREA
The Subantarctic Region, extending between the Antarctic convergence and the loosely defined Subtropical Convergence or Front, entirely under the West Wind Drift influence, can be divided into two sub-regions or provinces (De Broyer and Jazdzewski, 1993): the Magellanic sub-region which embraces the seas around the southern tip of South America, and the Subantarctic Islands sub-region which comprises several groups of islands.The Antipodes Islands, Auckland Islands, Campbell Islands, Macquarie Island and The Snares belong to these groups of islands in the Subantarctic Region (Fig. 1).A detailed geological and biological description of these islands is given in Lowry and Fenwick (1983).
Ecology: Although McCain and Steinberg (1970) reported a depth range of between 0 and 29 m for the species, McCain (1969) examined some material from 123 m deep.In the present study, the species has been found down to 103 m.Caprellina longicollis has been recorded from algae, under rocks and attached to buoys (Guerra-García, 2002).In the present study C. longicollis has been found in the majority of the stations, being the most frequent and abundant species in the area.According to McCain (1969), this was the most common species in his New Zealand collections.

Remarks:
The morphology of the specimens examined is in agreement with the figures of McCain (1968), Krapp-Schickel (1993), Guerra-García and Thiel (2001) of specimens of different world areas.Contrary to other cosmopolitan species of Caprella, such as C. penantis and C. scaura, which present a high degree of intraspecific variation throughout the world, the morphology of C. equilibra seems to be more constant.
Antennae.Antenna 1 (Fig. 7A) about the half of body length; peduncular articles robust; flagellum 9articulate.Antenna 2 (Fig. 7B) almost as long as antenna 1; swimming setae present well-developed; flagellum two-articulate, basal article about three times as long as distal one.
Gnathopods.Gnathopod 1 (Fig. 7C) setose, basis as long as ischium, merus and carpus combined; ischium and merus rectangular; carpus triangular; propodus length about 1.5 times width, palm with a pair of proximal grasping spines, grasping margin denticulate in the proximal half; dactylus margin minutely serrated.Gnathopod 2 (Fig. 7D) inserted in the middle of pereonite 2; basis about two-fifths as long as pereonite 2, provided with carina and projection distally; ischium and merus rectangular; carpus small and triangular; propodus oval, length about 2 times width, palm with a grasping spine proximally and a triangular projection distally.
Abdomen (Fig. 8D) with a pair of appendages, a pair of lateral lobes and a single dorsal lobe; appendages one-articulate although slightly constricted medially; lateral lobes setose; dorsal lobe provided with a pair of plumose setae.

Remarks:
The specimens examined in the present study have been identified as Caprella manneringi on the basis of the combination of the following characteristics: short antennae, body robust, a ventral projection between gnathopods 2, gnathopod 2 with a tringular projection and propodus of the pereopods with the grasping spines medially in the palm.The original description and figures of C. manneringi are not complete and although McCain (1979) reported that the type material of the species is deposited in the Canterbury Museum, New Zealand, this material has not been located during the present study.McCain (1979) only illustrated the lateral view of the holotype male and details of the gnathopod 1, gnathopod 2 and propodus of pereopod 5.The male specimens examined in the present study present the pereonite 2 shorter than the holotype figured by McCain (1979).Furthermore the basis of gnathopod 2 is provided with a well developed carine not visible in the figure of McCain (1979).Additionally, the number of spines between the grasping spines in the propodus palm of pereopod and the dactylus is higher in the specimens examined here.Nevertheless, these differences could be due to some intraspecific variation or to the lack of details in the simple figures of the original description.The length of pereonite 2 is quite variable depending on the degree of development, being more elongate in the oldest and largest males.
Ecology: Prior to this study, Caprella manneringi had only been found associated with the asteroid Calvasterias suteri (de Loriol).McCain (1979) suggested that the small number of spines and setae on the pereopods, the convex palm of the propodus and the short, massive dactylus of the pereopods were probably adaptations to living with Calvasterias, perhaps as an obligate commensal.In the present study the species were also collected in intertidal pools, as was the type material of the species, but from sponges and algae and not asteroids.This suggests that C. manneringi is not an obligate commensal of asteroids, unless the collection on algae and sponges were accidental and the species were really living close by on the surface of a starfish.Consequently, the striking propodus of the pereopods could also be useful to cling to some species of algae and sponges.The species Caprella andreae Mayer, 1890 shows a similar pereopod feature, in this case as a morphological adaptation for clinging to the algal substratum on the turtle caparaces (Aoki and Kikuchi, 1995).
Distribution: Type locality: Antipodes Islands (McCain, 1979).New record in The Snares.Etymology: The specific name refers to the type locality, Campbell Island.
Mouthparts.Upper lip (Fig. 10B) symmetrically bilobed, smooth apically.Mandibles (Fig. 11A, B) with mandibular molar present but reduced to a cone with a distal tubercle ending in a spine; incisor 6toothed, lacinia mobilis 5-toothed in left mandible (Fig. 11B) and minutely serrate in right mandible (Fig. 11A); a row of three plumose plated setae on both mandibles; molar flake absent; palp 3-articulate, second article with a single seta, distal article with a distal knob and a setal formula 1-x-1 being x=10 (all setae on distal article are plumose).Lower lip (Fig. 10C) without setulae.Maxilla 1 (Fig. 10D) outer lobe carrying six robust setae; distal article of the palp with three apical teeth and three robust setae distally, one setae laterally.Maxilla 2 (Fig. 10E) inner lobe triangular; outer lobe rectangular, about 1.8 times as long as inner lobe; inner and outer lobe with 4 setae apically.Maxilliped (Fig. 10A) inner plate small and rectangular with two setae; outer plate oval, three times as long as the inner plate, with four setae; palp 4-articulate, dactylus with rows of setulae.
Antennae.Antenna 1 (Fig. 12A) a little shorter than the half of body length; peduncular articles setose; flagellum 11-articulate.Antenna 2 (Fig. 12B) about a half of antenna 1 in length, with short setae although swimming setae absent; basal article of the peduncle with a distal projection; flagellum two-articulate, basal article about two times as long as distal one.
Penes (Fig. 13D) large, length about 3 times width, suture present apically.Abdomen (Fig. 13D) without appendages, with a pair of lateral lobes and a single dorsal lobe; lateral lobes setose; dorsal lobe provided with a pair of plumose setae.

Intraspecific variation:
The morphological characteristics of the specimens examined are very constant although there is some variation in the setal formula of the mandibular palp 1-x-1 with x varying between 6 and 12 depending on the specimens.
Remarks: Six species of Pseudaeginella were known up to now, P. antiguae Barnard, 1932from Antigua, P. biscaynensis (McCain, 1968) from Florida, P. montoucheti (Quitete, 1971) from Brasil, P. polynesica (Müller, 1990) from Bora Bora and Moorea, Society Islands, P. sanctipauli Laubitz, 1995 from St. Paul and Amsterdam Islands, and P. tristanensis (Stebbing, 1888) from Tristan da Cunha.Recently, after examination of specimens of Pseudaeginella tristanensis from Southern Indian Ocean, Laubitz (1995) considered the genus Fallotritella synonymous with Pseudaeginella mainly based on the presence of minute pereopods 3 and 4 also in Pseudaeginella.Consequently, the species P. biscaynensis, P. montoucheti and P. polynesica, previously belonging to the genus Fallotritella, were transferred to the genus Pseudaeginella.The idea that Fallotritella is synonymous with Pseudaeginella had been previously suggested by several authors (McCain, 1968;Laubitz, 1993) but due to the lack of available material of Pseudaeginella and that the location of the type material of P. tristanensis is unknown, probably missing, the genus Fallotritella was maintained as a valid genus until Laubitz (1995) redescribed Pseudaeginella based on the material newly collected from the Indian Ocean, and established Fallotritella as a junior synonymous of Pseudaeginella.
The six species of Pseudaeginella are compared in Laubitz (1995).Pseudaeginella campbellensis sp.nov. is closer to P. polynesica, differing in the following characteristics (see Müller, 1990): (1) P. campbellensis has three projections on pereonite 2, two medially and one distally; the distal projection is lacking in P. polynesica; (2) P. campbellensis presents a lateral projection on pereonites 3-5 (males) and pereonite 5 (females); these projections are lacking in P. polynesica; (3) there is a small rounded projection on the basis of gnathopod 2 males in P. campbellensis; this projection is absent in P. polynesica; (4) the propodus of gnathopod 2 in P. polynesica has strong spines laterally on the distal half, which are lacking in P. campbellensis; (5) the distal projection present in male propodus of gnathopod 2 in P. campbellensis is absent in P. polynesica; (6) pereopods 3 and 4 are larger in P. campbellensis and provided with two plumose setae apically, while in P. polynesica they carry only one simple seta.There are also some differences in the mouthparts: (7) the incisor is 5-toothed in P. polynesica and 6-toothed in P. campbellensis; (8) the molar is reduced to a cone and single setae in P. polynesica, whereas there is a cone, a small tubercle and single setae in P. campbellensis; (9) the setal formula of the mandible palp is 1-5-1 in P. polynesica and 1-x-1 with x between 6 and 12 in F. campbellensis; (10) the second article of the mandibular palp has a seta in F. campbellensis, this seta is absent in F. polynesica.Ecology: The species has been collected from shallow water (8-16 m. deep), from rock faces and underneath rock overhangs, sponges, coralline algae on boulders, red algae and hydroids from crevices in rock faces and encrusting sponges, tunicates, bryozoans and hydroids beneath boulders in beds of Macrocystis pyrifera C. Agardh, 1820 .
Distribution: So far, only known from Campbell Island, New Zealand.

Gender. Feminine.
Etymology: The term "aporema" reflects the difficulty in establishing the phylogenetic position of this genus."Aporema" is a word of Greek in origin which means "a difficult problem to solve".

Remarks:
The phylogenetic position of Caprellaporema new genus is difficult to establish because it shares characteristics with both caprellid groups, families Phtisicidae and Caprellidae (see Takeuchi, 1993).The flagellum of antenna 1 is two-articulate.This character is only present in another two genera inside the Caprellidea: Perotripus (LaFollette, 1915) belonging to the Phtisicidae and Pedoculina Carausu, 1940, belonging to the Caprellidae.According to the structure of the antenna, the general shape of the body, gnathopods and pereopods, and the lack of gills on pereonite 2, the new genus seems to be closer to Pedoculina.However, in the genus Pedoculina the molar process is present and the mandibular palp is absent, while Caprellaporema lacks a molar but has a 3-articulate palp.In this sense, it is more similar to Perotripus; in fact the lack of molar is the general tendency in the Caprellidae.Furthermore, the feature of the maxilliped plates and the inner lobes of the lower lip (which are fused) is very similar in Perotripus and Pedoculina.The abdomen is also very similar in Caprellaporema and Perotripus brevis (LaFollette, 1915), the only species of Perotripus described so far.Nevertheless, the two taxa differ in general features of the antennae and body, the setal formula of the palp, the gills (three pairs in Perotripus and two pairs in Caprellaporema), and the pereopods (pereopod 3 and 4 present in Perotripus and absent in Caprellaporema, pereopod 5 three-articulate in Perotripus and twoarticulate in Caprellaporema).In connection with the lack of pereopods 3 and 4, and the reduction of pereopod 5, Caprellaporema could be related to some genera of the family Caprellidae; however, the absence of molar seems to connect the new genus with Caprellinoides in the family Phtisicidae.Other characteristics present in Caprellaporema are unique among the Caprellidea, such as the location of the ocelli in an acute projection on the head (Fig. 14A), the short basal article of the flagellum of antenna 2 (Fig. 14B), and the striking ventral projection of the carpus of gnathopod 1 (Fig. 14C,D).Although extensive studies on the Caprellidea are still necessary to clarify the phylogeny of this group, this genus shares characteristics of the two large groups of caprellids, Phtisicidae and Caprellidae, perhaps linking both groups of the Caprellidea and raising again the question whether the Caprellidea is a monophyletic group, which is still under debate.Etymology: The specific name is an adjective qualifying the geographic area where the species have been found.
Mouthparts.Upper lip (Fig. 16D) symmetrically bilobed, smooth apically.Mandibles (Fig. 16A,B) without molar; left mandible with incisor 6-toothed, lacinia mobilis 5-toothed followed by a row of plates setulose distally; right mandible with incisor 6toothed, lacinia mobilis transformed into a wide plate, followed by three more plates setulose distal- ly; palp 3-articulate, second article with a single seta, distal article with a long simple setae medially, followed by four short and robust plumose setae, another long simple seta and a small hook projection distally.Lower lip (Fig. 16E) with inner lobes fused; outer lobes carrying fine and short setae apically.Maxilla 1 (Fig. 16G) outer lobe carrying six robust and serrate setae; distal article of the palp with five setae distally, no setae laterally.Maxilla 2 (Fig. 16F) inner lobe triangular with four setae; outer lobe rectangular with five setae.Maxilliped (Fig. 16C) inner plate small and rectangular with two setae; outer plate similar to inner one, with two setae as well; palp 4-articulate, dactylus with a row of ventral setae as serration and a short dorsal one.
Antennae.Antenna 1 (Fig. 17A) a little shorter than head to pereonite 2 combined; basal article of the peduncle with a distal acute projection and another round projection; flagellum 2-articulate.Antenna 2 (Fig. 17B) about two-thirds of antenna 1; basal article of the peduncle with an acute projection; distal article of the peduncle with a group of setae; flagellum 2-articulate, basal article very small (Fig. 14B), about one-fourth of distal article in length.
Gnathopods.Gnathopod 1 (Fig. 17C) basis as long as ischium, merus and carpus combined; ischium rectangular; merus rounded; carpus striking (Fig 14C , D), provided with a ventral acute projection carrying rows of small setulae and a pair of plumose setae; propodus length about 1.5 times width, palm with a pair of proximal grasping spines, grasping margin serrate proximally; dactylus margin short.Gnathopod 2 (Fig. 17D) inserted on the anterior part of pereonite 2; basis as long as pereonite 2, provided with a projection distally; ischium rectangular; merus rounded; carpus small and triangular; propodus oval, length about 1.5 times width, with four proximal grasping spines and two rows of smaller spines along the palm.
Abdomen (Fig. 18D) with a pair of appendages, a pair of lateral lobes and a single dorsal lobe; appendages small and triangular, carrying a strong setae distally; lateral lobes with a row of four setae each one; dorsal lobe smooth.
The morphological characteristics of the species are rather constant in the specimens examined.Only some variation was found in the number of setae on the distal article of the mandibular palp (ranging between 5-8).The setation of the inner and outer plates of the maxilliped is constant but the number and organisation of the setae along the maxilliped palp is variable.

Remarks: (See remarks under genus Caprellaporema).
Ecology: Caprellaporema subantarctica has been found in a depth range 8-103 m living on bryozoans on rock faces, encrusting platelet coralline alga from boulders in Macrocystis pyrifera C. Agardh, 1820, bed and coarse sediment and shell fragments.
Distribution: Antipodes Islands, Campbell Islands and The Snares.

DISCUSSION
The study area is interesting from the biogeographical point of view as it is a transition between the temperate region and the cold Antarctic waters.Although a great number of stations were sampled along these subantarctic islands and collections were targeted on amphipods (see Lowry and Fenwick, 1983) only six caprellid species are present in the collections.One of them, Caprella equilibra, is a cosmopolitan species, Caprellina longicollis is distributed in the cold-temperate region throughout the world, Caprellinoides mayeri is one of the common species of Antarctic waters (Guerra-García, 2001) and the remaining three species, Caprella manneringi, Pseudaeginella campbellensis and Caprellaporema subantarctica are, so far, endemic for the subantarctic Islands.The low caprellid number of species around the area could be due to the cold increase in waters towards the Antarctic region.Recently, Thiel et al., 2003 observed a latitudinal gradient with decreasing abundance and species richness of littoral caprellids towards the South along the Pacific coast of continental Chile.The same pattern was obtained by Laubitz (1970) for the Caprellidea of the North Pacific: the number of species was decreasing towards high latitudes with colder waters, so this tendency of the caprellids avoiding the coldest waters seems to be general.The number of littoral caprellid species recorded from Tasmania and nearby areas of South Australia is about twenty (Guerra-García, in prep.); this number decreases to six in the Subantarctic Islands studied in the present paper.This study seems to support the general tendency of decreasing species richness of the caprellidean amphipods with a decrease in water temperature.Additionally, Thiel et al., 2003 reported that this decrease was also affecting the abundance of species, not only the species richness.However, in the present study, Caprellina longicollis was very abundant in the majority of stations.This species is the most common in New Zealand waters (McCain, 1979), probably being very well adapted to the marine environments of New Zealand and nearby Subantarctic Islands.Since some species are numerous in colder waters, we could not explain the decrease of the species richness on the basis of a difficult environment.Rather, the absence of large algal habitats could play an important role to explaining why are there fewer species of caprellids in colder waters.
resurrected C. antarcticus, C. spinosus and C. tristanensis.Recently Guerra-García (2001) considered only C. mayeri and C. tristanensis as valid species.Caprellinoides spinosus and C. antarcticus were considered junior synonyms of C. mayeri and C. tristanensis, respectively.The specimens of C. mayeri collected from the Antipodes Islands and Macquarie Island are in agreement with the material of C. mayeri redescribed by Laubitz (1991) and the type material revised by Guerra-García (2001).