Ampithoidae (Crustacea, Amphipoda) from New Zealand

Abstract Ampithoidae is a family of marine Amphipoda with approximately 230 species, belonging to 16 genera. The family has a worldwide distribution as algal dwellers. So far only five species are known from New Zealand. Recent collections and examination of historic collection material added two new species, which are described herein. An overview of and a key to the New Zealand Ampithoidae is provided.


Introduction
The family, Ampithoidae, is a broadly distributed group of primarily algal-dwelling amphipods. They have been well described and reported from North and South American-, European-, African-, Australian-and Asian waters. The Ampithoidae record is quite sparse in boreal waters, but not unknown (De Broyer et al. 2007). Globally there are 231 species (Horton et al. 2017). However, despite this diversity, there have only been five species recorded from New Zealand.
The major source of information on New Zealand ampithoid amphipods is J.L. Barnard's detailed monograph of algal dwelling gammarid amphipods (1972). This paper documents four species of this family all in the genus, Ampithoe Leach, 1814. One of these species was originally described by Hurley (1954) (as Pleonexes lessoniae Hurley, 1954) and was subsequently designated the type species for the genus Pseudopleonexes (Conlan, 1982), two others were new descriptions (Ampithoe hinatore and Ampithoe aorangi) and the last an undesignated species (Ampithoe sp.). Recent work Peart 2015, Peart 2017, and this current work) has expanded and revised this previous research.
Using freshly collected material and type material from the NIWA Invertebrate collection, this paper provides a checklist to the Ampithoids from New Zealand waters, providing a diagnosis for each species and a key to the species of the family. Adding to the count of species from these is the description of two new species, Exampithoe plumosa sp. n. and Pseudopleonexes evensis sp. n.

Materials and methods
Recent collections were sampled via snorkelling from Macrocystis sp. in Wellington and collected from a large, drifting detached plant of Durvillaea antarctica from Otago Harbour. They were immediately preserved in 95% ethanol. Specimens were examined and dissected using a Leica MZ12.5, in Wellington and drawn using a camera lucida attachment. Small appendages (mouthparts, uropods, telson) were temporarily mounted in glycerin and examined and drawn using a compound microscope (Zeiss, in Wellington) fitted with a camera lucida. The body lengths of specimens examined were measured by tracing individual's mid-trunk lengths (tip of the rostrum to end of telson) using a camera lucida. For scanning electron microscope (SEM) imaging the specimens and appendages were dehydrated through a graduated ethanol series, acetone dried, mounted on studs, coated with gold-palladium and investigated via a SEM LEO1525.
Type material and other material examined is held at the National Institute of Water and Atmospheric Research Invertebrate Collection at Wellington, New Zealand (NIWA) and the CeNak, Zoological Museum Hamburg. In New Zealand waters, the fauna of the family Ampithoidae is represented by four genera comprised of seven species, two of which are newly described here. Gnathopod 1 robust and sexually dimorphic, coxa slightly produced anteriorly, basis anteroventral lobe prominent and setose, propodus subrectangular, anterodistal setose lobe absent, palm acute and concave, defined by a very small rounded posterodistal tooth and a large robust seta; dactylus shorter than palm. Gnathopod 2 slender and slightly longer than gnathopod 1, sexually dimorphic; basis anteroventral lobe medium sized and setose; carpus subovoid; propodus subequal in length to carpus, propodus narrow, anterodistal lobe absent, palm acute, midpalmar tooth/corner present, defining posterodistal tooth absent, robust seta present; dactylus shorter than palm length. Pereopods 3 and 4 similar in size and shape, basis expanded and glandular; merus slightly expanded, lobe present. Pereopod 5 basis ovoid; distal articles slender; propodus weakly prehensile. Pereopods 6-7 similar lengths; merus and carpus broader than propodus; propodus weakly prehensile.
Female. Similar to male except for gnathopod 1 merus lobe reduced and weakly setose, carpus more slender than male and less setose and subequal in length to the propodus; propodus narrow, weakly setose, palm convex, not sculptured.
Etymology. Named plumosa, a derivative of the latin plumosus meaning feathered, referring to the feathered nature of majority of the setae present on the type material. Remarks. This is an interesting species for a couple of reasons. Firstly, it is the first record of this genus from the South Island of New Zealand. The only other Exampithoe species recorded from New Zealand is Exampithoe taylori Hughes & Peart, 2015. These two species are recorded from almost opposite ends of the country with over 1000 km between them and situated on water bodies influenced by different currents and geophysical history. Though the two species have some similarities, such as the shape of gnathopod 2 propodus (narrow, palm with a subquadrate midmedial tooth), the shape of the lower lip outer plate (entire), similar setation and shape of uropod 3 (broad peduncle, small rami, 2 distal peduncular robust setae, 1 marginal robust seta), there are also a number strong differences that give the necessity of these being separate species. These differences include: the shape and length of the antennae (A1 and A2 similar length in E. plumosa sp. n. A1 shorter than A2 in E. taylori. Antenna 2 peduncular articles are robust but not elongated in E. plumosa sp. n. and are robust but considerably elongated in E. taylori); the shape and size of gnathopod 1 (robust with shortened articles, propodus ovoid to subrectangular, palm excavate with small posterodistal tooth, subquadrate predactylus tooth and large defining robust seta in E. plumosa n.sp. and narrow with elongated articles, propodus subrectangular, palm convex, no defining tooth or predactylus tooth or robust seta in E. taylori). The other main difference between the two species is the majority of the setae on every appendage of E. plumosa are feathered (plumose) giving this animal a strongly fuzzy look. Whilst E. taylori has numerous setae on the appendages, very few are plumose.   The second interesting aspect of the discovery of this species is that the specimens were collected from a kelp raft. While many organisms can be found on floating or rafting macroalgae, ampithoids are only occasionally recorded rafting (Thiel and Gutow 2005) but are not obligate rafters. As there are no other records of this species, it cannot be inferred whether it is an obligate rafter or not. The kelp was determined to have been drifting in the water for around five weeks (determined by the stage of goose barnacle settlement - Waters et al. in press) and probably originating from southern New Zealand. This is the first record of an ampithoid in this area of New Zealand.
Distribution. Only known from the type locality, Otago Harbour, South Island, New Zealand.
Remarks. This relatively rare species can be aligned to J.L. Barnard's (1972) material and can be identified by the shape of the gnathopods 1 and 2 propodi and palms. The other interesting feature which when first observed in Barnard's description is the reduced mandibular palp. When the Eve Bay material was collected and dissected it was found to have a very similar mandibular form. If this is a valid character, along with the distinct presence of a setose anterodistal lobe on each of the gnathopod 1 and 2 propodi and the reduced, angled palm of gnathopod 1, validates this material as a new species. Barnard (1972) described two males one 6.2 mm (E975), one 4.8 mm (E979), and mentioned in the description he only had two specimens and thought they maybe different species based on the presence/absence of the lobe on the uropod 2 peduncle (present on 6.2 mm male/absent on 4.8 mm male), the broadened articles of pereopod 5 (slightly broader than P. lessoniae) and the excavation of gnathopod 2 palm (more strongly excavated than P. lessoniae). He then mentions three stations where it was collected. The only material that has been able to be found is the 4.8 mm male and this material (when examined) matches to P. evensis sp. n. and differs from P. lessoniae by the shape and structure of gnathopod 1 (consistent across sizes -9 mm length described here and the 4.8 mm male he described). The description notes that the uropod 2 peduncular process is absent, however when examined this character is obvioiusly there. The 6.2 mm material was not able to be located and so cannot be verified.
Etymology. The specific name is taken from the name of the type locality, Eve Bay. Distribution. North Island, New Zealand.

Pseudopleonexes lessoniae (Hurley, 1954) Figs 9-12
Pleonexes lessoniae Hurley, 1954:  Diagnosis. Male: Eye absent (holotype), eyes prominent (additional material examined). Epistome and upper lip, in situ, directed posteriorly around 45°. Antenna 1 longer than antenna 2. Lower lip outer plate slightly notched, almost entire, margin sinusoidal to sometimes flat with larger, subacute corners. Mandible molar reduced and triturating, palp three-articulate, article three distally beaked. Maxilla 1 palp poorly developed and slender tipped with slender plumose setae. Gnathopods strongly setose. Pereopods weakly setose. Gnathopod 1 not sexually dimorphic; coxa not anteroventrally produced; basis anterodistal lobe reduced and rounded bearing on slender seta; propodus subrectangular, anterodistal setal lobe absent, palm transverse, entire, without midmedial tooth, with posterodistal tooth defining palm and one small defining robust seta; dactylus overreaching palm. Gnathopod 2 more robust and larger than gnathopod 1, sexually dimorphic, with long plumose setae on margins; basis anterodistal lobe large and rounded, bearing around 10 robust setae on the margin; carpus subtriangular; propodus longer than carpus; propodus broad, anterodistally setose lobe absent; palm acute, entire (sometimes slightly excavate), midpalmar tooth absent, with small suba- cute posterodistal tooth defining palm, and one defining robust seta; dactylus subequal to palm. Pereopods 3-4 similar in size and shape, basis expanded and glandular; merus expanded and glandular, forming an acute lobe. Pereopod 5 basis circular, distal articles broad to slender (depending on size), propodus prehensile. Pereopod 6-7 increasing in length, merus and carpus similar widths to propodus (slightly wider), propodi prehensile. Epimeron 3 posteroventral corner rounded without tooth. Uropod 1, in situ, reaching only to the end of uropod 2 peduncle; peduncle distoventral spur absent. Uropod 2 peduncle with large rounded distolateral process. Uropod 3 broad, peduncle without distal robust setae, rami short, outer ramus with two strongly recurved robust setae, patch of denticles; inner ramus with just slender distal setae. Telson subtriangular with strongly recurved cusps, denticles absent, with one slender seta per lobe. Remarks. Described by Hurley (1954) from Wellington, New Zealand, this species is a small, robust amphipod dwelling in Lessonia variegata. Hurley (1954) described it as having similarities to members of the Ampithoe group, Pleonexes. When the Figure 10. Pseudopleonexes lessoniae (Hurley, 1954), male, 9 mm, NIWA 96679, female, 8 mm, NIWA 96679, Breaker Bay Wellington. Scale bars: 0.5 mm. genus Pseudopleonexes was constructed (Conlan, 1982), this species was placed as the type of the genus. It has strongly plumose, long setae on the gnathopod 2, a character represented in most of the other species in the genus. Hurley's types have been located, and are in the NIWA Invertebrate Collection (NIC).   (Hurley, 1954), male, NIWA 120146, Breaker Bay, Wellington, New Zealand. A whole animal, habitus B close up of propodus and dactylus pereopod 6 C close up of pereon and coxa showing position pits on the surface D close up of Uropod 3 rami E, F magnification of the heart shaped (E) and butterfly shaped (F) pits on the coxae and pereon. Barnard (1972) assigned two specimens from New Zealand as P. lessoniae however, examination of one of the specimens (the other is not locatable) and some confusion in the description indicate that these are not of this species. Comparison with freshly collected material indicates these should be treated as a new species (described above as P. evensis sp. n.). Pseudopleonexes lessoniae sensu stricto differs from P. evensis sp. n. by the absence of an anterodistal setose lobe on the propodi of gnathopods 1 and 2 (strongly present in P. evensis sp. n.) and the strongly transverse gnathopod 1 palm, also half the width of the propodus (acute, greatly reduced palm in P. evensis sp. n.).
The material described here is from Breaker Bay, very close to the type locality of Island Bay (4.5 km ENE) and was very abundant in Macrocystis sp. and until molecular examination is carried out is placed with P. lessoniae (Hurley, 1954). The main differences involve the apparent presence/absence of the eye and presence of butterfly and heart-shaped pits and fine hairs covering the pereon and pereopods of the recently collected material (fig. 12).
Distribution. Wellington area, New Zealand.
Female. Not documented.
Remarks. This species has recently been redescribed (Peart 2017) and the original material confusion resolved. The differences between this species and the recently described only other species from New Zealand (S. mixtura Peart, 2017) are detailed in Table 1 of that publication.