Corresponding author: David J. Wildish (
Academic editor: Matthias Glaubrecht
A new specialist driftwood talitrid from the Swale, U.K., is figured and described as
Driftwood specialist hoppers are a rare, difficult to find, ecological group of
Currently known driftwood taxa (
As a result of molecular studies of
Slides were prepared as temporary mounts without staining and after dissecting mouthparts and limbs. Some were prepared as permanent mounts by Sara LeCroy, after staining with lignin pink and permanently mounted in CMCP-10 (Master’s Company, Inc.).
Photographs of limb parts were made with a Carl Zeiss photomicroscope and digital Canon 990 camera. Adobe Photoshop (version 7.0), Illustrator (version 11.0) and a Wacom tablet were used to draw limb parts and prepare figs, essentially as outlined in
Currently includes five species:
As in
Male holotype and 8 females (allotype and paratypes) on loan from Zoological Museum of Amsterdam, Amsterdam, the Netherlands (AMPH. 108.57). Collected by J. Stock on 2 August, 1987 from Gruta das Agulhas in Porto Judeus on the island of Terceira, Azores archipelago.
Known only from the type locality on the island of Terceira.
Not mentioned by
This is the type species and smallest
Male holotype (BMNH 1968:64), one female allotype (BMNH 1968:65) and 416 paratypes of all life history stages (BMNH 1968:66). Collected by D.J.Wildish(DJW) in August 1968, 0.2 km upstream from Chatham Ness in Limehouse Reach, Medway estuary, near Rochester, Kent, U.K.
Besides the type locality one other locality in the Medway estuary was found in 1968 with a few specimens in a driftwood log by DJW. The location was ~ 0.6 km upstream from the old Rochester Bridge in Tower Reach on the eastern shore. A few specimens collected by DJW in 1999 from the Swale, in Ferry Reach ~ 0.5 Km northwest of Kingsferry Bridge on the mainland shore.
Absent.
Two males, 4 females, 1 juvenile (Crust. 25468) ZMB Museum für Naturkunde, Berlin. Collected by A. Schellenberg from a seashore cave at St. Barthelemy, Corisca. A total of 47 individuals (combined sample) of all life history stages, including females with ova, collected by L. Pavesi on 20 January and 15 April 2007 at Principina a Mare, Tyrrhenian Sea, Italy. Sample location co-ordinates:
Besides the locations found by L. Pavesi for this species, published records include that of
Absent.
Holotype male of 8.0 mm TBL (NHMUK 2014. 408) and allotype female of 7.5 mm (NHMUK 2014. 409) collected by L. Pavesi on 31 October, 2006 at Lesina, Adriatic Sea, Italy. 13 paratypes collected on the same date (NHMUK 2014. 410 - 419). Paratypes have also been deposited in the Natural History Museum, Verona and Museum at Rome University, Rome, Italy by L. Pavesi.
Lesina, Adriatic Sea, Italy (
17 individuals collected by L.Pavesi in April 2006 at Varano, Adriatic Sea, Italy (
Based on male paratypes: total body lengths in the range of 8.0 to 6.7 mm. Figs
Head deeper than long (1: 0.7); eyes small, round, less than half the head length. Antenna 1 flagellum 5–articulate with tip just exceeding the junction of peduncle segments 4 and 5 of antenna 2. Antenna 2 short, flagellum 12–articulate, peduncle not incrassate.
Mouthparts. Lower lip with lateral lobes, minute setae on the inner clefts. Left mandible with a 4-dentate lacinia mobilis and large molar process. Right mandible with the tip of the dentate incisor bilobed, 6–dentate lacinia mobilis. Maxilla 1 inner fig narrow with 2 terminal plumose setae, inner margin with long, fine setae; outer fig with a palp, apical robust setae curved and serrated on the inner edge. Maxilla 2 both figs equal in size, inner with a single, plumose seta, with shorter robust setae on the distal edge; outer fig with simple robust setae. Maxilliped inner figs with 3 stout teeth apically, inner, outer and palp distal edges covered with robust setae; palp large and 3–articulated.
Peraeon. Gnathopod 1 weakly subchelate with palmate lobes on propodus and carpus; dactylus as long as propodus lobe; the largest robust setae are present on the posterior edge of the merus. Gnathopod 2 subchelate with propodus and dactylus massively enlarged, dactylus drawn out in a short, blunt tip, its inner surface lacking fine setae. Ventral edge of each coxal fig rounded and with fine robust setae. Peraeopods 3 to 5 short, peraeopods 6 and 7 longer, the latter just longer than uropod 1. Peraeopods 3 and 4 lack a dactylus notch (“pinched unguis”). Peraeopods 6 and 7 not sexually dimorphic in merus and carpus. Six distinctive tufts of long, slender setae originating from the propodus of peraeopod 7 as follows: anterodistal (2 setae), distal (6 setae), anterior side of peraeopod near the first insertion of robust, bifid-tipped setae (4 setae), then on the posterior side of the peraeopod: first insertion of robust, bifid-tipped setae (2 setae), second (4 setae) and third (3 setae). The maximum length of the longest seta from the distal tuft was 144 µm (Fig.
Pleosome. Pleopod basis not reduced and with a pair of hooked coupling spines, robust setae and fine marginal setae absent. All rami are are shorter than the basis. The second pleopod rami have 3 articles each bearing a pair of long, plumose setae: exopod –7, endopod -5.
Urosome. In uropods 1 and 2 the inner and outer rami are of similar length, with 2–4 apical robust setae and 1 or 2 inter-ramal robust setae, basis with 1 or 2 dorsoventral, robust setae distally. Uropod 3 basis longer than the ramus and with 2 large, robust setae dorso-laterally. Smaller robust setae at the ramus tip but lacks inter-ramal robust setae. Telson with a mid-dorsal groove and 6–7 dorso-lateral robust setae on each lobe.
Bbased on non-breeding adult female paratype of 7.3 mm total body length.
Gnathopod 1 without palmate lobes on propodus and carpus. Gnathopod 2 basis slender and with weak robust setae. Palmate lobes present on merus, carpus and propodus, dactylus small (described as “mitten-shaped”gnathopod 2). Pairs of non-ovigerous oostegites on peraeopods 2 to 5. Adult females greater than 7.5 mm body length with no more than 11 antennal flagellum articles (versus up to 13 in males). The 6 tufts of long, simple setae on the propodus of peraeopod 7 in males compares with 2 tufts, of sparser and shorter length setae in females.
Absent.
The name honours Dr. Laura Pavesi who originally discovered and collected the new species during graduate studies at the University of Rome, Italy.
There are three known locations for this species on the shores of the Adriatic Sea and one on Corfú Island, Ionian Sea.
Peraeopod 7 tip (dactylus and part of propodus) in male (M) and female (F)
Male holotype (No. 5-1963) and paratypes in the Museum National d’Histoire Naturelle, Paris. Collected in 1962 by Mr. C. Caussanel from Cap Ferret Point near Arcachon on the Atlantic coast of France. Paratypes also in L’Institut de Biologie Marine at Arcachon. Collection by DJW in the type locality on 11th September 1967 and deposited in the Natural History Museum, London (BMNH 1967 10.6.1–75).
- Sexually dimorphic tufts of long, slender, simple setae from the propodus of peraeopod P7, with no tuft at anterodistal position and 4 tufts on the posterior side of the propodus in males, versus a tuft at anterodistal position and 3 tufts on the posterior side of the propodus in males of
- its larger size, and
- lack of sexual dimorphism in pleopod and second antennal characters. Pleopod sexual dimorphism was discovered by
Known from the
and 3 other locations further south on the French Atlantic coast (
Absent.
Since the erection of
Taking only
An interim diagnosis is provided based on the type species,
Adult total body length up to 22 mm; dorsal pigment patterns present; eyes medium in size, approximately one quarter of head length; antenna 1 flagellum just reaching antenna 2 peduncle of article 4; antenna 2 sexually dimorphic, peduncle slightly incrassate in adult males and without ventral fig on peduncle article 3; upper lip without robust setae; mandible left lacinia mobilis 4 dentate; maxilliped palp 3 articulate, article 2 with well developed medial lobe; gnathopod 1 of male subchelate with palm equal to dactyl, carpus and propodus free and with rounded lobes covered with palmate setae; gnathopod 1 of female parachelate, without lobes on carpus and propodus; gnathopod 2 of male strongly subchelate, merus and carpus free, dactylus with blunted tip and is half the length of the enlarged propodus; gnathopod 2 of female, ovigerous oostegite long and wide with many, long, simple, marginal setae, basis expanded anteriorly; peraeopods 3–7 cuspidactylate; peraeopods 5–7 lack slender setae lining the anterior margin of the dactyl; peraeopod 7 sexually dimorphic, adult males with merus and carpus enlarged; distinctive tufts of long simple setae on propodus of peraeopod 7 absent in both sexes; pleon segments 1–3 lacking vertical slits; pleopod rami slightly, or not, reduced; uropods without apical, spade-like robust setae, uropod 1 not sexually dimorphic, peduncle lacking well developed dorsolateral robust setae distally, outer ramus with marginal robust setae, uropod 2 rami equal in length, uropod 3 ramus shorter than peduncle; telson apically notched with 6–8 robust setae per lobe and shorter than uropod 3.
Ecological habitats occupied by species of
Marine/estuarine supralittoral wrack | Marine/estuarine eulittoral wrack | Freshwater supralittoral wrack | Terrestrial rain forest leaf litter | Marine driftwood |
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Ecological habitats and proposed generic groupings of species listed in Table
Genus | Marine/estuarine supralittoral wrack | Marine/estuarine eulittoral wrack | Freshwater supralittoral wrack | Terrestrial rain forest leaf litter |
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Genus A | ||||
Genus B | ||||
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Genus C | ?( |
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Genus D | ? |
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Genus E | ?( |
Monotypic.
As in
- lack of dorsal pigment patterns (versus dorsal pigment patterns in
- smaller size by neoteny (largest total body length estimated to be 12 to16 mm, versus up to 20 mm in
Very similar to
Refers to the origin of the new genus by a form of neoteny and combination of the stem of this word with the genus
Summary of morphological and molecular data available for species of
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4 | 6 0 | 4 | ? |
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4 | 2 0 | 0 | Yes |
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5* | ? ? | ? | Yes |
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4-5 | 6 2 | 3 | Yes |
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4 | 6 2 | 3 | Yes |
Holotype–immature male of 7.2 mm total body length (NHMUK 2014. 397) and slide preparation from this individual (NHMUK 2014. 397). Nine juvenile paratypes (NHMUK 2014. 398 - 406) and 2 immature females (destructively sampled for temporary slide mounts and mtDNA analysis) removed from a cast-up driftwood log resting at the base of the seawall in the
Approximately 0.5 km west of Kingsferry Bridge, The Swale on the mainland shore in a single rotting driftwood log (~ 3 × 0.5 × 0.5 m) determined to be of Douglas fir by Dr. P. Gasson, Kew (
Unknown, the largest found was an 8.9 mm TBL immature female. Mature adults predicted by relative growth methods to be 12 to16 mm total body length (
Based on immature male holotype of 7.2 mm total body length. Figs
Head deeper than long (1: 0.5); eyes medium/large, round and greater than half the head length. Antenna 1 flagellum 4-articulate. Antenna 2 flagellum 13-articulate. Peduncle not incrassate.
Mouthparts. Upper lip with minute setae on the apical margin. Lower lip deeply cleft and with minute setae on the inner face. Maxilla 1 inner fig slim and with two terminal, plumose setae; inner margin with long fine setae; outer fig with a vestigial palp, apical robust setae curved inwards, some simple and others serrated on the inner edge. Maxilla 2 with inner fig subequal to the outer, inner with a single, plumose seta and fine marginal setae below it; both inner and outer figs with long, simple robust setae which curve inwards. Left mandible with a 4-dentate lacinia mobilis, 6-dentate incisor, strong molar process and setose accessory blades. Maxilliped with 3 strong apical teeth on the inner fig; inner, outer and palp edged with simple, robust setae; palp large and 3-articulated.
Peraeon. Gnathopod 1 weakly subchelate, palmate lobes on propodus and carpus. Gnathopod 2 weakly subchelate with dactylus shorter than the propodus lobe; palmate lobes on propodus, carpus and merus. Peraeopod 3 lacks a dactylus notch (“pinched unguis”), but this is present in an immature female. Peraopod 5 shorter than peraeopods 6 and 7, the latter not sexually dimorphic in the immature male.
Pleosome. Pleopods large and well developed, with 6–7 ramal segments in the endopod, 8 segments in the exopod; rami subequal to basis with paired coupling spines on the inner, distal margin of the basis; 6 simple setae present on the basis of pleopod 1.
Urosome. Uropod 1 rami subequal to peduncle. Peduncle with 2 rows of 2 robust setae. Terminal setae on each ramus consists of 1 large and 1 or 2 smaller robust setae. 3 interamal robust setae on inner and 2 on outer ramus.
Based on immature female of 8.9 mm total body length.
In the absence of sexually mature males and females the only unique female characters found were: absence of palmate lobes on propodus and carpus of gnathopod 1, presence of pinched unguis on peraeopod 3, and presence of small, rudimentary oostegites on coxae of peraeopods 2–5.
The name honours Kenneth J. Wildish who discovered and collected the new taxon in the Swale during the summer of 2011.
Absent.
Known only from the type locality.
1 | Medium size eyes and pleopod rami basis length | |
– | Small eyes and pleopod rami < basis length | 2 |
2 | Maximum adult size (TBL < 8 mm), female TBL > male | 3 |
– | Maximum adult size (TBL > 8 mm), male TBL ≥ female | 4 |
3 | Third pleopod exopod length ratio > 0.16 |
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– | Third pleopod exopod length ratio < 0.16 |
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4 | Maximum adult size (TBL = 15 mm), male TBL > female |
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Lacks sexual dimorphism in A2 and pleopods | ||
Males with no tuft at anterodistal and 4 tufts of long, simple setae on posterior edge of of P7 propodus | ||
– | Maximum adult size (TBL < 13 mm), male TBL ≤ female | 5 |
With sexual dimorphism either in pleopods or A2 flagellum articles | ||
Males with a single tuft at anterodistal and 3 tufts of long, simple setae on posterior edge of P7 propodus | ||
5 | Adult male TBL > 8 mm fit: y = 0.050x + 0.159 |
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– | Adult male TBL > 8 mm fit: y = 0.026x + 0.024 |
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– | Adult female TBL > 7.5 mm fit: y1 = 0.585x + 6.995 |
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– | Adult female TBL > 7.5 mm fit: y1 = 0.130x + 9.248 |
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(where × = TBL, y = Pl3 Ex L, and y1 = A2 FA) |
The following arguments were considered in deciding how to name the unknown taxon. Relative growth data was available to show that the unknown taxon fundamentally differed from juvenile
- being slower growing with a reduced terminal moult size,
- sexualization beginning at an earlier moult stage and with fewer moult stages per life history, and
- dorsal pigment patterns being absent.
The first two of these three phenotypic characters are described as neotenous dwarfism and are the basic adaptations possessed by all driftwood specialist talitrids of the genus
On the other hand molecular evidence suggests that the differences between the unknown taxon and
Pragmatically, and in the absence of conclusive molecular data, it is considered prudent to remove the unknown taxon from
Inclusive of the taxonomic actions taken above brings the total genera of driftwood talitrids to three:
The scarce locality records for each species documented here suggest either rareness and/or that they are difficult to find on shores of the northeast Atlantic and Mediterranean seas. Further evidence for this is that 2 of the 6 driftwood taxa dealt with here are known only from the type locality and the rest from only a few locations. A problem for future discoveries of driftwood talitrids is that the habitats are fast being destroyed by human activities. Documented examples include the destruction of the type locations for two species as mentioned above.
Both
1.
2.
evolution involves further neotenous dwarfism. Thus taxa to the left are larger and plesiomorphic, whereas those to the right are smaller and apomorphic. Neotenous dwarfism of this kind in driftwood talitrids poses a special challenge to taxonomy because many of the slope values between pairs of species are isometric. In these cases only regression constants, or plots, can be used to separate two species populations. Isometric relative growth is rare within the
Permanent slides of limb and mouth parts prepared by Sara LeCroy (Gulf Coast Research Lab, University of Southern Mississippi) of four species of
In considering current data of Table
- of missing data as indicated by question marks in Table
- The left mandible lacinia mobilis is 5 dentate according to
Further molecular and morphological studies are needed to resolve the subgeneric status of
Thanks to Sara E. LeCroy for preparing permanent slides of