Limnoria sellifera, Cookson & Cragg & Hendy, 2012

Cookson, L. J., Cragg, S. M. & Hendy, I. W., 2012, Wood-boring limnoriids (Crustacea, Isopoda) including a new species from mangrove forests of the Tukang Besi Archipelago, Indonesia, Zootaxa 3248 (1), pp. 25-34 : 26-30

Limnoria sellifera , new species

( Figs 1–7 )

Material examined. Holotype: Loho , Derawa Island , Tukang Besi Archipelago, Sulawesi, Indonesia, 5°33'09"S, 123°52'03"E, intertidal zone, dead mangrove wood, Ian Hendy, July 2010, MZB Cru.Iso. 013 (male, 3.0 mm, 0.7 mm wide pleotelson, with 1 slide).

Paratypes: Type locality, MZB Cru.Iso. 014 (3 males 2.2–2.6 mm, 7 non-ovig. females 2.1–2.6 mm, 2 ovig. females 2.6 mm, juvenile 1.7 mm). Type locality, MZB Cru.Iso. 010 (7 specimens). Type locality, NMV J62768 (ovig. female, 2.5 mm, with 1 slide). Type locality, NMV J62769 (3 males, 2.2–2.3 mm, 2 ovig. females, 2.5–2.6 mm, 2 non-ovig. females, 2.3–2.6 mm) .

Description. In preserved material, body creamy-yellow to white.

Pleonites 2–4 with anteriorly-directed teeth-like tubercles in transverse rows near posterior margins of dorsomedial not dorsolateral surfaces; with one erect pappose seta between and posterior to each tooth; pappose setal rows continuing laterally beyond tubercle rows.

Anterior margin of pleonite 5 may have similar though less developed row of tubercles as on pleonites 2–4. Pleonite 5 dorsomedially lacking carinae and puncta but with broad raised area undulating in lateral profile due to minor depressions anteromedially and posteromedially and deeper depression bridging the posterior margin of pleonite 5 and anterior margin of the pleotelson. Pleonite 5 1.5 times as long as pleotelson.

Pleotelson also lacking prominent carinae and tubercles, dorsal surface saddle-shaped, with broad raised dorsomedial area which medially may be smooth or coming to faint longitudinal carina; posterior and lateral perimeters upturned. Dorsal surface of pleotelson composed of nodular scales fringed posteriorly with fine spikes. Lateral crests with dorsal row of tubercles. Ventrolateral margin of pleotelson anterior to uropod with several pointed tubercles. Posterior margin of pleotelson with short sheathed setae, lacking tubercles, stout unsheathed setae and scale spikes.

Antenna 1 with 4 flagellar articles; second article with 2 short aesthetascs. Flagellum of antenna 2 with 4 articles.

Mandibular palp with 3 articles. Mandibular incisors with rasp and file. Lacinia mobilis of right mandible elongate and thin, with minor teeth apically.

Epipod of maxilliped broad, oval, 2.7 times as long as wide, reaching palp articulation; epipod lacking simple setae.

Secondary unguis of pereopod 1 bifid. Ventral comb seta on merus of pereopods 6 and 7 and carpus of pereopods 6 and 7.

Uropod peduncle with two prominent rows of pointed tubercles, with more dorsal row continuing on exopod and endopod; exopod small, 0.3 times as long as endopod; endopod as long as uropod.

Pleopod 1 with 2 coupling hooks.

Pleopod 2 with short plumose setae, up to 0.2 times length of exopod. Appendix masculina short, not reaching beyond endopod of pleopod, articulating distal to 60% of length of endopod.

Endopod of pleopod 5 anterior to exopod, triangular, 0.8 times as long as endopod of pleopod 2; peduncle of pleopod 5 with simple seta laterally.

Etymology. From the feminine Latin noun ‘sella’ a saddle, referring to the saddle shape of the pleotelson.

Remarks and comparisons. L. sellifera sp. nov. is an unusual species of Limnoria as the pleotelson is saddleshaped rather than flattened, and may have reduced involvement in bracing within a burrow. A greater role in bracing appears to have been transferred to the uropods. The pleotelson is relatively short, the hind margin upturned, and its posterior margin lacks the usual 4 (or more) posterior stout unsheathed setae that appear to aid bracing. The uropodal armature is well developed with two rows of pointed tubercles on the peduncle, when in other species if present there is usually only one row. The uropodal endopod also has a row of tubercles unlike other species of Limnoria . The uropodal exopod is reduced, apparently to conform with the line of tubercles on the peduncle and endopod. The dorsal rows of ‘teeth’ on pleonites 2–4 are also unusual, and have unknown function. By pointing forward, they may brace the animal when the pleopods beat and thus prevent it from driving itself head first into the end of the tunnel.

L. sellifera sp. nov. appears to be most similar to L. insulae and L. pfefferi , which interestingly shared the same habitat in the Archipelago. Each species has similar large oval maxillipedal epipod and four flagellar articles on antenna 2. Further similarities with L. pfefferi are four flagellar articles on antenna 1, similarly shaped pleopods (short plumose setae, short appendix masculina, similarly shaped pleopod 5), and the lack of stout unsheathed setae on the posterior margin of the pleotelson. Additional similarities with L. insulae are upturned pleotelson perimeters (cup-shaped in some specimens of L. insulae ), and on the uropod the presence of numerous pointed tubercles on the peduncle with several on the exopod as well.

A scanning electron microscope (SEM) examination of the four species found during this study ( L. sellifera sp. nov., L. insulae , L. pfefferi and L. unicornis ) highlights some of their differences ( Figs 3–7 ). Whereas there are few differences in the features of body segments anterior to the pleon, there were marked differences in the pleonites and pleotelson ( Figs 3–4 ). The lateral parts of the pleonites of L. sellifera sp. nov. extend further ventrally with each successive pleonite, with pleonites 4 and 5 being particularly extended ventrally: this difference is much less pronounced in the other species. The sculpturing of the dorsal surface of the pleon and pleotelson also varies considerably, as does the ratio of the length of pleonite 5 to that of the pleotelson ( Figs 3–4 ). Only L. sellifera sp. nov. has rows of teeth on the dorsal surface of the pleon ( Fig. 5A ). The pleotelson surfaces of L. sellifera sp. nov., L. insulae and L. pfefferi are covered with distinct scales, while in L. unicornis the surface is fused and pitted ( Fig. 6 ). The scales of L. sellifera sp. nov. have posteriorly directed spikes ( Fig. 6A ), whereas fine perpendicular setae cover much of the pleotelson in L. unicornis and L. pfefferi . The scales of L. insulae are almost smooth and lack spikes ( Fig. 6D ), although other specimens from Australia had scale spikes (Cookson 1991), similar to those shown for L. sellifera sp. nov.

There were also marked species differences in the uropods. Teeth on the lateral crests of the pleotelson and uropods of L. sellifera sp. nov. project posteriorly ( Figs 5B , 7A ). No such features are evident in the other species except in the case of the uropod of L. insulae . The shape of the peduncle of the uropods and the ratio between length of endopod and peduncle shows species specific characteristics ( Fig. 7 ), with the peduncle of L. insulae being completely different in shape from that of any other limnoriids. The uropods of L. pfefferi have profuse setae in rows on the outer margin ( Fig. 7C ).

Figure 4B shows an example of a lobed lorica of an epibiotic ciliate on the pleotelson of L. pfefferi . The size and shape of this lorica is consistent with descriptions of Mirofolliculina limnoriae ( Delgery et al. 2006) . Up to six such loricae were found on the pleotelson and/or pleonite 5 of this limnoriid. None were found on specimens of L. sellifera sp. nov. and a single non-lobed lorica was found on a specimen of L. insulae .

In summary, the main distinguishing features for L. sellifera sp. nov. are the two rows of tubercles on the uropod peduncle, the row of tubercles on the uropodal endopod, the mid-dorsal rows of tuberculate ‘teeth’ on pleonites 2–4, the short length of the pleotelson compared to pleonite 5, the shape of the pleotelson, and there are only two coupling hooks (not three) on the peduncle of pleopod 1. The latter feature can also be found in Limnoria orbellum .

Figures

FIGURE 1. Limnoria sellifera sp. nov. A–H, male, MZB Cru.Iso. 013, holotype: A, pleonite 2–5 and pleotelson, dorsal view (some setae omitted right side); B, distal articles of pereopod 1, lateral view; C, maxilliped; D, distal region of right mandible; E, medial region of pleonites 1–4; F, dorsal surface of pleotelson; G, posterior margin of pleotelson, dorsal view, H, uropod, lateral view. Scale: single bar = 50 µm, double bar = 100 µm.

FIGURE 2. Limnoria sellifera sp. nov. A–E, male, MZB Cru.Iso. 013, holotype. A, pleopod 5; B, pleopod 2; C, pleotelson and uropod, lateral view, setae omitted; D, flagellum of antenna 1; E, flagellum of antenna 2. Scale: single bar = 50 µm, double bar = 100 µm.

FIGURE 3. Lateral views of limnoriids from the Tukang Besi mangrove forests. A, Limnoria sellifera sp. nov.; B, Limnoria insulae; C, Limnoria unicornis; D, Limnoria pfefferi. Backscatter detector SEM images. Scale bars = 200 µm.

FIGURE 4. Oblique dorsal views of pleonites and pleotelson. A, Limnoria sellifera sp. nov.; B, Limnoria pfefferi (note lorica of folliculinid on the right hand side of the pleotelson); C, Limnoria insulae; D, Limnoria unicornis. Backscatter detector SEM images. Scale bars = 100 µm in A and D, and 200 µm in B and C.

FIGURE 5. Limnoria sellifera sp. nov. A, anteriorly pointing teeth on pleonites 2–5; B, lateral view of pleotelson; C, medial longitudinal carina of pleotelson; D, animal in burrow. A–C, backscatter SEM images, scales bars = 50, 100 and 20 µm for A, B and C respectively; D, stereo microscope image.

FIGURE 6. Detail of dorsal surface of pleotelson. A, Limnoria sellifera sp. nov.; B, Limnoria pfefferi; C, Limnoria unicornis; D, Limnoria insulae. Backscatter detector SEM images. Scale bars indicate 20 µm.

FIGURE 7. Uropods. A, Limnoria sellifera sp. nov., lateral view; B, Limnoria unicornis, lateral view; C, Limnoria pfefferi; D, Limnoria insulae, oblique ventral view. Backscatter detector SEM images. Scale bars indicate 50, 50, 100 and 200 µm for A, B, C and D respectively.