Research Article |
Corresponding author: B. Abdul Rahim Azman ( abarahim@gmail.com ) Academic editor: Alan Myers
© 2019 Jacqueline H.C. Lim, B. Abdul Rahim Azman, B.H. Ross Othman.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Lim JHC, Azman BAR, Othman BHR (2019) A new species of Aciconula (Amphipoda, Senticauda, Caprellidae) from Sultan Iskandar Marine Park, Malaysia. ZooKeys 859: 17-29. https://doi.org/10.3897/zookeys.859.33284
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A new species of caprellid, Aciconula tinggiensis (Amphipoda, Senticaudata, Caprellidae) was discovered from Pulau Tinggi, Sultan Iskandar Marine Park (SIMP), South China Sea, Malaysia. The new Malaysian species can be distinguished from the other Aciconula species by the combination of the following characters: 1. the presence of a very small suture between head and pereonite 1; 2. antenna 1 flagellum with 4 articles; 3. inner lobe of lower lip unilobed; 4. gnathopod 2 palm of propodus with a large proximal projection (stretching from the proximal margin of the palm to nearly mid-way of palm); 5. pereopods 3–4 with 2 articles (article 1 subrectangular, article 2 conical or tapering at the tip with 1 plumose seta and 2 normal setae) and; 6. pereopod 5 covered with relatively dense and long setae. An updated identification key for the five known species in the genus, including information on the respective geographical distribution and habitat, is presented.
Aciconula tinggiensis sp. nov., caprellid, new species, taxonomy, South China Sea
The amphipod genus Aciconula was established by
The Sultan Iskandar Marine Park (SIMP) is one of Malaysia’s marine protected areas located 15–65 km from Mersing, off the north-east coast of the Johor State, Malaysia in the South China Sea. This body of water covering an area of about 8000 hectares holds one of the most diverse marine ecosystems on the east coast of Peninsular Malaysia, ranging from sandy shores, coral reefs, mangroves, estuaries, mudflats to seagrass and open water habitats (see Harborne et al. 2000;
The caprellids examined in this study were collected from an artificial reef of Kampung Pasir Panjang, Pulau Tinggi, Sultan Iskandar Marine Park (SIMP) at 9–11 m water depth (Fig.
Appendages were dissected from the right side of the specimens and stored in several semi-permanent slides mounted in glycerol and then drawn under an optical microscope (Olympus BX43) and a stereomicroscope with a camera lucida. The drawings were digitized on Adobe Illustrator CS3 using the methods described in
Named after the type locality, Pulau Tinggi in SIMP, Malaysia.
Holotype: male, 2.2 mm, UMT Crus 01003, Mahkota artificial reef Pulau Tinggi, SIMP, Johor, 02°17.637'N, 104°05.817'E, SCUBA diving, 9 June 2009, 12.31 PM, depth 10.7 m, coll. Azman, B.A.R., Gan, S.Y., Lim, J.H.C., Chew, M.W.H. & Shamsul, B.
Paratypes: 1 female, UMT Crus 01004 (Fig.
[Based mostly on holotype (UMT Crus 01003), 2.2 mm, supplemented by paratype (UMT Crus 01004), 1.8 mm for female and (UMT Crus 01005) for lower lip and maxilliped]
Adult male. Body length, 2.2 mm. UMT Crus 01003. Head/pereonite 1 without dorsal projection. Head length 0.2 mm; pereonite 1, 0.07 mm; head and pereonite 1 partially fused (suture clear); pereonite 2, 0.34 mm with an acute mid-dorsal projection; pereonite 3 longest, 0.53 mm; pereonite 4, 0.44 mm; pereonite 5, 0.41 mm, subequal in length to pereonite 4; pereonite 6, 0.16 mm; pereonite 7 short, 0.12 mm. Eye small. Antenna 1 about 0.4× body length; peduncular article 1 with tuft of plumose setae; peduncular article 2 longest; peduncular article 3 lobed at posterodistal margin; flagellum approximately half of peduncular length with 4 articles, proximal article composed of 2 articles. Antenna 2 about 0.4× the length of antenna 1; peduncular articles lobus; flagellum 2-articulate.
Lower lip outer lobes with pair of ducts; inner lobes unilobed. Mandible left incisor with 6 teeth; lacinia mobilis plate like and serrated distally; accessory setal row with 3 setae; mandibular molar present without robust teeth; palp 3-articulate with distal article comprising a row of 5 teeth and setal formula of 1-3-1, second article of palp without seta on inner distal margin; right incisor with 5 teeth; lacinia mobilis with 7 teeth; accessory setal row with 2 setae; palp 3-articulate with distal article comprising a row of 5 teeth and setal formula of 1-3-1, second article of palp with one seta on inner distal margin. Maxilla 1 outer plate with 5 cuspidate and denticulate spines (robust apical setal-teeth); palp article 2 long, 4× length of article 1 with 3 setae apically. Maxilla 2 inner plate with 4 short and long setae distally; outer plate 1.3× length of inner plate with 5 slender setae apically. Maxilliped inner plate small, with one short and one long apical setae; outer plate about 2.5× inner plate with 3 setae at distal margin; palp 4-articulate, scarcely setose, article 2 with 1 seta at inner distal margin, article 3 with 5 distal setae; article 4 tapering to a tip with 2 setae distally and 1 seta at outer proximal margin.
Pereon. Gnathopod 1 basis longer than ischium, merus and carpus combined; propodus subtriangular, longer than wide, scarcely setose, palm with a pair of grasping spines; dactylus falcate, provided with fine setae along lateral margin, tip of dactylus bifid. Gnathopod 2 begins ¼-way along anterior margin of pereonite 2; basis about 0.7 × pereonite 2; ischium and merus subquadrate; carpus triangular; propodus 1.6 × as long as wide, 1.3× length of basis, palm with large proximal projection (stretching from proximal margin of palm to nearly mid-way of palm), provided with one robust grasping spine proximally, a small triangular projection medially and ending with a triangular projection provided with 1 seta, distal margin of palm with 1 triangular projection; dactylus falcate, fitting on palm.
Gill 3 length 0.2× corresponding pereonite, oval. Pereopod 3 reduced, about 0.5× gill length, 2-articulate, second article with one plumose seta and two simple setae apically. Gill 4 slightly larger than gill 3, 0.3 × corresponding pereonite, oval. Pereopod 4 reduced, about 0.5 × gill length, 2-articulate, second article of pereopod 4 more slender than article 2 of pereopod 3 with one plumose seta and two simple setae apically. Pereopod 5, 6-articulate, curved upwards anterodorsally and extending past pereonite 4, setose entire margin comprising short and very long setae, carpus and propodus subequal in length, dactylus reduced to a small cone with one plumose seta apically. Pereopod 6 propodus with a pair of grasping spines proximally, dactylus falcate with one plumose seta on anterior margin at proximal region. Pereopod 7 similar with pereopod 6 but more robust than pereopod 6.
Pleon. Uropod 1 vestigial with 4 setae; Uropod 2 vestigial with 2 setae distally and one facial seta on inner margin. Telson with one seta apically.
Adult female. Body length, 1.8 mm. UMT Crus 01004. Head length 0.2 mm; pereonite 1, 0.04 mm; head/pereonite 1 without dorsal projection; pereonite 2, 0.29 mm with rounded mid-dorsal projection; pereonite 3, 0.39 mm; pereonite 4, 0.32 mm with acute dorsodistal projection; pereonite 5, 0.38 mm, subequal in length to pereonite 3; pereonite 6, 0.13 mm; pereonite 7 short, 0.08 mm. Eye small. Antenna 1 about 0.4 × body length; peduncular article 1 with tuft of setae; peduncular article 2 longest; peduncular article 3-lobed at posterodistal margin; flagellum approximately 1.8 × peduncular length with 4 articles. Antenna 2 about 0.4 × the length of antenna 1; peduncular articles lobus; flagellum 2-articulate.
Mouthparts of the female are similar to those of male (refer to male mouthparts).
Pereon. Gnathopod 2 basis begins ¼-way along anterior margin of pereonite 2; basis about 0.7 × pereonite 2; ischium and merus subquadrate; carpus subtriangular; propodus 2.4 × as long as wide, 1.2 × length of basis, palm without large proximal projection, provided with one robust grasping spine distally; dactylus falcate, fitting on palm. Gill 3 length 0.3 × corresponding pereonite, oval. Pereopod 3 reduced, about 0.5 × gill length, 2-articulate, similar with the male, second article with one plumose setae and two simple setae apically. Gill 4 subequal with gill 3, 0.4 × corresponding pereonite, oval. Pereopod 4 reduced, about 0.4 × gill length, 2-articulate, subequal with pereopod 3 with one plumose setae and two simple setae apically. Oostegites on pereonite 3 and 4 with setae. Pereopod 5, 6-articulate, curved upwards anterodorsally and extending past pereonite 4, more slender than male pereopod 5, setose entire margin comprising short and very long setae, propodus longest, dactylus reduced to a small cone with one plumose seta apically.
Pleon. Uropod 1 vestigial with 1 simple setae; Uropod 2 vestigial with 1 setae distally. Telson with one plumose seta apically.
Considering the four reported species from the genus Aciconula, A. tinggiensis sp. nov. is most similar to A. australiensis in terms of antenna 1 and 2, gnathopod 1, mouthparts (maxilliped and maxillas) and abdomen. Pereopods 3 and 4 of the male are also similar except for the presence of a seta on article 1 of A. australiensis. The Malaysian specimen differs from the Australian counterpart in terms of the absence of 1) a head projection (present in A. australiensis); 2) inner lobe of lower lip unilobed (A. australiensis bilobed); 3) gnathopod 2 propodus proximal projection shallow and wide, about 1/2 of palm (A. australiensis more pronounced, about 1/3 of palm); 4) pereopod 3 of female similar to the male with only 2 articles while A. australiensis shows sexual dimorphism with 3 articles; 5) longer (articles 4 and 5 about 2 × longer) pereopod 5, 0.43 × body length, terminal article with one plumose seta and generally more setose (A. australiensis only 0.23 × body length; terminal articles with one normal seta); 6) mandibles with setal formula of 1-3-1 (setal formula 1-4-1 in A. australiensis).
Aciconula acanthosoma Chess, 1989 clearly differs from the Malaysian specimen firstly by its numerous dorsal projections throughout its body, maxilliped inner lobes more robust and wide, terminally with one tooth and three setae (slender with two normal setae in A. tinggiensis sp. nov.), maxilla 2 with very short terminal setae and mandibles with large, well-developed molar and palp with setal formula of 1-6-1. Apart from its body armature and mouthparts, it also varies in terms of appendages such as gnathopod 2 (basis with a distolateral projection, palmar margin of propodus with a proximal projection followed by a strong spine and a deep sinus), pereopod 5 with short and fine dense setae (setae longer and less extensive in A. tinggiensis sp. nov.) , and abdomen with one pair of well-developed, 1-articulate abdominal appendage. The species from southern California is also much larger than the present specimen (3.3 × longer) and the other two existing species from the Indo-Pacific. In spite of this, A. acanthosoma does have a few similarities in pereopods 3 and 4 with 2 articles and article 2 conical (except for the 3 terminal plumose setae) and pereopods 6 and 7 with 7 articles and grasping structure on article 6. There is more dissimilarity in these two species than similarities. According to
The female specimen of A. tinggiensis sp. nov. was primarily used to compare with
Aciconula tridentata Guedes-Silva & Souza-Filho, 2013 reported from Brazil, is similar to the present species in the: 1) presence of a small sharp median forward projection of the head; 2) pereopods 3 and 4 of male with two-articles, and absence of abdominal appendages but differs in the length of the outer plate of maxilliped (longer in Aciconula tinggiensis sp. nov. reaching the mid-length of palp article 2), the sculpturing on the palm of male gnathopod 2, (with a 3-dentate projection, followed by a large excavation leading to a projection with two sharp processes in A. tridentata) and number or articles in female pereopods 3 and 4 (pereopod 3 4-articulate and pereopod 4 3-articulate in A. tridentata)
In conclusion, Aciconula tinggiensis sp. nov. described here is recognized as distinct from the four existing species of this genus based on these combination of characters; 1) a very small suture between head and pereonite 1; 2) antenna 1 flagellum with 4 articles, its setal formula of 1-3-1; 3) unilobed inner lobe of lower lip with pair of ducts on outer lobe; 4) gnathopod 2 palm of propodus with a large proximal projection, (stretching from the proximal margin of the palm to nearly mid-way of palm) provided with one robust grasping spine proximally, a small triangular projection medially and ending with a triangular projection provided with 1 seta; 5) pereopods 3 and 4 with 2 articles (article 1 subrectangular, article 2 conical or tapering at the tip with 1 plumose seta and 2 normal setae); 6) pereopod 5 covered with relatively dense and long setae; and 7) abdomen region with penes situated medially, uropod 2 degenerated into 4 setae, uropod 2 degenerated into 1 seta medially and 2 setae distally.
The specimens have been found from 10–12 meters deep, living on stinging hyroids.
1 | Body dorsally strongly spinose, abdominal appendages present | A. acanthosoma Chess, 1989 |
– | Body dorsally not spinose, abdominal appendages absent | 2 |
2 | Head lacking a small sharp median forward projection | A. miranda Mayer, 1903 |
– | Head with a small sharp median forward projection | 3 |
3 | Antenna 1 article 1 bearing a setose hump proximally | A. australiensis Guerra-Garcia, 2004 |
– | Antenna 1 article 1 lacking setose hump proximally | 4 |
4 | Gnathopod 2 male first half of propodus palm bearing a 3-dentate followed by a large excavation | A. tridentata Guedes-Silva & Souza-Filho, 2013 |
– | Gnathopod 2 male first half of propodus palm without dentation | A. tinggiensis sp. nov. |
The authors would like to thank Shamsul B., Melvin C.W.H. and Ms. Gan S.Y. for their assistance in the field. Many thanks are also due to Sultan Iskandar Marine Park and Marine Park Section, Department of Fisheries, Malaysia. This study was supported by the Universiti Kebangsaan Malaysia research grant (LIV-2015-02) and the Japan Society for the Promotion of Science (JSPS) Core-to-Core Program (B.Asia-Africa Science Platforms).