Trimma helenae, Winterbottom, Richard, Erdmann, Mark V. & Dita Cahyani, N. K., 2014

Winterbottom, Richard, Erdmann, Mark V. & Dita Cahyani, N. K., 2014, Trimma helenae (Pisces; Gobioidei), a new species of gobiid fish from Indonesia, Zootaxa 3760 (3), pp. 420-428 : 421-426

Trimma helenae n. sp.

( Figures 1–6 )

Suggested common name: Helen’s pygmy goby

Material examined. Holotype. ROM 95780, 20.2 mm SL female, Indonesia, Raja Ampat, Penemu Island lagoon (00° 35' 32.0" S, 130° 17' 14.2" E), 32 m, 19 Aug., 2013, M. V. Erdmann.

Paratypes. MZB.21468, 18.0 mm SL female, collected with the holotype. ROM 94172, 18.1 mm SL female, Indonesia, Raja Ampat, Penemu Island lagoon (00°35'32.4” S, 130°17’14.2” E), 32 m, clove oil, 4 Feb., 2013, M. V. Erdmann. ROM 95781, 20.1 mm SL male, collected with the holotype.

Diagnosis. Trimma helenae has unbranched pectoral fin rays, a nasal capsule that is flush with the dorsal surface of the snout and a posterior nasal opening in the form of a simple pore without a raised rim, only 3 cycloid scales in the posterodorsal portion of the cheek, and cycloid scales in the midline and on the sides of the nape. The colour pattern of fresh material is also diagnostic, with an anterior yellow and posterior red half of the body, no dark spot or blotch over the hypural region, and four small white spots on the dorsal and ventral midlines of the caudal peduncle.

Description. Dorsal fins VI + I 8, second spine very elongate, reaching posteriorly to between mid-peduncle and base of first branched caudal fin ray when adpressed, rays of second dorsal fin branched except, usually, posterior element of last ray, last ray reaching posteriorly 33– 36 –39% of distance from its base to first dorsal procurrent caudal fin ray; anal fin I 8, all but posterior element of posteriormost ray branched (first ray unbranched in holotype); posteriormost ray 30– 32 –34% of distance from its base to first ventral procurrent caudal fin ray; pectoral fin 14– 15 (mean = 14.3), all rays unbranched, fin reaching posteriorly to a vertical line between anus and anal fin origin; pelvic fin I 5, no frenum, basal membrane vestigial, with either no fold of skin across ventral midline or with a very slight curtain of tissue, first four rays with one sequential branch, fifth ray unbranched and 47– 52 % (mean = 47.8%) length of fourth ray, fourth ray reaching posteriorly to base of anal fin ray 1 –2. Lateral scales 23; anterior transverse scales 7 –8 (mean = 7.5); posterior transverse scales 7; predorsal scales 8 –9 (mean = 8.3); vertical row of three very delicate, adherent cycloid scales on posterodorsal portion of cheek (two or all of these scales apparently abraded off in all specimens but holotype), ventralmost scale lying just below sensory papillae line b, other two, smaller, scales above line b; opercular scales in 3 horizontal rows of 3, 2 and 1 cycloid scales (n = 2); pectoral-fin base with 2–3 vertical rows of cycloid scales with 3 scales in posterior row (n = 2); 6 cycloid prepelvic scales (in midline anterior to basal membrane, n = 2); scales on cheek, opercle and paired fin bases deciduous and easily abraded off; 12 circumpeduncular scales; 8 –9 scales in ventral midline between base of last anal ray and first procurrent caudal ray; body scales mostly ctenoid except for cycloid scales on anterior belly midline, beneath pectoral fin base and on sides and midline of nape; body scales extend anteriorly to just behind eye. Gill opening extending anteroventrally to a vertical below mid- pupil. Teeth not examined in detail, but appear to be typical of other Trimma . Cephalic sensory papillae row counts given in Table 1 and illustrated in Figs. 1–3 ). Tongue broad with rounded edges and a central slightly pointed tip (“}”- shaped). Gill rakers on first arch 3 + 12– 13 = 15– 16 (mean = 15.5). Nasal apparatus unusual for Trimma , with anterior tube and posterior pore without raised rim, and no visible nasal sac, area between two nares flush with rest of snout ( Fig. 4 ). Bony interorbital 98– 100 % pupil width, interorbital convex with slight furrow between interorbital papillae on each side, and no postorbital groove ( Fig. 2 ). No ridge of tissue (or dermal crest) extending anterior to first dorsal spine. Epaxialis extending anteriorly to above a vertical with posterior margin of pupil. Transition between abdominal and caudal vertebrae (as defined by Winterbottom, 2011: 130) not examined, but predicted to be Type A (see Winterbottom, 2003, Fig. 14, inset, and Winterbottom & Zur, 2007, Fig. 3 B).

Colour pattern (from two anaesthetized live specimens, Fig. 5 ). The 18.1 mm SL female (ROM 94172, Fig. 5 A) has the sides of the snout, upper jaw, and cheek suffused with orange red, a pale lower jaw, and the opercular region pale purplish red (due to transfusion of the gill colour). There is a small diffuse purple blotch on the upper cheek between the vertical limb of the preopercle and the ventral margin of the eye, and two very small white spots horizontally aligned over the hyomandibular articulation with the cranium behind the middle of the eye. The body anterior to the anal spine is primarily pale yellow, with some red dorsally (especially at the margins of the scales). Posterior to the anal spine, the body grades to red, somewhat intensified as a vague bar over the bases of the caudal fin rays, with two equidistant, almost pupil-diameter width white spots in the dorsal and ventral midlines of the caudal peduncle, and another pair of such spots over the bases of the procurrent caudal-fin rays. A third, much smaller such spot lies on the dorsal peduncle midline below the middle of the last dorsal fin ray. The dorsal spines and dorsal and anal fin rays are red, with an ill-defined yellow stripe basally, and the distal fin membranes with numerous large iridocytes. The membranes of the caudal fin are dirty yellow, with a diffuse darker bar near the bases of the rays. The pelvic fin rays are reddish, while those of the pectoral fin are hyaline. The iris is golden-red, somewhat intensified at the perimeter. The freshly captured holotype ( Fig. 5 B, ROM 95780, 20.2 mm SL female) is essentially the same colour as above, although the white peduncular spots are smaller (about one-third pupildiameter in width), the iris is orange red, and the membranes of the pelvic fin are suffused with iridocytes.

Live colouration: An underwater photograph of what we presume to be this species (specimen not collected) is presented in Fig. 6 . However, we are not certain of its identity, as the overall colouration differs from that of the anaesthetized live specimens shown in Fig. 5 . The body is mainly translucent pale pink, with a pale yellow neural canal. The swimbladder is yellowish green; the pleural ribs and abdominal vertebrae are red. Two equidistant pale blue to white spots are visible in the dorsal midline of the caudal peduncle (there is no evidence of a third, smaller such spot below the middle of the last dorsal fin ray, nor of the white spot at the bases of the procurrent caudal fin rays). The upper lip is reddish and there is a diffuse red-yellowish pupil-width band between the anterior of the eye and the upper lip. The iris is red and yellow, with a pale purplish-blue stripe over the top of the pupil (such a stripe is not discernable in the two anaesthetized type specimens illustrated in Fig. 5 ). The dorsal and caudal fin rays are pink, and there is a thin reddish internal bar over the ends of the hypurals. The stripe over the iris and the red bar at the base of the caudal peduncle are present in T. habrum but not the other two specimens of T. helenae photographed. However, in T. habrum the bases of the dorsal fin spines and rays lie in distinct red spots, and such spots are not visible in the illustrated specimen ( Fig. 6 ).

Colour pattern in alcohol: Background colour straw-yellow. A few scattered brown chromatophores are present on the head behind the eye and on the nape, on the flanks above and posterior to the anal fin and dorsally posterior to the middle of the second dorsal fin, at the tip of the spine of the second dorsal fin, and a few small, dark chromatophores are visible in the region overlying the distal ends of the hypurals. The second dorsal spine membrane has brown chromatophores mixed with melanophores. Brown chromatophores on the peritoneum may be visible through the body wall beneath the pectoral fin.

No specimens are currently available for genetic analysis.

Comparisons. Trimma helenae belongs to the phenetic grouping defined by a broad interorbital space (width of bony interorbital> 80% of pupil diameter). All of the other eleven species in this group have a nasal apparatus in which the nasal sac is elevated above the profile of the snout, and the posterior opening is a pore with a raised rim (except in T. marinae , in which there are no separate openings and the nasal apparatus is in the form of an open depression or pit). In T. helenae , the nasal sac is not elevated above the profile of the snout, and there is no raised rim to the pore forming the posterior opening. In addition, T. helenae is unusual among the species in this grouping in having cycloid scales in the midline and on the sides of the nape (vs. ctenoid), a trait shared only with T. griffithsi , T. marinae and T. nasa . Five of the species with a broad interorbital have a dark spot or blotch overlying the base of the caudal fin ( T. caudomaculatum , T. griffithsi , T. nasa , T. tevegae and T. xanthochrum ), which is lacking in the other species, including T. helenae . Trimma fishelsoni , T. gigantum , T. hoesei , and T. taylori have at least some branched pectoral fin rays (vs. all pectoral fin rays unbranched in T. helenae ). Trimma habrum has 1–2 rows of cheek scales (total of 7–10 scales; vs. an abbreviated row of 3 scales in the posterodorsal region of the cheek in T. helenae ), and T. marinae has a branched fifth pelvic fin ray (vs. unbranched in T. helenae ) and lacks scales on the cheek (in addition to the form of the nasal capsule mentioned above). The bipartite live colour pattern of a yellow anterior half and red posterior half with four small white spots in the dorsal and ventral midlines of the caudal peduncle of the new species are unique among species of this genus.

Distribution. Trimma helenae is currently known only from 4 specimens from the southeastern lagoon of Penemu Island (Fam Islands group) off the southwest coast of Waigeo, Raja Ampat (West Papua Province), Indonesia.

Etymology. It is a pleasure to name this beautiful species helenae in honour of Helen Newman, one of the founders of Sea Sanctuaries Trust, and leader of the survey that led to the discovery of this species, for her tireless conservation efforts on behalf of Raja Ampat and its indigenous communities over the past decade.

Figures

FIGURE 1. Trimma helenae, 18.1 mm SL female, ROM 94172. Left lateral view of head to show cephalic sensory papillae. Specimen stained with cyanine blue. Photo: R. Winterbottom.

FIGURE 2. Trimma helenae, 18.1 mm SL female, ROM 94172. Dorsal view of head to show cephalic sensory papillae. Specimen stained with cyanine blue. Photo: R. Winterbottom.

FIGURE 3. Trimma helenae, 18.1 mm SL female, ROM 94172. Ventral view of head to show cephalic sensory papillae. Specimen stained with cyanine blue. Photo: R. Winterbottom.

FIGURE 4. Trimma helenae, 18.1 mm SL female, ROM 94172. Left lateral (A) and dorsal (B) views of snout to show nares. Specimen stained with cyanine blue. Posterior naris indicated by red arrow. Photo: R. Winterbottom.

FIGURE 5. Trimma helenae (live, anaesthetized specimens), left lateral views. A: 18.1 mm SL female (image reversed), ROM 94172. Photo: G. R. Allen. B: 20.2 mm SL female holotype, ROM 95780. Photo: M. V. Erdmann.

FIGURE 6. Trimma helenae? (live), Penemu lagoon, Raja Ampat. Photo: M. V. Erdmann. Identification uncertain.

Tables

TABLE 1. Number of cephalic sensory papillae in each row in Trimma helenae. Data given as the minimum count, maximum count, and mean. Based on 4 specimens, except for row g (n = 1), rows z, ot and oi (n = 2) and row x (n = 3). No counts were possible for row os based on the material available (although the row is present).

Papilla row	Min.	Max.	Mean
Row a	5	5	5.0
Row b	3	5	4.0
Row c	6	6	6.0
Row cp	4	5	4.3
Row d	5	6	5.5
Row e -anterior	10	12	10.5
Row e - posterior	10	14	11.5
Row i - anterior	6	7	6.3
Row i - posterior	7	7	7.0
Row p	8	8	8.0
Row r	2	2	2.0
Row f	3	3	3.0
Row cs"	3	3	3.0
Row g	3	3	3.0
Row x	6	7	6.7
Row z	7	7	7.0
Row ot	11	12	11.5
Row os	-	-	-
Row oi	4	4	4.0