Zevinaella volentis

Shalaeva, Kate & Newman, William A., 2016, Zevinaella — a new barnacle genus (Scalpellomorpha: Arcoscalpellinae) associated with crinoids (Echinodermata) from the Caribbean, Zootaxa 4072 (2), pp. 151-170 : 154-159

Zevinaella volentis gen. et sp. nov.

Figs. 2–6

Material examined. Holotype and paratype. NHM UK 1962.4.16.1; Natural History Museum, London. Collected near Barbados, Caribbean Sea. Collector J.B. Lewis, presented by R. Read. Both specimens attached to fragments of crinoid cirri found in the jar but no substantive external differences between these fragments were observed. The holotype was dissected to study the appendages.

Remarks. We are unable to interpret the notation “NR 12-4” found on the label.

Supplementary material. Five specimens. MCZ USA CRI 301, Museum of Comparative Zoology, USA. Collected III/3/1879 near St. Vincent, off Milligan's Key, Station 269, US CSS Blake Expeditions, 13°7'55''N, 61°5'36''W. Depth 227 m. Collector Alexander Agassiz. One specimen attached to a whole S. spinifera and four specimens attached to fragments of cirri of the same species.

One specimen and some fragments of Z. volentis . MCZ USA CRI 303; Museum of Comparative Zoology, USA. Collected II/16/1879 near St. Lucia, Station 220, US CSS Blake Expeditions, 13°50'18''N, 61°3'48''W. Depth 212 m. Collector Alexander Agassiz. The specimen attached to fragments of cirri of S. spinifera .

Distribution and habitat. The depth, precise locality, date of collection and habitat of the holotype and paratype of Z. volentis are not stated on the Natural History Museum collection label. However, there is no question that the sample was from Barbados and that the new species was attached to a crinoid, which now seems very likely to have been S. spinifera , the crinoid species ranging throughout most of the Caribbean.

Diagnosis. As for the genus. RL three times as long as high; umbo conspicuously pronounced and protruding beyond occludent margin. CL thickened; inflation and depression in basal part pronounced, basal margin with strong S-form bend. Peduncle protected by 8 tiers of imbricating plates (r-rl-l-cl-c) covering all surfaces, reaching up to ~ 25 plates high. Cuticle between plates ranging from light to dark brown.

Description of holotype ( Fig. 2 ). Hermaphrodite. Capitulum 7.0 by 4.0 mm, peduncle 6.0 by 2.0 mm.

Plates in ethanol off-white with slight pinkish markings, smooth, relatively thin, with faint striations; cuticle between plates varying from light to dark brown. Specimen bent towards crinoid.

T smaller than S, flat, triangular, without apicobasal ridge. Occludent margin almost straight, carinal slightly convex, basal margin convex. S trapezoidal, height twice width, flat, with conspicuous apicobasal ridge. Occludent margin convex, tergal and lateral margins slightly concave, basal margin straight. C uniformly bowed, ~ 1/4 height of capitulum, reaching almost 1/3 of carinal margin of S, eventually converging from base to apex. Tectum evenly rounded, parietes flat, narrow. Umbo apical. Basal margin rounded.

L1 triangular, flat. Growth lines becoming roughened at carinal margin. Umbo apical, apex pointed. Tergal and scutal margins straight, carinal margin convex.

CL triangular, not flat, thickened, bending towards occludent side. External surface with inflation in carinal part and depression in rostral basal area. Internally, visible dark stripe extending from depression in middle of basal part towards umbo. Umbo apical, apex pointed. Carinal margin convex, rostral margin concave, basal margin bent in S-form. CLs abutting at base of C.

RL essentially rectangular, narrowing slightly towards occludent margin, more than 3 times as long as high, with conspicuous ridge running from apex to basal angle of CL. Plates interdigitating asymmetrically above rostrum. Umbo on occludent margin, projecting beyond it.

R small, triangular, situated between lower portions of RLs.

Peduncle nearly same length but half width of capitulum, slightly arcuate, twisted anticlockwise at ~90°. Scales large, elongate, covering all surfaces; protruding apices bending upwards. Arranged in 8 distinct, continuous, vertical tiers (r-rl-l-cl-c), generally comprised of whorls consisting of sr-l-sc and rl-cl, number of plates per tier reaching up to 16–17 plates on rostral side, 20–21 on lateral sides, increasing to 22 on carinal side.

During dissection, two clusters of eggs found in mantle cavity, each containing ~ 25 round eggs ranging in color from light brown to dark yellow.

Notes on paratype ( Fig. 3 ). Capitulum 10.0 by 5.5 mm, peduncle 7.0 by 2.5 mm; measurements representing maxima for studied specimens. Specimen more mature than holotype; peduncle bent, not twisted. Large calcareous tube of commensal polychaete growing on right side, possibly affecting development of specimen.

Color off-white, pink hue more apparent. Basal margin of T rather convex. RLs interdigitating asymmetrically, but in opposite way compared with holotype. CLs not abutting. Depression on CL marked with darker color in rostral basal area.

Peduncle bent rather than straight, not twisted. Plates organized in 8 tiers from attachment point up to ~ middle of peduncle, where lateral plates split into two tiers. Number of plates per tier ranging from 22 (rostral and carinal sides) to 25 (lateral sides).

Notes on supplementary material ( Fig. 4 ). All specimens less than 8.0 mm in total length, all belonging to the same species, Z. volentis gen. et sp. nov., and differing from Z. rodstromi mainly in general shape, the color of the cuticle between the plates being light to dark brown, the shape of RL and CL and the ratio of the capitular width to the width of the peduncle. RL abutting or not touching above R.

Mouthparts. Labrum ( Fig. 5 a) bullate, rounded, with three non-pronounced lobes, broad, moderately short; cutting edge slightly concave distally; outer surface covered with numerous ctenoid scales, inner surface with short spikes not arranged in rows.

Labrum palp ( Fig. 5 b) long, slender, pointed; outer margin armed with simple setae getting progressively longer distally. Distal extremity clothed with longer setae.

Mandible ( Fig. 5 c) with three teeth. First and second triangular, sharp; second equidistant between first and third; third spatulate, not prominent, not well separated from inferior angle, densely covered by stout spinules. Inferior angle serrate, densely covered by acicular/spatulate spinules. Lateral surface covered by simple setae, slightly longer on upper edge.

Maxilla I ( Fig. 5 d) rectangular, cutting edge straight. Cutting edge with longest spines at corners, intermediate spines straight, about 2/3 length of longest spines, distributed evenly along cutting edge. Lateral surface covered with setae, becoming progressively longer closer to cutting edge.

Maxilla II ( Fig. 5 e) triangular in outline; setae segregated in 3 clusters along margin; lateral sides covered by simple short setae. Maxillary gland papilla not pronounced.

Appendages. Cirrus I ( Fig. 5 f) with unequal rami, anterior ramus ~ 0.8 length of posterior. Anterior ramus with protuberant articles in midsection.

Cirrus II to VI with long, subequal to equal rami.

Median articles of cirrus VI ( Fig. 5 g) twice as long as wide, 4 or 5 pairs of simple, long setae and 1 short stiff bristle on anterior margin, with 5 short setae at postero-distal angle; row of short bristles in middle of lateral sides. Cirral counts as follows.

I II III IV V VI LC 8/9 13 /16 15/16 19/20 18/18 19+ Caudal appendages ( Fig. 6 b) small, not reaching half length of basal segment of cirrus VI, rounded, uniarticulate, ornamented with long setae.

Penis ( Fig. 6 a) long, sparsely covered with short bristles.

Remarks. Although we have only one specimen of Z. rodstromi , the morphological data of Z. volentis came from three independent samples, and this greatly increases the likelihood that these two species are distinct. Specimens of Z. volentis have heavier plates and are stouter in appearance. Approximate capitulum:peduncle width ratio (capitulum measured in widest part, peduncle—the middle) 2: 1 in Z. volentis compared to 3: 1 in Z. rodstromi . CL and RL plates also differ from those of Z. rodstromi . Despite the fact that the date of collection and the preservation method may impact on specimen color, in the case of Z. volentis the color does not vary significantly depending on the preservation time. Both species are from the Caribbean and, therefore, potentially sympatric, but they presently are reported from different regions—the western ( Z. rodstromi ) and the eastern ( Z. volentis ) parts of the Caribbean Sea. Characters distinguishing the two species of Zevinaella are summarized in Table 2 .

Etymology. Volentis means “willing, not obligatory” in Latin. The species is named after the volunteers and all who support them in the Natural History Museum—making discoveries happen.

Figures

FIGURE 2. Zevinaella volentis gen. et sp. nov. Holotype: a—right lateral view, b—left lateral view, c—rostral view, dcarinal view. Scale bar 10 mm.

FIGURE 3. Zevinaella volentis gen. et sp. nov. Paratype: a—right lateral view, b—left lateral view, c—rostral view, dcarinal view. Scale bar 10 mm.

FIGURE 4. Zevinaella volentis gen. et sp. nov. Supplementary material, MCZ USA CRI 301: a—right lateral view, b—left lateral view, c—carinal view. Scale bar 5 mm. Supplementary material, MCZ USA CRI 303: d—showing position on a cirrus of S. spinifera. Note that the scalpellids settled above the bearing spines distal part of a crinoid cirrus. Scale bar 10 mm.

FIGURE 5. Zevinaella volentis gen. et sp. nov. Holotype, mouth parts and appendages: a—labrum, b—labrum palp, cmandible, d—maxilla I, e—maxilla II, f—cirrus I, g—median article of cirrus VI. Scale bars: a, b, d, e, f— 0.3 mm; c— 0.2 mm, g— 0.1 mm.

FIGURE 6. Zevinaella volentis gen. et sp. nov. Holotype, penis and caudal appendages: a—penis, b—caudal appendages. Scale bars 0.5 mm (a) and 0.3 mm (b).