Alvinocaris komaii Zelnio & Hourdez, 2009
Carapace: The integument is thin, reflective, and minutely punctuate. The rostrum is almost distally curved, and is perceptibly elevated above the horizontal in the distal half, with a sharply pointed tip. It reaches one-third to three-quarters the length of the second peduncular article of the antennule. The rostrum length measures one-quarter to one-third the carapace length. The dorsal margin is raised into a thin serrate crest containing 9–12 teeth (with 4–6 teeth on the carapace proper) of decreasing strength towards the distal end. About two-thirds of the length of the crest is continued onto the carapace, with a posterior-most tooth arising from two-thirds of the carapace length. The base of the rostrum deflects from the dorsal line of the carapace at ca. 15°. The ventral margin is less prominent and is armed with 2–6 subterminal teeth. The rostral tooth formulas (dorsal/ventral) from collected specimens are 12/6, 10/2, 10/4, 10/4, 10/2, 10/3, 9/4,10/4, 11/4, and 9/6. The lateral carina is broadened proximally and is confluent with the orbital margin. The carapace has a distinct acuminate antennal spine, and there is a pterygostomian that is acuminate and prominent. A prominent antennal carina curves posteroventrally to intersect obliquely with a carina that extends from the pterygostomial spine at about the mid-length of the carapace. An associated groove continues indistinctly posterior.
Abdomen: The abdomen of both the male and female are broadly arched dorsally, with the narrowest part of sixth somite about one-half the width of first somite. The fourth somite is drawn posterolaterally into an acuminate spine, and is flanked dorsally by 0–4 much more slender and smaller spines. The posterolateral corner of the fifth pleuron is acuminate and has 2–4 spines dorsally that are analogous to those on the fourth somite. The sixth somite has a mid-dorsal length about 1.5–1.8 times that of the fifth somite, and is 1.2–1.8 times as long as wide, and has a smaller acute posterolateral spine. Only the fifth somite has a strong, posteriorly directed spine on the sternite.
Telson: The telson is elongate and subrectangular. It has a length of ca. 2.4–2.9 times its anterior width, 2.9–3.3 times posterior width, and is about 1.4–1.8 times the length of sixth somite (not including the posterior spines). The telson is armed with 7 pairs of dorsolateral spines that are nearly uniform in size. The anterior-most pair are slightly smaller than the 6 posterior-most pairs. The posterior margin is concave with a distinct notch that has a depth of 0.1–0.2 times the posterior width of the telson. The posterior margin of telson has 6–10 pairs of spines on each side of the notch, which can be unequally paired. Sample telson spine formulas from several specimens are 7/8, 6/6, 8/10, 6/6, 7/7, 6/6, and 7/6 on left and right sides of the notch, respectively. The telson overreaches the posterior margin of the uropods.
Eyes: The eyes have a cornea that is imperfectly developed and unfaceted, though it is diffusively pigmented in adults (no juveniles were analyzed), and an internal facet-like pattern is evident. The cornea is ovate in outline though fused to each other mesially, and each with a small upturned spine on the anterodorsal surface.
Antennae: The antennular peduncle reaches the distal margin of the antennal scale. The first article measures 1.1–1.5 times the length of second, and about 1.9–2.3 times the length of third (all measured on the ventral margin). The stylocerite is well separated from the peduncle, and has a tapering to slender elongate tip that variably reaching as far as three-quarters to the full length of the second article. The basal article has a dorsolateral margin that extends into a strong lateral spine that reaches half the length of second article and that is closely appressed to the second article. There is a small distal spine ventrally, but no obvious distomesial spine. The second article is shorter but has a stronger mesiodistal spine. The dorsolateral and ventromesial flagella are approximately equal in length, measuring about the same length as the carapace. The flagella are thickened in the basal half. The antennal scale has a length 1.6–2.3 times its width. There is a strong distolateral tooth that falls short of the broadly rounded distal margin of the blade.
Mandible: The mandibles are similar, having a 2-segmented palp, a distal segment with long setae on the lateral margin, and a proximal segment with 4 long, plumose setae on the distolateral margin. The incisor process has an upper portion that bears 1 blunt tooth, whilst the lower portion projects further than upper, with 8 sharp teeth. The process distinct from the incisor process, separated from it by a deep notch, and having a rounded tip that lacks minute setae.
First maxilla: The proximal endite is oval, curving anteriorly (dished anteriorly) and bears numerous distal marginal setae that are densest around the narrow anteromesial tip. The proximal endite armed with teeth on the distolateral margin. The distal endite has a broad base, and the distal margin curves anteriorly. It is not armed with teeth, but there are numerous setae on the proximal margin and the posterior surface, with longer plumose setae placed regularly around the distal tip and the lateral margin of the endite. The palp has a round tip and mesial, subterminal notch that does not have setae.
Second maxilla: The endites are dished anteriorly, and are densely setose distally on the margins and submarginally. The proximal endite consists of 2 lobes, with distal lobe having a small, setose protrusion on the anterior margin. The distal endite is spatulate in the posterior view, with a uniform row of small setae along the lateral margin. The palp is straight with a short row of small, plumose setae on the lateral margin, and with an unarmed tip. The scaphognathite is almost rounded anteriorly, and is fringed with long plumose setae anteriorly. There are shorter plumose setae on the mesial and lateral margins, that narrow to acuminate. The posterior lobe is armed around the tip and the mesial margin with a series of very long, strong setae. There is a row of small setae proximally on the mesial margin.
First maxilliped: The endite is strongly dished anteriorly, and is fringed along the lateral margin by dense setae. Along the anterior margin there is a fringe of numerous plumose setae. The exopod is ovate, fringed distally by long plumose setae, and has a submarginal ridge laterally. The palp is reduced and is rounded with setae. The epipod is bilobed and unarmed.
Second maxilliped: Pediform, but rather flattened. The coxa is fringed mesially by long, dense, plumose setae. The fused basis-ischium has a regular mesial row of long, strong, sparsely plumose setae opposite the margin and merus. The carpus and propodus are bordered by long, plumose setae, whilst the dactylus is bordered by long plumose or serrate setae, which form a particularly dense, nest-like pad around the mesial part of the dactyl. The epipod is leaf-like, and unarmed. The podobranch is rudimentary with a pointed tip, and the mesial branch is without terminal seta, and there are no tooth-like projections observed on the lateral margin.
Third maxilliped: Long and 4-segmented, reaching as far as the distal end of the antennal scale. The terminal segment is triangular in cross-section, and tapers distally. The tip has 2 spines and additional setae. There is an irregular row of about 4 additional spines subterminally on the mesial face. 5 groups of distally directed serrate setae are arranged in close-set, transverse tracts along the mesial face, with the groups overlapping to form a longitudinal pad. The posterolateral face of the terminal segment is somewhat dished, and the angle between the posterolateral and anterolateral faces is armed with a row of 7 or 8 slender spines or spine-like setae. The carpus has pads of dense setae on the distal two-thirds that are similar and adjacent to those of the terminal segment. The merus-ischium has a row of long, plumose setae. The coxa has a small epipod, with tuft of long, plumose setae at the junction.
First pereopod (P1): Reaches to half the length of the terminal segment on the third maxilliped. P1 is robust, and has fingers that curve downwards and outwards, together being concave laterally. The fixed finger is twice the width of the dactyl basally, and the opposing edges of the fingers are each armed with a row of minute uniform teeth that are close-set against one another. The teeth on the dactyl are somewhat longer than on the fixed finger. The row on the dactyl is angled towards the convex side to interdigitate with the teeth on the fixed finger. The finger tips are slightly spooned by the teeth fanned around the edge, with the teeth of the fixed finger fused to form a corneous edge around the lateral border of the dactyl tip. There is a line of sensory setae on moving finger’s concave surface that run parallel to the teeth, although the setae on the fixed finger are not obvious. The dactyl fractionally outreaches the fixed finger, with the palm measuring half the length of the finger in both males and females. The carpus is short, cone-shaped, and is cupped distally to accommodate the palm. The is a small blunt protuberance on distomesial margin of the carpus, and a lateral ridge that is produced distally into a strong process with a pinched tip. A dense, clearly delineated pad of strong, serrate setae are situated posteriorly between the pinched and smaller process. The merus and ischium are somewhat flattened.
Second pereopod (P2): Shorter and more slender than P1, reaching half the length of the antennal scale. The fingers are subequal to the palm, and are similar in size and shape. The opposing edges are without a gap, each is pectinate with a single row of short teeth that are directed obliquely distally. Each row begins about 0.2 mm from base of the dactyl. The fixed finger has teeth along its entire length that increase slightly in size distally, and terminating in a larger spine at each finger tip. The terminal spines cross when the chela is closed, with 2 tufts of long setae on the dactyl. The ischium has a single spine at about three-quarters length.
Third to fifth pereopods (P3–P5): Similar in length although the merus becomes progressively shorter from P3 to P5 and the propodus longer. P3 outreaches the antennal scale by 0.5 times the propodus. The dactyls is short, and is armed with a single corneous spine and a single accessory spinule in the holotype. There were 2 rows of 4 or 5 accessory spinules in the paratypes on the flexor surface, with the smallest located proximally and longest distally. The propodus has an irregular, composite row of spines ventrolaterally that become denser distally. This row is shortest and sparsest on P3, and longest and densest on P5. The carpus of each pereopod has a distodorsal extension over the proximal extensor surface of the propodus. The ischium and merus of P3 are stronger than in P4-P5. The meri of P3-P4 have 3 spines, but are without spines on P5. The ischium of the pereopods is armed with 2 posteroventral spines on P3-P4, whilst there are none or 1 on P5.
Pleopods: Well developed, with endopods about half the length of exopod on the first pleopod, and subequal with the exopod in pleopods 2–5. The appendix interna of pleopods 2–4 are well developed and smooth, whilst that of pleopod 5 is twice as wide, parallel-sided, and has 30–50 cincinnuli distributed in a fingernail-shaped pad at the tip on the mesial surface. The appendix masculina has approximately 8 slender spines around the tip and subterminally.
Uropods: The uropods have a subequal exopod and endopod, and are slightly shorter than the telson. The exopod has a movable spine mesial to a distolateral tooth that is half its length. The diaresis is sinuous.
(Zelnio & Hourdez, 2009)
Ecology and Distribution
Lau Basin, Kilo Moana 20°9'S, 176°12'E at 2,620 m; 20°19'S, 176°8'E at 2,700 m; 20°45'S, 176°11'E at 2,145 m (Zelnio & Hourdez, 2009).